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
Contaminated sediments present a global public health challenge that requires new, innovative approaches. Under this project, the research team achieved their long-term objectives of research, particularly a new type of permeable, reactive geocomposite for remediation and management of contaminated sediments.
The reactive core mat (RCM), which consists of one or more filtering layers surrounding a reactive layer, can be placed on the sediment surface. By immobilizing and/or neutralizing contaminants, the composite can minimize further contaminant migration and, in subaqueous environments, contaminant resuspension and diffusion into the overlying water column. This will limit the bioavailability of contaminants and bioaccumulation in aquatic food webs, which can be a pathway for human exposure via ingestion.
Two types of bench-scale testing devices were also developed. The Integrated Contaminated Sediment Testing Apparatus Column (ICSTAC) and a continuous flow rate, up flow column device were designed and completed during the project. Both devices were designed to physically model the sediment-RCM-surcharge soil column. The research team sampled natural contaminated sediments and spiking operations in the Neponset River behind Tilestone and Hollingsworth Dam.
The bench-scale testing from this project indicate that the application of the RCM on PAH- and PCB-contaminated aquatic sediment results in significant reductions in the bioavailability of contaminants in both the overlying soil and water column when compared to sand caps. A consolidation-coupled contaminant transport model developed in this project accurately depicts bench-scale results and was effectively used in a field case study to demonstrate potential scalability to predict aquatic sediment remediation efficacy.
The ICSTAC tests showed that in bench-scale tests, RCM capping effectively isolated contaminant breakthrough from capped sediment to the biogeneration zone and overlying water column. Up flow column tests results indicated that the RCM provides isolation of contaminants associated with sediment under conditions of significant upwelling gradient (i.e., submarine discharge, tidal up flow) by exhibiting delayed breakthrough of contaminants into overlying soil and water column when compared to sand capping alone. Finally, bio-uptake tests on post-test sediment and initially clean sand layer showed significant reduction in bioavailability of contaminants.
A consolidation-coupled contaminant transport model was also developed in this project that accurately depicted bench-scale results. The model was effectively used in a field case study to demonstrate potential scalability to predict aquatic sediment remediation efficacy.