SLCP Research Digest
(May 2014)
The SLCP Research Digest is a bi-monthly publication aimed at compiling the top research in fields related to short-lived
climate pollutants. While the Digest draws from a wide list of scientific research publications it is not meant to be a fully
exhaustive compilation of the relevant published research. Suggestions for published research to be included in future
Digests should be emailed to ccac_secretariat@unep.org, with the subject line 'For SLCP Research Digest' we particularly
welcome published research from non-English sources.
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Note - To jump directly to a particular article or section, simply hold ctrl and left click on the title of the article or section
you wish to read.
Table of Contents
Methane ................................................................................................................................................................. 5
Russian policy on methane emissions in the oil and gas sector: A case study in opportunities and challenges in
reducing short-lived forcers ................................................................................................................................................................. 5
Mapping of North American methane emissions with high spatial resolution by inversion of SCIAMACHY satellite
data........................................................................................................................................................................................................... 5
Spatial variability of methane: Attributing atmospheric concentrations to emissions ............................................................... 5
Efficient anaerobic digestion of whole microalgae and lipid-extracted microalgae residues for methane energy
production .............................................................................................................................................................................................. 6
Black Carbon ......................................................................................................................................................... 6
Trend in Global Black Carbon Emissions from 1960 to 2007 ...................................................................................................... 6
Comparison of Carbon Monoxide and Particulate Matter Emissions from Residential Burnings of Pelletized
Biofuels and Traditional Solid Fuels .................................................................................................................................................. 6
High Sensitivity of Diesel Soot Morphological and Optical Properties to Combustion Temperature in a Shock Tube ..... 7
Mixing state of regionally transported soot particles and the coating effect on their size and shape at a mountain site
in Japan ................................................................................................................................................................................................... 7
Concentrations, seasonal and diurnal variations of black carbon in PM2.5 in Shanghai, China................................................ 7
Aerosol black carbon characteristics over Central India: Temporal variation and its dependence on mixed layer
height ....................................................................................................................................................................................................... 8
Black carbon in soils from different land use areas of Shanghai, China: level, sources and relationship with
polycyclic aromatic hydrocarbons ...................................................................................................................................................... 8
Source sector and region contributions to BC and PM2.5 in Central Asia .................................................................................... 8
Hydrofluorocarbons & Alternatives....................................................................................................................... 9
Retrofit assessment of refrigerator using hydrocarbon refrigerants ............................................................................................. 9
Analysis and optimization of subcritical two-stage vapor injection heat pump systems ........................................................... 9
Theoretical energy performance evaluation of different single stage vapour compression refrigeration
configurations using R1234yf and R1234ze(E) as working fluids ............................................................................................... 10
Scroll compressor modelling for heat pumps using hydrocarbons as refrigerants ................................................................... 10
Theoretical investigation on gas-phase reaction of CF3CH2OCH3with OH radicals and fate of alkoxy radicals
(CF3CH(O)OCH3/CF3CH2OCH2O)............................................................................................................................................... 10
Solubility of 4-Aminosalicylic Acid in Supercritical Carbon Dioxide and Subcritical 1,1,1,2-Tetrafluoroethane ............... 11
Tropospheric Ozone ............................................................................................................................................. 11
Projections of future summertime ozone over the U.S. ............................................................................................................... 11
Long-term changes in lower tropospheric baseline ozone concentrations: Comparing chemistry-climate models and
observations at northern midlatitudes ............................................................................................................................................. 11
Current ozone levels threaten gross primary production and yield of Mediterranean annual pastures and nitrogen
modulates the response ...................................................................................................................................................................... 12
Air Pollution .......................................................................................................................................................... 12
The modifying effect of the building envelope on population exposure to PM2.5 from outdoor sources ........................... 12
Quantifying aerosol direct effects from broadband irradiance and spectral aerosol optical depth observations ................ 13
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Local and remote impacts of direct aerosol forcing on Asian monsoon ................................................................................... 13
Impact of pollution on the optical properties of trans-Pacific East Asian dust from satellite and ground-based
measurements ...................................................................................................................................................................................... 13
Radiative forcing of organic aerosol in the atmosphere and on snow: Effects of SOA and brown carbon ........................ 14
Characterization of levels and emission rates for roadside PM2.5 and BTEX in Ho Chi Minh city, Vietnam ..................... 14
Air Pollution & Health .......................................................................................................................................... 14
Environmental exposures and asthma morbidity in children living in urban neighborhoods ............................................... 14
Modelling spatial variability in concentrations of single pollutants and composite air quality indicators in health
effects studies ....................................................................................................................................................................................... 15
Evaluation of adverse human lung function effects in controlled ozone exposure studies.................................................... 15
An evidence-based appraisal of global association between air pollution and risk of stroke ................................................. 15
Acute effects of black carbon and PM2.5 on children asthma admissions: A time-series study in a Chinese city ............... 16
Prenatal exposure to airborne polycyclic aromatic hydrocarbons and IQ: Estimated benefit of pollution reduction ....... 16
Chronic PM2.5 exposure and inflammation: Determining sensitive subgroups in mid-life women....................................... 16
Agriculture ............................................................................................................................................................ 17
Optimizing rice yields while minimizing yield-scaled global warming potential ....................................................................... 17
Enteric methane in dairy cattle production: Quantifying the opportunities and impact of reducing emissions ................. 17
Estimation of methane emission using the CO2 method from dairy cows fed concentrate with different
carbohydrate compositions in automatic milking system ............................................................................................................. 18
Methane yield potential of novel perennial biogas crops influenced by harvest date .............................................................. 18
Biomass Burning & Cooking and Heating .......................................................................................................... 19
Effects of crop residue burning on aerosol properties, plume characteristics, and long-range transport over
northern India ...................................................................................................................................................................................... 19
Characterization of operating conditions of two residential wood combustion appliances ................................................... 19
Pollutant Emissions and Energy Efficiency of Chinese Gasifier Cooking Stoves and Implications for Future
Intervention Studies ............................................................................................................................................................................ 20
Waste ..................................................................................................................................................................... 20
Biosolid stockpiles are a significant point source for greenhouse gas emissions ...................................................................... 20
Transport & Industry ............................................................................................................................................ 21
Black Carbon Emissions in Gasoline Exhaust and a Reduction Alternative with a Gasoline Particulate Filter ................. 21
Emissions from South Asian Brick Production ............................................................................................................................. 21
Fossil Fuels ........................................................................................................................................................... 21
A bridge to nowhere: methane emissions and the greenhouse gas footprint of natural gas ................................................... 22
A new look at methane and non-methane hydrocarbon emissions from oil and natural gas operations in the
Colorado Denver-Julesburg Basin .................................................................................................................................................... 22
Vulnerable Regions ............................................................................................................................................... 22
Isolating the anthropogenic component of Arctic warming ........................................................................................................ 22
Reconstructing glacier retreat since the Little Ice Age in SE Tibet by glacier mapping and equilibrium line altitude
calculation ............................................................................................................................................................................................. 23
Origin and Sources of Dissolved Organic Matter in Snow on the East Antarctic Ice Sheet ................................................. 23
Cross Cutting & Emerging SLCP Source Sectors ................................................................................................ 23
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Environmental Impacts of Shale Gas Extraction in Canada: The Expert Panel on Harnessing Science and
Technology to Understand the Environmental Impacts of Shale Gas Extraction .................................................................. 24
Aircraft Engine Exhaust Emissions And Other Airport-Related Contributions To Ambient Air Pollution: A Review ... 24
The fate of residual treatment water in gas shale ........................................................................................................................... 24
Oil and gas wells and their integrity: Implications for shale and unconventional resource exploitation .............................. 25
Two-stroke scooters are a dominant source of air pollution in many cities .............................................................................. 25
Implications of Shale Gas Development for Climate Change ..................................................................................................... 25
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METHANE
Russian policy on methane emissions in the oil and gas sector: A case study in opportunities and challenges in
reducing short-lived forcers
Abstract - Methane is a potent greenhouse gas, 21 times as powerful as carbon dioxide in contributing to climate change on
a ton-for-ton basis. Methane, along with other short-lived forcers such as black carbon and tropospheric ozone, could play
an important role in addressing global climate change. This stems both from their overall effect on climate systems, and from
their concentrated impact in the short term. Because reducing emissions of such short-lived pollutants may have a large nearterm impact in slowing climate change, the United States and other countries have come together to cooperate under the
Climate and Clean Air Coalition to Reduce Short-Lived Climate Pollutants, and other partnerships such as the Global
Methane Initiative. For global impact, the success of such partnerships depends on their ability to scale up project-specific
emission reductions. This paper assesses options and challenges for scaling based on a case study of Russia's oil and gas
sector. We examine the challenges to achieving far-reaching emission reductions, successes of companies to date, how Russia
has sought to influence methane emissions through its environmental fine system, and options for helping companies
achieve large-scale emission reductions in the future through simpler and clearer incentives.
Evans, M., & V. Roshchanka (2014) Russian policy on methane emissions in the oil and gas sector: A case study in opportunities and
challenges in reducing short-lived forcers, ATMOSPHERIC ENVIRONMENT 92:199-206.
Mapping of North American methane emissions with high spatial resolution by inversion of SCIAMACHY satellite
data
Abstract - We estimate methane emissions from North America with high spatial resolution by inversion of SCIAMACHY
satellite observations using the GEOS-Chem chemical transport model and its adjoint. The inversion focuses on summer
2004 when data from the INTEX-A aircraft campaign over the eastern US are available to validate the SCIAMACHY
retrievals and evaluate the inversion. From the INTEX-A data we identify and correct a water vapor-dependent bias in the
SCIAMACHY data. We conduct an initial inversion of emissions on the horizontal grid of GEOS-Chem (1/2ox2/3o) to
identify correction tendencies relative to the EDGAR v4.2 emission inventory used as a priori. We then cluster these grid
cells with a hierarchical algorithm to extract the maximum information from the SCIAMACHY observations. A 1000-cluster
ensemble can be adequately constrained, providing ~100 km resolution across North America. Analysis of results indicates
that the Hudson Bay Lowland wetlands source is 2.1 Tg a-1, lower than the a priori but consistent with other recent
estimates. Anthropogenic US emissions are 30.1 ± 1.3 Tg a-1, compared to 25.8 Tg a-1 and 28.3 Tg a-1 in the EDGAR v4.2
and EPA inventories respectively. We find that US livestock emissions are 40% greater than in these two inventories. No
such discrepancy is apparent for overall US oil and gas emissions, although this may reflect some compensation between
overestimate of emissions from storage/distribution and underestimate from production. We find that US livestock
emissions are 70% greater than the oil and gas emissions, in contrast to the EDGAR v4.2 and EPA inventories where these
two sources are of comparable magnitude.
Wecht, K. J., D. J. Jacob, C. Frankenberg, Z. Jiang, & D. R. Blake (2014) Mapping of North American methane emissions with high
spatial resolution by inversion of SCIAMACHY satellite data, JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES (Accepted
Article).
Spatial variability of methane: Attributing atmospheric concentrations to emissions
Abstract - Atmospheric methane concentrations were quantified along transects in Switzerland, using a mobile laser
spectrometer combined with a GPS, to identify their spatio-temporal patterns and their controlling factors. Based on these
measurements in complex terrain dominated by agriculture, three main factors were found to be responsible for the diurnal
and regional patterns of atmospheric methane: (1) magnitude and distribution of methane sources within the region, (2)
efficiency of vertical exchange, and (3) local wind patterns within the complex topography. An autocorrelation analysis of
measured methane concentrations showed that nighttime measurements close to the ground provide information about
regional sources (up to 8.3 km), while daytime measurements only carry information about sources located up to 240 m away
in the upwind fetch. Compared to daytime concentrations, nighttime methane concentrations do also better reflect emissions
obtained from a spatially explicit methane emission inventory and allowed the investigation of inconsistencies in this
emission inventory.
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Bamberger, I., J. Stieger, N. Buchmann, & W. Eugster (2014) Spatial variability of methane: Attributing atmospheric concentrations to
emissions, ENVIRONMENTAL POLLUTION 190:65-74.
Efficient anaerobic digestion of whole microalgae and lipid-extracted microalgae residues for methane energy
production
Abstract - The primary aim of this study was to completely investigate extensive biological methane potential (BMP) on
both whole microalgae and its lipid-extracted biomass residues with various degrees of biomass pretreatment. Specific
methane productivities (SMP) under batch conditions for non-lipid extracted biomass were better than lipid-extracted
biomass residues and exhibited no signs of ammonia or carbon/nitrogen (C/N) ratio inhibition when digested at high I/S
ratio (I/S ratio ⩾ 1.0). SMP for suitably extracted biomass ranged from 0.30 to 0.38 L CH4/g VS (volatile solids). For both
whole and lipid-extracted biomass, overall organic conversion ranged from 59.33 to 78.50 as a measure of %VS reduction
with greater percentage biodegradability in general found within the lipid-extracted biomass. Higher production levels
correlated to lipid content with a linear relationship between SMP and ash-free lipid content being developed at a R2 of
0.814.
