Abstract:

Concentrations of trace chemical constituents were determined in ambient air aerosol samples collected in Lahore, Pakistan. In this paper we report aerosol data from field studies carried out from 25 Dec. 1999 to 08 Jan. 2000 and later during January 9-11 2001. PM2.5 mass and speciation of the carbonaceous aerosol component was evaluated during winter 2005. Higher pollutant levels were observed in all the field samples with SO¬4-2 from 4 to 141 µg/m3, and NO-3 from 3 to 74.5 µg/m3. High trace elements concentrations were also observed, for example Se concentrations up to 258 ng/m3, As of 26 ng/ m3, and Sb of 84.8 ng/ m3. Pb concentration up to 4.8 µg/m3 were observed well above the WHO guideline of 1 µg/m3. Source apportionment revealed three major groupings. Group I consisted of the crustal elements Al, Mg, Co, Cr, Mn, Ca, and Ni and was associated with airborne soil material. Group II contained SO4-2, NO3-, and Se, which were ascribed to coal and oil combustion sources. The third grouping contained Pb, Sb, As, Zn, and Cu due to vehicular emissions and various industrial processes. During winter 2005 the mean PM2.5 mass was 185 µg/m3 although 12 hours values as high 400 µg/m3 were found. The city is clearly highly polluted with particulate matter. Total carbon averaged 45.6 µg/m3 or 23% of the mass. The relative peak to valley ratio is highest for elemental carbon (EC) 8.0, followed by black carbon (BC), 6.7 µg/m3. Higher aerosol concentrations observed in Lahore pose a serious health risk in a highly populated urban center. An in-depth study of the aerosol chemistry and aerosol size measurements are required in order to develop appropriate control strategies and to assess possible impacts on human health, agriculture, climate and economy.

Presentation: http://www.cleanairnet.org/baq2006/1757/docs/SW23_2.ppt