The recovering of the pollutant release history in heterogeneous aquifer

The increasing interest in environmental issues has led to greater attention to the quality of groundwater. The huge number of pollution events, which have been discovered in the last two decades, makes protection and restoration a basic aim. Scientific efforts in subsurface flow study have primarily focused on flow and transport characteristics and on the corresponding parameters identification issues. Since '90, besides the analysis of transport phenomena, increasing attention has been paid to the problem of recovering the release history of a pollutant because the knowledge of the pollution injection function gives information about the future pollution spread and allows a better planning of remediation action (Liu et al., 1999). Moreover, from a legal and regulatory point of view, it is also important to determine the release time period and the highest values of concentration released (Snodgrass et al., 1997); in fact, an available release history can be a useful tool for sharing the costs of remediation of a polluted area among the actors (Skaggs et al., 1994). In this work the temporal release history of a pollutant is recovered by the geostatistical methodology that was developed by Snodgrass et al. (1997) for one dimensional flow and transport; the writers (Butera et al. 2001, 2003) widened the procedure to the case of two dimensional transport, investigating also the sensitivity to different types of errors, and additional improvements as non point sources and multiple sources were developed. In this workshop new developments dealing with the recovering of the release history in heterogeneous aquifers are presented. The errors resulting from the use of the classical approach of equivalent homogeneous porous media are analyzed and, more particularly, the differences due to the use of constant dispersion coefficients or variable, in agreement with the stochastic theory of transport, are investigated both theoretically and with a numerical exampl