Baseline Research And Application Of Water Quality Assessment For Groundwater Environmental Damage In Polluted Sites

In the environmental damage identification and evaluation system,the determination of the baseline is the key to the evaluation work,which is related to the formulation of environmental restoration goals and the determination of damage compensation.The four existing baseline determination methods in the Environmental Damage Identification and Assessment Guidelines have good applicability in the soil environment,but in the groundwater environment,there are defects such as poor applicability,poor accuracy,and long investigation time.There is a lack of water quality baseline determination specially formulated for groundwater contaminated sites.method,which hinders the development of assessment work in the groundwater environment.Therefore,this thesis proposes a new method for determining the water quality baseline according to the pollution characteristics of groundwater environment,establishes the work procedure for determining the water quality baseline,and improves the identification and evaluation system of groundwater environmental damage.Based on the advantages and disadvantages of existing baseline determination methods in groundwater environment,a new method for water quality baseline determination is proposed:（1）Referring to the mathematical"limit"idea and the principle of groundwater solute migration dynamics,the same-layer reverse point method is proposed.The research results show that the water quality baseline determined by the same-level reverse point method is close to the industry-accepted control data method,which proves the accuracy of the method.The same-layer reverse point method is suitable for sites with a single point source of groundwater pollution or where the pollution situation is clearly delineated.The application steps are:（1）preliminary investigation;（2）preliminary sampling;（3）delineation of potential clean areas;（4）Sampling;（5）Arrange data;（6）Obtain the baseline level of water quality;（2）Two models for determining the water quality baseline are proposed,namely the UC model method and the trend surface analysis method.The research results show that the water quality baseline determined by the UC model is close to the results determined by the same-layer reverse point method and the control data method,and can make up for the defect that the water quality baseline cannot be determined in the standard benchmark method because the indicator limits of pollutants are not specified;trend;The surface analysis method fits the pollution trend through preliminary sampling data.The fitted water quality baseline is close to the measured value and has high accuracy.It is suitable for determining the water quality baseline of pollutants with uniform pollution levels in the site.In order to further improve the efficiency of water quality baseline determination,by analyzing the"accuracy","applicability"and"high efficiency"of the existing four methodsand the newly proposed three methods,a work procedure for groundwater quality baseline determination is established.Collect historical groundwater water quality data from autonomous regions,provinces,and municipalities,screen available data and eliminate outliers,and establish a resource database supporting water quality baseline determination procedures.Take the contaminated site of a chemical industry park in Liaoning Province as a demonstration case.The site data was obtained through the preliminary adjustment work in the early stage,and the sampling points were planned in combination with the land use,and the water quality baseline was determined under the guidance of the groundwater quality baseline determination procedure..For the first time,based on the water quality baseline,the Nemerow index method was used to evaluate the pollution of the site,in which As and Hg were slightly damaged,Pb was mildly damaged,toluene was severely damaged,and Cr⁶⁺was the most severely damaged.Cr⁶⁺requires significant attention.The same-layer reverse point method,UC model method,and trend surface analysis method are all proposed on the basis of groundwater environment,with strong pertinence,high applicability in groundwater environment,and more accurate water quality baselines.The establishment of the groundwater quality baseline determination procedure has further improved the efficiency of groundwater quality baseline determination.