Study Of Phosphorus Flow In Minjiang River Watershed Based On GIS

Phosphorus(P)is not only the essential nutrient of organism,but also critical factor of environmental pollution.With the increasingly severe disturbances of human activities to P natural metabolism,phosphorus pollution has become an important global issue.In this paper,the P flow of Minjiang River Watershed is chosen as the study object,and quantitative analysis of the P flow and the P footprint in Minjiang River Watershed of 2009 by constructing P substance flow model.It reveals the pattern and spatial distribution of the P flow in food production-consumption system and find the key approaches and mechanism which impact on environment,then providing the basis for optimizing the P nutrient management.The main conclusions show as follows:(1)The amount of exogenous P input to the food production-consumption system in Minjiang River Watershed is 53434.43t P,and fertilizer is the largest P input,which occupied 70.72%of the total input P in the system.The amount of the P output is 53297.85t P,including part for other purposes and loss in the environment.Crop production stage has the largest amount of P loss,which accounting for 69.82%of the total P loss.Finally,the amount of P entering the human body is only 5381.01t P,10.07%of the total P input,it indicates that 89.93%of P can not be directly used,and each input 1kg P into the body,there will be loss of 9.2kg P to the environment.(2)In Minjiang River Watershed,the average PUEcrop(Phosphorus use efficiency of cropland)is 46.46%,and between the different tributaries have large gaps,ranging from 35.73%-60.43%,which similar to the average level of China(34%-59%).With more input of fertilizer,PUEcrop is much lower,it means excessive fertilizer input will lead to more loss of P to the environment.The average PUEanimal(Phosphorus use efficiency of livestock)is 5.31%,which is lower than the average level of China(16%-17%),and PUEanimal has differences between each tributaries,ranging from 2.13%-9.18%,this difference related to the management level of livestock.(3)The system exports 12657.99t P to the waterbody.Livestock breeding subsystem is the main contributor,which exports 7381.79t P,responsible for 58.32%of total output.From the spatial point of view,Futunxi Basin exports 4471.54t P to water,which accounting for 35.33%of total P output,is the control focus of watershed water pollution.(4)The per capita food P footprint of Minjiang River Watershed is 4.77(kg P)/a,ranging from 35.73%-60.43%in different tributaries,Futunxi Basin has the largest per capita food P footprint.The per capita food consumption P footprint is 0.40(kg P)/a,and the per capita food consumption P footprint in different tributaries is positively correlated with the level of urbanization.In addition,solid waste and sewage treatment also have an impact on the food consumption P footprint.The per capita food production P footprint is 4.40(kg P)/a,where cropland production virtual P is the largest,accounting for 76.17%,it indicates that most of P in food production stage is lost in the cropland cultivation process.