Temporal variations in the chemical composition of aerosols over the coastal Bay of Bengal

Abstract

Variations in source, ionic composition and carbonaceous components of aerosols are expected in the atmosphere due to reversing the direction of winds from winter to summer over the coastal Bay of Bengal (BoB). To examine this monthly, samples were collected at the weekly interval between March 2016 and February 2017 in the coastal BoB. The air mass back trajectories suggested that the study region received aerosols from Indo-Gangetic Plain from October to February whereas from central India during June to September and south or southwest during March to May. A higher concentration of total suspended particulate matter (TSP) was observed from November to February (winter) compared to other months. The concentration of sulphate contributed more than half of water-soluble inorganic species followed by sodium, ammonium and nitrate. The dominant contribution of anthropogenic SO4(2-) (>90%) to total SO4(2)- was observed. The ambient elemental carbon loadings and organic carbon to EC ratios indicate the dominant contribution of biomass burning emissions in the study region. The significant contribution of non-sea salt sulphate and nss-K+ indicates a dominant contribution from the continental sources throughout the year. The mass ratio of NO3-/anthropogenic SO4(2-) suggests stationary sources (i.e., coal burning in power plants) contribute significantly over vehicular emissions during the entire study period. The mass balance of ionic composition suggests the acidic nature of aerosols. The estimated secondary aerosols accounted for ~50% of organic carbon and 7% of TSP in the study region. This study has implications for understanding the source, composition and nature of aerosols and possible impacts on coastal water upon its deposition.