Formation, transformation, and removal of aerosol over a tropical mangrove forest

A comprehensive size‐segregated characterization of the chemical properties (water‐soluble inorganic fraction) of the sea‐salt aerosol originated from the surf zone at the land‐ocean boundary of Sundarban Mangrove forest, NE coast of Bay of Bengal, and an analysis of the relevant meteorological parameters revealed how the combined effect of anthropogenic gases and aerosol advected to the virgin mangrove forest and micrometeorological conditions could change the marine character of the aerosol before the onset of SW monsoon. The average aerosol mass concentration was 99.94 ± 41.9 μ g m −3 with production rate of 0.19 μ g m −2 s −1 (during January) to 4.29 μ g m −2 s −1 (during April) and dry deposition rate of 0.019 μ g m −2 s −1 (during January) to 13.21 μ g m −2 s −1 (during June). 72.35% of the total aerosol mass was leachable by water, and relatively large concentrations of phosphorus were observed. More chloride depletion from the coarse (2.0 < d p < 10 μ m) and nucleation ( d p < 0.4 μ m) modes compared to the accumulation mode (0.4 < d p < 2.0 μ m) was observed in winter (Cl/Na = 0.6023 ± 0.1798), and a reverse trend was observed in summer (Cl/Na = 0.644 ± 0.262). A significant positive correlation was obtained for chloride loss with non‐sea‐sulphate and nitrate for particles > 2.0 μ m. Distributions of Na + , K + , Ca 2+ , Mg 2+ , NH 4 + , Cl − , NO 2 − , NO 3 − , SO 4 2− , and PO 4 3− in different size modes were considered to collate their source apportionment. The proximity of Calcutta and Haldia metropolis to the mangrove forest could influence the forest air quality and depositional processes.