Analysis Of Spatial-temporal Characteristics Of Phosphorus Flow In China Based On MFA

It takes millions of years for phosphorus recycling in the natural world,however,human activities accelerate this process.Human activities turn mineral phosphorus into vegetal phosphorus and creatural phosphorus though phosphate industry,agricultural cultivation,residents living,livestock breeding.And phosphorus flows into water and ground in the end.While human activities accelerate the process of phosphorus recycling,it also results in environment problems.With the high-speed development of industrialization and urbanization,phosphorus shortages and water eutrophication in China are increasingly severe,which affect the development of the national economy.Therefore,we may use MFA for phosphorus to uncover the root of the problems and to propose specific solutions so that provide basis for making relevant policies.Basic data from year 1995 to year 2013 of China and year 1995,year 2000,year 2005,year 2010,year 2013 of Northeast,East area,Southwest have been collected,besides,flow model of phosphorus flowing has been established for phosphorus material flow analysis.Neural network has been built to forecast the amount of phosphorus that flow into water.The main contents and conclusions of this paper are as follows:This paper analyses the flow of phosphorus in China and phosphorus utilization efficiency of each system.Results show that the amount of phosphorus flowed into social system has been growing unceasingly,it was 3.14 million t P in year 1995 and was 8.73 million t P in 2013,85%of the input was used for producing fertilizer.The utilization efficiencies of different systems from high to low were phosphate industry(91～92%),agricultural cultivation(90～93%),rural living(80～90%),family breeding(50～95%),livestock breeding(3～30%)and urban living(1～5%).This paper analyses the flow of phosphorus in Northeast,East area and Southwest.Results show that,Southwest is a phosphorus exporting area and Northeast is a phosphorus importing area,the amount of phosphorus flowed into social system were 0.02 million t P,0.88 million t P and 3.75 million t P,the amount of phosphorus brought from straws were 0.19 million t P,0.23 million t P and 0.13 million t P,the amount of phosphorus brought from animal manure of scale breeding were 0.78 million t P,14.75 million t P and 0.30 million t P respectively correspond to Northeast,East area and Southwest in 2013.Main reasons of these conditions are that East area is the main area of crop production and scale breeding,southwest area is the main mining area.Results of prediction and optimization from three layers BP neural network shows that,the most efficient way of reducing livestock manure P that flow into surface water is to increase the scale breeding ratio of mutton,while improve it from 24%to 30%,livestock manure P that flow into surface water will decrease about 20%.