Contribution of Atmospheric Reactive Nitrogen to Acid Deposition in China

Elevated nitrogen (N) deposition has negative impacts on the terrestrial ecosystems, including acidification, N leaching, and eutrophication. The contribution of N deposition to acid deposition, the acidification of soil and surface water, acidification buffering processes, and future prospects of acid rain control in China were synthesized in this chapter. It is clear that N deposition has an increasing contribution to acid deposition in China in recent decades. Surface waters across China are generally not acidic by N deposition. The nitrate (NO3−) concentrations had a tiny increase in surface waters under elevated N deposition, indicating much less acidifying effects of N deposition than sulfur (S) deposition on surface water. However, soil acidification, accompanied by N leaching, has been commonly reported in China. Currently, the N deposition seems having more critical contribution than S deposition to soil acidification due to N transformations, especially in the well-drained soils with low denitrification rate. Elevated base cation (BC, including Ca2+, Mg2+, K+, and Na+) deposition, soil weathering, and effective sinks of N and S play important roles in acidification buffering under elevated acid deposition. The significant sinks of N and S may attribute to the denitrification and S sorption (including reduction and adsorption). The recovery of acidification of soil and surface water requires additional abatements of the emissions of acidifying precursors, especially NOx and NH3, and try more effective measures of acidification remediation.