Analysis Of Nitrogen And Phosphorus Non-point Source Pollution In Tianmu Lake Basin And Study On Nitrogen And Phosphorus Runoff Control In Tea Garden

China is a country with severe drought and water shortage.Severe water pollution not only reduces the use function of water bodies,but also aggravates the contradiction of water shortage.At present,the current status of surface water pollution in the country is still serious,and the problem of eutrophication of lakes and reservoirs is outstanding Non-point source pollution is an important cause of water eutrophication,and agricultural non-point source pollution is the main form of pollution.The Shahe Reservoir located in the Tianmu Lake Basin of Liyang City is the most important drinking water source reservoir in the area.In recent years,the total nitrogen and total phosphorus in its water quality are at a relatively high level.It is of great significance to analyze the sources of nitrogen and phosphorus and study the measures for reduction and control.From 2018 to 2019,this study conducted field surveys to clarify the nitrogen and phosphorus emissions and contribution rates of different types of non-point source pollution such as farmland emissions,tea garden emissions,liv estock and poultry farming,and domestic sewage.Under simulated rainfall conditions,the effects of different fertilization treatments,biochar application,and ecological cover on nitrogen and phosphorus output forms and loads in tea garden runoff are studied,with a view to exploring measures to reduce and control nitrogen and phosphorus emissions from tea garden runoff.Provide necessary technical support for ecological restoration.The study found that the order of non-point source nitrogen and phosphorus pollution in the Tianmu Lake watershed is agricultural non-point source pollution>total domestic pollution>breeding pollution;agricultural non-point source pollution is the main source of pollution in the reservoir area,and the main pollution type is farmland and tea garden runoff The total nitrogen accounted for 24.97%and 23.24%of the non-point source pollution load of the reservoir respectively;and the tea garden runoff accounted for a higher proportion of nitrogen and phosphorus runoff emissions,15.8%of the tea garden soil contributed 41.70%of the agricultural non-point source pollution Total nitrogen and 31.68%of total phosphorus.Domestic sewage is also an important part of nitrogen and phosphorus pollution.Domestic sewage accounts for 23.09%of total nitrogen and 27.36%of total phosphorus in the non-point source pollution load of the reservoir.The proportion of aquaculture pollution and tourism pollution is relatively small.The results of studies on the effects of different fertilizers and biochar application on soil nitrogen and phosphorus runoff in tea gardens showed that,compared with conventional chemical fertilizers,nitrogen and phosphorus emissions from runoff of special organic fertilizers and slow-release fertilizers for tea plants were reduced.The application of biochar can increase the pH of the acid soil in tea gardens.Excessive addition will increase the soil pH too much and is no longer suitable for the growth of tea trees.The application of appropriate amount of biochar can reduce the nitrogen and phosphorus runoff losses.Excessive addition will increase the surface runoff and increase the runoff nitrogen and phosphorus losses.The addition of biochar will not have a negative impact on soil fertility,but will instead increase the content of soil available phosphorus.The addition of biochar to nitrogen has a certain adsorption capacity,especially the adsorption of ammonia nitrogen is strong,but the adsorption of phosphorus is not obvious,and even shows an increase in the soil available phosphorus content.Studies on ecological cover and biochar addition to nitrogen and phosphorus runoff have found that white clover alone can have an effect of reducing nitrogen concentration,with little effect on phosphorus concentration.The combined effect of appropriate amount of biochar and white clover planting can significantly reduce the nitrogen and phosphorus concentration in the runoff.In each treatment,OF+1B+T had the lowest total nitrogen runoff concentration,which was 29.45%lower than that of OF+1B and OF+T And 25.47%,OF+1B+T is 34.29%lower than the average concentration of OF+1B.Excessive addition of biochar and white clover did not further reduce the nitrogen and phosphorus runoff concentration,but increased.The excessive addition of biochar and white clover will increase the surface runoff,which is the main reason for the increase in nitrogen and phosphorus loss.The amount of nitrogen loss between the treatment group planted with white clover and the group without planted white clover showed a significant difference;the lowest total nitrogen outflow was OF+1B+T(2.19 mg),and the proportion of outflow was NO3--N It is the main form of surface runoff.Planting white clover alone can not effectively control the amount of phosphorus loss from runoff,but the combination of appropriate amount of biochar and white clover can effectively reduce the total phosphorus content in runoff.And due to the effect of white clover,the proportion of PP in the outflow decreased and the proportion of TDP increased.