The Vertical Distribution and Stratification of VOC in the Atmosphere at
Kaohsiung Area
Chia- chun cheng1*, ying- hui kao1, Chitsan Lin2, chung- hsin yuan3, chung- hsuan hung4
1
Graduate Student of the Department of Marine Environment Engineering, National Kaohsiung Marine
University, Kaohsiung 81157, Taiwan.
2
Professor of the Department of Marine Environmental Engineering, National Kaohsiung Marine University,
Kaohsiung 81157, Taiwan.
3
Professor of the Institute of Environmental Engineering, National Sun Yat-sen University, Kaohsiung 80424,
Taiwan.
4
Assistant Professor of the Department of Safety Health and Environment Engineering, Kaohsiung First
University of Science and Technology, Kaohsiung 81164, Taiwan.
*E-mail : freek297278@yahoo.com.tw
Abstract
According to a report published by EPA , Kaohsiung and Pingtung area has the poorest ozone air quality
among all others throughout Taiwan. The efficacy of improvement in the past 2 decades has not been obvious
compared to PM10. Ozone is a product of photochemical reaction, and its precursors include Volatile Organic
Compounds (VOCs) and Nitrogen Oxides (NOX). The models of ozone air quality have assumed the precursor
pollutants to be uniformly mixed in the vertical distribution, with no stratification. Recently however, a number
of studies have pointed out that the concentration of atmospheric VOCs is affected by weather conditions, season
etc., which result in stratification. The ozone precursor stratification phenomenon in the atmosphere, will therefore
affect AQM mode to evaluate the accuracy of issues discussed?
In order to verify the vertical distribution profile of VOCs, this study used a tethered balloon to collect air
samples at the ground level to 800 m and intervals six hours of continuous 24 hours, and collected
meteorological data to observed VOCs vertical stratification in northern Kaohsiung. The samples were collected
at stations set up at National Kaohsiung Marine University(NKMU) and Wen-Fn Elementary School(WFES)
simultaneously.
The results show TVOC- C2 in terms of diurnal variations, the highest average concentration at NKMU was
found at 12:00, while WFES was found at 06:00. In vertical distribution, detection concentrations are mostly
higher in the upper atmosphere compared to that near the surface, regardless of day or night. This distribution
covers 89.5% of all samples, indicating a sign of stratification of TVOCs-C2, especially at 12:00. The VOCs
stratification at 700m in summer, while the winter dropped to 100 and 400m. With photochemical reactivities,
the highest likelihood for ozone production at the NKMU site in summer is at a height of 400 m, while that at
WFES is 800 m, the main contributors being toluene and acetone. In winter the highest probability occurs at 500
m for both sites, with BTEX and dodecane as main contributors. That information of station have accumulated
concentrations about 400 meters, we suspected that existence of inversion layer, and pollutants easily to
accumulate. Suggested to increase the vertical height of the temperature measurement, observation and
verification of phenomenon.
Keywords: Volatile organic compounds (VOCs), ozone air quality, VOC vertical distribution, stratification,
inversion
1. Introduction
Deterioration of air quality in many of the world’s cities is raising concerns over the health of their
residents. however, southern Taiwan of Kaohsiung, , is a comprehensive development of commercial and
industrial areas, frequent transport within the region, oil refining, petrochemical industry, steel industry and the
semiconductor industry and other factories. According to the EPA under the Executive Yuan announced 98 years
of data Kaohsiung and Pingtung areas of high non-performing rate of ozone air quality ranks highest in Taiwan,
and the last years, compared to improving the efficiency of PM10, ozone, air quality improvement is not obvious.
Product of the photochemical reaction of ozone and its precursor pollutants as volatile organic compounds
(Volatile Organic Compounds, VOCs) and nitrogen oxides (NOX). The area North of Kaohsiung, because of oil
refineries, societies, and Jen Wu industrial areas and factories Nanzih intensive export processing zones, but also
affect in the north Kaohsiung area the results of air quality. So VOCs in the atmosphere pollution in the North
Kaohsiung area larger potential【Lin et al., 2004；Chiang et al., 2007】
。Most of the VOCs with high toxicity and
carcinogenicity, is not only the human body has hazards【Atkinson, 2000；Kuran and Sojak, 1996；Dewulf and
Van Langenhove, 1997】, and the photochemical reaction of ozone produced by the high (Ozone, O 3)
concentrations【Cheng et al., 2000】. Therefore, Kaohsiung-Pingtung region into the most polluted in the region
seven areas air quality.
