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

Abstract

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.

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