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Influence of calcium and sulphate on the pH of rainwater at Delhi

Tiwari, S and Singh, JV and Momin, GA and Rao, PSP and Safai, PD and Ali, K (2001) Influence of calcium and sulphate on the pH of rainwater at Delhi. Indian Journal of Radio and Space Physics, 30 (6). pp. 325-331.

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Rainwater samples were collected at three different locations during two consecutive summer monsoons of 1990 and 1991 at Delhi. These locations were Okhla, Red Fort and Rajinder Nagar which represent industrial, commercial and residential locations, respectively. The major anions (Cl, SO 4, and NO 3) and cations (Na, K, Ca, Mg and NH 4) along with pH of the above samples were determined. The bicarbonate (HCO 3) concentrations were also calculated. High levels of Ca and SO 4 were observed. Together, Ca and SO 4 made up more than 50 of the total ion mass, while Ca alone contributed over 55 of the total cations mass. The pH value of rainwater was found to be alkaline in nature with an average of 6.13 and the values varied from 5.01 to 7.12. The relative importance of natural and anthropogenic sources was estimated by chemical balancing. In some cases, acidity was found due to the presence of sulphuric and nitric acid. High concentration of soil-oriented elements especially Ca has been found to play an important role in neutralizing the acidity of rainwater and maintaining high alkaline pH. Most of the SO 4 in rainwater was in the form of CaSO 4. The results of the present study suggested that the atmospheric composition in the city has been strongly influenced by natural sources (sea and soil) rather than anthropogenic sources.

Item Type: Article
Additional Information: Copyright of this article belongs to NISCAIR
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 26 Apr 2015 05:02
Last Modified: 26 Apr 2015 05:02

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