Zhao, B., M. Jingwei, Q. Zhao, L. Laurens, E. Jarvis, S. Chen, & C. Frear (2014) Efficient anaerobic digestion of whole microalgae and
lipid-extracted microalgae residues for methane energy production, BIORESOURCE TECHNOLOGY 161:423-430.
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BLACK CARBON
Trend in Global Black Carbon Emissions from 1960 to 2007
Abstract - Black carbon (BC) plays an important role in both climate change and health impact. Still, BC emissions as well as
the historical trends are associated with high uncertainties in existing inventories. In the present study, global BC emissions
from 1960 to 2007 were estimated for 64 sources, by using recompiled fuel consumption and emission factor data sets.
Annual BC emissions had increased from 5.3 (3.4−8.5 as an interquartile range) to 9.1 (5.6−14.4) teragrams during this
period. Our estimations are 11−16% higher than those in previous inventories. Over the period, we found that the BC
emission intensity, defined as the amount of BC emitted per unit of energy production, had decreased for all the regions,
especially China and India. Improvements in combustion technology and changes in fuel composition had led to an increase
in energy use efficiency, and subsequently a decline of BC emission intensities in power plants, the residential sector, and
transportation. On the other hand, the BC emission intensities had increased in the industrial and agricultural sectors, mainly
due to an expansion of low-efficiency industry (coke and brick production) in developing countries and to an increasing
usage of diesel in agriculture in developed countries.
Wang, R., S. Tao, H. Shen, Y. Huang, H. Chen, Y. Balkanski, O. Boucher, P. Ciais, G. Shen, W. Li, Y. Zhang, Y. Chen, N.
Lin, S. Su, B. Li, J. Liu, & W. Liu (2014) Trend in Global Black Carbon Emissions from 1960 to 2007, ENVIRON. SCI. TECHNOL.
(As Soon As Publishable).
Comparison of Carbon Monoxide and Particulate Matter Emissions from Residential Burnings of Pelletized
Biofuels and Traditional Solid Fuels
Abstract - Widespread use of solid fuels affects indoor/outdoor air quality, human health, and climate change significantly.
Replacing traditional solid fuels with affordable cleaner fuels is a challenge for most developing countries. In this study,
carbon monoxide (CO) and particulate matter (PM) emissions and financial costs of a potential cleaner fuel-pelletized
biofuels were compared to those of traditional solid fuels, including coal, crop residue, and wood, and a conventional
modern fuel, liquid petroleum gas (LPG), in terms of fuel-mass-based emission factor (EF), delivered-energy-based emission
factor (EFE), and delivered-energy-based cost (CE). The combustions of pelletized fuels and LPG had not only relatively
higher thermal efficiencies but also lower EFs, leading to much lower EFE of these cleaner fuels. The adoption of pelletized
fuels burned in a modern pellet burner could reduce pollutant emissions significantly in comparison to traditional solid fuels.
When both EFE and CE are taken into consideration, it could be found that the nearly free ordinary biomass fuels and highcost coals had much higher pollutant emissions, while LPG was the most expensive, although it would produce the lowest
emission. Pelletized fuels appear to be a good alternative in rural households because of not only lower pollutant emissions
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but also relatively low cost. Future studies, including but not limited to emission measurements, potential reductions in air
concentrations and health outcome, systematic cost−benefit analysis, and identification of key enablers and barriers affecting
the large-scale uptake, are strongly recommended.
Shen, G., & M. Xue (2014) Comparison of Carbon Monoxide and Particulate Matter Emissions from Residential Burnings of Pelletized
Biofuels and Traditional Solid Fuels, ENERGY FUELS (As Soon As Publishable).
High Sensitivity of Diesel Soot Morphological and Optical Properties to Combustion Temperature in a Shock Tube
Abstract - Carbonaceous particles produced from combustion of fossil fuels have strong impacts on air quality and climate,
yet quantitative relationships between particle characteristics and combustion conditions remain inadequately understood.
We have used a shock tube to study the formation and properties of diesel combustion soot, including particle size
distributions, effective density, elemental carbon (EC) mass fraction, massmobility scaling exponent, hygroscopicity, and
light absorption and scattering. These properties are found to be strongly dependent on the combustion temperature and
fuel equivalence ratio. Whereas combustion at higher temperatures (∼2000 K) yields fractal particles of a larger size and high
EC content (90 wt %), at lower temperatures (∼1400 K) smaller particles of a higher organic content (up to 65 wt %) are
produced. Single scattering albedo of soot particles depends largely on their organic content, increasing drastically from 0.3
to 0.8 when the particle EC mass fraction decreases from 0.9 to 0.3. The mass absorption cross-section of diesel soot
increases with combustion temperature, being the highest for particles with a higher EC content. Our results reveal that
combustion conditions, especially the temperature, may have significant impacts on the direct and indirect climate forcing of
atmospheric soot aerosols.
Qiu, C., A. F. Khalizov, B. Hogan, E. L. Petersen, & R. Zhang (2014) High Sensitivity of Diesel Soot Morphological and Optical
Properties to Combustion Temperature in a Shock Tube, ENVIRON. SCI. TECHNOL. 48(11):6444–6452.
Mixing state of regionally transported soot particles and the coating effect on their size and shape at a mountain site
in Japan
Abstract - Soot particles influence the global climate through interactions with sunlight. A coating on soot particles increases
their light absorption by increasing their absorption cross section and cloud condensation nuclei activity when mixed with
other hygroscopic aerosol components. Therefore, it is important to understand how soot internally mixes with other
materials to accurately simulate its effects in climate models. In this study, we used a transmission electron microscope
(TEM) with an auto particle analysis system, which enables more particles to be analyzed than a conventional TEM. Using
the TEM, soot particle size and shape (shape factor) were determined with and without coating from samples collected at a
remote mountain site in Japan. The results indicate that ~10% of aerosol particles between 60 and 350 nm in aerodynamic
diameters contain or consist of soot particles and ~75% of soot particles were internally mixed with nonvolatile ammonium
sulfate or other materials. In contrast to an assumption that coatings change soot shape, both internally and externally mixed
soot particles had similar shape and size distributions. Larger aerosol particles had higher soot mixing ratios, i.e., more than
40% of aerosol particles with diameters >1 µm had soot inclusions, whereas <20% of aerosol particles with diameters <1
µm included soot. Our results suggest that climate models may use the same size distributions and shapes for both internally
and externally mixed soot; however, changing the soot mixing ratios in the different aerosol size bins is necessary.
Adachi, K., Y. Zaizen, M. Kajino, & Y. Igarashi (2014) Mixing state of regionally transported soot particles and the coating effect on their
size and shape at a mountain site in Japan, JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES 119(9):5386-5396.
Concentrations, seasonal and diurnal variations of black carbon in PM2.5 in Shanghai, China
Abstract - Concentration of black carbon (BC) in PM2.5 was measured continuously with an aethalometer during January
2010 and December 2011 at an urban site in Shanghai, China. The impact of the emission control measures for the 2010
World Expo and the World Expo event itself on the concentration and temporal variation of BC in Shanghai was discussed.
The annually averaged BC concentrations in 2010 and 2011 in Shanghai were 3.8 ± 2.3 μg m− 3 and 3.3 ± 2.1 μg m
−3
respectively. Higher BC concentrations were found in winter and the lowest monthly concentration occurred in
September. Comparing with the BC concentration in 2011, lower BC concentration was found in spring of 2010 due to the
emission control measures for the Shanghai World Expo and higher BC concentration in summer due to the huge increase
of visitors to the World Expo. Distinct bi-modal diurnal variation of BC was found with the highest evening peak
concentration in Friday and the lowest in Monday. The diurnal variation of BC matched well with the living style of people
in Shanghai and indicated that traffic emission was the main source of BC in urban Shanghai.
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Feng, J., M. Zhong, B. Xu, Y. Du, M. Wu, H. Wang, & C. Chen (2014) Concentrations, seasonal and diurnal variations of black
carbon in PM2.5 in Shanghai, China, ATMOSPHERIC RESEARCH 147–148:1–15.
Aerosol black carbon characteristics over Central India: Temporal variation and its dependence on mixed
layer height
Abstract - In a first of its kind study over the Indian region, concurrent and extensive measurements of black carbon (BC)
concentration and atmospheric boundary layer parameters are used to quantify the role of atmospheric boundary layer in
producing temporal changes in BC. During this study, 18 months (2011–12) data of continuous measurements of BC
aerosols, made over a semi-urban location, Nagpur, in Central India are used along with concurrent measurements of vertical
profiles of atmospheric thermodynamics, made using weekly ascents of GPS aided Radiosonde for a period of 1 year. From
the balloon data, mixed layer heights and ventilation coefficients are estimated, and the monthly and seasonal changes in BC
mass concentration are examined in the light of the boundary layer changes. Seasonally, the BC mass concentration was
highest (~ 4573 ± 1293 ng m− 3) in winter (December–February), and lowest (~ 1588 ± 897 ng m− 3) in monsoon (June–
September), while remained moderate (~ 3137 ± 1446 ng m− 3) in pre-monsoon (March–May), and post-monsoon
(~ 3634 ± 813 ng m− 3) (October–November) seasons. During the dry seasons, when the rainfall is scanty or insignificantly
small, the seasonal variations in BC concentrations have a strong inverse relationship with mixed layer height and ventilation
coefficient. However, the lowest BC concentrations do not occur during the season when the mixed layer height (MLH) is
highest or the ventilation coefficient is the highest; rather it occurs when the rainfall is strong (during summer monsoon
season) and airmass changes to primarily of marine origin.
Kompalli, S. K., S. S. Babu, K. K. Moorthy, M. R. Manoj, N. V. P. K. Kumar, K. H. B. Shaeb, & A. K. Joshi (2014) Aerosol
black carbon characteristics over Central India: Temporal variation and its dependence on mixed layer height, ATMOSPHERIC RESEARCH
147–148:27-37.
Black carbon in soils from different land use areas of Shanghai, China: level, sources and relationship with
polycyclic aromatic hydrocarbons
Abstract - Black carbon (BC) in soils plays a key role of carrying hydrophobic pollutants like polycyclic aromatic
hydrocarbons (PAHs). However, little is known about the spatial distribution, sources of BC and its relationship with PAHs
in urban soils. We studied BC, total organic carbon (TOC) and PAHs concurrently in 77 soils collected from downtown
area, suburban and rural area and industrial area of Shanghai, China. BC was determined by both chemical oxidation
(dichromate oxidation, BCCr) and chemo-thermal oxidation (CTO-375, BCCTO). BC sources were identified qualitatively by
BC/TOC concentration ratios and BC-cogenerated HWM PAH isomer ratios and quantitatively by principal component
analysis followed by multiple linear regression (PCA-MLR). Results showed that BCCrconcentration (4.65 g/kg on average)
was significantly higher than BCCTO (1.91 g/kg on average) in Shanghai soils. BCCrconcentrations in industrial area were
significantly higher than those in other two. Stronger correlation was found between PAHs and TOC, BCCr than that
between PAHs and BCCTO, which indicates the possibility of PAHs being carried by charcoal and other organic matters thus
negating its exclusive dependence on soot. Charcoal was therefore suggested to be taken into account in studies of BC and
its sorption of PAHs. BC/TOC ratios showed a mixed source of biomass burning and fossil fuel combustion. PCA scores of
BC-cogenerated HWM PAHs isomer ratios in potential sources and soil samples clearly demonstrated that sources of BC in
urban soils may fall into two categories: coal and biomass combustion, and traffic (oil combustion and tire wear). PCA-MLR
of HWM PAHs concentrations in soil samples indicated that coal and oil combustion had the largest contribution to BC in
urban soils while tire wear and biomass combustion were important in downtown and rural area, respectively, which
indicated they were main sources of HWM PAHs and presumably of BC.
Wang, Q., M. Liu, Y. Yu, F. Du, & X. Wang (2014) Black carbon in soils from different land use areas of Shanghai, China: level, sources
and relationship with polycyclic aromatic hydrocarbons, APPLIED GEOCHEMISTRY (In Press).
Source sector and region contributions to BC and PM2.5 in Central Asia
Abstract - Particulate matter (PM) mass concentrations, seasonal cycles, source sector and source region contributions in
Central Asia (CA) are analyzed for the period April 2008–July 2009 using the Sulfur Transport and dEposition Model
(STEM) chemical transport model and modeled meteorology from the Weather Research and Forecasting (WRF) model.
