Chemistry and buffering capacity of fog water collected in and around New Delhi, India.

In this study, fog water samples collected from New Delhi and its satellite township Sonipat for 2 years 2015-16 and 2016-17 are characterized by soluble ions and internal buffering capacity. The pH of fog water is close to 5.6 due to the limited contributions of Ca 2+ and Mg 2+ ions by virtue of low wind speed during winters. NH 4 + and Ca 2+ were dominant cations in fog at both sites during both sampling years. NH 4 + and Ca 2+ contributions were similar in New Delhi during 2015-16, but Ca 2+ increased during 2016-17 on account of construction activities. Emissions from agriculture fields through fertilizer applications and animal breeding lead to an increase of NH 4 + compared to Ca 2+ at Sonipat. SO 4 2- was comparable with Cl - , followed by NO 3 - ions. Plastic burning in this region during wintertime was a possible source of Cl - ions. Acid neutralization decreases as NH 4 +  > Ca 2+ and Mg 2+ for all samples in Sonipat and as Ca 2+  > NH 4 + and Mg 2+ in New Delhi. Higher NO 3 - in New Delhi was due to vehicular emissions. Vehicular emissions in New Delhi and agriculture fields in Sonipat were dominant sources of organic acids. Observed internal buffering capacity was different than theoretical values over a pH range from 4 to 7 in New Delhi, whereas both buffering capacities were close to each other in Sonipat samples. Lead in fog water at both sites was higher than prescribed safe limits for drinking water. Pollution sources were responsible for higher concentrations of metals, organic acids, and soluble ions in fog in New Delhi compared to that in Sonipat.