Indian Journal of Radio & Space Physics Vol 40, August 2011, pp 203-210 Measurements of PM 10 and PM 2.5 aerosols in Agra, a semi-arid region of India P Gursumeeran Satsangi 1,$,* , A Kulshrestha 2 , Ajay Taneja 2 & P S P Rao 3 1 Department of Chemistry, University of Pune, Pune 411 007 2 Department of Chemistry, St John’s College, Agra 282 002 3 Indian Institute of Tropical Meteorology, Pashan, Pune 411 008 $ E-mail: pgsatsangi@chem.unipune.ac.in Received 15 July 2010; revised 2 June 2011; accepted 22 June 2011 Measurements of PM 10 and PM 2.5 have been carried out at three locations in Agra, viz. St. John’s College (SJC), Dayalbagh (DB) and Balkeshwar (BS). PM 10 and PM 2.5 have been collected by respirable dust sampler (APM 460DX) and Wins Anderson impactor (APM 550), respectively. The average 24 h PM 10 and PM 2.5 concentrations have been found to be 121.8 ± 28.3 and 73.5 ± 14.6 μg m -3 for SJC; 68.7 ± 24.8 and 28.6 ± 14.6 μg m -3 for DB; and 54.9 ± 20.3 μg m -3 and 39.4 ± 16.3 μg m -3 for BS, respectively. The mean coarse particle concentrations (i.e. PM 10 -PM 2.5 ) have been found to be 39, 62 and 29% for SJC, DB and BS of the average PM 10 for respective sites suggesting that the sites are also influenced by re-suspended surface dust and soil. The average ratios of PM 2.5 /PM 10 indicate that about 40-71% of PM 10 are made up of PM 2.5, i.e. fine particles comprise a large fraction in PM 10 at all the sites. PM 2.5 concentrations have been highly correlated with SO 2 and NO 2 at SJC and DB sites while no correlations have been found between PM 10 and these gaseous species. Regression analysis showed that at DB, 90% of PM 2.5 and 10% of PM 10 of the average particle mass concentrations contributed from the road traffic, whereas at SJC it was only 52% of the PM 2.5 . 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. Keywords: Particulate matter, Aerosol, Air quality, Crustal pollutants, Gaseous pollutants PACS Nos: 92.60.Mt; 92.60.Sz 1 Introduction Particulate matter is a ubiquitous component of the atmosphere and has become a persistent and pervasive environmental problem that imposes significant health risk. The sources, characteristics and potential health effects of the larger or coarse particles (> 2.5 μm in diameter) and smaller or fine particles (< 2.5 μm in diameter) are very different. The fine airborne particles have a high probability of deposition deeper into the respiratory tract and are likely to trigger or exacerbate respiratory diseases. These particles also have higher burdens of toxins, which when absorbed in the body can result in health consequences other than respiratory health effects. Therefore, the US Environmental Protection Agency promulgated a new PM 2.5 National Ambient Air Quality Standard to effectively control the aerosol problem 1 . Exposures to particulate matters (PM) have recently received considerable attention as the result of epidemiological findings showing association between ambient PM, PM 10 and PM 2.5 concentrations and mortality 2-4 . These findings have underlined the importance of ambient particles and the need for monitoring of PM 10 (inhaled particles) and its fractions PM 2.5 (fine particles) and coarse particle (PM 10-2.5 ). In view of the air quality status, some of the Indian cities are considered to be among the most polluted cities in the world 5-8 . The existing studies on PM 10 are very few in India. Most of the studies have focused only on characterization, suspended particulate matter (SPM) and size distribution for urban, semi-urban and forest sites 9-18 . Some studies have been done on metal composition of PM 10 (refs 19-22) and PM 2.5 (refs 20,23-24). Recently, metal concentration of PM 2.5 and PM 10 particles and their seasonal variations have been reported in urban and rural locations at Agra 25 . To the best of our knowledge, no detailed study has been reported on the mass concentration of PM 10 and its fraction PM 2.5 from semi-arid sites of Agra. Moreover, the present site represent semi-arid region of Indian subcontinent, where significant portion of total suspended