Long-term trend of chemical composition of wet atmospheric precipitation during 1986–2006 at Shenzhen City, China

In order to understand the long-term trend of chemical composition of wet atmospheric precipitation, the precipitation samples were collected for the time period from 1986 to 2006 at Shenzhen City, China. All the rainwater samples were analyzed for pH, conductivity, Cl−, F−, SO42−, NO3−, NH4+, Na+, K+, Ca2+ and Mg2+ concentration. Average pH during 1986–2006 was 5.02, which is considerably higher compared to those reported in many other cities of the typical acid precipitation regions around the world. A significantly increasing trend (r=0.44 at 2% level) was observed for NO3− and a decreasing trend for SO42− (r=−0.12 at 31% level), NH4+ (r=−0.34 at 7% level) and Ca2+ (r=−0.33 at 7% level), and they together result in the overall decreasing trend (at