Study of chemical composition of precipitation at an alpine site and a rural site in the Urumqi River Valley, Eastern Tien Shan, China

We report on a 1-year continuous precipitation sampling record from an alpine site and a rural site in the Urumqi River Valley, East Tien Shan, China. The 128 samples, collected from April 2003 to February 2004, at two sites were analyzed for the major inorganic ions, pH, electrical conductivity and insoluble microparticles. The precipitation was typically alkaline with a volume-weighted mean pH of 6.99 and 7.27 at the alpine site and the rural site, respectively. Ca2+ was the dominant cation, and SO42− was the dominant anion. The precipitation chemistry in this region was mainly controlled by regional Asian dust storms, local dust and anthropogenic activities. The relative impact of anthropogenic activities, specifically uncontrolled coal combustion, was larger at the rural site compared to the alpine monitoring site.