Predicted Aerosol Optical Depth (AOD) values (annual mean value ∼0.2) in CA vary seasonally with lowest values in the
winter. Surface PM2.5 concentrations (annual mean value ∼10 μg m−3) also exhibit a seasonal cycle, with peak values and
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largest variability in the spring/summer, and lowest values and variability in the winter (hourly values from 2–90 μg m−3).
Surface concentrations of black carbon (BC) (mean value ∼0.1 μg m−3) show peak values in the winter. The simulated values
are compared to surface measurements of AOD, and PM2.5, PM10, BC, organic carbon (OC) mass concentrations at two
regional sites in the Kyrgyz Republic (Lidar Station Teplokluchenka (LST) and Bishkek). The predicted values of AOD and
PM mass concentrations and their seasonal cycles are fairly well captured. The carbonaceous aerosols are underpredicted in
winter, and analysis suggests that the winter heating emissions are underestimated in the current inventory. Dust, from
sources within and outside CA, is a significant component of the PM mass and drives the seasonal cycles of PM and AOD.
On an annual basis, the power and industrial sectors are found to be the most important contributors to the anthropogenic
portion of PM2.5. Residential combustion and transportation are shown to be the most important sectors for BC. Biomass
burning within and outside the region also contributes to elevated PM and BC concentrations. The analysis of the transport
pathways and the variations in particulate matter mass and composition in CA demonstrate that this region is strategically
located to characterize regional and intercontinental transport of pollutants. Aerosols at these sites are shown to reflect dust,
biomass burning and anthropogenic sources from Europe, South, East and CA, and Russia depending on the time period.
Simulations for a reference 2030 emission scenario based on pollution abatement measures already committed to in current
legislation show that PM2.5 and BC concentrations in the region increase, with BC growing more than PM2.5 on a relative
basis. This suggests that both the health impacts and the climate warming associated with these particles may increase over
the next decades unless additional control measures are taken. The importance of observations in CA to help characterize
the changes that are rapidly taking place in the region are discussed.
Kulkarni, S., N. Sobhani, J. P. Miller-Schulze, M. M. Shafer, J. J. Schauer, P. A. Solomon, P. E. Saide, S. N. Spak, Y. F.
Cheng, H. A. C. Denier van der Gon, Z. Lu, D. G. Streets, G. Janssens-Maenhout, C. Wiedinmyer, J. Lantz, M. Artamonova,
B. Chen, S. Imashev, L. Sverdlik, J. T. Demint, B. Adhikary, A. D'Allura, C. Wei, & G. R. Carmichael (2014) Source sector and
region contributions to BC and PM2.5 in Central Asia, ATMOS. CHEM. PHYS. DISCUSS. 14:11343-11392.
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HYDROFLUOROCARBONS & ALTERNATIVES
Retrofit assessment of refrigerator using hydrocarbon refrigerants
Abstract - This study used hydrocarbon (HC) refrigerants in a small R134a refrigerator to evaluate the refrigeration
performance and feasibility of using these alternative refrigerants by conducting the no-load pull-down test and 24-hour onload cycling test. The mixed mass ratios of the HC refrigerants, R290 and R600a, were 65% and 35% (HC 1), 50% and 50%
(HC2), and 0% and 100% (HC3), respectively. The charged ratios were 30%, 40%, 50%, and 60% based on the charged mass
of R134a for HC refrigerants. The results of the no-load pull-down test revealed that the optimal charged mass for all the
HC refrigerants was 40% of that of R134a. Most of the experimental results of the HC refrigerators obtained using the
optimal charged masses showed that freezer temperature and power consumption were higher than those of the R134a
refrigerator. Therefore, the capillary tube lengths of R134a, HC1, HC2, and HC3 were recalculated to be 2.77, 5.05, 5.34, and
5.60 m, respectively, and the recalculated capillary tube was used in the 24-hour on-load cycling test. The results of the 24hour on-load cycling test showed that the freezer temperatures considerably decreased when the HC refrigerants were used,
and that all of the HC refrigerants could be used in the R134a refrigerator after changing the capillary tube lengths. All of the
HCs refrigerants yielded lower electricity consumption, lower on-time ratios, and higher energy factors (EFs) than R134a did.
The EFs of HC1, HC2, and HC3 were 9.1%, 12.2%, and 42.3% higher than that of R134a, respectively. Using a higher
proportion of R600a in HC refrigerants can enhance the EFs of refrigerators.
Yu, C., & T. Teng (2014) Retrofit assessment of refrigerator using hydrocarbon refrigerants, APPLIED THERMAL ENGINEERING 66(1–
2):507-518.
Analysis and optimization of subcritical two-stage vapor injection heat pump systems
Abstract - Two of the major problems of heat pump systems working in extreme conditions are the loss of efficiency of the
system and the high compressor discharge temperatures. One possibility in order to overcome these issues is to perform the
compression in two stages. In this frame the use of vapor injection two stage cycles represent an economic and effective
solution. This study analyzes the influence of design parameters and injection conditions for two different configurations of
two stage cycles, for four refrigerants (R407C, R290, R22 and R32). Design parameters, such as the displacement ratio, are
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optimized in terms of COP in ideal conditions for both injection systems. A deeper analysis taking into account the
efficiencies of the compressor is done finding that two stage systems could reach improvements of 30% in terms of COP
compared with one stage systems and that a bad design of this type of systems could represent a loss of improvement
between 6% and 10%. Finally a method to control the system at any operating point in order to make it works in its
optimum is done. From all the analysis, guidelines for the optimum design and control of such systems are obtained in terms
of capacity, Coefficient of Performance (COP), seasonal performance factor and discharge temperature criteria.
Redón, A., E. Navarro-Peris, M. Pitarch, J. Gonzálvez-Macia, & J. M. Corberán (2014) Analysis and optimization of subcritical
two-stage vapor injection heat pump systems, APPLIED ENERGY 124:231-240.
Theoretical energy performance evaluation of different single stage vapour compression refrigeration
configurations using R1234yf and R1234ze(E) as working fluids
Abstract - R1234yf and R1234ze(E) have been proposed as alternatives for R134a in order to work with low GWP
refrigerants, but this replacement results generally in a decrease of the performance. For this reason, it is interesting to
explore ways to improve the system performance using these refrigerants. In this paper, a comparative study in terms of
energy performance of different single stage vapour compression configurations using R1234yf and R1234ze(E) as working
fluids has been carried out. The most efficient configuration is the one which uses an expander or an ejector as expansion
device. On the other hand, using an internal heat exchanger in a cycle which replaces the expansion valve by an expander or
an ejector could produce a detrimental effect on the COP. However, for all the configurations the introduction of an internal
heat exchanger produces a significant increment on the cooling capacity.
Molés, F., J. Navarro-Esbrí, B. Peris, A. Mota-Babiloni, & Á.Barragán-Cervera (2014) Theoretical energy performance evaluation of
different single stage vapour compression refrigeration configurations using R1234yf and R1234ze(E) as working fluids, INTERNATIONAL
JOURNAL OF REFRIGERATION (In Press).
Scroll compressor modelling for heat pumps using hydrocarbons as refrigerants
Abstract - Hydrocarbons are today considered as promising alternatives to hydrofluorocarbons thanks to their low
environmental impact and their easy implementation. However, some precautions have to be taken to thwart their
flammability. European regulations impose to take stringent measures regarding components and to install heat pumps in
unoccupied spaces. Nevertheless manufacturers keep working on components for hydrocarbons. In the frame of a research
project on heat pumps for simultaneous heating and cooling, an R407C prototype working with a scroll compressor was
built and tested. A near-industrial prototype is today being designed for propane with the help of recent modelling
techniques. After having detailed the main issues regarding hydrocarbons as refrigerants, this article reviews scroll
compressor modelling studies and presents the development of a thermodynamically realistic scroll compressor model. It
was first developed for R407C and then adapted to thermodynamic properties of hydrocarbons and to other sizes of
compressors.
Byrne, P., R. Ghoubali, & J. Miriel (2014) Scroll compressor modelling for heat pumps using hydrocarbons as refrigerants,
INTERNATIONAL JOURNAL OF REFRIGERATION 41:1-13.
Theoretical investigation on gas-phase reaction of CF3CH2OCH3with OH radicals and fate of alkoxy radicals
(CF3CH(O)OCH3/CF3CH2OCH2O)
Abstract - Detailed theoretical investigation has been performed on the mechanism, kinetics and thermochemistry of the gas
phase reactions of CF3CH2OCH3 (HFE-263fb2) with OH radicals using ab-initio and DFT methods. Reaction profiles are
modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels, respectively. Our
calculations reveal that hydrogen abstraction from the CH2 group is thermodynamically and kinetically more facile than that
from the CH3 group. Using group-balanced isodesmic reactions, the standard enthalpies of formation for CF 3CH2OCH3 and
radicals (CF3CHOCH3 and CF3CH2OCH2) are also reported for the first time. The calculated bond dissociation energies for
the CH bonds are in good agreement with experimental results. At 298 K, the calculated total rate coefficient for
CF3CH2OCH3 + OH reactions is found to be in good agreement with the experimental results. The atmospheric fate of the
alkoxy radicals, CF3CH(O)OCH3 and CF3CH2OCH2O are also investigated for the first time using the same level of theory.
Out of three plausible decomposition channels, our results clearly point out that reaction with O 2 is not the dominant path
leading to the formation of CF3C(O)OCH3 for the decomposition of CF3CH(O)OCH3 radical in the atmosphere. This is in
accord with the recent report of Osterstrom et al. [CPL 524 (2012) 32] but found to be in contradiction with experimental
finding of Oyaro et al. [JPCA 109 (2005) 337].
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Mishra, B. K., M. Lily, R. C. Deka, & A. K. Chandra (2014) Theoretical investigation on gas-phase reaction of CF3CH2OCH3with OH
radicals and fate of alkoxy radicals (CF3CH(O)OCH3/CF3CH2OCH2O), JOURNAL OF MOLECULAR GRAPHICS AND MODELLING
50:90-99.
Solubility of 4-Aminosalicylic Acid in Supercritical Carbon Dioxide and Subcritical 1,1,1,2-Tetrafluoroethane
Abstract- The equilibrium solubilities of 4-aminosalicylic acid (PAS) in supercritical carbon dioxide (SCCO2) and subcritical
1,1,1,2-tetrafluoroethane (R134a) are crucial to the process of supercritical and subcritical extraction. After reliability tests of
the experimental apparatus were carried out and confirmed, measurements of the solubilities of PAS in SCCO2 and
subcritical R134a were implemented from (11.0 to 21.0) MPa at temperatures of (308 to 328) K by the dynamic method in
SCCO2 and from (5.0 to 15.0) MPa at temperatures of (308 to 328) K by the static method in subcritical R134a, respectively.
It was found that the solubility of PAS is much higher in subcritical R134a than in SCCO2 under the same operational
conditions (temperature and pressure). The solubility enhancement factor (δ) was calculated and analyzed. Four densitybased models (Chrastil, K-J, M-S-T, and S-S) were used to correlate the PAS solubility data in SCCO2 and subcritical R134a.
The calculated results showed that the reasonable agreement was obtained with the experimental solubility data.
Jin, J., X. Fan, H. Zhang, Y. Wang, & Z. Zhang (2014) Solubility of 4-Aminosalicylic Acid in Supercritical Carbon Dioxide and
Subcritical 1,1,1,2-Tetrafluoroethane, J. CHEM. ENG. DATA (As Soon As Publishable).
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TROPOSPHERIC OZONE
Projections of future summertime ozone over the U.S.
Abstract - We use a regional coupled chemistry-transport model to assess changes in surface ozone over the summertime
U.S. between present and a 2050 future time period at high spatial resolution under the A2 climate and Representative
Concentration Pathway (RCP) 8.5 anthropogenic precursor emission scenarios. Predicted changes in regional climate and
globally enhanced ozone are estimated to increase surface ozone over most of the U.S.; the 95th percentile for daily 8 h
maximum surface ozone increases from 79 ppb to 87 ppb. The analysis suggests that changes in meteorological drivers likely
will add to increasing ozone, but the simulations do not allow separating meteorological feedbacks from that due to
enhanced global ozone. Stringent emission controls can counteract these feedbacks; if implemented as in RCP8.5, the 95th
percentile for surface ozone is reduced to 55 ppb. A comparison of regional to global model projections shows that the
global model is biased high in surface ozone compared to the regional model and compared to observations. On average,
both the global and the regional model predict similar future changes but reveal pronounced differences in urban and rural
regimes that cannot be resolved at the coarse resolution of the considered global model. This study confirms the key role of
emission control strategies in future air quality projections and demonstrates the need for considering degradation of air
quality with future climate change in policy making. It also illustrates the need for high-resolution modeling when the
objective is to address regional and local air quality or establish links to human health and society.
