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

Category: Aerosol and Atmospheric Chemistry

Volume: 16 | Issue: 8 | Pages: 1805-1819
DOI: 10.4209/aaqr.2015.08.0529
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Atar Singh Pipal1, Suresh Tiwari2, P. Gursumeeran Satsangi 1

  • 1 Department of Chemistry, Savitribai Phule Pune University (Formerly University of Pune), Pune -411007, India
  • 2 Indian Institute of Tropical Meteorology, New Delhi-110060, India

Highlights

Seasonal trend of PM and its chemical constituents along with SOC and POC particles.
Light extinction coefficients (bext) and its contribution from individual chemical species.
The abundance of bext (82%) by OC, (NH4)2SO4, NH4NO3 and coarse than (18%) by EC.
Sources of PM and associated chemical constituent along with their correlation with AOD.


Abstract

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 PM2.5 and PM10 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 PM2.5 and PM10 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 PM2.5, while, 34.2 ± 6.2 and 5.0 ± 2.3 µg m–3 for PM10, 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 SO42– were at a higher concentration amongst all the ionic species. The estimated light extinction coefficient (bext) 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%), (NH4)2SO4 (17%), NH4NO3 (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.

Keywords

Ionic chemistry OC and EC Light extinction (NH4)2SO4 and NH4NO3 AOD Sources


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