Urban Phosphorus Metabolism through Food Consumption

The Case of China


Yong-Guan Zhu Key Lab of Urban Environment and Health, Institute of Urban Environment Chinese Academy of Sciences, 1799 Jimei Road, Xiamen, China, 361021, ygzhu@iue.ac.cn, http://www.iue.cas.cn


Urbanization has significant impacts on local, regional, and global biogeochemical cycles, including through nutrient enrichment by food consumption, and especially in rapidly urbanizing countries. This article presents a time-series estimation of phosphorus (P) metabolism through food consumption in Chinese cities and examines its relationship to income level during the period 1985–2006. Our results show that approximately 39% of the total dietary P inflow is exported through direct sewage discharge without treatment, 35% is exported via the output of solid human excreta, 7% is exported through sewage sludge landfill, and 19% is left within urban areas. The total inflow of dietary P to urban systems increases with per capita disposable income level. Furthermore, the ratio of dietary P remaining in urban systems to total dietary P inflow, the dietary P remaining in urban systems per capita, and the dietary P remaining per unit urban built-up area respond in an inverted U shape to increases in per capita disposable income; the per capita outflow of dietary P shows a U-shaped response. These relationships may indicate that the impact of urban dietary P on urban environmental systems follows the traditional environmental Kuznets curve, while the environmental impact of urban dietary P on surrounding nonurban ecosystems initially decreases but then increases with the rising income of urban residents.