Substance flow analysis as a tool for the elucidation of anthropogenic phosphorus metabolism in China

Substance flow analysis was used to develop a stock and flow model that was applied to time-series data from 1984 to 2008 to explore the correlation between change traits of anthropogenic phosphorus (P) metabolism in China and socioeconomic variables, quantify the accumulation of P in natural reservoirs and search for man-made stocks with the greatest potential for recovering P resources. The results showed that a total of 154.5 Tg P was extracted in China, but 80.5% was lost to natural water and soil, indicating the unsustainability of societal P metabolism. Urbanization, improved standards of living and population growth are responsible for the rising magnitudes of the P flows related to ore extraction, use and waste generation and the declining ratio of recycled P wastes, while inefficient small mines and corresponding restrictive policies contributed to the large fluctuation in ore extraction and waste generation in 2001-2008. Financial and policy support, combined with technological advances, strongly promoted the progress of the phosphate fertilizer industry in China, which transformed the country from a net importer into a net exporter of P materials after 2000. Three anthropogenic stocks were formed: 38.3 Tg P in agricultural soil, 19.0 Tg P in natural water and 105.3 Tg in natural soil. The last stock included 41.4 Tg P in mining wastes abandoned by small mines, which will be valuable human-induced mines for the secondary recovery of P resources in the future. Model uncertainties are analyzed, and conclusions and suggestions are presented.