Integral quantification of contaminant mass flux in groundwater - conditioning of the numerical inversion of concentration-time series of integral pumping tests

摘要

a series of integral pumping tests (IPts) were conducted at a former gasworks site to quantify the contaminant mass flux and average concentration in groundwater along three control planes. the resulting concentration-time series were analysed numerically with the help of the inversion code CSTREAM and a flow and transport model representing the highly heterogeneous aquifer. Since the control planes cover the entire downstream width of the potentially contaminated area, they allow conclusions to be drawn about the current location and spread of the contaminant plume. Previous evaluations of integral pumping tests could calculate three scenarios concerning the spread of the plume around the IPt well: (i) the plume is located to the right of the well, (ii) to the left, or (iii) is distributed symmetrically around it. to create a more realistic picture of the plume position, a series of direct-push monitoring wells were installed along one control plane. the concentrations found in these wells were included in the numerical analysis to condition the inversion results, and resulted in a more pronounced plume centre and fringe, which supports the development of optimised remediation strategies.