Study On Groundwater Contamination Risk Assessment And Screen Of Typical Pollutants In Disu Underground River Basin Area

Groundwater contamination risk assessment and selection of the typical pollutants was of great significance in protecting, managing, and reasonable utilizing karst groundwater. In this paper, various groundwater contamination risk assessment system was compared and reviewed. In view of the disadvantage of the current systems. Based on the European model, intrinsic vulnerability and specific vulnerability of groudwater was synthetically considered, which can be used to assess the groundwater vulnerability in research area.The research area contamination load assessment was based on the attenutans of pollutans, which was implement the process of quantification. Finally, a new groundwater contamination risk assessment system which was suitable for karst region was proposed based on the groundwater vulnerability and contamination load assessment overlaying analysis. The method system had been used in Disu underground river system karst basin area as a case. In this study, Classified and rating method and multiplication of factors method were applied to screen the typical pollutants in groundwater of the research area. Main conclusions obtained are as follows:(1) The reduced coefficient was proposed in the contamination load assessment module of groundwater contamination risk assessment system. The reduced coefficient considered the factors of contamination load in surface water and hydrogeology conditions, which summarized the process of migration and transformation from the surface to the water table of pollutants and made the evaluation results more convincing. The regional groundwater quality figure drew was compared with the results of groundwater contamination risk assessment. The results showed that the assessment results was basically consistent with the actual situation of groundwater.(2) The results of groundwater contamination risk assessment in Disu underground river system karst basin indicated that the wastewater from industrial zones and residential areas are the most seriously pollution sources of groudwater. isk of groundwater contamination in research area was relatively low. The area with moderate and above groundwater contamination risk was 424.41km2, 39.03% proportion of research area. The high-risk area included Disu town, Dongmiao town, Liuye town, which place have frequently human activities and Disu underground river main stream middle and lower reaches area. The terrain of former area is relatively flat. It was further concluded that the spatial characteristics of the groundwater contamination risk in the areas was affected not only by the natural factors such as lithology、gradient、development degree of karst etc,but also by human activities.The gently terrain slopes, strongly development of karst network and frequent human activities were the reasons which lead to highly groundwater contamination risk of regions.(3) The classified and rating method and multiplication of factors method could both realized the process of screening typical pollutants. The result of sensitivity analysis indicated that the toxicity factor was of greater significance in screening typical pollutants. More attention should be paid when setting the weight of toxicity factor using the classified and rating method. The screening result of classified and rating method was lack of scientificity and objectivity because of the artificially and uncertainty when setting the weight of evaluation factors. The result of multiplication of factors method was reasonable and reliable. The result of typical pollutants was regional differences obviously, which was differed from the result of traditional priority control pollutants, because of the contamination load and geological environmental factors were considered comprehensivly.