Wet Nitrogen Deposition in the Three Gorges Reservoir Area, China

In this paper, wet deposition of nitrogen in a small watershed of the Three Gorges Reservoir Area (TGRA) was investigated from 2004 to 2008. These results indicated that average TN concentration in rainwater was 2.02 mg L^-1, which exceeded the threshold of eutrophication. TN concentrations were higher in the dry season than that in the wet season, but the wet season was the key period for N deposition. The annual average wet deposition of TN was 14.36 kg ha^-1 yr^-1, among which NO₃^--N accounted for approximately 50%, while NH₄⁺-N and DON were about 25%. TN deposition reached the critical load value for vulnerable terrestrial ecosystems. Expected dominant sources for nitrogen deposition were the agricultural activities in this area. In addition, these results also implied that excessive N deposition could induce the water quality of TGRA degeneration as well as severely effect on ecological environment. Therefore, it is necessary to take some measures for nitrogen deposition control and ecosystems protection.