Currently, the world's major developed countries develop ozone air quality improvement strategies, mainly
by air quality model (AQM). However, the air quality model has long been assumed during the development of
AQM in the vertical height of VOCs in the atmosphere is uniformly mixed; but in recent years, scientists began
to doubt the reasonableness of this assumption 【Flocas et al., 2003】, and some studies have shown that the
layers of VOCs in the atmosphere phenomenon, 【WÖhrnschimmel et al., 2006】its emphasis on the need to be
discussed.
In Greece, VOCs data was collected using a specially instrumented Falcon 20-E5 research aircraft. High
concentrations of VOCs (150-350 ppb) were observed near the ground and within the first 300-400 m above
ground and remained relatively high (100-200 ppb) even at much higher altitudes (1400-1600 m) 【Flocas et al.,
2003】. In Mexico, VOCs levels were measured using tethered balloons floating from 0 to 200 m above ground.
The VOCs concentration decreased with increasing height within the mixing layer before 06:00 am, and between
07:00 am and 10:00 am【WÖhrnschimmel et al., 2006】. In Beijing in autumn 2005, atmospheric VOCs were
measured at the heights of 8, 32, 140 and 280 m on the Beijing 325 m meteorological tower. That study found
concentrations of TVOCs (Total Volatile Organic Compounds) to range from 51.2±39.7 ppb to 83.6±44.4 ppb on
clear days, but from 62.9±19.0 ppb to 105.0±59.2 ppb on hazy days. While the vertical distribution of VOCs is
complex; most distribution profiles show that VOC levels decrease at greater heights on clear days. On hazy
days, however, VOCs concentrations gradually decrease at increasing heights from 8 m to 140 m, and then
increase dramatically at heights greater than 140m until 280 m is reached【Ting et al., 2008】. These results may
suggest that the vertical distributions of VOCs are affected jointly by several factors including meteorological
and transport. Additionally, principal components (PCA) and cluster analyses show that VOCs of different
origins can be found at different heights.
Concluding from the above research result, the VOCs concentration in the atmosphere is affected by climate
conditions（for example, height change of the mixer layer or formation of the temperature inversion layer）,
photochemical reactions, long range transport, or pollution from nearby high chimneys, led to the phenomenon
of stratification. However, due to lack of detailed meteorological information, the specific causes for this layered
phenomenon could not be found. Therefore, this study used a tethered balloon to collect VOCs samples,
exploring the phenomenon stratification of VOCs. The results of this study can be used for the simulation of air
quality so that scientific researchers can further grasp the ozone generation and transmission mechanisms. The
study also provides suggestions for the government to optimally control pollution sources.
2. Materials and Methods
This study aimed to explore the North in the Kaohsiung area of high pollution petrochemical industrial
area of near the regional, to collect the vertical profile of samples. Therefore, On 16-17 August 2010（summer）
and 18-19 February 2011（winter）, to collect VOCs samples from the atmosphere at the ground level（0 m）, and
the heights of 100 m, 200 m, 300 m, 400 m, 500 m, 600 m, 700 m, 800 m above National Kaohsiung Marine
University（NKMU）and Wen-Fu Elementary School（WFES）at 12:00, 18:00, 00:00, and 06:00（Figure 1）.
Figure 1 Sample map
This study used a tethered balloon to collect the VOCs samples from the atmosphere. A pump was
connected to a 10 L sampling bag, and the samples were immediately transferred into a stainless canister to
ensure the accuracy of the data.The NIEA A715.13B Method was used to analyze the ambient VOCs
quantitatively and qualitatively. This method uses two sets of standards, i.e. Urban Air Toxics and Photochemical
Assessment Monitoring System, to analyze alkanes, alkenes, aromatics and halogenated VOCs. Of the 101
VOCs we measured, forty are listed in the United States as Hazardous Air Pollutants (HAPs). Silica-coated
canisters made of stainless steel were used to store the ambient VOCs grab samples. Before sampling, all
canisters were cleaned, moisturized, and checked for leaks to ensure a vacuum could be created and maintained.
