Black carbon and chemical characteristics of PM10 and PM 2.5 at an urban site of North India

Abstract

The concentrations of PM10, PM2.5 and their water-soluble ionic species were determined for the samples collected during January to December, 2007 at New Delhi (28.63° N, 77.18° E), India. The annual mean PM10 and PM2.5 concentrations (± standard deviation) were about 219 (± 84) and 97 (±56) μgm -3 respectively, about twice the prescribed Indian National Ambient Air Quality Standards values. The monthly average ratio of PM 2.5/PM10 varied between 0.18 (June) and 0.86 (February) with an annual mean of ∼0.48 (±0.2), suggesting the dominance of coarser in summer and fine size particles in winter. The difference between the concentrations of PM10 and PM2.5, is deemed as the contribution of the coarse fraction (PM10-2.5). The analyzed coarse fractions mainly composed of secondary inorganic aerosols species (16.0 μgm-3, 13.07%), mineral matter (12.32 μgm-3, 10.06%) and salt particles (4.92 μgm-3, 4.02%). PM2.5 are mainly made up of undetermined fractions (39.46 μgm-3, 40.9%), secondary inorganic aerosols (26.15 μgm-3, 27.1%), salt aerosols (22.48 μgm-3, 23.3%) and mineral matter (8.41 μgm-3, 8.7%). The black carbon aerosols concentrations measured at a nearby (∼300 m) location to aerosol sampling site, registered an annual mean of ∼14 (±12) μgm-3, which is significantly large compared to those observed at other locations in India. The source identifications are made for the ionic species in PM10 and PM2.5. The results are discussed by way of correlations and factor analyses. The significant correlations of Cl-, SO 4 2-, K+, Na+, Ca2+, NO 3 - and Mg 2+ with PM2.5 on one hand and Mg2+ with PM 10 on the other suggest the dominance of anthropogenic and soil origin aerosols in Delhi. © 2010 Springer Science+Business Media B.V.