Assessment of Heavy Metals in Street Dust in Kathmandu Metropolitan City and their Possible Impacts on the Environment
Street dust often contains elevated concentrations of heavy metals and can influence on environment and human health. Therefore, a study on the characteristics of heavy metals in street dusts at different localities was carried out in the metropolitan city of Kathmandu of Nepal. A total of 20 street dusts have been sampled from four sampling sites with various activities or characteristics such as mechanical workshops (MWK), motor parks (MPK), market areas (MKA) and residential areas (RDA) and analyzed for Zn, Pb, Ni, Cr and Cd using the atomic absorption spectrophotometric method. Results showed that street dust samples contained significant levels of the metals studied compared to the values from the control site. The variation in concentration of most of the heavy metals determined decreased in an order represented as MWK>MPK>MKA>RDA>Control. While the RDA and MKA give the same element abundance order as Zn > Pb > Ni > Cr > Cd, the MPK and MWK show different abundance order in some elemental contents. In all the street dusts, zinc is the most available and labile element followed by lead. From the place of low activity (RDA) to the place of high activity (MWK), the metal concentrations in street dusts varied from 55.4-419.3 g g-1 for Zn, 12.3-116.8 g g-1 for Pb, 4.986.3 g g-1 for Ni, 1.4-14.3 g g-1 for Cr and 0.3-39.6 g g-1 for Cd respectively. Results indicate that the metal pollutants in street dusts could significantly contribute to deteriorate the environmental status of the city of Kathmandu metropolis.
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