Characteristics of nitrogen flow and environmental cost of reactive nitrogen in the source area of the Yellow River Basin, China

Evaluating reactive nitrogen (Nr) flow characteristics and its environmental damage costs can help formulate effective ecological environmental mitigation methods. Here, the amount of Nr emissions and its environmental damage costs in the source area of Yellow River Basin were evaluated using the methods of material flow analysis and cost–benefit analysis, and the mitigation potential of its Nr emissions was also explored. The total input and output of N were 5201.2–4986.7 Gg N yr−1, respectively, with atmospheric deposition and biological N fixation which were the main input sources. About 15.1% of the total N input was emitted into the atmosphere and hydrosphere, with the grassland and forest subsystems being the main contributors. The potential damage cost of Nr emissions was about 8.5 billion ¥ yr−1, and 66.1%, 21.6% and 12.3% were, respectively, related to health damage, climate impact, biodiversity and aesthetic loss. The potential damage costs caused by gaseous Nr was 3.0 times that of water bodies, and the unit damage cost of surface water Nr was 2.1 times that of gaseous Nr. Soil erosion of grassland and forest subsystems and industrial production activities were the main causes of environmental damage and economic losses. It is particularly important to strengthen water and soil conservation of grassland and forest subsystems in the source area of the rivers.