Pfister, G. G., S. Walters, J.-F. Lamarque, J. Fast, M. C. Barth, J. Wong, J. Done, G. Holland, & C. L. Bruyère (2014)
Projections of future summertime ozone over the U.S., JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES 119(9):5559-5582.
Long-term changes in lower tropospheric baseline ozone concentrations: Comparing chemistry-climate models and
observations at northern midlatitudes
Abstract - Two recent papers have quantified long-term ozone (O3) changes observed at northern midlatitude sites that are
believed to represent baseline (here understood as representative of continental to hemispheric scales) conditions. Three
chemistry-climate models (NCAR CAM-chem, GFDL-CM3, and GISS-E2-R) have calculated retrospective tropospheric
O3 concentrations as part of the Atmospheric Chemistry and Climate Model Intercomparison Project and Coupled Model
Intercomparison Project Phase 5 model intercomparisons. We present an approach for quantitative comparisons of model
results with measurements for seasonally averaged O3 concentrations. There is considerable qualitative agreement between
the measurements and the models, but there are also substantial and consistent quantitative disagreements. Most notably,
models (1) overestimate absolute O3 mixing ratios, on average by ~5 to 17 ppbv in the year 2000, (2) capture only ~50% of
O3 changes observed over the past five to six decades, and little of observed seasonal differences, and (3) capture ~25 to
45% of the rate of change of the long-term changes. These disagreements are significant enough to indicate that only limited
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confidence can be placed on estimates of present-day radiative forcing of tropospheric O3 derived from modeled historic
concentration changes and on predicted future O3 concentrations. Evidently our understanding of tropospheric O3, or the
incorporation of chemistry and transport processes into current chemical climate models, is incomplete. Modeled O 3 trends
approximately parallel estimated trends in anthropogenic emissions of NOx, an important O3 precursor, while measured
O3 changes increase more rapidly than these emission estimates.
Parrish, D. D., J.-F. Lamarque, V. Naik, L. Horowitz, D. T. Shindell, J. Staehelin, R. Derwent, O. R. Cooper, H. Tanimoto,
A. Volz-Thomas, S. Gilge, H.-E. Scheel, M. Steinbacher, & M. Fröhlich (2014) Long-term changes in lower tropospheric baseline
ozone concentrations: Comparing chemistry-climate models and observations at northern midlatitudes, JOURNAL OF GEOPHYSICAL
RESEARCH: ATMOSPHERES 119(9):5719-5736.
Current ozone levels threaten gross primary production and yield of Mediterranean annual pastures and nitrogen
modulates the response
Abstract - Pastures are among the most important ecosystems in Europe considering their biodiversity and distribution area.
However, their response to increasing tropospheric ozone (O3) and nitrogen (N) deposition, two of the main drivers of
global change, is still uncertain. A new Open-Top Chamber (OTC) experiment was performed in central Spain, aiming to
study annual pasture response to O3 and N in close to natural growing conditions. A mixture of six species of three
representative families was sowed in the field. Plants were exposed for 40 days to four O3 treatments: filtered air, non-filtered
air (NFA) reproducing ambient levels and NFA supplemented with 20 and 40 nl l-1 O3. Three N treatments were considered
to reach the N integrated doses of “background”, +20 or +40 Kg N ha-1. Ozone significantly reduced green and total
aboveground biomass (maximum reduction 25%) and increased the senescent biomass (maximum increase 40%).
Accordingly, O3decreased community Gross Primary Production due to both a global reduction of ecosystem CO2 exchange
and an increase of ecosystem respiration. Nitrogen could partially counterbalance O3effects on aboveground biomass when
the levels of O3 were moderate, but at the same time O3 exposure reduced the fertilization effect of higher N availability.
Therefore, O3 must be considered as a stress factor for annual pastures in the Mediterranean areas.
Calvete-Sogo, H., S. Elvira, J. Sanz, I. González-Fernández, H. García-Gómez, L. Sánchez-Martín, R. Alonso, & Vi.
Bermejo-Bermejo (2014) Current ozone levels threaten gross primary production and yield of Mediterranean annual pastures and nitrogen
modulates the response, ATMOSPHERIC ENVIRONMENT (In Press).
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AIR POLLUTION
The modifying effect of the building envelope on population exposure to PM2.5 from outdoor sources
Abstract - A number of studies have estimated population exposure to PM2.5 by examining modeled or measured outdoor
PM2.5 levels. However, few have taken into account the mediating effects of building characteristics on the ingress of
PM2.5 from outdoor sources and its impact on population exposure in the indoor domestic environment. This study describes
how building simulation can be used to determine the indoor concentration of outdoor-sourced pollution for different
housing typologies and how the results can be mapped using building stock models and Geographical Information Systems
software to demonstrate the modifying effect of dwellings on occupant exposure to PM2.5 across London. Building
archetypes broadly representative of those in the Greater London Authority were simulated for pollution infiltration using
EnergyPlus. In addition, the influence of occupant behavior on indoor levels of PM2.5 from outdoor sources was examined
using a temperature-dependent window-opening scenario. Results demonstrate a range of I/O ratios of PM2.5, with detached
and semi-detached dwellings most vulnerable to high levels of infiltration. When the results are mapped, central London
shows lower I/O ratios of PM2.5 compared with outer London, an apparent inversion of exposure most likely caused by the
prevalence of flats rather than detached or semi-detached properties.
Taylor, J., C. Shrubsole, M. Davies, P. Biddulph, P. Das, I. Hamilton, S. Vardoulakis, A. Mavrogianni, B. Jones, & E.
Oikonomou (2014) The modifying effect of the building envelope on population exposure to PM2.5 from outdoor sources, INDOOR AIR (Early
View).
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Quantifying aerosol direct effects from broadband irradiance and spectral aerosol optical depth observations
Abstract - We outline a methodology using broadband and spectral irradiances to quantify aerosol direct effects on the
surface diffuse shortwave (SW) irradiance. Best Estimate Flux data span a 13 year timeframe at the Department of Energy
Atmospheric Radiation Measurement Program's Southern Great Plains (SGP) site. Screened clear-sky irradiances and aerosol
optical depth (AOD), for solar zenith angles ≤ 65°, are used to estimate clear-sky diffuse irradiances. We validate against
detected clear-sky observations from SGP's Basic Radiation System (BRS). BRS diffuse irradiances were in accordance with
estimates, producing a root-mean-square error and mean bias errors of 4.0 W/m2 and −1.4 W/m2, respectively. Absolute
differences show 99% of estimates within ±10 W/m2 (10%) of the mean BRS observations. Clear-sky diffuse estimates are
used to derive quantitative estimates of aerosol radiative effects, represented as the aerosol diffuse irradiance (ADI). ADI is
the contribution of diffuse SW to global SW, attributable to scattering of atmospheric transmission by natural plus
anthropogenic aerosols. Estimated slope for the ADI as a function of AOD indicates an increase of ~22 W/m2 in diffuse
SW for every 0.1 increase in AOD. Such significant increases in the diffuse fraction could possibly increase photosynthesis.
Annual mean ADI is 28.2 W/m2, and heavy aerosol loading at SGP provides up to a maximum increase of 120 W/m2 in
diffuse SW over background conditions. With regard to seasonal variation, the mean diffuse forcings are 17.2, 33.3, 39.0, and
23.6 W/m2 for winter, spring, summer, and fall, respectively.
Creekmore, T. N., E. Joseph, C. N. Long, & S. Li (2014) Quantifying aerosol direct effects from broadband irradiance and spectral aerosol
optical depth observations, JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES 119(9):5464-5474.
Local and remote impacts of direct aerosol forcing on Asian monsoon
Abstract - The impact of heating by black carbon aerosols on Indian summer monsoon has remained inconclusive. Some
investigators have predicted that black carbon aerosols reduce monsoon rainfall while others have argued that it will increase
monsoon rainfall. These conclusions have been based on local influence of aerosols on the radiative fluxes. The impact of
aerosol-like heating in one region on the rainfall in a remote region has not been examined in detail. Here, using an
atmospheric general circulation model, it has been shown that remote influence of aerosol-like heating can be as important
as local influence on Indian summer monsoon. Precipitation in northern Arabian Sea and north-west Indian region increased
by 16% in June to July when aerosol-like heating were present globally. The corresponding increase in precipitation due to
presence of aerosol-like heating only over South Asia (local impact) and East Asia (remote impact) were 28 and 13%,
respectively. This enhancement in precipitation was due to destabilization of the atmosphere in pre-monsoon season that
affected subsequent convection. Moreover, pre-monsoon heating of the lower troposphere changed the circulation
substantially that enabled influx of more moisture over certain regions and reduced the moist static stability of the
atmosphere. It has been shown that regional aerosol heating can have large impact on the phase of upper tropospheric
Rossby wave in pre-monsoon season, which acts as a primary mechanism behind teleconnection and leads to the change in
precipitation during monsoon season. These results demonstrate that changes in aerosol in one region can influence the
precipitation in a remote region through changes in circulation.
Chakraborty, A., R. S. Nanjundiah, & J. Srinivasan (2014) Local and remote impacts of direct aerosol forcing on Asian monsoon,
INTERNATIONAL JOURNAL OF CLIMATOLOGY 34(6):2108-2121.
Impact of pollution on the optical properties of trans-Pacific East Asian dust from satellite and groundbased measurements
Abstract - We investigate changes in the optical properties of a large dust plume originating from East Asian deserts during
its transport over the northwestern Pacific Ocean in March 2013. The study makes use of observational products from two
sensors in the NASA A-Train satellite constellation, the Moderate Resolution Imaging Spectroradiometer and the CloudAerosol Lidar with Orthogonal Polarization. Forward trajectory clustering analysis and satellite observations show that dust
initiating from the Taklimakan and Gobi deserts experienced thorough mixing with industrial pollution aerosols shortly after
leaving the source region and were lofted by a strong midlatitude weather system to more than 4 km in height. The dust
plume accompanied the weather system and reached the east coast of the North American continent within 7–10 days. The
dust aerosols became spectrally absorptive during transport due to mixing with other aerosol types such as soot.
Furthermore, a decrease in the depolarization ratio suggests that the complexities in aerosol particle morphologies were
reduced during transport over the ocean. More than half of the dust aerosol layers surviving the trans-Pacific transport were
polluted and exhibited different optical properties and radiative effects from those of pure dust.
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Yi, B., P. Yang, & B. A. Baum (2014) Impact of pollution on the optical properties of trans-Pacific East Asian dust from satellite and
ground-based measurements, JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES 119(9):5397-5409.
Radiative forcing of organic aerosol in the atmosphere and on snow: Effects of SOA and brown carbon
Abstract - Organic aerosols (OA) play an important role in climate change. However, very few calculations of global OA
radiative forcing include secondary organic aerosol (SOA) or the light-absorbing part of OA (brown carbon). Here, we use a
global model to assess the radiative forcing associated with the change in primary organic aerosol (POA) and SOA between
present day and pre-industrial conditions, both in the atmosphere and land snow/sea-ice. Anthropogenic emissions are
shown to substantially influence the SOA formation rate, causing it to increase by 29 Tg/yr (93%) since pre-industrial times.
We examine the effects of varying the refractive indices, size distributions for POA and SOA, and brown carbon fraction in
SOA. The increase of SOA exerts a direct forcing ranging from -0.12 to -0.31 Wm-2 and a first indirect forcing in warm
phase clouds ranging from -0.22 to -0.29 Wm-2, with the range due to different assumed SOA size distributions and
refractive indices. The increase of POA since pre-industrial times causes a direct forcing varying from -0.06 to -0.11 Wm-2,
when strongly and weakly absorbing refractive indices for brown carbon are used. The change in total OA exerts a direct
forcing ranging from -0.14 to -0.40 Wm-2. Atmospheric absorption from brown carbon ranges from +0.22 to +0.57 Wm-2,
which corresponds to 27% ~ 70% of the black carbon (BC) absorption predicted in the model. The radiative forcing of OA
deposited in land snow and sea ice ranges from +0.0011 to +0.0031 Wm-2, or as large as 24% of the forcing caused by BC in
snow and ice simulated by our model.
Lin, G., J. E. Penner, M. G. Flanner, S. Sillman, L. Xu, & C. Zhou (2014) Radiative forcing of organic aerosol in the atmosphere and
on snow: Effects of SOA and brown carbon, JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES (Early Edition).
