Risk Assessment Of Groundwater Pollution In Karst Area

Groundwater risk assessment is an assessment of the possibility of contamination of the groundwater environment.The development of groundwater pollution risk assessment will help identify high-risk areas of regional groundwater pollution and enhance the level of regional groundwater pollution risk supervision.Groundwater pollution early warning can issue warnings before possible groundwater pollution incidents to avoid pollution accidents.At present,the research on groundwater pollution risk assessment and early warning in my country is mainly concentrated in the pore water area,and relatively few in the karst water area.Therefore,in view of the shortcomings of research on groundwater pollution risk assessment and early warning in karst areas,this study takes Qiannan Buyi and Miao Autonomous Prefecture,a typical karst area in southwest China,as an example to carry out research on groundwater pollution source load,groundwater vulnerability research and groundwater pollution status.The main research results are as follows:(1)The evaluation results of groundwater pollution source load in Qiannan Prefecture show that the pollution source load value of Qiannan Prefecture is between0.25 and 179.93,and 67.79%of the area belongs to the low load area.At the same time,due to the unique geographical characteristics of Qiannan Prefecture,the spatial distribution of pollution sources in Qiannan Prefecture is relatively concentrated,and the pollution sources are mainly concentrated in the Pingba area and the inter-mountain valleys,which makes the superposition of pollution source loads in some areas obvious,and the regional pollution loads are at high and high levels.In addition,the aggregation of phosphate mining enterprises and large-scale farms in the northern part of Qiannan Prefecture are also the main reasons for the increase of load values in some areas.(2)The groundwater vulnerability assessment results of Qiannan Prefecture show that the groundwater vulnerability of Qiannan Prefecture is at a medium level,with an area of 15310.13 km~2 of moderate vulnerability,accounting for 58.44%of the total area of Qiannan Prefecture.On a large scale,the groundwater vulnerability of Qiannan Prefecture is obviously controlled by the development strength of the epikarst zone and the karst network development strength.Weng’an County and Fuquan City,where the epikarst zone is most strongly developed,are also more vulnerable.On a small scale,the distribution of skylight funnels and underground rivers will increase the vulnerability of regional groundwater.(3)The results of groundwater prevention and control value show that the groundwater prevention and control value of Qiannan Prefecture is at a low level.The area of the area with low prevention and control value is 11002.74km~2,accounting for42%of the total area of Qiannan Prefecture.The prevention and control value is affected by the pollution source load evaluation results.The impact is obvious,and the areas with high prevention and control values are mostly distributed in areas where pollution sources are concentrated,which meets the actual needs of groundwater risk assessment.(4)Finally,according to the research results,construct the groundwater pollution risk prevention and control zone in Qiannan Prefecture,and delineate the strategic reserve area,pollution prevention area,pollution warning area and pollution control area.Finally,the area of the strategic reserve area of Qiannan Prefecture is19909.72km~2,the area of pollution prevention area is 5501.37km~2,the area of pollution warning area is 523.94km~2,and the area of pollution control area is 261.97km~2.