Improving nitrogen safety in China: Nitrogen flows, pollution and control

The impacts of nitrogen on environmental quality, greenhouse gas balances, ecosystem and biodiversity in China are of great concern given the magnitude of demand for food and energy. Comprehensive summaries of historic N flows and their critical threats and sustainable management are urgently needed. This paper initially reviews the historical trends of N flows in China and identifies the critical threats of N loss. Subsequently, it describes some recent success stories of N management, and finally indicates barriers to N pollution control. This review highlights three key points. Firstly, a steady increase of N input in China has led to a series of environmental problems via leaching and runoff, ammonia emissions and denitrification. Secondly, although great efforts to improve N management and N safety in China, further quantifications of N flows and analysis of their underlying mechanisms are needed to improve the understanding of the N cycle and pollution control. Finally, it proposes that the best available technologies combined with regulatory plans, laws, projects and policies should be implemented to overcome current barriers in N control and achieve a balance between the sustainable use of N resources and environmental conservation in China.