土壤地下水环境损害因果关系判定方法及应用

因果关系判定是环境损害鉴定评估的关键环节. 为了应对我国日益增加的土壤、地下水环境损害事件和诉讼需求,开展土壤与地下水环境损害因果关系判定技术方法研究十分必要. 环境损害因果关系判定主要是通过构建污染源到受体的途径,来确定污染源与损害之间的关联性. 基于该原则,结合土壤地下水调查评估实践,构建了土壤和地下水环境损害鉴定评估过程中因果关系判定的技术框架,包括源和受体中污染物的同源性分析、污染物在污染源与受体之间传输载体和介质的识别、传输污染物的载体的运动方向和污染物浓度梯度方向的确定、污染物在源和受体之间迁移途径的连续性和完整性分析4个步骤. 同源性利用指纹图谱、多元统计、同位素等方法进行分析,载体和介质基于地质和水文地质调查、污染调查等手段识别,载体和污染物迁移方向判断以及迁移途径连续性和完整性分析通过空间模拟等技术实现. 将所构建的技术框架和方法在某企业与下游池塘污染事件案例中进行应用,指纹图谱分析结果显示,污染源(企业)和受损资源(池塘水体)中污染物主要为Zn,具有同源性；通过地质和水文地质调查识别出污染物传输的载体和介质为土壤和地下水；运用取样分析和空间模拟方法判断载体的运动方向为污染源向载体的方向,但地下水Zn污染羽在该方向上不连续；进一步结合影像分析、地质条件分析、人员访谈等,证实迁移途径不连续的原因为存在优势通道,最终判定污染源(企业)与下游池塘污染之间确实存在因果关系. 案例应用也证实了该研究所提出的技术框架的合理性与可行性. 

Determining Causality of Soil and Groundwater Damage

Abstract: Identifying causality of pollution sources and receptors is a key step in assessing environmental damages. In order to cope with the increasing events and litigation needs around soil and groundwater damage, it is necessary to explore the technologies and methods to identify the causation of soil and groundwater damage. The causality judgment of environmental damage is mainly through seeking the path from pollution sources to receptors, so as to determine the relationship between pollution sources and damages resulting from environmental contamination. Based on the above principle, we put forward a technical framework to identify the causation from assessing the environmental damages of soil and groundwater after an investigation on the soil and groundwater. The framework includes four steps:1) homology analysis of the pollution sources and receptors; 2) identification of the transmission carriers and mediums in charge of transporting the pollutants from pollution sources to receptors; 3) confirming the motor direction of transmission carriers and concentration gradient direction of pollutants; and 4) analyzing the continuity and integrity of the migration path of the pollutants from the pollution sources to receptors. Fingerprints, multivariate statistics and isotopic analysis were used for homology analysis; carriers and mediums were identified through geological and hydrogeological investigations, as well as pollution surveys; migration direction and the continuity of migration path were analyzed using space simulation and other techniques. The framework was implemented in practice in a case about a contamination event of a pond which is located downstream to an enterprise. The results showed that the pollutant zinc (Zn, a primary pollutant) from the pollution source (enterprise) and receptor (water of the pond) were homological based on a fingerprint analysis. We also surveyed the geological and hydrogeological conditions, found that the transmission carriers and mediums of zinc were soil and groundwater, and confirmed the motor direction of transmission carriers was from source to receptor. While the groundwater Zn contamination plume was not consistent judging from the results of a sampling analysis and a space simulation method, we analyzed the reasons about the spatial discontinuity of the migration path of Zn based on some analysis including image analysis, geological condition analysis and dominant channel analysis. Taken together, we considered that there is a certain relationship between the enterprise and the pollution of downstream pond. The success in the application of this technical framework to the current case also proved its reasonability and feasibility.