Atmospheric wet deposition of nitrogen in a subtropical watershed in China: characteristics of and impacts on surface water quality.

Atmospheric wet deposition of nitrogen (N) is an important process in global N cycling, having significant impacts on both water quality and aquatic ecosystems worldwide. The aims of this study were to clarify the N wet deposition first flush effect and estimate the contribution of N wet deposition on both N export and water quality in a subtropical watershed. Results showed that total nitrogen (TN) flux was 41.72 kg N hm-2 year-1 and dissolved total nitrogen (DTN) was 23.18 kg N hm-2 year-1, respectively. Light rain events lead to the highest DTN and dissolve inorganic nitrogen (DIN) concentrations of wet deposition. Rainstorm concentrations were lowest during spring rainfall-runoff events. In contrast to the baseflow, the different N forms were higher than they were under the rainfall-runoff. Rainfall event contributions on N export were greater than 93.2% in the watershed for the whole year. Finally, TN concentrations were higher than river eutrophication thresholds for the entire watershed.