Nitrogen-derived environmental behavior, economic performance, and regulation potential by human production and consumption in a mega river basin

Human disturbances of the nitrogen (N) cycle have exceeded the carrying threshold of ecological environmental systems. To explore paths for mitigating the environmental impacts and damage costs of N loss in mega river basins, the N-derived environmental behavior, economic performance, and regulation potential by humans in the Yangtze River Basin from 2011 to 2019 were studied using substance flow analysis and life cycle impact assessment. The results show that the intensity of N loss increased until 2015 and then decreased; the average value over the study period was 7413.55 kg N km(-2) yr(-1). Moreover, fertilizer application intensity was the dominant factor in the decrease of N input and loss. Environmental N loss was higher in the east and lower in the west, while high environmental implications were mainly concentrated in plain areas with a megacity. The mean environmental impact potentials of climate change, acidification, and eutrophication were 3.34 x 10(10) kg CO(2)eq, 7.01 x 10(9) kg SO2-eq, and 1.06 x 10(10) kg NO3-, respectively. The mean total potential damage costs due to climate change, acidification, eutrophication, and human health were 0.68, 4.34, 17.36, and 12.97 billion $ y(-1), respectively; the total potential cost of damage to human health is closely related to the N loss to atmosphere and hydrosphere. This study demonstrates that integrating the reduction of N losses with improved N use efficiency can effectively reduce N loss and its impact. Future optimized N management for human activities should carefully consider the environmental economy under the changing environment.