2.8 BAPHIM – BAckground and Polluted atmosphere in the
HIMalaya.
CNR - Institute of Atmospheric Sciences and Climate
Principal investigator: Prof. Paolo Bonasoni
The background concentration of atmospheric compounds can be investigated at
measurement stations sited in high mountain areas. In these regions the chemical physical atmosphere conditions can be strongly affected by short and long range
transport of air masses coming from polluted and densely inhabited areas. The aim of
the BAPHIM project is to study the atmosphere in the Himalayan area in order to acquire
useful information on background composition characterising some atmospheric
compounds. This is particularly important for studying climatic change and to define the
pollution level of this part of Asiatic continent. This project is based on research
frameworks which interact also with other EV-K2-CNR programs.
Continuous monitoring will concern the tropospheric ozone and aerosol concentration,
while air samplings in flasks and absorption tubes will be carried out in order to
evaluate the concentration of 21 halogenated greenhouse gases (CFC-11 ,CFC-12, CFC113, CFC-114, CFC-115, H-1211, H-1301, HCFC-22, HCFC-141b, HCFC-142b, HCFC-124,
HFC-125, HCFC-152a, HFC-134a, HFC-143a, C2F6, SF6, CH3Cl, CH3Br, CHCl3, CH2Cl2 ) and
volatile organic compounds (VOC). Moreover, measurements of hydrofluorocarbons
(Trifluoroacetic acid, TFA) in snow and water basin samples will be performed. The
collaboration with other projects (e.g. RATEAP) will permit metals and trace elements to
be detected on aerosol samples and radiochemical analysis on aerosol filters to define
atmospheric concentration of the cosmogenic radio nuclide Be-7 (the main tracer of
stratospheric intrusions).
The main natural contribution to the increasing of ozone concentration in free
troposphere is due to stratosphere-troposphere exchange processes. During these
events stratospheric air rich in O3 and Be-7 can reach the middle and low troposphere.
These intrusion phenomena are best identified in very high mountain areas, so that
measurements performed in the Himalayan area may significantly contribute to these
studies. The verifying and evaluating how this uncontaminated area can be affected by
local pollution events or by long range transport of polluted air masses will be an other
important aim of the BAPHMON research project. Ozone is not directly emitted in
atmosphere by human activities, but is mainly produced by photochemical reaction with
anthropogenic pollutants. For this reason it is considered one of the most dangerous
pollutants in the low troposphere, because of its high oxidant power and damages which
it can cause in the human and vegetal environment. Moreover, the tropospheric ozone
production processes are influenced by biogenic emissions of VOC. In these reactions
the oxygenated VOC play a key role strongly contributing to tropospheric ozone
formation. Due to short lifetime, their presence in the Himalayan area will allow to
identify local biogenic sources. The possible presence of non biogenic VOC
characterised by a longer lifetime can be due to pollution sources or long range
transport of anthropogenic polluted air masses. Aerosol measurements are very
important for a better investigation of the pollution problem, because during
atmospheric pollution events their chemical – physical properties can significantly
change. In fact, the aerosol concentration measure on 15 dimensional channels (0.3 to
20 ?m) will be able to characterise the Himalayan atmosphere, while the analysis
(RATEAP collaboration) on the OPC sampled filters will permit to determine the metals
and trace elements.
Finally, three dimensional back-trajectory analysis will permit to define air mass origins
and their contribution to the mean concentration of ozone and other atmospheric
compounds.
In addition, the project intends to investigate the greenhouse gases in the Himalayan
area atmosphere. Among these gases, the ozone present in the middle and high
troposphere has great importance, being able to absorb and emit infrared radiation
previously emitted from the ground. This is the reason why so many studies are
performed to analyse the space and time ozone behaviour also in remote areas.
Particularly, measurements and studies on halogenated greenhouse gases is of great
importance, because they have a key role in the climate changing. Their origin is mostly
anthropogenic and their emissions, even if regulated under International Protocols
(Montreal and Kyoto), show a steady increase. Monitoring these chemical species will
allow to assess the behaviour of their background concentration at more than 5000 m
asl during the next years and also to evaluate the influence of local sources.
Hydrofluorocarbons (anthropogenic compounds used as alterative to ozone depleting
chlorofluorocarbons) as a consequence of gas phase reaction with OH radicals and other
atmospheric components, yield to Trifluoroacetic acid (TFA). The high water solubility of
TFA causes its removal from atmosphere by wet deposition via rainfall (following uptake
into tropospheric clouds). Long persistence of TFA, due to the lack of sinks for this
compound, causes its accumulation in water basins and in soils where it can exploit its
phytotoxicity. The possible occurrence of TFA in the different environmental matrices
(i.e. snow, fresh water) collected in the Himalayan area will allow to evaluate whether it
is only of anthropogenic or also biogenic origin and to estimate the significance of rain
for deposition of this compound.
Therefore, this project will permit to acquire through “in situ” measurements valuable
information on the background concentrations of ozone, aerosol, halogenated
greenhouse gases, VOC, TFA and other compounds and to analyze air mass horizontal
and vertical transport events affecting their behaviour. Consequently, it will be possible
to establish the pollution level and concentration of the main greenhouse gases in a part
of atmosphere representative of background condition for a wide area of the Asiatic
continent.
The research proposal is based on experience gained in several years of measurements
at high mountain remote sites like the Mt. Cimone-CNR Station.