HR: 08:00h
AN: A31C-01    [Abstracts]
TI: Emission Sources and Chemical Composition of the Atmosphere of a Mega-city in South Asia
AU: * Husain, L
EM: husain@wadsworth.org
AF: Wadsworth Center, New York State Dept. of Health, Albany, NY 12201-0509, United States
AU: * Husain, L
EM: husain@wadsworth.org
AF: Dept. of Environmental Health Sciences, School of Public Health State University of New York, Albany, NY 12201-0509, United States
AU: Farhana, B K
EM: bkf01@health.state.ny.us
AF: Wadsworth Center, New York State Dept. of Health, Albany, NY 12201-0509, United States
AU: Ghauri, B M
EM: b_ghauri@yahoo.com
AF: Division of Space and Environment, SUPARCO, PO Box 8402 University Road, Karachi, Pakistan
AB: The environmental regulations in the countries in the western hemisphere have greatly decreased the concentrations of PM_2.5, black carbon (BC), SO_4, SO₂, and trace elements. Owing to rapid industrialization, concentrations of many chemical species in South Asia are rising and are expected to continue to increase. The impact of aerosols on global climate and on human health would also increase with time. Therefore, we conducted an extensive campaign to determine PM_2.5 mass, concentrations of 25 trace elements, 13 ions, black and organic carbon, acidic gases and NH₃ in the mega-cities of Karachi (population, ~14.5 million), and Lahore (population, 10 million), Pakistan. Here we present the data from Lahore. Continuous sampling of PM_2.5 (particulate matter of <2.5 µm aerodynamic diameter) and acidic and alkaline gases was carried out in winter (2005-2006) in Lahore which is highly impacted by urban and agricultural emissions but has remained unexplored in terms of atmospheric chemistry. While sampling continued from November 2005 to February 2006, it was possible to collect several samples during fog episodes. A low volume sampler equipped with two inlets was deployed for simultaneous collection of aerosol on quartz and PTFE filters, the latter being coupled to an annular diffusion denuder to collect acidic and alkaline gases. Water soluble ions in denuder gas samples and PM_2.5 collected on PTFE filters were analyzed using ion chromatography, trace elements by ICP-MS, and organic and elemental carbon on quartz filters using thermal-optical carbon analyzer. Concentrations of BC were determined every 5 min with an Aethalometer. PM_2.5 mass concentration varied an order of magnitude, 53 to 476 μg m^-3 (mean, 191 μg m^-3). Concentrations of the anthropogenic elements were exceedingly high, as much 100 to 1000 fold of those observed in cities such as New York. Maximum concentrations of BC, OC, Pb, Zn, SO₄ ^2- , NH₄⁺ were 110, 250, 12, 48, 66, and 60 μgm-3, respectively. HONO and NH₃ concentrations of up to 25 and 117 ppb were observed. A strong diurnal pattern was evident in the concentration of elemental and organic carbon which was perhaps controlled by variation in mixing heights. We used HYSPLIT4 air trajectories, intercomponent relationships and meteorological observations to explain the sources and the impacts of fog chemistry and mixing heights on atmospheric processing of the chemical constituents. Aerosols collected on this campaign were found to carry the signatures of emissions from Afghanistan, North and Central Pakistan, North India in addition to the local pollution sources. Statistical analysis suggests emissions from coal and oil combustion, industrial processes, building construction sites and biomass burning as the primary emission sources. Carbonaceous aerosols contributed about 69% of the PM_2.5 mass. Findings of our study will improve the understanding of the critical roles and interactions between chemical composition and size of atmospheric particles, atmospheric boundary layer and meteorological phenomena that manipulate the chemistry of an urban atmosphere. The results should play a vital role in any strategy to regulate emissions and improve air quality in the region.
DE: 4251 Marine pollution (0345, 0478)
DE: 4801 Aerosols (0305, 4906)
DE: 4906 Aerosols (0305, 4801)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly