Research Project:
Subsurface Contamination Modeling and Remediation Techniques
University: University of Lousiville
Principal Investigator(s): Omid Ghasemi-Fare
Project Description:
More than half of the US population consumes groundwater for drinking. Thus, introducing any type of contaminants into the groundwater table can risk the lives of more than half of the population. Contaminants from multiple sources can impact the drinking water wells and other receptors. When contaminants are transferred to the groundwater, they will make their way to water wells and drinking water supplies. Soluble contaminants, such as road salts, can easily migrate into the ground, reach the groundwater, and negatively affect the shallow groundwater and freshwater systems. An increase in road salts will have a negative effect on groundwater. Recently, several private wells in the town of Orleans in New York State reported the presence of road salts that were transferred through the groundwater flow. However, non-aqueous phase liquids (NAPLs) that are not highly soluble may have considerably longer residence times in the soil zone (see Fig. 1). NAPLs are hydrocarbons and are classified into two categories: (i) light non-aqueous phase liquids (LNAPLs), which have less density than water, and (ii) dense non-aqueous phase liquids (DNAPLs), which are denser than water. In either case, a physical interface between the water and NAPLs prevents the mixing of groundwater and contaminants (see Fig. 2).
Figure 1: Contaminations scenarios from LNAPL and DNAPL
Figure 2: Distribution of NAPL contaminants in (a) unsaturated and (b) Saturated soils
In this proposed study, a finite element model (FEM) will be developed to analyze contaminant transport within the vadose zone and saturated zone. The developed multiphase fluid flow models will be used to study the movement of soluble contaminants, such as road salts, as they precipitate downward to the groundwater table. Additionally, the FEM model will be further modified to capture the flow of NAPL contaminants through the soil medium. The proposed research project consists of three phases: (1) Developing and validating an FEM that can simulate the movement of precipitation and rainfall from the ground surface and unsaturated zone into the groundwater. (2) Modifying the developed FEM model to analyze the contaminants flow in the soil medium by considering the advection and the interplay of diffusion limitation, adsorption, and partitioning between contaminants and soil. (3) Reviewing and proposing several remediation techniques for various contaminants, depending on the specific job site, to be employed in practical sites selected by local and state level DOTs.
Outputs:
This project aims to predict the transport of both soluble contaminants (e.g., road salts) and non-aqueous phase liquids (NAPLs) contaminants (e.g., gasoline and diesel) in subsurface conditions. Most contaminants are introduced into the ground through stormwater, rainfall, or spills (e.g., leaks from gas tanks). The primary objective of this project is to forecast the potential risk of a contaminated drinking water supply due to the flow of contaminants from various sources. Subsequently, based on site characterizations and the nature of contaminants, several remediation techniques will be proposed for implementation at the job site.
Outcomes/Impacts:
This research provides a reliable model that can predict soil and groundwater toxicity when exposed to a variety of contaminants stemming directly and indirectly from the transportation sector. These contaminants include leakages from aboveground storage tanks, spills from gas stations, road salts, and chemical deicers. The developed model will prove valuable to local DOTs and federal level agencies, aiding in the prediction of contaminant concentrations (e.g., salt concentrations) in groundwater. Moreover, it will estimate the extent of subsurface contaminated zones, ensuring they do not encroach upon drinking water supplies like wells. A specific site will be selected for model validation and to propose remediation techniques if necessary. Research findings will be disseminated through peer-reviewed journal articles, conference publications, and teaching modules for undergraduate students. Additionally, this project contributes to the prevention of soil and groundwater contamination.
The proposed research facilitates modeling of subsurface contaminant flow and implementing necessary remediation actions to avert the risk of groundwater contamination. Furthermore, it assists DOTs in monitoring the potential migration of road salts into private wells, thus helping maintain their integrity.
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