A laboratory blank check was performed to guarantee that all canisters were properly cleaned. All team members
who participated in the sampling activities were trained to follow standard sampling procedures. Taiwan NIEA
A715.13B11 QA/QC protocols were followed during the course of sampling, preservation, transport and analysis.
Samples were collected using a 16-inlet-position auto sampler, and pre-concentrated with an Entech 7100 before
they were analyzed for polar and non-polar VOCs using a GC (Hewlett-Packard,HP6890) and a mass
spectrometry detector (MSD, HP5973) equipped with DB-VRX capillary column (Agilent, 60 m × 0.25 mm ×
1.4 μm, 100% dimethylpolysiloxane, non-polar, low bleed column).
3. Results and Discussion
3.1 Diurnal variation
The total volatile organic compounds (TVOCs) is defined as the concentration of the sum of volatile
organic compounds, and subtract ethylene+acetylene+ethane (C2) concentration, due to C2 concentration is the
higher proportion at total TVOCs, analysis of data likely to cause false positives, therefore, the discussion of C2
was not included.
Figure 2 and 3 is NKMU and WFES of the 12:00, 18:00, 00:00 and 06:00 four period of TVOCs-C2 diurnal
variation. In NKMU at summer, daytime TVOCs-C2 the average were higher than concentration during the
evening session, especially the highest concentration of 12:00. However, the WFES trends and NKMU contrast,
the TVOCs-C2 daytime average concentrations were lower than during the evening session. In winter of
NKMU, TVOCs-C2 average concentration at 12:00 and 00:00 was higher than 18:00 and 06:00, however the
WFES station daytime TVOCs-C2's average were higher than concentration during the evening session.
Figure 2 The TVOCs-C2 concentration in summer.
Figure 3 The TVOCs-C2 concentration in winter.
3.2
Discussion of diurnal stratification
Refer to Figure 4. It was average concentration of TVOCs-C2 that in 400m height of NKMU daytime was
higher than ground. At night, the average concentration of TVOCs-C2 in 700m was higher than low level. That
showed significant stratification. In WFES, in 100m of daytime’s average concentration of TVOCs-C2 was
higher than ground. The average concentration of TVOCs-C2 in 700m at night was higher than low level. That
also displayed significant stratification.
Figure 5 was average of TVOCs-C2 diurnal variation in winter. In NKMU, it was the average concentration
of TVOCs-C2 that in 500m height of daytime was higher than ground. At night, on the high level 200m to 500m
average concentration of TVOCs-C2 was higher than low level. This showed significant stratification. In WFES,
in 100m height of daytime’s average concentration of TVOCs-C2 was higher than low level. At night, the
average concentration of TVOCs-C2 in 800m was higher than low level. It also has stratification. In addition, the
concentration of each two stations of high-level divided by the surface concentration. If the ratio is greater than 1,
that will come into being the stratification. The results indicate that easily to show the phenomenon of
stratification at 700m in summer, and the winter was at 100 and 400m.
Figure 4 Average TVOCs-C2 diurnal variation in summer.
Figure 5 Average of TVOCs-C2 diurnal variation in winter.
3.3 Relationship of Vertical VOCs and meteorological conditions
Figure 6 is NKMU and WFES of the vertical profile trends in summer, the NKMU vertical profile trends
have pollutants accumulation in 200 to 500m at 12:00, maybe have the presence of the inversion layer. In WFES,
mainly southerly winds, but when they contact Ban-Ping Mountain, leading to wind turn. Because upwind no
pollution sources, so WFES is cleaner. The vertical profile trends at 18:00, wind through the processing zone,
coupled with the height of the inversion layer down to 200-400 meters, therefore, the concentration most of the
accumulation on the ground. The WFES station, the wind only encountered the edge of oil refinery, coupled with
the Ban-Ping Mountain of impact, so the high level of the concentration higher, there is maybe high in the
chimney or long-range transport. At 00:00, there is find that inversion layer exists in the 100 and 600 meters,
NKMU major is Northeasterly wind , so pollutants are accumulated in the 200-500 and 700 meters, so the
bottom of concentration of pollutants lower. In WFES, the main wind direction is southeast of the east or
northeast, pollution sources may from the industrial zone. In addition, the two stations had measured higher
value at 700-800 m, plus the wind was almost static, possibly from upwind, industrial sources of pollution. In
06:00, NKMU the main wind direction is northeast, while the upwind no pollution sources, it is relatively clean.