Characterization of levels and emission rates for roadside PM2.5 and BTEX in Ho Chi Minh city, Vietnam
Abstract - A monitoring program was designed and implemented to characterize roadside levels of PM2.5 and BTEX in Ho
Chi Minh City, Vietnam, and to generate input data for CALINE (California LINE Source Dispersion Model) inverse
modeling. Monitoring was done during Dec 2007-Jan 2008, on both weekdays and weekends, and yielded 284 hourly BTEX
samples (adsorption tubes), 24 samples of 8h-PM2.5 and 42 samples of 24h-PM2.5 (by MiniVol samplers). The air sampling
was done at 8 points on both sides of one street that had an average traffic flow, simultaneously meteorology data and
vehicle flows were recorded. Roadside 24h-PM2.5 levels were 97 ± 31 (53 – 151) μg m-3, higher on weekdays than
weekends. Diurnal BTEX variation patterns were consistent with the diurnal flows of 6 vehicle categories moving on the
street. BTEX levels were reduced with the increase in downwind distance from traffic lanes (approximately by 15% for each
5 m increment). Principal component analysis also confirmed the association between roadside pollution levels and traffic. A
calculation algorithm was developed to remove the urban background, contributed by other sources than traffic in the
selected street, from the roadside measured pollution levels. Urban background contributed a majority of PM2.5 (90-98%)
and hourly BTEX (67-97%) with higher contributions at upwind side of the street and at late evening hours when less traffic
was observed. CALINE inverse modeling produced explainable fleet hourly emission rates (g km -1 h-1) and vehicle emission
factors (EF, mg veh-1 km-1). The obtained EF for gasoline and diesel vehicles were comparable with recent measurements
made in Asian cities, as well as with calculated EFs for European and US urban fleets about 10-15 years ago. To minimize
the collinearity problem encountered in inverse traffic modeling it is essential that the monitoring is done at different times
to capture significant variations in the street traffic compositions.
Giang, N. T. H. & N. T. K. Oanh (2014) Characterization of levels and emission rates for roadside PM2.5 and BTEX in Ho Chi Minh
city, Vietnam, ATMOSPHERIC ENVIRONMENT (In Press).
AIR POLLUTION & HEALTH
Environmental exposures and asthma morbidity in children living in urban neighborhoods
Abstract - A substantial disparity in asthma prevalence and morbidity among urban children compared with their nonurban
counterparts has been recognized for more than two decades. Because of the nature of urban neighborhoods, pest allergens,
such as cockroach and mouse, are present in high concentrations in US urban housing and have both repeatedly been linked
to asthma morbidity in sensitized children. In addition, there is a growing body of evidence demonstrating that
14
concentrations of many pollutants are higher indoors than outdoors in both US and European urban communities and that
exposures to indoor pollutants such as particulate matter (PM) and nitrogen dioxide (NO2) are independently associated with
symptoms in children with asthma. Although environmental interventions are challenging to implement, when they reduce
relevant indoor allergen and pollutant exposures, they are associated with clear improvements in asthma. Other modifiable
risk factors in urban childhood asthma that have emerged include dietary and nutritional factors. Overweight and obese
children, for example, may be more susceptible to the pulmonary effects of pollutant exposure. Insufficiency of vitamin D
and folate has also emerged as modifiable risk factors for asthma morbidity in children. The identification of these
modifiable risk factors for urban childhood asthma morbidity offers a ripe opportunity for intervention.
Matsui, E. C. (2014) Environmental exposures and asthma morbidity in children living in urban neighborhoods, ALLERGY 69(5):553-558.
Modelling spatial variability in concentrations of single pollutants and composite air quality indicators in
health effects studies
Summary - The health impact resulting from a few days of elevated air pollution concentrations has been the focus of much
recent research, most of which assesses the effects of single pollutants rather than composite air quality indicators. The
average concentrations of these pollutants across the study region are typically estimated by averaging the measurements
from the available network of monitors, and this simplistic approach has several deficiencies. Firstly, it is unlikely to be the
average concentration across the region under study, owing to the likely non-random placement of the monitoring network.
Secondly, the true spatial average is an unknown quantity, and hence the uncertainty in any estimate should be allowed for
when estimating its health effects. This paper proposes a novel Bayesian hierarchical framework for addressing these
problems, which consists of statistical models for estimating spatially representative measures of single pollutants and
composite air quality indicators, and the health effects of these pollution measures while correctly allowing for their
uncertainty. This methodological development is motivated by an epidemiological study of the effects of air pollution on
respiratory mortality in Greater London, England, between 2003 and 2005. The key findings from this study are that
traditional approaches are likely to underestimate the uncertainty in the health effects of air pollution compared with the
approach proposed here and increased risks of between 1.4% and 3.1% are associated with 1-standard-deviation increases in
the concentrations of ozone, particulate matter (PM10) and the composite air quality indicator that is adopted here.
Powell, H., & D. Lee (2014) Modelling spatial variability in concentrations of single pollutants and composite air quality indicators in health
effects studies, JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A 177(3)607-623.
Evaluation of adverse human lung function effects in controlled ozone exposure studies
Abstract - The US EPA is evaluating controlled human ozone exposure studies to determine the adequacy of the current
ozone National Ambient Air Quality Standard of 75 ppb. These studies have shown that ozone exposures of 80 ppb and
greater are associated with lung function decrements. Here, we critically review studies with exposures below 80 ppb to
determine the lowest ozone concentration at which decrements are causally associated with ozone exposure and could be
considered adverse using the Adverse Effects/Causation Framework. Regarding causation, the framework includes
consideration of whether exposure-related effects are primary or secondary, statistically significant, isolated or independent,
or due to study limitations. Regarding adversity, the framework indicates one should consider whether effects are adaptive,
compensatory, precursors to an apical effect, severe, transient and/or reversible. We found that, at exposures below 72 ppb
ozone, lung function effects are primary effects, but are isolated, independent and not statistically different compared to
effects observed during filtered air exposure, indicating a lack of causation. Up to 72 ppb, lung function effects may be
precursors to an apical effect, but are not likely adverse because they are transient, reversible, of low severity, do not interfere
with normal activity and do not result in permanent respiratory injury or progressive respiratory dysfunction. Overall, these
studies do not demonstrate a causal association between ozone concentrations in the range of the current National Ambient
Air Quality Standard and adverse effects on lung function.
Goodman, J. E., R. L. Prueitt, J. Chandalia, & S. N. Sax (2012) Evaluation of adverse human lung function effects in controlled ozone
exposure studies, JOURNAL OF APPLIED TOXICOLOGY 34(5):516-524.
An evidence-based appraisal of global association between air pollution and risk of stroke
Background - The aim of this study was to evaluate the transient effects of air pollutants on stroke morbidity and mortality
using the meta-analytic approach. Methods - Three databases were searched for case-crossover and time series studies
assessing associations between daily increases in particles with diameter < 2.5 μm (PM2.5) and diameter < 10 μm (PM10),
sulfur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide (NO2), ozone, and risks of stroke hospitalizations and
15
mortality. Risk estimates were combined using random-effects model. Results - A total of 34 studies were included in the
meta-analysis. Stroke hospitalizations or mortality increased 1.20% (95%CI: 0.22–2.18) per 10 μg/m3 increase in PM2.5,
0.58% (95%CI: 0.31–0.86) per 10 μg/m3 increase in PM10, 1.53% (95%CI: 0.66–2.41) per 10 parts per billion (ppb) increase
in SO2, 2.96% (95%CI: 0.70–5.27) per 1 ppm increase in CO, and 2.24% (95%CI: 1.16–3.33) per 10 ppb increase in NO2.
These positive associations were the strongest on the same day of exposure, and appeared to be more apparent for ischemic
stroke (for all 4 gaseous pollutants) and among Asian countries (for all 6 pollutants). In addition, an elevated risk (2.45% per
10 ppb; 95%CI: 0.35–4.60) of ischemic stroke associated with ozone was found, but not for hemorrhagic stroke. Conclusion
- Our study indicates that air pollution may transiently increase the risk of stroke hospitalizations and stroke mortality.
Although with a weak association, these findings if validated may be of both clinical and public health importance given the
great global burden of stroke and air pollution.
Yang, W., X. Wang, Q. Deng, W. Fan, & W. Wang (2014) An evidence-based appraisal of global association between air pollution and
risk of stroke, INTERNATIONAL JOURNAL OF CARDIOLOGY (In Press).
Acute effects of black carbon and PM2.5 on children asthma admissions: A time-series study in a Chinese
city
Abstract - Epidemiologic evidence for an association between black carbon (BC) and health outcomes is limited. We
estimated associations and exposure–response relationships between childhood asthma admission and concentration of BC
and PM2.5 (particle less than 2.5 mm in aerodynamic diameter) in ambient air in Shanghai using a lag distributed model. The
PM2.5 and the BC were significantly associated with childhood asthma admissions in single-pollution model. However, the
effects of BC on asthma attacks were slightly stronger than those of PM 2.5 after adjusting or not adjusting for NO2and SO2.
In conclusion, our study suggests combustion-associated particles are important in China. Black carbon should be considered
as one of the air quality indicators in China.
Hua, J., Y. Yin, L. Peng, L. Du, F. Geng, & L. Zhu (2014) Acute effects of black carbon and PM2.5 on children asthma admissions: A
time-series study in a Chinese city, SCIENCE OF THE TOTAL ENVIRONMENT 481:433-438.
Prenatal exposure to airborne polycyclic aromatic hydrocarbons and IQ: Estimated benefit of pollution
reduction
Abstract - Outdoor air pollution, largely from fossil fuel burning, is a major cause of morbidity and mortality in the United
States, costing billions of dollars every year in health care and loss of productivity. The developing fetus and young child are
especially vulnerable to neurotoxicants, such as polycyclic aromatic hydrocarbons (PAH) released to ambient air by
combustion of fossil fuel and other organic material. Low-income populations are disproportionately exposed to air
pollution. On the basis of the results of a prospective cohort study in a low-income population in New York City (NYC)
that found a significant inverse association between child IQ and prenatal exposure to airborne PAH, we estimated the
increase in IQ and related lifetime earnings in a low-income urban population as a result of a hypothesized modest reduction
of ambient PAH concentrations in NYC of 0.25 ng/m3. For reference, the current estimated annual mean PAH
concentration is ~1 ng/m3. Restricting to NYC Medicaid births and using a 5 per cent discount rate, we estimated the gain in
lifetime earnings due to IQ increase for a single year cohort to be US$215 million (best estimate). Using much more
conservative assumptions, the estimate was $43 million. This analysis suggests that a modest reduction in ambient
concentrations of PAH is associated with substantial economic benefits to children.
Perera, F., K. Weiland, M. Neidell, & S. Wang (2014) Prenatal exposure to airborne polycyclic aromatic hydrocarbons and IQ: Estimated
benefit of pollution reduction, JOURNAL OF PUBLIC HEALTH POLICY.
Chronic PM2.5 exposure and inflammation: Determining sensitive subgroups in mid-life women
Background - Several cohort studies report associations between chronic exposure to ambient fine particles (PM2.5) and
cardiovascular mortality. Uncertainty exists about biological mechanisms responsible for this observation, but systemic
inflammation has been postulated. In addition, the subgroups susceptible to inflammation have not been fully elucidated.
Methods - We investigated whether certain subgroups are susceptible to the effects of long-term exposure to PM2.5 on Creactive protein (CRP), a marker of inflammation directly linked to subsequent cardiovascular disease. We used data from the
SWAN cohort of 1923 mid-life women with up to five annual repeated measures of CRP. Linear mixed and GEE models
accounting for repeated measurements within an individual were used to estimate the effects of prior-year PM2.5 exposure
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on CRP. We examined CRP as a continuous and as binary outcome for CRP greater than 3 mg/l, a level of clinical
significance. Results - We found strong associations between PM2.5 and CRP among several subgroups. For example a
10 µg/m3increase in annual PM2.5 more than doubled the risk of CRP greater than 3 mg/l in older diabetics, smokers and
the unmarried. Larger effects were also observed among those with low income, high blood pressure, or who were using
hormone therapy, with indications of a protective effects for those using statins or consuming moderate amounts of alcohol.
Conclusions - In this study, we observed significant associations between long-term exposure to PM2.5 and CRP in several
susceptible subgroups. This suggests a plausible pathway by which exposure to particulate matter may be associated with
increased risk of cardiovascular disease.
Ostro, B., B. Malig, R. Broadwin, R. Basu, E. B. Gold, J. T. Bromberger, C. Derby, S. Feinstein, G. A. Greendale, E. A.
Jackson, H. M. Kravitz, K. A. Matthews, B. Sternfeld, K. Tomey, R. R. Green, & R. Green (2014) Chronic PM2.5 exposure and
inflammation: Determining sensitive subgroups in mid-life women, ENVIRONMENTAL RESEARCH 132:168-175.
