Spatial and temporal variability in concentration and characteristics of aerosols at Visakhapatnam (east) and Goa (west) coasts of India

Abstract

Knowledge on the variability in quantity and compositions of various size groups of aerosols is important to understand their sources and their role in biogeochemical and climate processes. Here, we studied total suspended particles (TSP), PM10 and PM2.5 for their quantitative and water soluble compositional (F-, Cl-, SO42-, NO3-, NH4+, Na+, K+, Ca2+, and Mg2+) distributions, and to understand their nature and potential sources at Goa and Visakhapatnam on the west and east coasts, respectively, of India. While the mean concentrations of TSP were found to be 117 ± 44 and 85 ± 51 μg/m3 its maximal levels occurred in spring intermonsoon (SIM; 141 ± 52) and winter monsoon (WM; 155 ± 145 μg/m3) seasons at Goa and Visakhapatnam, respectively. PM10 and PM2.5 exhibited higher ranges at Visakhapatnam than Goa. The increase in PM2.5 abundance from WM to SIM at Visakhapatnam seems to occur in coincidence with decrease in TSP favored by topography and ambient meteorological conditions. Locally released and seasonally transported (from land and sea) constituents contributed to the observed variability in aerosol compositions. Sulphate dominated the aerosol composition at both Goa (57-64%) and Visakhapatnam (43-55%) followed by NO3- (5-16% and 6-18%, respectively) where the former component was higher in PM10 and PM2.5. The NO3- was more in TSP. Relations between SO42- and NH4+ suggested possible presence of NH4HSO4. Examination of ionic ratios and balance suggested near neutrality in PM10 and PM2.5 while TSP was acidic at the both locations. Notable relations between Ca2+ and NO3-, particularly in PM10 at Goa, indicated their release from mining related activities.