Seasonal Chemical Characteristics of Atmospheric Aerosol Particles and its Light Extinction Coefficients over Pune, India

• Published in: Aerosol and Air Quality Research 2016-08, Vol.16 (8), p.1805-1819
• Main Authors: Pipal, Atar Singh, Tiwari, Suresh, Satsangi, P. Gursumeeran
• Format: Article
• Language: English
• ISSN: 1680-8584; 2071-1409
• DOI: 10.4209/aaqr.2015.08.0529

The present study has been conducted to characterize atmospheric aerosol particles in terms of carbonaceous species and ionic constituents for a yearlong period at Pune, India. This study provides the evidence for the ionic chemistry, secondary aerosols formation, temporal variability and its climatic effect in the atmosphere. The average concentrations of PM 2.5 and PM 10 were 109.6 ± 23.2 and 166.9 ± 4 µg m –3 , respectively, by far exceeding National Ambient Air Quality (NAAQ) and World Health Organization (WHO) standards. Seasonal analyses indicated that PM 2.5 and PM 10 mass concentrations were higher in the post-monsoon followed by the winter season and lower during the monsoon period. The average concentrations of organic carbon (OC) and elemental carbon (EC) were 31.3 ± 7.4 and 4.2 ± 2.4 µg m –3 for PM 2.5 , while, 34.2 ± 6.2 and 5.0 ± 2.3 µg m –3 for PM 10 , respectively. OC and EC data splits into seasons and their mass loadings were in the order of post-monsoon > monsoon > winter > summer for OC and for EC, it was as winter > post-monsoon > summer > monsoon. The overall chemical analysis revealed that particulate matter (PM) consist higher concentrations of OC followed by cations and the lowest one is EC. The ionic composition analysis indicated that cations were the abundant parts of PM in comparison to anions and Na + and SO 4 2– were at a higher concentration amongst all the ionic species. The estimated light extinction coefficient ( b ext ) of the aerosol particle was 291.2 ± 55.3 Mm -1 during the study period. Further apportionment of particle extinction coefficient was estimated and the contributions of light scattering coefficient by particles ( bsp ) were OC (45%), (NH 4 ) 2 SO 4 (17%), NH 4 NO 3 (8%) and coarse mass (12%), while, the contribution of light absorption coefficient by particle ( bap ) was 18% (EC). This indicates that in the present study the abundance of aerosol particles are more scattering in nature in comparison to absorption. The average value of Aerosol optical depth (AOD) was 0.46 and their positive correlation with anions and relative humidity (RH) showing same properties, while, in the case of EC, it showed contrast nature with respect to climate effect. Trajectory analysis indicated that the air masses appear as a result of long-range transportation during summer and monsoon period while during the winter and post-monsoon seasons local manmade activities showed dominant influence.