Research On Analysis And Control Technology And Model Of Agricultural Non-point Source Pollution In Small Watersheds In Hilly Areas

Agricultural non-point source pollution has a wide range of sources and complex migration and transformation process,which has become the key and difficult point in the control of agricultural and rural water pollution in China.The results of the"Second National Pollution Source Census Bulletin"showed that the total nitrogen and total phosphorus emissions from agricultural sources accounted for 46.5%and67.2%.This data has further increased in the hilly and mountainous areas of China that are prone to rainfall and runoff and sensitive to soil erosion in my country.However,due to the unclear understanding of agricultural non-point source sources and the imperfect technology and application mode,agricultural non-point source pollution has become a serious obstacle to the implementation of China’s rural environmental remediation and Rural Revitalization Strategy.Therefore,this paper analyzes the source of nitrogen and phosphorus loss in the small watershed of Tanjiahe hilly area through field investigation,and develops a new ecological interception ditch technology for nitrogen and phosphorus loss in farmland.And focusing on the problem of lack of internal motivation for long-term use of technology,an"industrial controlling pollution"model for the prevention and control of agricultural non-point source pollution has been constructed,striving to achieve a win-win situation between environmental protection and agricultural development.The specific research results are as follows:1.Taking the Tanjia River Basin in Zhushan County,Shiyan City,Hubei Province as an example,the agricultural non-point source pollution was investigated and analyzed.The survey data show that the scale of planting industry in this area is large,and the application amount of chemical fertilizer per hectare of farmland is not high,but there are great differences between regions.In some areas,the amount of chemical fertilizer per hectare is as high as 1224.26 kg,and a large amount of agricultural waste such as straw is produced every year.The scale of livestock and poultry breeding industry is small,the infrastructure is poor,and the collection and treatment of fecal sewage is insufficient.The regional livestock and poultry land carrying capacity analysis shows that the livestock and poultry stocks in the basin are far less than the livestock and poultry land carrying capacity,and the farmland can meet the capacity of livestock and poultry manure consumption.Therefore,the prevention and control of nitrogen and phosphorus loss in farmland is the focus of governance.2.Using iron loaded biochar as filler,a new ecological interception ditch was constructed.Iron loaded biochar uses ferric chloride（Fe Cl₃·6H₂O）as the iron source to prepare industrial grade iron modified coconut shell biochar by impregnation method,which is filled into the ecological interception ditch in the form of bag.XRD,XPS,FT-IR,SEM and EDS results showed that this method could successfully load iron on biochar in the form of iron oxide（Fe₂O₃）.By fitting the results of indoor adsorption experiments,the maximum saturated adsorption capacities of nitrogen and phosphorus by iron-loaded biochar were 4.87 mg/g and 2.47 mg/g,respectively,which were consistent with Langmuir and pseudo-second-order reaction kinetic models.When the p H is 3-11,the performance of the material to adsorb nitrogen and phosphorus is less affected by p H.The practical application results of the new ecological interception ditch show that it can effectively intercept nitrogen and phosphorus in runoff and strengthen the effect of the original ecological interception ditches,the highest removal rate of nitrogen and phosphorus is 77.46%and 60.24%.Potted experiments of modified biochar returning to the field show that the adsorbent can promote the growth of brassica chinensis after the adsorption is saturated.3.Combined with the pilot project of comprehensive treatment of agricultural non-point source pollution in a typical watershed in Zhushan County,Hubei Province,the"industrial controlling pollution"model of the application of agricultural non-point source pollution prevention and control technology was constructed and demonstrated.The demonstration statistical results show that the"industrial controlling pollution"model takes industrial development as the core to drive pollution control,and focuses on the recycling of agricultural waste resources.It can solve the problems of difficult implementation,supervision and sustainability of agricultural non-point source pollution control,achieve both environmental and economic benefits,and provide a reference model for non-point source pollution control in hilly areas of China.