High Rates of Wet Nitrogen Deposition in China: A Synthesis

Abstract

Anthropogenic reactive nitrogen emissions (especially NH 3 and NO x ) have been increasing rapidly since the late 1970s in China and may lead to increased atmospheric input of reactive nitrogen to the Earth's surface through wet and dry deposition. Analyzing the temporal and spatial patterns of nitrogen (N) deposition is a high priority in order to assess environmental impacts of N deposition on a national scale. To this end, we have established a database for China, based on wet N deposition measured between 1995 and 2007. High rates of wet N deposi- tion have been observed in large areas, particularly in central and eastern China. Average rates of wet deposition for dissolved inorganic nitrogen (DIN), NH 4 + -N and NO x − -N were 17.36 ± 10.53, 10.66 ± 6.54 and 6.57 ± 4.93 kg N ha −1 year −1 . The average ratios of NH 4 + -N/NO x − -N in wet deposition were as high as 1.96 ± 1.27 and showed no significant difference among urban, rural and remote sites. Average wet deposition for DON was 4.84 ± 2.80 kg N ha −1 year −1 accounting for 25.4 ± 13.5 % of the total dissolved nitrogen (TDN) deposition. Wet N deposition exceeded 15 kg N ha −1 year −1 at 52 % of the rural sites. The high rates of wet N deposition in central and eastern China suggest heavy atmospheric reactive nitrogen pollution and substantial negative effects on the terrestrial and aquatic ecosystems of China.