Pollution Characteristics of Pb, Zn, As, Cd in the Bijiang River

The Bijiang River is an important tributary of the Lancang River. Within its upstream watershed, the water body was seriously affected by various human activities carried out in Jinding lead-zinc mine and its adjacent areas. To fully understand the heavy metal pollution in the river, 15 water samples and 10 surface sediments were collected along the river in January 2010, and Zn, Pb, As and Cd in all samples were determinated. Based on data analyses, this paper evaluated the status of water pollution, illustrated the distribution of heavy metal pollutants in the water body, discussed the spatial variation of Zn, Pb, As and the relevant causes, as well as analyzed changes of heavy metal pollutants over time in the river. The results indicated that: (1) water quality of the Bijiang River met National Grade III, and it has been significantly affected by mining activities as compared to the background value of the river water. Current principal pollutants were Zn, Pb and As, while no Cd was detected. (2) with distance away from Jinding mining area, the concentration of heavy metals in water gradually decreased, wherein significant irregular changes were found, possibly resulting from hydropower barrages, river sediment, relevant hydrological and geological factors, and other human activities. (3) water quality of the river is changing for the better along with the reinforcement of harnessing measures. Before 2003, water qualities in the dry season were better than those in the wet season, thereafter a reverse trend was witnessed as water qualities in the dry season seemed even worse in recent years, but the transition mechanism was not clear and called for further exploration. (c) 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of School of Environment, Beijing Normal University.