Groundwater Contamination Risk Assessment In Plain Area Of Longkou City

Groundwater is an important component of water resources, which plays an important part in protecting urban and rural residents, supporting sustainable socio-economic development and maintaining the ecological balance. However, groundwater contamination becomes more and more serious, with the rapid development of economy, continued growth of population and the acceleration of urbanization. The contamination led to decreasing the amount of available resources and exacerbating the water crisis and contradiction between supply and demand, directly influence the industrial and agricultural production, and do harm to the ecological environment and human health. Adopting a regional groundwater protection policy is the most basic and also the most cost-effective method to prevent groundwater contamination. Study on groundwater contamination risk assessment will provide the important theoretical basis for the policy-making.The risk of groundwater contamination is defined as the product of probability and consequences of the contamination. Generally, the rating of the contamination source equates to the probability component and the combination of the rating of groundwater vulnerability and groundwater value equates to consequence. A high-risk value implies that the highly valuable groundwater resource will be impacted, or has already been impacted, due to the severity of the contamination source. In accordance with this evaluation ideas, and protection and exploitation problems of groundwater in the northern coastal region of our country, study on groundwater contamination risk assessment for a regional area was conducted, taking plain area of Longkou City as an example. The main content of the thesis are as follows:(1) A comprehensive analysis and summary of the concepts about groundwater contamination risk at home and abroad were conducted, and the existing problems in studies on risk assessment were also pointed out.(2) A detailed investigation on the main types and distribution of groundwater pollution sources in the plain area of Longkou City was made. The combination of general screening approaches and object-specific approaches were applied to rate the hazard of groundwater pollution sources to be three classes: high, medium, and low. And geographical mapping was made to get the hazard rating results of pollution sources(3)From the impact factors of groundwater vulnerability, the most popular DRASTIC evaluation index system was selected to assess the groundwater vulnerability of the study area. Zoning mapping and superposition of the seven different factors were carried out, based on MAPGIS software. According to DRASTIC index, groundwater vulnerability of the study area could be divided into five levels: much higher vulnerability, high vulnerability, medium vulnerability, low vulnerability,much lower vulnerability.At last, the assessment results were analyzed.(4)The total value of groundwater is composed by "exploitation value" and "in-situ value" In this thesis, the basic analysis framework was set up with the two aspects of the total value of groundwater. Combined with the specific circumstances of the study area, five different factors, such as the population density, regional GDP per capita, groundwater quality, groundwater overexploitation degree, module of groundwater resources, were selected to establish the entropy fuzzy evaluation model. And MATLAB software was applied to calculate the score and weight of each index. According to the total score, evaluation results of value of groundwater could be obtained, based on the application of MAPGIS software.(5)After the superposition of groundwater pollution hazard rating map, groundwater vulnerability map and groundwater valuation map, the groundwater contamination risk assessment result was obtained, which was the distribution of the much higher-risk areas, the high-risk areas, the medium-risk areas, the low-risk areas and the much lower-risk areas. Then the causes of the contamination risk assessment results were analyzed and methods for groundwater contamination risk management were proposed, combined with the actual situation of the study area.