Assessing Conceptual Models for Subsurface Reactive Transport of Inorganic Contaminants

In many subsurface situations where human health and environmental quality are at risk, scientists and engineers are tasked with predicting the fate of chemical species under conditions where reactions and transport are critically important. A working group was formed by representatives from various federal agencies to assess the role of reactive transport modeling (RTM) in these contexts. The primary objectives were to evaluate the current state of conceptual model development and parameterization for RTM in soil, vadose zone, and groundwater systems, and to identify research directions to enhance the utility of RTM. The working group addressed the complexities associated with the fate of reactive solutes in spatially and temporally variable subsurface properties and their influence on physical processes and biogeochemical reactions. Through literature review, internal meetings, and a sponsored workshop, the group focused on conceptual model evaluation rather than numerical methods or computer code comparisons. Key findings highlight the limitations in characterizing subsurface property variability and emphasize the need for calibration against field observations to improve model predictions. Ultimately, addressing these research issues could significantly enhance RTM applications for public health, leading to better decision-making and cost savings for federal agencies.