Spatial and decadal variations in inorganic nitrogen wet deposition in China induced by human activity

Atmospheric nitrogen (N) deposition, an important component in the global N cycle, has increased sharply in recent decades in China. Here, we constructed national-scale inorganic N wet deposition (N-dep) patterns in China based on data from 280 observational sites and analysed the effects of anthropogenic sources and precipitation on N-dep. Our results showed that the mean N-dep over China increased approximately 25%, from 11.11 kg ha(-1) a(-1) in the 1990s to 13.87 in the 2000s. N-dep was highest over southern China and exhibited a decreasing gradient from southern to western and northern China. The decadal difference in N-dep between the 1990s and 2000s was primarily caused by increases in energy consumption and N fertiliser use. Our findings conformed that anthropogenic activities were the main reason for the N-dep increase and provide a scientific background for studies on ecological effects of N deposition in China.