江汉平原浅层地下水防污性能模糊综合评价与验证

Fuzzy comprehensive evaluation and its validation for shallow groundwater vulnerability in Jianghan Plain

为开展江汉平原浅层地下水防污性能评价,以江汉平原沙洋-旧口地区浅层地下水为研究对象,针对传统DRASTIC模型评价指标存在关联性、权重主观性强、评分值缺乏连续性以及评价结果缺乏实测数据验证等缺点,考虑研究区实际条件,建立了基于改进DRASTIC模型的模糊综合评价模型,并利用研究区浅层地下水关键污染因子Cl^-、NO3^-和NH4^+实测数据验证了模型的准确性和可靠性。该模型使用包气带黏性土厚度代替包气带介质指标,含水层厚度代替含水层介质指标、土壤饱和渗透系数代替土壤介质指标,采用全定量评价指标体系,评价指标更加客观、合理;采用三标度层次分析方法确定各评价指标权重,减少了传统DRASTIC模型人为确定权重的主观性;在改进的DRASTIC模型基础上,引入模糊数学理论,以隶属度函数代替传统DRASTIC模型固定评分值,克服了传统DRASTIC模型使用定额评分带来的不连续性。模糊综合评价结果表明:研究区浅层地下水防污性能整体表现为差-较差,占研究区总面积的76.53%。研究结果可为平原地区开展浅层地下水脆弱性评价提供方法参考,为江汉平原浅层地下水污染防治工作提供科学依据。

Taking shallow groundwater of shayang-jiukou area in Jianghan plain as the research object to evaluate shallow groundwater vulnerability of Jianghan plain,is directed against the shortcomings of the traditional DRASTIC model,suchas strong relevance and weight subjectivity of evaluation indexes,discontinuity of the scoring values,and absence of measured data verification to the evaluation result.Considering the reality in the study area,a fuzzy comprehensive evaluation model is established on the basis of the improved DRASTIC model,and the accuracy and reliability of the model are verified by key pollution factors such as Cl-,NO-3 and NH4+in shallow groundwater.In this model,a new quantitative evaluation index system was built to make the evaluation indexes more objective and reasonable,which the impact of the vadose zone media,aquifer media and soil media were replaced by the thickness of cohesive soil in vadose zone,thickness of aquifer and soil saturated hydraulic conductivity respectively.The three-scale AHP method was adopted to determine the weight of each index,which reduced the subjectivity of the index weights from the traditional DRASTIC model.Based on the improved DRASTIC model,a fuzzy mathematics method was introduced,and the fixed scoring values of the indexes were replaced by the subordinating degree function to overcome the discontinuity of traditional DRASTIC model for using the quota scoring.The fuzzy comprehensive evaluation result showed that vulnerability evaluation of shallow groundwater in the study area is poor or comparatively poor on the whole,accounting for 76.53%of the study area.This research can provide method reference for shallow groundwater vulnerability evaluation in plain regions and scientific evidence for the prevention and control of shallow groundwater pollution in Jianghan Plain.