Atmospheric reactive nitrogen in China: sources, recent trends, and damage costs.

Human activities have intensely altered the global nitrogen cycle and produced nitrogenous gases of environmental significance, especially in China where the most serious atmospheric nitrogen pollution worldwide exists. We present a comprehensive assessment of ammonia (NH(3)), nitrogen oxides (NO(x)), and nitrous oxide (N(2)O) emissions in China based on a full cycle analysis. Total reactive nitrogen (Nr) emission more than doubled over the past three decades, during which the trend of increase slowed for NH(3) emissions after 2000, while the trend of increase continued to accelerate for NO(x) and N(2)O emissions. Several hotspots were identified, and their Nr emissions were about 10 times higher than others. Agricultural sources take 95% of total NH(3) emission; fossil fuel combustion accounts for 96% of total NO(x) emission; agricultural (51%) and natural sources (forest and surface water, 39%) both contribute to the N(2)O emission in China. Total atmospheric Nr emissions related health damage in 2008 in China reached US$19-62 billion, accounting for 0.4-1.4% of China's gross domestic product, of which 52-60% were from NH(3) emission and 39-47% were from NO(x) emission. These findings provide policy makers an integrated view of Nr sources and health damage to address the significant challenges associated with the reduction of air pollution.