Composition of wet deposition in the central Qilian Mountains, China

A total of 90 individual precipitation samples have been collected in the central Qilian Mountains from August 2012 to November 2013. All samples were analyzed for major cations (Na+, K+, Ca2+ and Mg2+), anions (Cl-, NO3 (-) and SO4 (2-)) and conductivity. Precipitation EC ranged from 2.26 to 482 mu c/cm with an average value of 41.9 mu s/cm. Precipitation was of SO4 (2-)-Mg2+-Ca2+ type, and these three ions contributed > 70 % to the total ionic concentration. Precipitation events occurred around summer displayed lower concentrations, whiles it had higher concentrations in winter and spring with little precipitation and larger wind speed. The major sources for these ions are regional crustal aerosols and species from central Asia and northwestern China arid regions brought by the westerly, and some aerosols from human pollution are secondary sources. It is also interesting that precipitation chemistry is different under diversely atmospheric circulation in Hulugou basin: the monsoon precipitation, the interaction precipitation influenced both by monsoon and westerly, and the westerly precipitation events.