A Study on the Understanding of Chemical Compositions of Deposited Fog Water over Central Indo-Gangetic Plain in India

Fog preserves information about air pollution by pausing air movement and capturing chemical compositions of pollutants into fog droplets. The current study presents a chemical analysis of fog water collected in January 2021 at a rural site, Arthauli, located over the central Indo-Gangetic Plain (IGP) in India. Fog water collected on 11 foggy days during 1^st to 21^st January 2021, were analyzed for anions (SO₄²⁻, Cl⁻, NO₂⁻, NO₃⁻), and cations (NH₄⁺, Na⁺, Ca²⁺, Mg²⁺, K⁺) using Ion Chromatography. pH of fog water ranged from 6.4 to 6.8 (Mean = 6.6 ± 0.1), depicting its alkaline nature. Total ionic composition (TIC) comprised majorly of NH₄⁺ (35%), followed SO₄²⁻ (23%), Ca²⁺ (15%), Cl⁻ (10%), NO₃⁻ (8%), Mg²⁺ (3%), and Na⁺, K⁺, NO₂⁻ (2% each). Back-trajectories analysis indicated air movement from western IGP passing over major urban areas before reaching the sampling site. NH₄⁺ had the highest neutralizing factor in fog samples (1.13), followed by Ca²⁺ (0.48) and Mg²⁺ (0.07). Analyses from enrichment factors, correlation coefficients, and principal components suggest that NH₄⁺, NO₃⁻, NO₂⁻, SO₄²⁻, and Cl⁻ were from anthropogenic sources like agricultural activities, factories, vehicular emissions, brick kilns, thermal plants, fossil fuels combustion, and, biomass burning, while Ca²⁺, K⁺, and Mg²⁺ were from the crustal source from agricultural fields.