The Environmental Risk Evaluation Of Soil Phosphorus Base On Landuse In Liuxi River Watershed

Along with people further the point source pollution, the problem of entironment appears more prominent aroused by the non-point source pollution. Because of the special function of the eutrophication evoked by phosphorus, it is necessary and significative to study the runoff of soil phosphorus in agricultural non-point source pollution and evaluate the effect for environment.In recent years, economy has developed quickly and population has increased rapidly in the Pearl River Delta, they result in the lack of the aqueous source. And the aqueous eutrophication pollution induces the scarcity of water quality, it aggravates the crisis. Liuxi River is an important water source of Guangzhou, there is a lot of soil in different landuse. It is woodland in upriver, and the important producing area of foodstuff and the second linear vegetable base are in the middle river. The backward position is the first linear vegetable base. Therefore, the assessment of the runoff of soil phosphorus in different landuse in Liuxi River and the valuable assessment outcome can enhance our knowledge effectively in the non-point source pollution of soil phosphorus. And we can strengthen the forecast assessment, the prevention and cure of the pollution and the implement of the controllable measures. Thus we are able to reduce the pollution of soil phosphorus in the runoff, economize the quantity of the fertilization, improve the water quality and renew the effect of the entironment.In this study, depending on the collection information and observing of the river area, we choose and sampling in the river of woodland, garden, paddy field and vegetable soil. We orient them in GPS, and collect 50 samples. Through the analysisof soil phosphorus and the adsorption isotherms experiment, we know the total phosphorus (P2O5) of the samples is 0.013~0.78 %, and the average is 0.17 %. The potent phosphorus (P) is 2.20~224.00mg/kg, and the average is 49.14mg/kg. In the total phosphorus, the first and second grade has occupied 38.00%, the third and fourth are 36.00% and others are 26.00%. And in the potent phosphorus, the first and second grade has occupied 60.00%, the third and fourth are 28.00% and the fifth and sixth are only 12.00%. The level of the soil phosphorus is vegetable soil, garden, paddy field and woodland in turn. The total and effect content of soil phosphorus in infield layer are higher. The adsorption isotherms of soil phosphorus shows the maximal adsorption of soil phosphorus varies from 178.57 to llll.llmg/kg, and the order is woodland, paddy field, garden and vegetable soil. The range of MBC is 5~ 711.11mg/kg, and the order is woodland, paddy field, garden and vegetable soil. The range of RDP is 3.17~32.49mg/kg, and the order is vegetable soil, paddy field, garden and woodland. The range of EPCo is 0.053~3.74mg/L, and the order is vegetable soil, paddy field, garden and woodland. The range of DPS is 0.2~70.56%, and the order is vegetable soil, garden, paddy field and woodland. The standard adsorption of soil phosphorus for the landuse type is very adjacent, and the range is 4.67~6.19mg/L. At the same time, we choose xintian small drainage area to inspect the runoff of soil phosphorus, and observe the relation between the runoff of soil phosphorus and the rainfall. So that we validate the contribution to the non-point source pollution evoked by phosphorus of the differentlanduse. The autoptical result shows the rainfall is the main approach and the transferred force. The rainfall of the original rainy season brings more runoff of soil phosphorus. The mutative degree of the runoff of soil phosphorus accords with the process of the rainfall, rising then dropping.Finally, we estimate the runoff of soil phosphorus of the different landuse in the drainage area. The runoff of the different landuse is vegetable soil, garden, paddy field and woodland integrated different parameters and the autoptical result. The vegetable soil is the critical source in agricultural non-point source pollution. We advance manipulative policy and measure according the assessment outcome and thesocioeconomic status in the drainage area and offer academic reference and decision-making basis for environmental managing and the fertilization in the drainage area.In this study, we adopt adsorption isotherms of soil phosphorus, supervising the adaptability of the Langmuir adsorption isotherms in the drainage area. We gain many parameters and make them applied the assessment of the runoff of soil phosphorus. Linking the secular oriental data in the small drainage area synchronously, we investigate the relation between the runoff of soil phosphorus and the rainfall and the actual runoff situation.