Study On The Characteristic Of Diffuse Pollution And Its Control In The Residential Area Of Mountain Urban

Recently, with the accelerating development of Chinese urbanization process, and under the condition of continuing mature improvement in governance urban point source pollution in China, diffuse pollution caused by splash, scouring and other urban surface runoff effects on the surface sediments has become one of the major causes to the water environment quality, and become the third largest pollution sources after the point pollution and agricultural non-point pollution. This article chooses the Shuizhu estates community of Dazhulin Town, Yubei, Chongqing, which is a Three Gorges Reservoir area in the upper Yangtze River as a research object. The area of the Three Gorges project is 1084 square kilometers, and the water safety and ecological environmental health directly affect the comprehensive benefit of the Three Gorges. Chongqing is the largest city beside the Three Gorges Reservoir and more than 60% wastewater discharge is produced here, and it has an important influence on the safety of the reservoir. Therefore, to survey and study the diffuse pollution in Chongqing becomes necessary. By continuous monitoring the quality and quantity of five typical surface runoff of the typical mountain urban area for two years, pollution process and pollution load of the rainfall runoff are considered. And through the adsorption and desorption of matrix experiments, the treatment effects of surface runoff on some land infiltration combined technologies are also discussed. At last, the effect of the runoff pollution compared with green roof and asphalt roof is studied.The main results of research are as follows:(1) The average concentration order of major pollutants TSS, COD, TP in the surface runoff of the monitoring sites is:the asphalt pavement> the cement pavement> the cement courtyard> the ordinary roof, and the biggest concentration of pollutants is the pavement, so pavement is the first control object.(2) The correlation of the concentration of TSS with COD, TN, TDN, NO3-N, TP of the rainfall runoff is very significant positive in alpha= 0.01 level, and TSS is the main pollutants in urban runoff, and it's the carrier of the other pollutants, so TSS is the major management object of polluted runoff control process.(3) The cumulative curve of pollution load showed that the monitoring sites have different degrees of first pollutants'flush phenomenon, the average ratio of first 30% runoff of impervious land surface carrying TSS, COD, TN, NO3-N, NH3-N, TP and TDP is 56.00%,45.19%,45.17%,41.38%,38.04%,48.94% and 39.25% respectively, so we should focus on the intercepting polluted runoff. (4) Each pollutant load cumulative curves showed that the same pollutant accumulation curve of different monitoring sites has different deviation with diagonal in the same rainfall events, and the same pollutant accumulation curve of the same monitoring sites has different deviation with diagonal in the different rainfall events. It shows that both the accumulation amount of pollutants from different underlying surfaces and the randomness of the rainfall intensity affect the cumulative curve.(5) The experimental results of different matrix on the adsorption and analytical capacity showed that the adsorption quantity size of each matrix is as follows:the garden soil and the peat soil> vermiculite> ceramsite, pearlite, sand> zeolite, because the purification capacity is closely related to matrix on the adsorption capacity of phosphorus, so the purify ability obtains of matrix is as follows:the garden soil and the peat soil> vermiculite> ceramsite, pearlite, sand> zeolite. Vermiculite, pearlite and peat soil are light materials, and the peat, vermiculite have stronger adsorption ability. Although pearlite adsorption ability is weaker, it is rich in nutrients which plant needed, so the planting matrix of green roof is the best choice among them.(6) Green roof has obvious interception effect to rainfall runoff, green roof runoff capatity is only the 20-60% compared with the bare asphalt roof, it slows the pressure of the peak of the experiment site from the rainstorm apparently. Although some pollutant concentrations are higher than the bare asphalt roof, because of the significant reduced runoff volume, except for TN, NO3-N, the total output of pollutants all decreased significantly, the removal rate of TP, PO4-P, COD, NH3-N is 55.5%,30%,70.3%,44.5% respectively, so overall, the green roof reduced the total output of pollutants.(7) The ratio of phosphorus particles is 65-80% of total phosphorus in the green roof runoff. The ratio of nitrogen particles is more than 95% in the green roof runoff, the elements such as nitrogen and phosphorus are carried with TSS, so the direct particulate is still the main object to control runoff pollution of green roof.