Study On Distribution Characteristics Of Agricultural Non-point Source Pollutants And Water Quality Control Measures In Drainage Ditch Of Yellow River Irrigation District

Agricultural non-point source pollution is a serious ecological environment problem,which is widely dispersed,complex,and harmful.Drainage ditch is the key object to study non-point source pollution in agriculture.Taking the ditch No.1 and it's branches as typical research areas,this paper focus on the water quality and flow rate of the main ditch and branch ditch.The relationship among pollutant discharge concentration,flow rate and season,between the upper and lower reaches of ditch,between main ditch and branch ditches is studied by analyzing the spatial and temporal distribution characteristics of pollutant concentration and pollutant flow characteristics.According to the pollution sources,the characteristics of non-point source sources in agriculture are analyzed from two aspects:the structure of pollution sources and the pollution load.Considering the goal and implementation of river administrator system of drainage ditch,this paper also analyzes the problem of water quality control and puts forward corresponding water quality control suggestions.The main findings are as follows:1)The water quality of ditch No.1 is the inferior Class V water quality standards.The main pollutant is nitrogen.The characteristics of pollutants are seasonally superimposed and the water quality of the outlet is limited.So the comprehensive influence of concentration and flow rate should be taken into account in the study of pollutant discharge from the outlet section.2)From the structural analysis of the pollution sources,the total pollution load of the planting industry in the branch ditch is the highest,accounting for 59%of the total load.From the pollution load calculation analysis,the total nitrogen and nitrate nitrogen load of farmland is higher and the change is greater.The ammonia nitrogen in the village is relatively high and the fluctuations are relatively stable.3)In order to improve the water quality of branch of the first ditch to be near-term target of Class IV.,the reduction of the total nitrogen of the main pollutants is 78.965 t/a for crop production,46.063 t/a for aquaculture,and 6.581 t/a for domestic sewage.In order to improve the water quality of branch of the first ditch to be long-term target of Class ?,the reduction of the total nitrogen of the main pollutants is 99.518 t/a for crop production,58.06 t/a for aquaculture,and 6.581 t/a for domestic sewage.4)The countermeasures and Suggestions for water quality target management of drainage ditch in the Yellow River diversion irrigation area are:source emission reduction,process control and end treatment.Three different models of water quality control are proposed:zero emission model,improvement model and conservative model.