干旱区生态环境知识资源中心

The fine particles (PM2.5) were collected for 24 h from Agra atmosphere and chemically characterized during the one year study period. The average concentration of PM2.5 was 90.21 +/- 20.62 mu g m(-3) which is higher than NAAQS and WHO annual standards and their seasonal trend was winter > summer > monsoon. Ionic study indicates that cations were dominant in comparison to anions. Seasonally, F-, Ca2+ and Mg2+ were higher during summer period and Cl-, NO3-, NH4+ and K+ were higher during monsoon period while SO42- was higher during winter season. The ratios Ca2+/Na+, Mg2+/Na+ and SO42-/Na+ were higher, while Cl-/Na ratio was lower than sea water ratio indicating the incorporation of non marine constituents in aerosols. The observed Cl-/Na+ (average 0.71) deviate considerable from the Sea water ratio suggesting either a fractionation of Cl- or enrichment of Na+ as there was significant deviation from marine sources. Linear correlation was observable between nss-Ca2+ and nss-Mg2+ with HCO3- throughout the annual seasonal cycle (HCO3- : Ca = 0.59, HCO3-: Mg2+ = 0.53) suggesting the origination of these species from soil dust. The calculated conversion ratio of ’s’ (CRS) was lower than ’N’ (CRN) which suggests that the secondary formation of NO3- aerosol from NO2 was more predominant than SO42-. Trajectory analysis indicates that long range transportation also contributes to PM2.5 mass over the measurement site. Copyright (C) 2016 Turkish National Committee for Air Pollution Research and Control. Production and hosting by Elsevier B.V. All rights reserved.