In-cloud and below-cloud scavenging of aerosol ionic species over a tropical rural atmosphere in India |
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| Authors: | Abhijit Chatterjee Achutan Jayaraman T Narayana Rao Sibaji Raha |
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| Institution: | 1. National Atmospheric Research Laboratory, Gadanki, India
2. Environmental Sciences Section, Bose Institute, Kolkata, India
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| Abstract: | The temporal variation in concentrations of major water soluble ionic species has been studied from several rain events occurred over Gadanki (13.5 °N, 79.2 °E), located in tropical semi arid region in southern India. The contribution from rain-out (in cloud) and wash-out (below cloud) processes to the total removal of ionic species by rain events is also estimated using the pattern of variations of ionic species within an individual event. A number of rain samples were collected from each rain event during June–November in 2006, 2007 and 2008. On average, nearly 20% of the total NH 4 + and non-sea SO 4 2? is removed by in-cloud scavenging, suggesting that their removal by “below cloud” washout is relatively dominant. In contrast Na+, Ca2+, Mg2+, NO 3 ? and sea-SO 4 2? are mainly removed by below-cloud scavenging or wash-out process. A significant variation in the acidity was observed within rain events with successive precipitation showing higher acidity at the final stage of the precipitation due to partial neutralization of non-sea SO 4 2? . Overall, greater influence of both terrestrial and anthropogenic sources is recorded in the rain events compared to that from marine sources. |
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