Phosphorus Cycle Research In Upstream Of Miyun Reservoir Watershed Based On Material Flow Analysis

Phosphorus (P) is an important limiting factor in eutrophication. The existing pollution control measures can not effectively prevent continuing deterioration of the eutrophication, because they are confined to the local and the end pollution load reduction, but have been neglected the structure optimization and eco-efficiency improvement of P metabolism system for a long-term. Upstream watershed of Miyun Reservoir is chosen as a study area. This system is divided into four parts - planting subsystem, breeding subsystem, population subsystem and the other subsystem. This paper tries to find key approaches and mechanism that impact on the water environment by systematically analysing basic processes of P input, output, recycling of P in the region. The main conclusions are as followed:1) P cycle in planting system is deficient at amount of 2460.52 t. But deficits in different districts are various. 90% P of the products of livestock breeding subsystem, 1309.35 t, is export sales. The else part satisfy the local people demand; The imports of grain P plays an important role in the population subsystem, and it is exported mainly in the form of excreta and garbage; The other subsystem has little impact on P cycle of the whole system.2) Chemical products, which mainly are fertilizers, feed additives and pesticides, are the main souces of P input in the basin, responsible for 3430.1 t, 43.6% of total import. The system export 4484.76 t P to the environment, among which 13% (582.41 t) enters into non-cultivated soil, 87% (3902.35 t) directly enters into the waterbody. Breeding subsystem is the largest contributor, which exports 3508.05t, responsible for 78.2% of total output. Planting and population subsystems export 206.78t and 178.43 t. And the other subsystem exports 9.1t, the smallest contributor3) The pollution loads of different districts are related with the industrial structure and urbanization rate. Districts dominated by animal husbandry emit more pollutants than the districts dominated by planting industry because of more drainage of pollutant and lowerer efficiency of pollutant processed in breeding subsystem, in which the cattle plays a domeinant roel. It shows that the average P output in different towns is positively correlated with the number of cattle in different towns. The corresponding sewage treatment facilities have not kept up with the acceleration of urbanization process, so it shows that people pollute the water body becomes more and more serious.4) The overall structure of the system is incompatible, presenting one-way and open-type satus. The system is incompatible because P cycle in planting system is deficient but in livestock breeding system is surplus. P of livestock breeding and people excreta has not been effectively reused and recycled, so it results in P accumulation in the water, and further results in a serious waste of sources and a wide range of entironmental impact, so the system present one-way and open-type satus.So it is essential to systematically promote ecological transformation of material production, consumption and waste disposal. It should been focused on improving nutrient cycling between agricultural subsystem and breeding subsystem, reducing imports of pesticide and chemical fertilizers. Reducing the size and quantity of livestock breeding, especially the cattle and reducing the dosage of feed additives. Develop green and ecological farming making full use of local source. It is necessary to speed up the construction of urban environmental infrastructure, and to research new modes to control urban and rural domestic pollution source.