Measurements of PM10 and PM2.5 aerosols in Agra, a semi-arid region of India

Measurements of PM10 and PM2.5 have been carried out at three locations in Agra, viz. St. John’s College (SJC), Dayalbagh (DB) and Balkeshwar (BS). PM10 and PM2.5 have been collected by respirable dust sampler (APM 460DX) and Wins Anderson impactor (APM 550), respectively. The average 24 h PM10 and PM2.5 concentrations have been found to be 121.8 ± 28.3 and 73.5 ± 14.6 μg m for SJC; 68.7 ± 24.8 and 28.6 ± 14.6 μg m for DB; and 54.9 ± 20.3 μg m and 39.4 ± 16.3 μg m for BS, respectively. The mean coarse particle concentrations (i.e. PM10-PM2.5) have been found to be 39, 62 and 29% for SJC, DB and BS of the average PM10 for respective sites suggesting that the sites are also influenced by re-suspended surface dust and soil. The average ratios of PM2.5/PM10 indicate that about 40-71% of PM10 are made up of PM2.5, i.e. fine particles comprise a large fraction in PM10 at all the sites. PM2.5 concentrations have been highly correlated with SO2 and NO2 at SJC and DB sites while no correlations have been found between PM10 and these gaseous species. Regression analysis showed that at DB, 90% of PM2.5 and 10% of PM10 of the average particle mass concentrations contributed from the road traffic, whereas at SJC it was only 52% of the PM2.5. The higher contribution at DB may be because the site lies downwind during the monsoon period. A source apportionment study has also been performed to characterize the particulate matter sources at both SJC and DB sites. At SJC site, rotated factor analysis grouped the variables into two factors: re-suspension of soil (42.6%); and traffic and secondary pollutants (36.3%) as major contributors. The long range transport has been found to be major source to the particulate mass (35.2%) together with crustal (34.9%) and biomass burning (20%) at DB site.