Analysis And Control Strategy Of Pollution Load In Small Watersheds

Yingzhou West Lake Wetland Park in Fuyang City,Anhui Province belongs to a typical small agricultural watershed.There is a West Lake Scenic Area in the watershed.It is one of the important subjects of the Fuyang Municipal Government’s planning of"two rivers and one lake".To comprehensively understand the current situation of pollution in the West Lake Basin of Yingzhou and provide a reference for the municipal construction of the Yingzhou Municipal Government,this study takes Yingzhou West Lake Wetland Park as the background and relies on the"14th Five-Year Plan"of Fuyang City.Environmental quality,analysis of watershed pollution load,and survey of rural pollution status were carried out.The survey of rural pollution status was conducted through field visit records and questionnaires;pollution load analysis included two aspects:pollution source analysis and trace organic pollution load analysis.By synthesizing the above contents,the corresponding conclusions and suggestions are put forward on the current situation of the water environment of the West Lake in Yingzhou.The following are the main conclusions of this study:（1）Environmental quality assessment of surface water.The water quality of surface water in the basin shall meet the surface water quality standard of Class III.In this study,the three main rivers in the basin and the main body of the West Lake were evaluated by the single-factor water quality evaluation and the Nemerow comprehensive pollution index water quality evaluation.The results show that the water quality of the Quanhe,Fulin River,Caohe,and the West Lake in the flat water period in January all met the surface water quality standard of Class III and above;while in the dry season in April,the water quality in the basin dropped sharply,and the three main rivers and The water quality of the main body of the West Lake did not meet the Class III water quality standards.The water quality of the West Lake and Caohe was Class IV,and the water quality of Quanhe and Fulin River was inferior to Class V.The water quality deteriorated because the TN and TP in the water exceeded the standard;the water quality in the wet season in June was significantly The water quality of the three main rivers and the main body of the West Lake met the Class III water quality standard for surface water.（2）Analysis of pollution sources in the watershed.The pollution sources in the small watershed of West Lake in Yingzhou can be divided into industrial pollution sources,residential pollution sources,and agricultural pollution sources.As a typical small agricultural watershed,residential pollution sources and agricultural pollution sources should be the main pollution sources in the watershed.The COD contributed by agricultural pollution in the basin is relatively low,and the contribution of TN and TP is relatively high,accounting for 35.51%and33.73%,respectively.Due to less industrial source pollution in Xihu Town,the proportion of industrial source pollution in the West Lake Basin is very low;domestic source pollution is the most important source of pollution in the basin,and the proportion of COD,NH3-N,TN,and TP emissions is 96.54%,87.55%,64.05%,and 50.85%.（3）Investigation of the current situation of rural pollution.In this study,questionnaires and field visits were used to investigate the current situation of rural pollution discharge.The number of surveyed villages reached 12,with 154 valid questionnaires and a total of 666 farmer households.The survey results,excluding invalid questionnaires,showed that 50.4%of the peasant households adopted the direct drainage method,and the generated sewage was directly discharged without any treatment.There are 42.28%of farmers in their villages with sewage treatment facilities,which have not been widely used.The drinking water of farmers is mainly tapping water.63.77%of the farmers have drinking water from tap water plants,and 14.5%of the respondents still use well water as the only source of drinking water.The rest of the households use tap water as the main drinking water,supplemented by well water,drinking water safety cannot be guaranteed.In the survey area,73.4%of the farmers’households have septic tanks,and 46.7%of the farmers are still using dry toilets.The manure produced by the livestock and poultry raised by farmers is directly discharged into the natural water environment.（4）Analysis of trace organic pollutant loads.In this study,two trace organic pollutants（29pesticides,and 14 PFASs）were detected in the watershed,and the possible environmental risks of these micropollutants were calculated.Pesticides and PFASs micropollutants showed a trend of enrichment in West Lake.The main pesticides in the watershed are carbendazim,metolachlor,paclobutrazol,tebuconazole,and triadimenol.The ecological risks are derived from carbendazim,tebuconazole,carbofuran,imidacloprid,and Metolachlor.The pollution status of alachlor,among which carbendazim,needs attention the most.The most important PFASs micropollutants in the watershed are PFOA(1.0～36.1 ng·L^-1)and PFBA(Nd～15.7 ng·L^-1),and the PFASs micropollutants with the highest potential ecological risks are PFOA and PFOS,and other PFASs micropollutants have no ecological risk.The correlation analysis of PFASs micropollutants shows that the main pollution source of PFASs micropollutants in the watershed is Quan he.