Source Characterization of Trace Elements in Indoor Environments at Urban, Rural and Roadside Sites in a Semi Arid Region of India

The present study investigated the particle size distribution of trace metals (Fe, Pb, Mn, Cu, Ni, Cr, Zn, Cd, Hg, and As) in the domestic environment, and examined the relationships among the levels of these metals and identified the related sources. Five homes at each site i.e., urban, rural and roadside, were selected for sampling. PM 10 and PM 2.5 samples were collected by using an APM-550 particulate sampler. Metals were analyzed by AAS after acid digestion. The monthly average PM 2.5 concentration ranged from 80 to 184.67 µg/m 3 , while the PM 10 monthly concentration ranged from 167.56 to 307.95 µg/m 3 . PM 2.5 contributed 50–56% of PM 10 . The total contribution of the analyzed trace metals in PM 2.5 was 6.2% while in PM 10 it was 2.2%. This followed the order Fe > Zn > Pb > Cr > Ni > Cu > Mn. Pb and Ni exceeded the prescribed annual National Ambient Air Quality Standards (NAAQS) given by the Central Pollution Control Board (CPCB) by up to 5 and 36 times, respectively. For Pb and Ni it is 0.50 µg/m 3 and 0.02 µg/m 3 , respectively. The particle mass was concentrated in the coarse size fraction, and the mass of individual trace metals was concentrated in finer sizes (except Fe), which is a major issue of concern. Intercorrelations and Principal Component Analysis were used to classify the two groups of sources, one from house dust and anthropogenic activities indoors, and the other from infiltration from outdoors. Enrichment factors with respect to outdoor metal concentrations have been identified for each metal. Fe was found to be totally contributed by outdoor dust. Mn and Cr are found to be less enriched, while Pb, Ni, Zn and Cu were found to have indoor sources.