Net Anthropogenic Phosphorus Accumulation in the Beijing Metropolitan Region

Phosphorus (P) is one of main pollution elements of eutrophication. P emissions from different pathways and sources are a key issue in the protection of water quality and sustainable watershed management practices. We have estimated net anthropogenic P accumulation (NAPA), as an index of P pollution potential in the Beijing metropolitan region, China. The NAPA estimation is based on an inventory of P fertilizer use, consumption of human food and animal feed, non-food P, and riverine P net flux. The overall average NAPA for 1991, 1997, 2003, and 2007 are 777, 943, 1218, and 1084 kg P km(-2) y(-1), about two times that reported in developed countries. The Urban unit has the largest NAPA (5526 kg P km(-2) y(-1)), whereas Mentougou P was negative, outputting 34 kg P km(-2) y(-1). P input of fertilizer is the largest source of NAPA, accounting for 40.7% (455 kg P km(-2) y(-1)) of the total P input, followed by non-food P and P in human food and animal feed. NAPA is closely related to land use, on average 5433 kg P km(-2) y(-1) in densely populated developed land, 503 kg P km(-2) y(-1) in agricultural land and 84 kg P km(-2) y(-1) in forest land. Human population density is the best single predictor of NAPA. Our results provide a basis for understanding the potential impact of anthropogenic P inputs on environmental problems, such as nation-wide water quality degradation under the current rapid urban expansion in modern China.