The WFES maybe have a inversion layer in the 150-300 meters, so the pollutants accumulate in the 100 meters.
Figure 7 is NKMU and WFES of the vertical profile trends in winter, the vertical profile trends pollutants
have accumulated 600 to700m in NKMU at 12:00, maybe that exist in the inversion layer. So pollutants
concentrated in the vicinity of 500 meters. In WFES, pollutants mainly accumulated on the ground. By the
photochemical reactions, atmospheric dispersion and mixing layer higher effect at noon. The vertical profile
trended at 18:00, two stations closed to static wind so that it would reduce concentrations. At 00:00, the
inversion layer maybe drop from 400m to 200m pollutants accumulated in NKMU. Maybe the chimney or
long-range transport resulted in 500m height. The concentration of TVOCs height level is higher than lower
level. Because WFES station was impacted by Ban-Ping Mountain and below 500 meters lower concentration.
But they had significantly high values in 600m and coupled with the northwest wind. It maybe came from
NKMU. The NKMU at 06:00 was similarity with 00:00. But the concentration was much lower .And the sources
of pollution were also drop to 100m.The WFES station's pollutants accumulated maybe existed in inversion layer
in the 200 and 400 m.
Figure 6 Trends of vertical profiles in summer.
Figure 7 Trends of vertical profiles in winter.
3.4 VOCs photochemical reaction in different high level
The highest ozone production of two station is summer and winter. (Table 1) In summer of NKMU, we
found that the highest of ozone production was at noon, however the ozone production is highest of WFES at
night. In winter of NKMU, we found the highest of ozone production was at night, however the ozone
production of highest of WFES was at noon.
Table 1 Two stations maximum ozone formation potential in summer and winter (different time)
4. Conclusion
In terms of diurnal variations, the highest average concentration at NKMU was found at 12:00 while the
lowest was at 06:00; the highest average concentration at WFES was found at 06:00 however, with the difference
in patterns possibly due to geographical influences and life styles of local residents. In vertical distribution,
detection concentrations are mostly higher in the upper atmosphere compared to that near the surface, regardless
of day or night. This distribution covers 89.5% of all samples, indicating a sign of stratification of TVOCs-C2,
especially at 12:00. Between height and pollutant concentrations relationship. In the concentration of cumulative
situation, therefore, we would suspect that exist in the inversion layer, leading to the accumulation of pollutants.
With photochemical reactivities, the highest likelihood for ozone production at the NKMU site in summer is at a
height of 400 m, while that at WFES is 800 m, the main contributors being toluene and acetone. In winter the
highest probability occurs at 500 m for both sites, with BTEX and dodecane as main contributors. That
information of station have accumulated concentrations about 400 meters, we suspected that existence of
inversion layer, and pollutants easily to accumulate. Suggested to increase the vertical height of the temperature
measurement, observation and verification of phenomenon.
5. References
Atkinson, R.（2000）. "Atmospheric chemistry of VOCs and NOx." Atmospheric Environment, 34（12-14）,
2063-2101.
Carter, W.P.L.,（1995）"Computer modeling of environment chamber studies of maximum incremental
reactivities of volatile organic compounds." Atmospheric Environment, 29（18）, 2513-2527.
Chiang, H. L., Tsai, J. H., Chen, S. Y., Lin, K. H., and Ma, S. Y.（2007）. "VOC concentration profiles in an ozone
non-attainment area: A case study in an urban and industrial complex metroplex in southern Taiwan."
