Priority Control Pollutants In Groundwater Screening Study In Plain Terrain Of Beijing

Selection of the priority control pollutants in groundwater has significance to groundwater pollution prevention.In this study,we establish a screening method system for prioritizing pollutants in groundwater based on the process contaminants in surface environment arrive to aquifers through the aeration zone.In this system mainly includes three steps: quantify contaminates emission in surface environment,quantitative calculation about the attenuation of pollutants in aeration area using the reduction factor method,then emission quantities-toxicity coupled by weighting grading law and receive a composite score,and finally got the priority control pollutants according to the scores sorted,respectively.Meanwhile,in order to get more accurate results,sensitivity analysis was done to parameters in the screening system and weights of coupling factors.Main conclusions obtained are as follows:(1)A screening method system is established for prioritizing pollutants in groundwater which includs quantify contaminates emission in surface environment,quantitative calculation about the attenuation of pollutants in aeration area and finally scores sorted.The best advantage of the method is that focusing on the quantification of contaminates emission and hydrogeology conditions.In addition,take the emission quantities and toxicity as coupling factors,and scores sorted.And results prove that th e method is more reliable.(2)Reduction factor method is used to calculate contaminants emission quantities in the screening process.Where these factors are adequately considered,such as lithology structures in aeration zone and the physic-chemical properties of contaminates.The reduction factor method makes the attenuation quantitative process of contaminants from surface to groundwater easier and more accurate.(3)The results of priority control pollutants in plain terrain of beijing show that comprehensive index and inorganic indicators have high contaminants emission quantities and attenuation of pollutants in aeration area weakly,which are in front of the list of priority control pollutants in groundwater.It is also verified that the list of priority control pollutants in groundwater reasonably,when toxicity weights are bigger than pollutant emission amount weights.(4)Results of sensitivity analysis show that concentration limit of pollutants,permeability coefficient and the depth of aeration zone can have a significant influence on the list of priority control pollutants.Inorganic indicators are more obvious than organic indicators.Toxicity weights of pollutants are more sensitive than the weights of pollutant emission quantities.The uncertain result is mainly from the calculation formula.For this reason,it is particularly important to reasonably determine calculation formula.