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The use of chemical and statistical methods to identify sources of selected elements in ambient air aerosols in Karachi, Pakistan

1967; Elsevier BV; Volume: 21; Issue: 6 Linguagem: Inglês

10.1016/0004-6981(67)90073-x

1878-2442

P.P. Parekh, Badar Ghauri, Zikrur Rehman Siddiqi, Liaquat Husain,

Air Quality and Health Impacts

Concentrations of 23 elements plus NO3−, SO42− and Cl− were determined for samples collected continuously every 3 or 6 h during 22–27 July, 1985 at a suburban site in Karachi, Pakistan. Concentrations of lithophilic elements and several anthropogenic elements were ~ 80 % higher during daytime than at night. These elevated levels were attributed to daytime increases in wind velocity and anthropogenic activity. Factor analysis showed that ~ 50% of the variance was associated with soil, and ~ 14 % each with oceanic Na and Cl−, anthropogenic Sb and Pb, and Zn, Se and SO42−. A cement (limestone/dolomite) factor was not separated even though Ca and Mg concentrations were unusually high and a cement factory was located nearby. This led to an investigation of a chemical approach to determine the sources. Concentrations of Na, Mg and Ca were determined in water-extracts of the samples. Assuming soluble Na (~ 92 % of total) to be sea derived, marine components of Mg, SO42−, Ca and Br were determined. Solubility considerations were then used to reveal the cement source and apportion the aerosol sources. On the average, approximately 48 % of the total aerosol mass could be accounted for by the 'cement' and 'soil' components; about 12 % by the 'sea salt', about 3% by the 'fossil fuel' SO42− (as (NH4)2SO4); about 1 % by the NO3− (as NH4NO3); the remaining 36 % of the aerosol mass was unassigned.