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AGRICULTURE
Optimizing rice yields while minimizing yield-scaled global warming potential
Abstract - To meet growing global food demand with limited land and reduced environmental impact, agricultural
greenhouse gas (GHG) emissions are increasingly evaluated with respect to crop productivity, i.e., on a yield-scaled as
opposed to area basis. Here, we compiled available field data on CH4 and N2O emissions from rice production systems to test
the hypothesis that in response to fertilizer nitrogen (N) addition, yield-scaled global warming potential (GWP) will be
minimized at N rates that maximize yields. Within each study, yield N surplus was calculated to estimate deficit or excess N
application rates with respect to the optimal N rate (defined as the N rate at which maximum yield was achieved).
Relationships between yield N surplus and GHG emissions were assessed using linear and nonlinear mixed-effects models.
Results indicate that yields increased in response to increasing N surplus when moving from deficit to optimal N rates. At N
rates contributing to a yield N surplus, N2O and yield-scaled N2O emissions increased exponentially. In contrast,
CH4 emissions were not impacted by N inputs. Accordingly, yield-scaled CH4 emissions decreased with N addition. Overall,
yield-scaled GWP was minimized at optimal N rates, decreasing by 21% compared to treatments without N addition. These
results are unique compared to aerobic cropping systems in which N2O emissions are the primary contributor to GWP,
meaning yield-scaled GWP may not necessarily decrease for aerobic crops when yields are optimized by N fertilizer addition.
Balancing gains in agricultural productivity with climate change concerns, this work supports the concept that high rice yields
can be achieved with minimal yield-scaled GWP through optimal N application rates. Moreover, additional improvements in
N use efficiency may further reduce yield-scaled GWP, thereby strengthening the economic and environmental sustainability
of rice systems.
Pittelkow, C. M., M. A. Adviento-Borbe, C. van Kessel, J. E. Hill, & B. A. Linquist (2014) Optimizing rice yields while minimizing
yield-scaled global warming potential, GLOBAL CHANGE BIOLOGY 20(5):1382-1393.
Enteric methane in dairy cattle production: Quantifying the opportunities and impact of reducing emissions
Abstract - Many opportunities exist to reduce enteric methane (CH4) and other greenhouse gas (GHG) emissions per unit
of product from ruminant livestock. Research over the past century in genetics, animal health, microbiology, nutrition, and
physiology has led to improvements in dairy production where intensively managed farms have GHG emissions as low as
1 kg of CO2 equivalents (CO2e)/kg of energy-corrected milk (ECM), compared with >7 kg of CO2e/kg of ECM in extensive
systems. The objectives of this review are to evaluate options that have been demonstrated to mitigate enteric CH 4emissions
per unit of ECM (CH4/ECM) from dairy cattle on a quantitative basis and in a sustained manner and to integrate approaches
in genetics, feeding and nutrition, physiology, and health to emphasize why herd productivity, not individual animal
productivity, is important to environmental sustainability. A nutrition model based on carbohydrate digestion was used to
evaluate the effect of feeding and nutrition strategies on CH4/ECM, and a meta-analysis was conducted to quantify the
effects of lipid supplementation on CH4/ECM. A second model combining herd structure dynamics and production level
was used to estimate the effect of genetic and management strategies that increase milk yield and reduce culling on
CH4/ECM. Some of these approaches discussed require further research, but many could be implemented now. Past efforts
in CH4 mitigation have largely focused on identifying and evaluating CH4 mitigation approaches based on nutrition, feeding,
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and modifications of rumen function. Nutrition and feeding approaches may be able to reduce CH4/ECM by 2.5 to 15%,
whereas rumen modifiers have had very little success in terms of sustained CH 4 reductions without compromising milk
production. More significant reductions of 15 to 30% CH4/ECM can be achieved by combinations of genetic and
management approaches, including improvements in heat abatement, disease and fertility management, performanceenhancing technologies, and facility design to increase feed efficiency and life-time productivity of individual animals and
herds. Many of the approaches discussed are only partially additive, and all approaches to reducing enteric CH 4 emissions
should consider the economic impacts on farm profitability and the relationships between enteric CH4 and other GHG.
Knapp, J.R., G.L. Laur, P.A. Vadas, W.P. Weiss, & J.M. Tricarico (2014) Enteric methane in dairy cattle production: Quantifying the
opportunities and impact of reducing emissions, JOURNAL OF DAIRY SCIENCE 97(6):3231-3261.
Estimation of methane emission using the CO2 method from dairy cows fed concentrate with different
carbohydrate compositions in automatic milking system
Abstract - Two concentrates (MELK and VEM) with two different carbohydrate compositions were supplemented during
milking in an Automatic Milking System (AMS). The objectives of this study were to estimate the effect of the concentrates
on CH4 emission from dairy cows and to investigate the precision of the CO2-method when measuring in an AMS for
different length of time. Holstein cows (n=36) were used with mean body weight of 660 kg (SD=75.13) and average milk
production of 31.7 kg (SD=8.98), mixed parity and mixed lactation. Cows were allocated in two groups (n=18). After an
adaptation period (period 1), each group received either 100% MELK (More Energy Lactating Cows; a newly introduced
feeding system) or 100% VEM (Feed Value System for milk production) during periods 2 and 3. Besides, both groups were
fed the same Total Mixed Ration (TMR) ad libitum in the stable. Air samples in the AMS from a point near the cows head
were analysed every 20 s using the Gasmet equipment based on Fourier Transform Infrared (FTIR) Spectroscopy
Technique. The equipment ran continuously for 15 days over the three measurement periods (5 days×3 periods) with a 14
days waiting time in between the periods. Individual records of the CH4 and CO2 concentrations in the cows breath was
calculated after subtracting the CH4 and CO2 concentrations in the stable air from the measured concentrations. The
CH4:CO2 ratio was then multiplied with the calculated total CO2 production by the individual cows to get the quantitative
CH4 production. Milk production and total dry matter intake (DMI, kg/day) were very similar in the two groups. The
supplemented concentrate was allocated according to the individual milk yield and the intake ranged from 1.60 to
7.30 kg/day in MELK cows and from 2.06 to 7.20 kg/day in VEM cows. No significant difference was found for
CH4 production in MELK and VEM groups over the three periods. A linear positive relation between the CH 4 (g/day) and
energy corrected milk (ECM, kg/day) production and the feed intake (DMI, kg/day) was observed for the entire period. The
calculated CO2 and CH4 production were very similar in the two groups throughout the entire measurement period. The
analysis of the precision of the CO2-method, using a 95% significance level, indicated that showing a difference of 9 or 5% in
methane production requires a measuring period of 5 or 15 days, respectively, when using 18 cows per group. The study
shows no effect of a limited change in supplementation of starch and sugar on CH4 production through feeding concentrates
MELK or VEM in the AMS. To obtain an effect of changing the carbohydrate composition of the diet on the
CH4 production, it is likely that a larger change in the diet is necessary. This can only efficiently be done by changing the
TMR part of the diet.
Haque, M.N., C. Cornou, & J. Madsen (2014) Estimation of methane emission using the CO2 method from dairy cows fed concentrate with
different carbohydrate compositions in automatic milking system, LIVESTOCK SCIENCE 164:57-66.
Methane yield potential of novel perennial biogas crops influenced by harvest date
Abstract - In the past decade biogas production has experienced a strong increase in Germany, and along with that the
demand for biogas substrate increased equally. In most cases, maize is used as feedstock for biogas production due to its
high biomass and methane yields; however, by now, different alternative crops have been considered as potential feedstocks
for biogas production. In the present study, four novel perennial crops – cup plant (Silphium perfolatium), energy dock (Rumex
schavnat), giant knotweed (Falopia sachalinensis var. Igniscum) and Szarvasi (Elymus elongatus ssp. ponticus cv. Szarvasi-1) – were
investigated in a field experiment located in Southwest Germany for their suitability as biogas crops. The study focused on
the impact of different harvest dates on biogas potential expressed by the specific methane yield (SMY). Moreover, further
parameters such as dry matter yield (DMY), dry matter content (DMC) and methane hectare yield (MHY) were determined.
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Each crop was harvested several times over a certain period; methane yields were determined by batch fermentation
experiments. The results showed that harvest date influenced the tested crops and parameters in the most cases significantly.
Szarvasi was found to provide the highest SMY, which decreased over the harvest period in summer (0.376–
0.311 Nm3 kg oDM−1). In contrast SMY of energy dock (0.297–0.187 Nm3 kg oDM−1) and cup plant (0.274–
0.232 Nm3 kg oDM−1) showed a lower biogas potential on a medium level. An overall low potential regarding SMY was
found for Igniscum. In general, the results indicated an adequate biogas potential of all tested crops with exception of
Igniscum.
Mast, B., A. Lemmer, H. Oechsner, A. Reinhardt-Hanisch, W. Claupein, & S. Graeff-Hönninger (2014) Methane yield potential
of novel perennial biogas crops influenced by harvest date, INDUSTRIAL CROPS AND PRODUCTS 58:194-203.
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BIOMASS BURNING & COOKING AND HEATING
Effects of crop residue burning on aerosol properties, plume characteristics, and long-range transport over
northern India
Abstract - Aerosol emissions from biomass burning are of specific interest over the globe due to their strong radiative
impacts and climate implications. The present study examines the impact of paddy crop residue burning over northern India
during the postmonsoon (October–November) season of 2012 on modification of aerosol properties, as well as the longrange transport of smoke plumes, altitude characteristics, and affected areas via the synergy of ground-based measurements
and satellite observations. During this period, Moderate Resolution Imaging Spectroradiometer (MODIS) images show a
thick smoke/hazy aerosol layer below 2–2.5 km in the atmosphere covering nearly the whole Indo-Gangetic Plains (IGP).
The air mass trajectories originating from the biomass-burning source region over Punjab at 500 m reveal a potential aerosol
transport pathway along the Ganges valley from west to east, resulting in a strong aerosol optical depth (AOD) gradient.
Sometimes, depending upon the wind direction and meteorological conditions, the plumes also influence central India, the
Arabian Sea, and the Bay of Bengal, thus contributing to Asian pollution outflow. The increased number of fire counts
(Terra and Aqua MODIS data) is associated with severe aerosol-laden atmospheres (AOD500 nm > 1.0) over six IGP locations,
high values of Ångström exponent (>1.2), high particulate mass 2.5 (PM2.5) concentrations (>100–150 µgm−3), and enhanced
Ozone Monitoring Instrument Aerosol Index gradient (~2.5) and NO2 concentrations (~6 × 1015 mol/cm2), indicating the
dominance of smoke aerosols from agricultural crop residue burning. The aerosol size distribution is shifted toward the finemode fraction, also exhibiting an increase in the radius of fine aerosols due to coagulation processes in a highly turbid
environment. The spectral variation of the single-scattering albedo reveals enhanced dominance of moderately absorbing
aerosols, while the aerosol properties, modification, and mixing atmospheric processes differentiate along the IGP sites
depending on the distance from the aerosol source, urban influence, and local characteristics.
Kaskaoutis, D. G., S. Kumar, D. Sharma, R. P. Singh, S. K. Kharol, M. Sharma, A. K. Singh, S. Singh, Atinderpal Singh, &
D. Singh (2014) Effects of crop residue burning on aerosol properties, plume characteristics, and long-range transport over northern India,
JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES 119(9):5424-5444.
Characterization of operating conditions of two residential wood combustion appliances
Abstract - This work presents the main physical characteristics and operating conditions of a fireplace and a stove
commonly used in Portugal for domestic heating based on biomass combustion. The fuel used was wood from pine
(softwood) and eucalyptus (hardwood). The general trend during the batch combustion of wood logs was characterized by
three main periods: i) a first period of fuel heating followed by fuel drying and initial steps of devolatilization without the
existence of a visible flame, ii) a second period characterized by devolatilization, ignition, combustion of volatiles and char,
during which a vigorous flame is observed, and iii) a third period, mainly identified by the combustion of the char, during
which there are only localized small visible flames over the char particles. Each of these periods is characterized by specific
fuel consumption rate, flue gas temperature and flue gas composition. The main differences between the wood combustion
conditions in the fireplace and in the stove include: i) a lower flue gas temperature in the fireplace, ii) a higher combustion
flue gas flow rate in the fireplace, iii) a higher rate of fuel consumption in the stove, and iv) higher CO, total hydrocarbon
and particle emission factors during the combustion of wood in the fireplace. Differences between hardwood and softwood
combustion were also pointed out.
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Calvo, A. I., L. A. C. Tarelho, C. A. Alves, M. Duarte, T. Nunes (2014) Characterization of operating conditions of two residential
wood combustion appliances, FUEL PROCESSING TECHNOLOGY 126:222-232.