Atmospheric Environment, 41（9）, 1848-1860.
Chen H. C.（2010）. "Tempospatial distribution of volatile organic compounds in the atmosphere at onshore and
offshore of South Kaohsiung." National Kaohsiung Marine University, Department of Marine
Environmental Engineering, Master thesis.
Dewulf, J., and Van Langenhove, H.（1997）. "Analytical techniques for the determination and measurement data
of 7 chlorinated C1- and C2-hydrocarbons and 6 monocyclic aromatic hydrocarbons in remote air masses:
An overview." Atmospheric Environment, 31（20）, 3291-3307.
Fitz, D.（1999）. "Surfce and Upper Air VOC Sampling and Analysis During The 1997 Southern California
Oxidant Study." California.
Flocas, H. A., Assimakopoulos, V. D., and Helmis, C. G.（2003）. "VOC and O3 Distributions over the Densely
Populated Area of Greater Athens, Greece." American Meteorological Society, 42（1799-1810）.
Greenberg, J. P., Guenther, A., Zimmerman, P., Baugh, W., Geron, C., Davis, K., Helmig, D., and Klinger, L. F.
（1999）. "Tethered balloon measurements of biogenic VOCs in the atmospheric boundary layer."
Atmospheric Environment, 33（6）, 855-867.
Hass, U., Lund, S.P., SImonsen, L., and Fries, A.S.,（1995）"Effects of prenatal exposure to xylene on
postnatal development and behavior in rats." Neuotoxicology And Teratology, 17, 341-349.
Hou C. H. （2010） "Profile discussion of volatile organic compound （VOCs）in petroleum refinery process
area and ground flare." National Kaohsiung Marine University, Department of Marine Environmental
Engineering, Master thesis.
Kuran, P., and Sojak, L.（1996）. Journal of Chromatography A, 733（1-2）, 119-141.
Kostiainen, R.,（1995）Volatile organic compounds in the indoor air of normal and sick houses."
Atmospheric Environment, 29（6）, 693-702.
Lin, C.Y., Wang, Z., Chou, C.C.–K., and Liu, S.C.,（2007）"A numerical study of an autumn high pzpne
episode over southwestern Taiwan." Atmospheric Environment, 41（17）, 3684-3701.
Lin, T. Y., Sree, U., Tseng, S. H., Chiu, K. H., Wu, C. H., and Lo, J. G. （2004）. "Volatile organic compound
concentrations in ambient air of Kaohsiung petroleum refinery in Taiwan." Atmospheric Environment, 38
（25）, 4111-4122.
Liu Y. F. （2010）"Vertical profile and correlation analysis of ozone and Its precursors in coastal region of
Kaohsiung." National Kaohsiung Marine University, Department of Marine Environmental Engineering,
Master thesis.
Ono, A., Sekita, K., Ogawa, Y., and Hirose, A., （1996）"Repreductive and developmental toxicity studies
of toluene. II. Effects of inhalation exposure on fertility in rats." Journal of Environmental Pathology,
Toxicology and Oncology, 15, 9-20.
Tseng, K.H., Chen, C.L., Lin, M.D., Chang, K.H., and Tsuang, B.J.,（2009）"Vertical profile of ozone and
accompanying air pollutant concentrations observed at a downwind foothill site of industrial and
urban areas." Aerosol and Air Quality Research, 9, 421-434.
Ting, M., Yue-si, W., Jie, J., Fang-kun, W., & Mingxing, W.（2008）. The vertical distributions of VOCs in the
atmosphere of beijing in autumn. Science of the Total Environment, 390（1）, 97-108.
WÖhrnschimmel, H., Marquez, C., Mugica, V., Stahel, W. A., Staehelin, J., Cardenas, B., and Blanco, S.（2006）.
"Vertical profiles and receptor modeling of volatile organic compounds over Southeastern Mexico City."
Atmospheric Environment, 40（27）, 5125-5136.
Yeh M. H.（2007）. "Surface and upper air VOC sampling and analysis in Kaohsiung area."National Kaohsiung
Marine University, Department of Marine Environmental Engineering, Master thesis.