oa Evaluation of contaminant transport and vulnerability of groundwater using the emission-transmission-immission-concept (ETI)

The evaluation of the contaminant transport is dictated by the Federal Soil Protection Regulation (BBodSchV, 1999) for sites that are suspected to endanger the groundwater. Vulnerability maps are often used for this evaluation. However, vulnerability maps consider the intrinsic vulnerability according to different methods taking some soil properties into account. Such qualitative method is not accurate when it comes to calculate the contaminant transport and looking at the specific vulnerability. Within the framework of a research project, a new investigation concept for the prediction of contaminants input into the groundwater was developed. This concept considers the estimation of the emission (E) of the contaminants, i.e., the time dependent amount and concentration of the leachate of the contamination source. The amount of leachate can be estimated by the infiltration of the groundwater recharge for every hydrological year using hydrological parameters. The expected concentration can be obtained from elution tests. In a second step, the transmission (T), i.e., the pollutant transport through the unsaturated zone into the groundwater is evaluated. This evaluation considers the transport mechanisms advection, diffusion and the retardation potential of the transmission zone. As a result, the immission (I) into the groundwater, the amount and concentration of the contaminants input can be estimated. Finally, it is important to evaluate the sensitivity of the system by classifying the groundwater according to the source value. This evaluation technique comprises a characterization of the site and an estimation of the contamination potential by conducting laboratory and in-situ tests and a numerical simulation modelling involving iteration for a contaminant mass balance. In this paper, a new testing method in a diffusion cell for the determination of the characteristic parameters for the transport mechanisms including the retardation potential is described and an evaluation concept for the contaminant transport based on the testing results is presented and discussed.