Chemistry of sulphur and nitrogen species and other major cations/anions in fog water

Abstract

Fog water, aerosols and gas phase samples were collected during the months of December 2000 and January 2001 at Dayalbagh, Agra. Major cations (Ca²⁺, Mg²⁺, Na⁺ and K⁺) and anions (F¯, Cl¯, NO₃¯ and SO₄^2-) were analysed by ICP-AES and ion chromatography in the fog and aerosol samples, while gaseous species like SO₂, HNO₃, NH₃ (as NH₄⁺) and O₃ were

measured by colorimetric method. The species NH₄⁺, NO₃^¯, and SO₄^2-<i> </i>were the dominant ions in fog water, which was inferred as the influence of agricultural and fuel combustion activities on fog composition. In all the samples, Ca²⁺/Mg²⁺ ratio was almost constant indicating their origin from soil, while the Ca²⁺/K⁺ ratios was highly variable indicating release of K⁺ from combustion sources. High concentration of SO₄^2-<i> </i>in fog water samples are attributed to its formation by the aqueous phase oxidation of SO₂. Calculated values show that oxidation of SO₂ is facilitated by O₃ concentration rather than Mn²⁺ catalyzed reactions. High concentrations of NO₃^¯and NH₄⁺ in fog water samples may be due to dissolution of NO₃^¯and NH₄⁺ aerosols.