The Evaluation And Prediction Of Non-point Source Pollution In Poyang Lake Area

The non-point source pollution from agriculture is one major cause of water pollution with intensive,modern and industrial agriculture developing.but the spatial distribution of pollution source,polltion assessment at watershed scale and polltion management are issues and difficulty because the non-piont source pollution fron agriculture associated with site-specified,diffusing potential and intermittent characteristics,and therefore its spatial and temporal distribution Characteristics is a major study problem in nowadays.Poyang Lake is the largest freshwater lake in china, systematic analysis of the nitrogen and phosphorus's distribution feature and source pollution's contribution rate will provide necessary basis for the rational allocation of agricultural resource in Poyang Lake and scientific planning agricultural industries and promote friendly saved agricultural technology in Poyang Lake Ecological & Economic Zone.(1)In this paper,we regard Poyang Lake 12 counties& cities as study area, N,P this two things as study object, land use and livestock and agricultural population output as source pollution, and combined with GIS, evaluate the base year 1997-2007 point source load through output coefficient model. Meanwhile, with the help of Markov model and Gray predication model to predict in next ten years the change of land use and livestock population, then forecast the source pollution in the year of 2011 to 2020. After compared analysis, following conclusions have been obtained:(2) compared with the base year 1997-2007, in predict year 2011-2020,Poyang Lake area's point source nitrogen and phosphorus's pollution load has got significant increasing trend. In base year the average output load of N and P are 60496.692 and 5498.059 tons, but in the predict years, the figure has increased to 71768.374 and 6976.882 tons. Average annual growth rate has come to 18% and 26%.It-is forecasted that the contribution rate of every nutrient source in the Poyang Lake has the same variation tendency in 2011-2020 compared with 1997-2007:the contribution rate of the output load of the beasts and birds has significant increasing trend as time goes on, which is because the scale of the poultry farming is growing gradually with the development of the social economy, and the area-source pollution is also growing; the contribution rate of the output load of the agricultural population has a downward trend, which is mainly because the agricultural population gradually reduces with the development of urbanization; the total land area within Poyang Lake is unchanging, and the urban land increases and arable land shrinks, which makes the contribution rate of the TN/TP load of the land output has a decreasing tendency over time, and the decreasing tendency of the TN load contribution rate is faster than that of the TP load.(3) In TN/TP load outputted by various kinds of land use types, the TN/TP load by the cultivated land, waters and urban land top the front three, and the contribution rate of the land which did not use is the smallest. The reasons are mainly as follows: first, in six types of land use, the occupancy rate of the cultivated land and waters is in the top two, while the occupancy rate of land without using is the smallest; second, the cultivated land suffers from great impact from the agricultural practices, which is the direct patient of the agriculture chemical, and the aquiculture has a direct impact on the water quality of the water area, however, the land without using is basically in water quality comparatively, which was less affected by t human production and life.(4)Among counties and cities of Poyang Lake, point source pollution load intensity in four counties of Nanchang is higher than that of the whole area. Among six counties in Jiujiang city, four counties'point source pollution load intensity is lower than that of the whole area. Compared to base years 1997 to 2007, point source pollution load intensity in each counties and cities have increased in forecast years 2011 to 2020, especially Nanchang increased most. The main pollution in Nanchang is livestock output, contribution rate has come to 50%. land output is regarded as two major source pollution of TN load in Jiujiang area and Shangrao area, and agricultural population is the major source pollution of TP load in this two areas. That is because pollution load intensity of each county and city have close relationship with its social & economic development and industrial structure.