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.