Dissolution Dynamics and Temporal Variations of Groundwater Flux in the Subsurface Source Zone of Nonaqueous Phase Liquids

Abstract

Widespread production and use of industrial solvents and liquid petroleum products have created problems of subsurface contamination by nonaqueous phase liquids (NAPLs). The objective of this study is to relate NAPL dissolution dynamics to temporal variations of groundwater flux in the NAPL source zone. The approach is based on the idea that the source zone NAPL mass discharge into the aqueous phase is related to the temporal variations of the NAPL source zone groundwater flux. By incorporating this new idea, the NAPL source dynamics including source zone contaminant concentrations, reduction in the NAPL mass discharge to the aqueous phase, reduction in the NAPL mass in the source zone can be effectively related. In illustrating the new model development, an exponential form of the NAPL source zone groundwater flux is used to accommodate a range of potential temporal variations of groundwater flux. These models simply predict how NAPL source zone characteristics change with time, which can be easily used in modeling subsequent fate and transport. The models developed have automatically taken in account the requirement of NAPL mass conservation. Based on the developed models, this paper discusses how source zone contaminant concentrations, NAPL mass discharge, and remaining NAPL mass in the source zone are interrelated. Preliminary comparison with field data demonstrates that the models are capable of capturing the source zone NAPL discharge dynamics.