Pollutant Emissions and Energy Efficiency of Chinese Gasifier Cooking Stoves and Implications for
Future Intervention Studies
Abstract - Household air pollution from solid fuel combustion is the leading environmental health risk factor globally. In
China, almost half of all homes use solid fuel to meet their household energy demands. Gasifier cookstoves offer a
potentially affordable, efficient, and low-polluting alternative to current solid fuel combustion technology, but pollutant
emissions and energy efficiency performance of this class of stoves are poorly characterized. In this study, four Chinese
gasifier cookstoves were evaluated for their pollutant emissions and efficiency using the internationally recognized water
boiling test (WBT), version 4.1.2. WBT performance indicators included PM2.5, CO, and CO2 emissions and overall thermal
efficiency. Laboratory investigation also included evaluation of pollutant emissions (PM2.5 and CO) under stove operating
conditions designed to simulate common Chinese cooking practices. High power average overall thermal efficiencies ranged
from 22 to 33%. High power average PM2.5 emissions ranged from 120 to 430 mg/MJ of useful energy, and CO emissions
ranged from 1 to 30 g/MJ of useful energy. Compared with several widely disseminated “improved” cookstoves selected
from the literature, on average, the four Chinese gasifier cookstoves had lower PM2.5 emissions and higher CO emissions.
The recent International Organization for Standardization (ISO) International Workshop Agreement on tiered cookstove
ranking was developed to help classify stove performance and identify the bestperforming stoves. The results from this study
highlight potential ways to further improve this approach. Medium power stove operation emitted nearly twice as much
PM2.5 as was emitted during high power stove operation, and the lighting phase of a cooking event contributed 45% and
34% of total PM2.5 emissions (combined lighting and cooking). Future approaches to laboratory-based testing of advanced
cookstoves could improve to include greater differentiation between different modes of stove operation, beyond those
evaluated with the WBT.
Carter, E. M., M. Shan, X. Yang, J. Li, & J. Baumgartner (2014) Pollutant Emissions and Energy Efficiency of Chinese Gasifier
Cooking Stoves and Implications for Future Intervention Studies, ENVIRON. SCI. TECHNOL. 48(11):6461–6467.
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WASTE
Biosolid stockpiles are a significant point source for greenhouse gas emissions
Abstract - The wastewater treatment process generates large amounts of sewage sludge that are dried and then often stored
in biosolid stockpiles in treatment plants. Because the biosolids are rich in decomposable organic matter they could be a
significant source for greenhouse gas (GHG) emissions, yet there are no direct measurements of GHG from stockpiles. We
therefore measured the direct emissions of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) on a monthly
basis from three different age classes of biosolid stockpiles at the Western Treatment Plant (WTP), Melbourne, Australia,
from December 2009 to November 2011 using manual static chambers. All biosolid stockpiles were a significant point
source for CH4 and N2O emissions. The youngest biosolids (<1 year old) had the greatest CH4 and N2O emissions of
60.2 kg of CO2-e per Mg of biosolid per year. Stockpiles that were between 1 and 3 years old emitted less overall GHG
(∼29 kg CO2-e Mg−1 yr−1) and the oldest stockpiles emitted the least GHG (∼10 kg CO2-e Mg−1 yr−1). Methane emissions
were negligible in all stockpiles but the relative contribution of N2O and CO2 changed with stockpile age. The youngest
stockpile emitted two thirds of the GHG emission as N2O, while the 1–3 year old stockpile emitted an equal amount of N2O
and CO2 and in the oldest stockpile CO2 emissions dominated. We did not detect any seasonal variability of GHG emissions
and did not observe a correlation between GHG flux and environmental variables such as biosolid temperature, moisture
content or nitrate and ammonium concentration. We also modeled CH4 emissions based on a first order decay model and
the model based estimated annual CH4 emissions were higher as compared to the direct field based estimated annual
CH4 emissions. Our results indicate that labile organic material in stockpiles is decomposed over time and that nitrogen
decomposition processes lead to significant N2O emissions. Carbon decomposition favors CO2 over CH4 production
probably because of aerobic stockpile conditions or CH4 oxidation in the outer stockpile layers. Although the GHG emission
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rate decreased with biosolid age, managers of biosolid stockpiles should assess alternate storage or uses for biosolids to avoid
nutrient losses and GHG emissions.
Majumder, R., S. J. Livesley, D. Gregory, & S. K. Arndt (2014) Biosolid stockpiles are a significant point source for greenhouse gas
emissions, JOURNAL OF ENVIRONMENTAL MANAGEMENT 143:34-43.
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TRANSPORT & INDUSTRY
Black Carbon Emissions in Gasoline Exhaust and a Reduction Alternative with a Gasoline Particulate
Filter
Abstract - Black carbon (BC) mass and solid particle number emissions were obtained from two pairs of gasoline direct
injection (GDI) vehicles and port fuel injection (PFI) vehicles over the U.S. Federal Test Procedure 75 (FTP-75) and US06
Supplemental Federal Test Procedure (US06) drive cycles on gasoline and 10% by volume blended ethanol (E10). BC solid
particles were emitted mostly during cold-start from all GDI and PFI vehicles. The reduction in ambient temperature had
significant impacts on BC mass and solid particle number emissions, but larger impacts were observed on the PFI vehicles
than the GDI vehicles. Over the FTP-75 phase 1 (cold-start) drive cycle, the BC mass emissions from the two GDI vehicles
at 0 °F (−18 °C) varied from 57 to 143 mg/mi, which was higher than the emissions at 72 °F (22 °C; 12−29 mg/mi) by a
factor of 5. For the two PFI vehicles, the BC mass emissions over the FTP-75 phase 1 drive cycle at 0 °F varied from 111 to
162 mg/mi, higher by a factor of 44−72 when compared to the BC emissions of 2−4 mg/mi at 72 °F. The use of a gasoline
particulate filter (GPF) reduced BC emissions from the selected GDI vehicle by 73−88% at various ambient temperatures
over the FTP-75 phase 1 drive cycle. The ambient temperature had less of an impact on particle emissions for a warmed-up
engine. Over the US06 drive cycle, the GPF reduced BC mass emissions from the GDI vehicle by 59−80% at various
temperatures. E10 had limited impact on BC emissions from the selected GDI and PFI vehicles during hot-starts. E10 was
found to reduce BC emissions from the GDI vehicle by 15% at standard temperature and by 75% at 19 °F (−7 °C).
Chan, T. W., E. Meloche, J. Kubsh, & R. Brezny (2014) Black Carbon Emissions in Gasoline Exhaust and a Reduction Alternative
with a Gasoline Particulate Filter, ENVIRON. SCI. TECHNOL. 48(10):6027–6034.
Emissions from South Asian Brick Production
Abstract - Thirteen South Asian brick kilns were tested to quantify aerosol and gaseous pollutant emissions. Particulate
matter (PM2.5), carbon monoxide (CO), and optical scattering and absorption measurements in the exhaust of six kiln
technologies demonstrate differences in overall emission profiles and relative climate warming resulting from kiln design and
fuel choice. Emission factors differed between kiln types, in some cases by an order of magnitude. The kilns currently
dominating the sector had the highest emission factors of PM2.5 and light absorbing carbon, while improved Vertical Shaft
and Tunnel kilns were lower emitters. An improved version of the most common technology in the region, the zig-zag kiln,
was among the lowest emitting kilns in PM2.5, CO, and light absorbing carbon. Emission factors measured here are lower
than those currently used in emission inventories as inputs to global climate models; 85% lower (PM2.5) and 35% lower for
elemental carbon (EC) for the most common kiln in the region, yet the ratio of EC to total carbon was higher than
previously estimated (0.96 compared to 0.47). Total annual estimated emissions from the brick industry are 120 Tg CO2, 2.5
Tg CO, 0.19 Tg PM2.5, and 0.12 Tg EC.
Weyant, C., V. Athalye, S. Ragavan, U. Rajarathnam, D. Lalchandani, S. Maithel, E. Baum, & T. C. Bond (2014) Emissions
from South Asian Brick Production, ENVIRON. SCI. TECHNOL. 48(11):6477–6483.
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FOSSIL FUELS
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A bridge to nowhere: methane emissions and the greenhouse gas footprint of natural gas
Abstract - In April 2011, we published the first peer-reviewed analysis of the greenhouse gas footprint (GHG) of shale gas,
concluding that the climate impact of shale gas may be worse than that of other fossil fuels such as coal and oil because of
methane emissions. We noted the poor quality of publicly available data to support our analysis and called for further
research. Our paper spurred a large increase in research and analysis, including several new studies that have better measured
methane emissions from natural gas systems. Here, I review this new research in the context of our 2011 paper and the fifth
assessment from the Intergovernmental Panel on Climate Change released in 2013. The best data available now indicate that
our estimates of methane emission from both shale gas and conventional natural gas were relatively robust. Using these new,
best available data and a 20-year time period for comparing the warming potential of methane to carbon dioxide, the
conclusion stands that both shale gas and conventional natural gas have a larger GHG than do coal or oil, for any possible
use of natural gas and particularly for the primary uses of residential and commercial heating. The 20-year time period is
appropriate because of the urgent need to reduce methane emissions over the coming 15–35 years.
Howarth R. W. (2014) A bridge to nowhere: methane emissions and the greenhouse gas footprint of natural gas, ENERGY SCIENCE &
ENGINEERING (Early View).
A new look at methane and non-methane hydrocarbon emissions from oil and natural gas operations in
the Colorado Denver-Julesburg Basin
Abstract - Emissions of methane (CH4) from oil and natural gas (O&G) operations in the most densely drilled area of the
Denver-Julesburg Basin in Weld County located in northeastern Colorado are estimated for 2 days in May 2012 using
aircraft-based CH4 observations and planetary boundary layer height and ground-based wind profile measurements. Total
top-down CH4 emission estimates are 25.8 ± 8.4 and 26.2 ± 10.7 t CH4/h for the 29 and 31 May flights, respectively. Using
inventory data, we estimate the total emissions of CH4 from non-O&G gas-related sources at 7.1 ± 1.7 and 6.3 ± 1.0 t CH4/h
for these 2 days. The difference in emissions is attributed to O&G sources in the study region, and their total emission is on
average 19.3 ± 6.9 t/h, close to 3 times higher than an hourly emission estimate based on Environmental Protection
Agency's Greenhouse Gas Reporting Program data for 2012. We derive top-down emissions estimates for propane, nbutane, i-pentane, n-pentane, and benzene from our total top-down CH4 emission estimate and the relative hydrocarbon
abundances in aircraft-based discrete air samples. Emissions for these five nonmethane hydrocarbons alone total 25.4 ± 8.2
t/h. Assuming that these emissions are solely originating from O&G-related activities in the study region, our results show
that the state inventory for total volatile organic compounds emitted by O&G activities is at least a factor of 2 too low for
May 2012. Our top-down emission estimate of benzene emissions from O&G operations is 173 ± 64 kg/h, or 7 times larger
than in the state inventory.
Petron, G., A. Karion, C. Sweeney, B. R. Miller, S. A. Montzka, G. Frost, M. Trainer, P. Tans, A. Andrews, J. Kofler, D.
Helmig, D. Guenther, E. Dlugokencky, P. Lang, T. Newberger, S. Wolter, B. Hall, P. Novelli, A. Brewer, S. Conley, M.
Hardesty, R. Banta, A. White, D. Noone, D. Wolfe, & R. Schnell (2014) A new look at methane and non-methane hydrocarbon
emissions from oil and natural gas operations in the Colorado Denver-Julesburg Basin, JOURNAL OF GEOPHYSICAL RESEARCH:
ATMOSPHERES (Early View).
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VULNERABLE REGIONS
Isolating the anthropogenic component of Arctic warming
Abstract - Structural equation modeling is used in statistical applications as both confirmatory and exploratory modeling to
test models and to suggest the most plausible explanation for a relationship between the independent and the dependent
variables. Although structural analysis cannot prove causation, it can suggest the most plausible set of factors that influence
the observed variable. We apply structural model analysis to the annual mean Arctic surface air temperature from 1900 to
2012 to find the most effective set of predictors and to isolate the anthropogenic component of the recent Arctic warming
by subtracting the effects of natural forcing and variability from the observed temperature. We find that anthropogenic
greenhouse gases and aerosols radiative forcing and the Atlantic Multidecadal Oscillation internal mode dominate Arctic
22
temperature variability. Our structural model analysis of observational data suggests that about half of the recent Arctic
warming of 0.64 K/decade may have anthropogenic causes.
Chylek, P., N. Hengartner, G. Lesins, J. D. Klett, O. Humlum, M. Wyatt, & M. K. Dubey (2014) Isolating the anthropogenic
component of Arctic warming, Geophysical Research Letters (Early View).
Reconstructing glacier retreat since the Little Ice Age in SE Tibet by glacier mapping and equilibrium line
altitude calculation
Abstract - Temperate glaciers in the eastern Nyainqêntanglha Range, southeastern Tibet, are highly sensitive to climate
change and therefore of particular high interest for research on late Holocene changes of the monsoonal climate in High
Asia. However, because of the remoteness of the area, the scarcity of empirical data, and the challenges to remote sensing
work posed by cloud and snow cover, knowledge about the glacier dynamics and changes in this region is still very limited.
