| SHENXI watershed is located in an important water sources-the upstream of the old SHIKAN Reservoir in Anji County,Zhejiang Province,at the same time as the main source of the Huangpu River.Because chemical fertilizers,pesticides,animal manure,sewage and soil erosion by rainfall and runoff,leaching and returned irrigation water flow into the water body causing agricultural non-point pollution which has been a serious threat to the water quality in the old SHIKan Reservoir and the downstream.It is more difficult to monitor,control and handle non-point pollution than that of the point pollution because it is characteristics of its broad impact on the ecological environment,the random of the occurrence,the non-fixity of the sources and emissions point of pollutants,the intermittent of emissions,the large magnitude in the temporal and spatial variation of pollution load.In this study pollution runoff is controlled and purified in sub-levels by using artificial reservoirs system, near-natural forest ecosystems and wetland ecosystems hierarchical against Anji SHENXI watershed agricultural area source pollution.By fixed-point sampling and analysis in the Zhang River and Deep River in Deep River basin of the river,researching the pond-wetland complex system to deal with water pollution performance and features in the basin-specific climate,soil conditions,analyzing the factors such as the influent concentration,time-varying which has the impact of removal of pollutants.The main conclusions are as follows:(1) in 2008,Hong Village,Deep River downstream of paddy field drainage total nitrogen,total phosphorus,COD analysis showed that:the total nitrogen concentration of farmland out of the water has exceeded of the V state water quality standards,effluent total phosphorus concentration in May in addition to higher,the concentration in the other month did not exceed 0.2mg/L.Emissions of TN reached a small peak in May and July,in which paddy field drainage total nitrogen in July reach the highest in the 33.3mg/L,total phosphorus content in May reach the highest in the 1.99mg/L, respectively,over the Chinese Environmental Quality Standard for Surface Water V-type set forth in the nitrogen and phosphorus in the water content of 16.7-fold and 5-fold.COD value of paddy field drainage is similar to the changes of total phosphorus and total nitrogen that in the monitoring of paddy field drainage the COD value is of an average of 51.4,much higher than the V state water quality standards,the peak appears in the May and July,the value of the water quality of COD were 121 mg/L,99mg/L.This cause mainly is that pollution from upstream sources of pollution caused by village life,HongJia village Deep River downstream pollution of farmland affected by the pollutants is basically the same as the loss of peak rainfall and peak agricultural fertilization,drugs to fight season.(2) in 2008 between May to October HongJia village artificial pond and Zhang Xi artificial pond water quality of farmland high removal of total nitrogen and total phosphorus results show:in 2008 between May to October,and Hong Zhang Ka artificial river pond water intakes of total nitrogen concentration of volatile.In mid-May and mid-June Tong Zhang Xi artificial compared to the influent total nitrogen concentration lower in other months,the corresponding artificial pond on the TN removal rate than the relatively low,only 9.9%and 14.5%;Hongjia artificial pond water in May-June with lower concentrations of total nitrogen,the corresponding artificial pond on the TN removal rate than the relatively low,the maximum is only 27.6%.Between July and August the two artificial pond influent total nitrogen concentration is higher such that ZhongZhangXi and hongjia village artificial pond influent total nitrogen concentration reached the highest 6.4mg/L and 6.9mg/L, this time in ZhongZhangXi and hongjia village artificial pond on the highest TN removal rate reached 63.4%and 37.4%.And ZhongZhangXi and hongjia village TP removal efficiency is of greater volatility.In the artificial pond water with higher concentrations of TP during the month,the system showed good removal efficiency,in June and August in 2008 ZhongZhangXi artificial pond water into the river samples higher concentrations of total phosphorus,total phosphorus concentration reached an average of 0.072mg/L and 0.155mg/L,removal rates of 40-60%.However, In the part time,two artificial TP content of the water pond system is higher than the volume of pond water TP.(3) in a wetland system,the plant bed purification TN,TP removal rate by a larger concentration of water quality,usually the higher the influent TN concentration,the higher the removal rate.Between July and early August,the wetlands system has better purification of total nitrogen,and wetland plants on sewage purification rate of total nitrogen get to about 50%,while in other months wetland water quality has little difference in influent water quality,because in June and August because it is the season of plant growth,removing pollutants is more obvious.However, in late August to early September is not out of the water concentration,the removal rate is also relatively low,mainly due to more rainfall during this period,resulting in some wetland plants were flooded,will not achieve the effect of water purification.(4) Hongjia village Deep River downstream-in the complex system of wetlands between May and October-the artificial pond complex system of wetlands on the removal of total nitrogen on agricultural land of high water quality results show that in May and July of farmland drainage in total nitrogen,the concentration of total phosphorus and COD value of the highest level of total nitrogen which peaked in July at 33.3mg/L,total phosphorus content of the highest in May in the 1.99mg/L,respectively,over China's surface water environmental quality standards set forth in the V category nitrogen and phosphorus in the water content of 16.7 percent and 5 times.At the same time, artificial pond-wetland eutrophication composite sewage system has reached the highest removal efficiency of total nitrogen removal efficiency in water up to 90%of the total phosphorus in the water removal rate of up to 98%of sewage COD removal rate of up to 82%,between May and August Tang-complex system of wetlands in effluent total nitrogen removal rate was 75.5 percent average of total phosphorus removal rate for an average of 74.2 percent,the average COD removal of 60%.Effluent water quality of wetlands,the average total nitrogen content of 1.50 mg/L,the average total phosphorus content of 0.039 mg/L,the average COD value of 23.8 mg/L,respectively, the three indicators of the state Classâ…¡Classâ…£and Classâ…¢surface water environment quality standards.Although some period of time the water quality of wetlands in the total nitrogen content of the water is still inferior toâ…¢water quality standard,but taking into account the high pollution of farmland drainage characteristics,to achieve such a high removal rate is more desirable.
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