Rapid growth of industrial nitrogen fluxes in China: Driving forces and consequences

Human activities are strongly modifying the global nitrogen (N) cycle through increasing input, N species diversity, and pool size of industrial reactive N (Nr). However, the fluxes, fates and environmental consequences of industrial Nr (excluding synthesized N fertilizer) remain poorly understood and quantified. We report here that industrial Nr flux has increased 13.4-fold over the past 30 years in China, reaching 3.7Tg N (1 Tg=10 12g) in 2008, accounting for over 50% of China's food Nr flux. Socioeconomic development (per capita GDP, urbanization and household size) significantly drives the growth of industrial Nr fluxes. This leads to "hotspots" of industrial Nr, mainly in relatively developed Eastern China. Industrial Nr loss rate during production is only 5%, much lower than that of cropland (50%) and livestock (80%). However, industrial Nr loss is point source pollution, and Nr release in concentrated doses produces serious risk in small regions. The contribution of structural N to total industrial Nr with a lifespan longer than one year (e.g., synthetic fiber, plastic) increased from 20% in 1980 to 70% in 2008. There was about 2.6 Tg N structural industrial Nr accumulated in human settlements in 2008, which could be one ex- planation of an unknown Nr sink of anthropogenic Nr input (mainly Haber-Bosch N fixation). Legacy effects caused by structural N accumulation have long-term consequences for environmental and human health, although structural N delays Nr release and reduces short-term Nr pollution. Industrial Nr use generates new features of modern global N biogeochemistry, such as increasing Nr species diversity, reducing Nr turnover rate. Future dynamics simulation of the earth system should involve industrial Nr. Explicit consideration and accounting of the fluxes and environmental consequences of industrial Nr would provide decision-makers a novel view of regional sustainable development.