A case against K-d-based transport models: natural attenuation at a mill tailings site
This study compares numerical modeling results of contaminant transport using a multi-component coupled reactive mass transport model and a distribution coefficient (K-d)-based transport model. The study site is a contaminated groundwater aquifer underneath a uranium mill tailings pond in the western USA. Advective-dispersive-reactive transport is simulated for a 5-year period of intrusion of tailings fluid into the shallow aquifer, followed by flushing with uncontaminated upgradient groundwater for 1600 years. The coupled model shows that groundwater-sediment interactions result in multiple concentration waves, strong interactions among solutes, and chemical heterogeneity in both space and time. As a result, calculated K-d values vary spatially and temporarily. None of these characteristics can be simulated with a K-d-based model. These results illustrate the shortcomings of the K-d approach, the usage of which is prevalent in the regulatory environment. (C) 2003 Elsevier Science Ltd. All rights reserved.
transport contaminant geochemical modeling coupled processes