Superfund Research Program
A Reactive Mat to Remediate Contaminated Sediments and Reduce Health Risks
Project Leader: Thomas C. Sheahan
Grant Number: R01ES016205
Funding Period: 2008-2011
Final Progress Reports
The goal of this project is to examine at the bench-top scale how effectively Reactive Core Mats (RCM) remediate and isolate polycyclic aromatic hydrocarbon (PAH) and polychlorinated biphenyl (PCB) contaminants in a sediment, and prevent overlying sediment from bioavailability of those contaminants. The research team developed the Integrated Contaminated Sediment Testing Apparatus Column (ICSTAC) to test the efficacy of the RCM when applied to a contaminated sediment layer undergoing consolidation and associated transient advective flux to overlying layers. The ICSTAC device physically models a column of contaminated sediment underlying the RCM and a layer of clean sand modeling a new biota habitat. The device allows water sampling to quantify contaminant transport. The sand layer is mixed with an organic admixture (3% by mass), which is later used for exposure testing conducted with oligochaete worms (Lumbriculus variegates) to measure bioavailability of breakthrough contaminants.
Twenty-two ICSTAC tests were conducted on sediment obtained from the Neponset River, Massachusetts, including the natural PCB-contaminated sediment and sediment spiked with PAH. Exposed worms, sands, controls, and sediment underwent chemical analysis for 54 PCB congeners. Principle Components Analysis (PCA) was used to discern possible correlations and patterns within the multi-dimensional data. Comparisons among resulting PCA plots demonstrated a consistency between the analyses and tested duplicates, as well as revealing trends in the PCB congener profiles of sand, sediments, and oligochaete samples. Further statistical analyses are underway to validate these findings.
Total PCB concentrations were similar to that of controls for the oligochaete and sand samples, indicating that breakthrough of PCBs through the RCM to the overlying sand layer did not occur under the conditions tested. ICSTAC testing of the RCM on sediments spiked with a known initial concentration of naphthalene indicate that that the RCM significantly reduced contaminant breakthrough as compared to control tests with only a sand layer and no RCM.
During the final phase of this research, a smaller, modified form of the ICSTAC device will be used for continuous upward flow through the spiked sediment and RCM. The new column will allow the research team to directly examine adsorption capacity and breakthrough potential of the RCM, which can be correlated to sorption isotherms and used in analytical modeling under development.