Chemistry of fogs at Agra, India: Influence of soil particulates and atmospheric gases

Abstract

Fog water samples were collected in the months of December and January during 1998-2000 at Agra, India. The samples were analyzed for pH, major anions (F(-), Cl(-), SO(4) (2-), NO(3) (-), HCOO(-) and CH(3)COO(-)), major cations (Ca(2+), Mg(2+), Na(+) and K(+)) and NH(4) (+) using ion chromatography, ICP-AES and spectrophotometer methods, respectively. pH of fog water samples ranged between 7.0 and 7.6 with a volume weighted mean of 7.2, indicating its alkaline characteristic. NH(4) (+) contributed 40%, SO(4) (2-) and NO(3) (-) accounted for 28%, while Ca(2+), Mg(2+), Na(+) and K(+) accounted for 16% of the total ionic concentration. The ratios of Mg(2+)/Ca(2+) and Na(+)/Ca(2+) in fog water indicates that 50-75% of fog water samples correspond to the respective ratios in local soil. Significant correlation between Ca(2+), Mg(2+), Na(+) and K(+) suggests their soil origin. The order of neutralization, NH(4) (+) (1.4) > Ca(2+) (0.28) > Mg(2+) (0.12), indicates that NH(4) (+) is the major neutralizing species. Fog water and atmospheric alkalinity were also computed and were found to be 873 and 903 neqm(-3), respectively. Both of these values are higher than values reported from temperate sites and thus indicate that at the present level of pollutants, there is no risk of acid fog problem. The study also shows that the alkaline nature of fog water is due to dissolution of ammonia gas and partly due to interaction of fog water with soil derived aerosols.

A Comparative Study on Fog and Dew Water Chemistry at New Delhi, India

“…When we compare percentage contribution of each ion to the total ionic sum of fog water samples studied with the other workers (supplementary Table 3), we find that we have observed higher percentage of nitrate, sulphate, potassium and calcium but lower percentage of sodium, ammonium and magnesium in comparison to those reported by other studies at New Delhi and at Agra (Ali et al, 2004;Lakhani et al, 2007). The reasons could be representativeness of samples as number of samples studied were very small (2-4 at one site) and increase in the emissions of precursor gases (NO x and SO 2 ) and sampling techniques.…”

The role of particulate matter in reduced visibility and anionic composition of winter fog: a case study for Amritsar city

“…Other Indian urban cities (Agra, New Delhi and Kanpur) have shown pH ranging between 7 ± 1 (ref. 6 , 27 , and 28 ) whereas the majority of the international studies having rural and semi-urban background has pH as low as pH of 3.1. 29 Agriculture residue burning, vehicular transport emissions and long-range transport could be the reason for variation in pH in fog water ( Fig.…”

Chemical Composition of Dew Resulting from Radiative Cooling at a Semi-arid Site in Agra, India

“…There is limited research devoted to the composition and role of dew in the cycling of elements. The chemistry of wet deposition in the form of rain, dry deposition and aerosol composition has been studied extensively at the site of current study (SAXENA et al, 1991(SAXENA et al, , 1996(SAXENA et al, , 1997KUMAR et al, 1993;KHARE et al, 1997;KHARE et al, 2000;SATSANGI et al, 1998;SINGH et al, 2001;PARMAR et al, 2001;LAKHANI, 2005;SINGH and KHARE, 2006;LAKHANI et al, 2007LAKHANI et al, , 2008, but dew chemistry has been less explored. In the present study, dew samples collected at this semi-arid site in India were analyzed to reveal the nature of deposition.…”