Chemical composition of size-separated aerosols at two rural locations in the Himalayan region

Abstract

Size-separated atmospheric aerosols were collected at Kothi (a hill top) and Mohal (a valley), situated at the foothills of western Himalayas during the summer season of 1999. Bimodal distribution of aerosols was observed at both the locations. However, at Kothi, fine size particles dominated (62%), whereas at Mohal, coarse size particles contributed more (75%). The SO₄ and NO₃<i> </i>particles together contributed ~ 30% of the total measured chemical composition of aerosols. Burning of biomass and emissions from tourist vehicles could be the main local sources for these components. However, aerosols showed alkaline nature (Σ^-Σ<i>⁺ </i>ratio< 1) due to the neutralizing effect of some cations such as Ca and NH₄.