Calculation of resident groundwater concentration by post-processing particle-tracking results

A post-processing technique that allows relatively simple random walk particle-tracking results to be extrapolated to transport scenarios of considerably more complexity has traditionally been used to calculate flux at specified monitoring locations. Previous extensions of the post-processing approach to calculate resident groundwater concentrations could not disentangle concentrations of mobile and immobile mass in dual-porosity systems, which limited their utility. A variant of the post-processing method that allows for the calculation of resident concentrations of mobile and immobile mass is introduced and tested. The resulting combination of methods—random walk particle tracking without retention processes followed by post-processing to add the effects of retention—is a powerful and practical strategy for assessing the transport of radionuclides or other contaminants in field-scale applications.