Reconstructing the release history of a groundwater contaminant based on AT123D

The reconstruction of the source release history for groundwater contamination provides useful environmental forensic information in identifying the responsible parties for a contaminant plume at a known source location if its owner changed several times in the past. The objective of this study is to develop a novel method consisting of function-fitting technique, simulated annealing, and a fundamental solution of the contaminant transport equation given in AT123D (Yeh, 1981) to recover the source release history of a groundwater contamination. AT123D is an analytical model for simulating transient, one-, two-, and three-dimensional groundwater contaminant transport in aquifer systems. The method developed herein is for recovering the release history of a continuous and finite release duration source and therefore can handle a great variety of realistic problems. Cases with various types of source geometry and aquifer configuration are considered. The influence of contaminant biodegradation, degree of dispersion, location of monitoring well, use of temporal concentration data or spatial concentration data, and presence of two contaminated sources are also investigated. Finally, a few guidelines for the optimal sampling strategy on the reconstruction of the source release history are recommended.