Date of Award
5-2024
Document Type
Thesis
Degree Name
Master of Civil Engineering (MCE)
Department
Civil Engineering
Committee Chair/Advisor
Dr. Abdul Khan
Committee Member
Dr. Brian Powell
Committee Member
Dr. Earl Hayter
Abstract
For many Superfund sites across the United States, arsenic is one of the most common contaminants of concern that must be cleaned up to protect human and environmental health. Past research and health studies have documented the harmful effects of inorganic arsenic on humans and the environment but selecting an appropriate remediation plan depends on several site-specific factors at each Superfund site. To assist in determining an appropriate remediation plan, sediment and contaminant transport models have been used to simulate the transport of arsenic and other contaminants of concern at contaminated sites to, e.g., make relative comparisons of the efficacy of different proposed remedial alternatives. This thesis describes a) the development of a three-tier contaminant fate and transport modeling system and b) the application of the model to a portion of the Maurice River watershed which includes the Vineland Chemical Superfund site in Vineland, NJ. This site is adjacent to the Blackwater Branch, a tributary of the Maurice River. This thesis also demonstrates the application of a speciation model, PHREEQC, which calculates the inorganic species of arsenic, arsenate and arenite using site-specific data from an arsenic contaminated unconfined aquifer on the Vineland Chemical site. This model serves as an important tool to assess the arsenic toxicity present at this site.
After developing and partially calibrating the three-tier modeling system, the model was used to demonstrate its ability to simulate two potential remediation alternatives for the Vineland Chemical Superfund site. The first alternative did not include any remediation except for the sediments and floodplain soils previously removed from Blackwater Branch. The second alternative included the remediated Blackwater Branch and dredging the contaminated sediments in the Maurice River from the confluence with this tributary down to Almond Road. In both alternatives, the arsenic concentration in the water column decreased throughout the model domain as the flow transported the contaminant further downstream. As for the arsenic concentration in the sediment bed approximately 1 mile [1.6 km] downstream of the confluence of the Blackwater Branch and Maurice River, both alternatives showed the exact same results concluding that the short simulation period used for this demonstration was not sufficient for comparing the long-term effectiveness of each alternative. In both alternatives, the arsenic concentration in the top layer of the sediment bed decreased as arsenic diffused into the water column and less contaminated sediment from upstream deposited onto the bed. Despite the limited data available to calibrate the three-tier modeling system and the shortness of the six-month simulations, the model results showed that quantitatively the model behaved as expected. Across the model domain, the average arsenic concentration in the sediment bed only reduced by one percent indicating that there was no significant concentration of arsenic transported downstream into Union Lake. The small percent of arsenic that was suspended and transported downstream was transported during high flow events in its colloidal bound phase and freely dissolved phase indicating that most of the arsenic sorbed to solids remained in the sediment bed. The results from PHREEQC indicated that the 16 groundwater samples collected from the Vineland Chemical Superfund site dominantly consisted of arsenate, the less toxic form of arsenic. The arsenic sorbed to the iron minerals present in the aquifer rather than dissolving into the groundwater. These results showed that there was less risk to humans because the arsenic was sorbed to the iron minerals in the aquifer and therefore less mobile.
This research demonstrated that the three-tier modeling system and PHREEQC are useful tools with separate applications, but with further investigation, future studies may use PHREEQC and contaminant transport model like that used in this study in conjunction to predict which species of arsenic are present in a highly contaminated area (hotspot) of the model domain. This could improve current arsenic transport modeling capabilities because existing arsenic transport models cannot simulate or identify arsenic species to better characterize the level of arsenic toxicity.
Recommended Citation
Eddleman, Christina, "Development and Evaluation of an Arsenic Transport Model for the Maurice River Watershed" (2024). All Theses. 4318.
https://tigerprints.clemson.edu/all_theses/4318