In this study, we applied a remote sensing approach in which 1964 glaciers were mapped from a Landsat ETM+ scene and
subsequently parameterized by DEM-supported measurements. Geomorphological evidence, i.e., trimlines and latero-frontal
moraines, were used to obtain quantitative data on the glaciers' morphological characteristics and the changes since the Little
Ice Age (LIA) maximum glacier advance. Statistical analysis of glacier length change revealed an average retreat of ~ 27%
and a trend toward stronger retreat for smaller glaciers. An evaluation of different methods to calculate equilibrium line
altitudes (ELAs) indicates that an optimized toe-to-ridge altitude method (TRAM) is more suitable than other methods in
settings with complex topography and a lack of mass balance measurements. A large number of glacier measurements are
crucial for high quality of TRAM results, and special attention has to be paid to different glacier characteristics. In order to
determine the best-fitting TRAM ratio value and to test the quality of the calculated ELAs, a remote sensing approach was
applied: for each investigated glacier, the altitudes of transient snowlines visible in the late summer Landsat scene were
measured from the DEM and compared to TRAM results. The interpolated ELA results show a SE–NW gradient ranging
from 4400 to 5600 m asl and an average ELA rise of ~ 136 m since the LIA. Because of the high spatial resolution of
measurements, the ELA distribution reveals topographic effects down to the catchment scale, specifically orographic rainfall
and leeward shielding. The interpretation of these patterns reveals that the eastern Nyainqêntanglha Range is influenced by
both, the Indian (ISM) and East Asian summer monsoon (EASM). However, the EASM does not reach the western part of
the study area. The results indicate that the monsoonal temperate glaciers' high sensitivity to climate change is driven by two
double forcings owing to the coincidence of accumulation and ablation phases.
Loibl, D., F. Lehmkuhl, & J. Grießinger (2014) Reconstructing glacier retreat since the Little Ice Age in SE Tibet by glacier mapping and
equilibrium line altitude calculation, GEOMORPHOLOGY 214:22-39.
Origin and Sources of Dissolved Organic Matter in Snow on the East Antarctic Ice Sheet
Abstract - Polar ice sheets hold a significant pool of the world’s carbon reserve and are an integral component of the global
carbon cycle. Yet, organic carbon composition and cycling in these systems is least understood. Here, we use ultrahigh
resolution mass spectrometry to elucidate, at an unprecedented level, molecular details of dissolved organic matter (DOM) in
Antarctic snow. Tens of thousands of distinct molecular species are identified, providing clues to the nature and sources of
organic carbon in Antarctica. We show that many of the identified supraglacial organic matter formulas are consistent with
material from microbial sources, and terrestrial inputs of vascular plant-derived materials are likely more important sources
of organic carbon to Antarctica than previously thought. Black carbon-like material apparently originating from biomass
burning in South America is also present, while a smaller fraction originated from soil humics and appears to be
photochemically or microbially modified. In addition to remote continental sources, we document signals of oceanic
emissions of primary aerosols and secondary organic aerosol precursors. The new insights on the diversity of organic species
in Antarctic snowpack reinforce the importance of studying organic carbon associated with the Earth’s polar regions in the
face of changing climate.
Antony, R., A. M. Grannas, A. S. Willoughby, R. L. Sleighter, M. Thamban, & P. G. Hatcher (2014) Origin and Sources of
Dissolved Organic Matter in Snow on the East Antarctic Ice Sheet, ENVIRON. SCI. TECHNOL. 48(11):6151–6159.
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CROSS CUTTING & EMERGING SLCP SOURCE SECTORS
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Environmental Impacts of Shale Gas Extraction in Canada: The Expert Panel on Harnessing Science and
Technology to Understand the Environmental Impacts of Shale Gas Extraction
Key Findings – Although the technologies and techniques used in extracting shale gas are understood, more research and
information is needed on the potential environmental impacts that could result from this process. In Canada, shale gas
development has moved forward in British Colombia and Alberta while potential development is still being explored in
Quebec, New Brunswick, and Nova Scotia. Unlike the United States, Canadian development has moved at a slower pace.
This slower pace of development presents a unique opportunity for Canada to take the time to explore and determine the
proper management practices to develop its shale gas resources responsibly. Overall, the Panel found that well-targeted
science is required to ensure a better understanding of the environmental impacts of shale gas development. Currently, data
about environmental impacts are neither sufficient nor conclusive.
Council of Canadian Academies (2014) ENVIRONMENTAL IMPACTS OF SHALE GAS EXTRACTION IN CANADA: THE
EXPERT PANEL ON HARNESSING SCIENCE AND TECHNOLOGY TO UNDERSTAND THE ENVIRONMENTAL IMPACTS OF
SHALE GAS EXTRACTION.
Aircraft Engine Exhaust Emissions And Other Airport-Related Contributions To Ambient Air Pollution: A
Review
Abstract - Civil aviation is fast-growing (about +5% every year), mainly driven by the developing economies and
globalization. Its impact on the environment is heavily debated, particularly in relation to climate forcing attributed to
emissions at cruising altitudes and the noise and the deterioration of air quality at ground-level due to airport operations.
This latter environmental issue is of particular interest to the scientific community and policymakers, especially in relation to
the breach of limit and target values for many air pollutants, mainly nitrogen oxides and particulate matter, near the busiest
airports and the resulting consequences for public health. Despite the increased attention given to aircraft emissions at
ground-level and air pollution in the vicinity of airports, many research gaps remain. Sources relevant to air quality include
not only engine exhaust and non-exhaust emissions from aircraft, but also emissions from the units providing power to the
aircraft on the ground, the traffic due to the airport ground service, maintenance work, heating facilities, fugitive vapours
from refuelling operations, kitchens and restaurants for passengers and operators, intermodal transportation systems, and
road traffic for transporting people and goods in and out to the airport. Many of these sources have received inadequate
attention, despite their high potential for impact on air quality. This review aims to summarise the state-of-the-art research
on aircraft and airport emissions and attempts to synthesise the results of studies that have addressed this issue. It also aims
to describe the key characteristics of pollution, the impacts upon global and local air quality and to address the future
potential of research by highlighting research needs.
Masiol, M., & R. M. Harrison (2014) Aircraft Engine Exhaust Emissions And Other Airport-Related Contributions To Ambient Air
Pollution: A Review, ATMOSPHERIC ENVIRONMENT (In Press).
The fate of residual treatment water in gas shale
Abstract - More than 2 × 104 m3 of water containing additives is commonly injected into a typical horizontal well in gas
shale to open fractures and allow gas recovery. Less than half of this treatment water is recovered as flowback or later
production brine, and in many cases recovery is <30%. While recovered treatment water is safely managed at the surface, the
water left in place, called residual treatment water (RTW), slips beyond the control of engineers. Some have suggested that
this RTW poses a long term and serious risk to shallow aquifers by virtue of being free water that can flow upward along
natural pathways, mainly fractures and faults. These concerns are based on single phase Darcy Law physics which is not
appropriate when gas and water are both present. In addition, the combined volume of the RTW and the initial brine in gas
shale is too small to impact near surface aquifers even if it could escape. When capillary and osmotic forces are considered,
there are no forces propelling the RTW upward from gas shale along natural pathways. The physics dominating these
processes ensure that capillary and osmotic forces both propel the RTW into the matrix of the shale, thus permanently
sequestering it. Furthermore, contrary to the suggestion that hydraulic fracturing could accelerate brine escape and make near
surface aquifer contamination more likely, hydraulic fracturing and gas recovery will actually reduce this risk. We
demonstrate this in a series of STP counter-current imbibition experiments on cuttings recovered from the Union Springs
Member of the Marcellus gas shale in Pennsylvania and on core plugs of Haynesville gas shale from NW Louisiana.
Engelder, T., L. M. Cathles, & L. T. Bryndzia (2014) The fate of residual treatment water in gas shale, JOURNAL OF
UNCONVENTIONAL OIL AND GAS RESOURCES 7:33-48.
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Oil and gas wells and their integrity: Implications for shale and unconventional resource exploitation
Abstract - Data from around the world (Australia, Austria, Bahrain, Brazil, Canada, the Netherlands, Poland, the UK and
the USA) show that more than four million onshore hydrocarbon wells have been drilled globally. Here we assess all the
reliable datasets (25) on well barrier and integrity failure in the published literature and online. These datasets include
production, injection, idle and abandoned wells, both onshore and offshore, exploiting both conventional and
unconventional reservoirs. The datasets vary considerably in terms of the number of wells examined, their age and their
designs. Therefore the percentage of wells that have had some form of well barrier or integrity failure is highly variable
(1.9%–75%). Of the 8030 wells targeting the Marcellus shale inspected in Pennsylvania between 2005 and 2013, 6.3% of
these have been reported to the authorities for infringements related to well barrier or integrity failure. In a separate study of
3533 Pennsylvanian wells monitored between 2008 and 2011, there were 85 examples of cement or casing failures, 4
blowouts and 2 examples of gas venting. In the UK, 2152 hydrocarbon wells were drilled onshore between 1902 and 2013
mainly targeting conventional reservoirs. UK regulations, like those of other jurisdictions, include reclamation of the well site
after well abandonment. As such, there is no visible evidence of 65.2% of these well sites on the land surface today and
monitoring is not carried out. The ownership of up to 53% of wells in the UK is unclear; we estimate that between 50 and
100 are orphaned. Of 143 active UK wells that were producing at the end of 2000, one has evidence of a well integrity
failure.
Davies, R. J., S. Almond, R. S. Ward, R. B. Jackson, C. Adams, F. Worrall, L. G. Herringshaw, J. G. Gluyas, & M. A.
Whitehead (2014) Oil and gas wells and their integrity: Implications for shale and unconventional resource exploitation, MARINE AND
PETROLEUM GEOLOGY 56:239-254.
Two-stroke scooters are a dominant source of air pollution in many cities
Abstract - Fossil fuel-powered vehicles emit significant particulate matter, for example, black carbon and primary organic
aerosol, and produce secondary organic aerosol. Here we quantify secondary organic aerosol production from two-stroke
scooters. Cars and trucks, particularly diesel vehicles, are thought to be the main vehicular pollution sources. This needs rethinking, as we show that elevated particulate matter levels can be a consequence of ‘asymmetric pollution’ from two-stroke
scooters, vehicles that constitute a small fraction of the fleet, but can dominate urban vehicular pollution through organic
and aromatic emission factors up to thousands of times higher than from other vehicle classes. Further, we demonstrate that
oxidation processes producing secondary organic aerosol from vehicle exhaust also form potentially toxic ‘reactive oxygen
species’.
Platt, S.M., I.El. Haddad, S.M. Pieber, R.-J. Huang, A.A. Zardini, M. Clairotte, R. Suarez-Bertoa, P. Barmet, L. Pfaffenberger,
R. Wolf, J.G. Slowik, S.J. Fuller, M. Kalberer, R. Chirico, J. Dommen, C. Astorga, R. Zimmermann, N. Marchand, S.
Hellebust, B. Temime-Roussel, U. Baltensperger & A.S.H. Prévôt (2014) Two-stroke scooters are a dominant source of air pollution in
many cities, NATURE COMMUNICATIONS 5.
Implications of Shale Gas Development for Climate Change
Abstract - Advances in technologies for extracting oil and gas from shale formations have dramatically increased U.S.
production of natural gas. As production expands domestically and abroad, natural gas prices will be lower than without
shale gas. Lower prices have two main effects: increasing overall energy consumption, and encouraging substitution away
from sources such as coal, nuclear, renewables, and electricity. We examine the evidence and analyze modeling projections to
understand how these two dynamics affect greenhouse gas emissions. Most evidence indicates that natural gas as a substitute
for coal in electricity production, gasoline in transport, and electricity in buildings decreases greenhouse gases, although as an
electricity substitute this depends on the electricity mix displaced. Modeling suggests that absent substantial policy changes,
increased natural gas production slightly increases overall energy use, more substantially encourages fuel-switching, and that
the combined effect slightly alters economy wide GHG emissions; whether the net effect is a slight decrease or increase
depends on modeling assumptions including upstream methane emissions. Our main conclusions are that natural gas can
help reduce GHG emissions, but in the absence of targeted climate policy measures, it will not substantially change the
course of global GHG concentrations. Abundant natural gas can, however, help reduce the costs of achieving GHG
reduction goals.
Newell, R. G., & D. Raimi (2014) Implications of Shale Gas Development for Climate Change, ENVIRON. SCI. TECHNOL. (As Soon
As Publishable).
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