Study On Phosphorus Societal Metabolism And Eutrophication Control Policy In China

Eutrophication is one of key water issues suffering China, and phosphorus (P) is considered as the critical control factor. As being different from natural cycle, P societal metabolism is rather of complexity in structure and of high intensity in flux, which thus leads to a significant difficulty in eutrophication control. Hitherto, fractional and end-of-pipe measures advocated by China's governments, however, can hardly alleviate the ongoing deterioration of eutrophication, because of their weak performance in costs and effects on the one hand, and lacking systematically structural control alternatives on the other.This study integrated Substance Flow Analysis (SFA) approach and Industrial Ecology Theory (IET) into a holistic methodology, and then applied it for analyzing P control strategy and related policies in China. Two static P flow analysis models, i.e., PHOSFLOW and DLPFA, were developed at national level in 1999 and local level in the case of Dianchi Basin in 2000, respectively. Characteristics of P metabolic structure and efficiency, as well as evolutionary trend were identified subsequently based on the models. Analogizing societal economy to natural ecology in relation to the metabolic features of P, this study illuminated P control mechanism and principles, and built a policy framework up, towards an ecological restructuring of P societal metabolism. Six selected key measures were examined with respect to its societal dynamics and restraints. Finally, potential effects of P load cutting-down related to these measures were simulated using the SFA models.Based on the PHOSFLOW model, China's P societal metabolism is characterized by high intensive input of resource and imported chemical fertilizers, low efficiencies of material productivities and nutrient recycling, high ratio of water pollutant loads and wastes accumulation, strongly materialization of critical eco-restructuring indicators, and the most intensive P load to water of livestock production. However, the general metabolic structure is quite of difference between national and local level. In the case of Dianchi Basin, input and output of crops and livestock products, nutrient recycling ratio and human source of P pollutant, are rather significant, according to the results of DLPFA model. By comparing two kinds of P metabolism within human society and natural system, this study proposed some key P-control mechanism, including shifting P input sources, restricting redundant P processes, fostering decomposers, closing nutrient flow loop, increasing P productivity, and optimizing spatial distribution of P flows. The simulated results show the related polices, i.e., substitution of chemical fertilizers requirement by crops input, output restriction of agricultural products, amount cutting-down of scaled-breeding animals, promoting P-assimilative ratio of livestock, reducing residents' consumption of pork meat and source-separated control of urban domestic wastewater, can certainly reduce P loads to surface water to some different degrees. The results suggest China should give the highest priority to reducing the amount of scaled-breeding livestock according to a rational carrying-capacity of farmlands. In Dianchi Basin, however, the most critical measure is proposed as source-separated control of urban domestic wastewater, while decreasing cropping and breeding activities also should be considered as effective measures.