Spatial variability in aerosol composition and its seawater acidification potential in coastal waters of the western coastal Bay of Bengal

Abstract

Deposition of atmospheric dust is reported to acidify surface waters in the northern Bay of Bengal (BoB).To examine the spatial variability in content and composition of total suspended matter (TSP), aerosol samples were collected at four locations (Damra, Chilika, Vizag and Chennai) along the east coast of India in the marine atmospheric boundary layer (MABL) to evaluate its impact on pH of surface waters due to deposition on surface waters using microcosm experiments.The concentration of total suspended matter (TSP) and [SO42- + NO3-] increased from southern (146 and 6.16 �g m-3, respectively) to northern coastal BoB (197 and 34.57 �g m-3, respectively) due to the influence of pollutants from Indo-Gangetic Plain (IGP) in the north and dominant marine sources in the southern coastal BoB.The ionic balance in aerosols suggested that acidification potential (neutralization potential) increased (decreased) from southern to northern BoB.The dissolution of aerosols in surface seawater lowered pH by 0.018 � 0.002 to 0.135 � 0.005 in the coastal BoB with a higher decrease in the north than south.Our study suggests that aerosol dissolution in seawater results in ocean acidification in proportion to acidic anions (e.g., SO42-, NO3-).In addition, organic acids, such as carboxylic acids, aromatic (Benzoic acid) and hydroxy acids (Lactic and glycolic acids) also contribute significantly to ocean acidification and their contribution needs further evaluation.