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.