Superfund Research Program
Geochemical Controls on the Adsorption, Bioavailability, Formation, and Long-term Environmental Fate of Polychlorinated Dibenzo-p-Dioxins (PCDDs)
Project Leader: Stephen A. Boyd
Grant Number: P42ES004911
Funding Period: 2006-2021
Final Progress Reports
Year: 2020 2012
Understanding the mechanisms of PCDD sorption to soil particles and the effects of sorption on bioavailability, serves two key purposes: First, previous studies show unequivocally that interaction with soil particles reduces the bioavailability of PCDDs, but are unable to explain why. The research team has demonstrated that bioavailability of sorbed PCDDs varies significantly among the major soil particle types, and the team now advances the hypothesis that only charcoal-like particles derived from fire are effective in reducing mammalian bioavailability. Such particles are ubiquitous in soils, which could perhaps explain previous data, and also may provide a basis for adjusting regulatory remediation goals on a site-specific basis. This may allow relaxed cleanup criteria at many sites, thereby enabling more sites to be remediated for a given budget. Second, remediation of dioxin-contaminated soils/sediments is typically expensive and destructive, relying on excavation/dredging and disposal in hazardous waste landfills. The research team is evaluating a new approach that utilizes activated carbon (AC) as a sorbent amendment to sequester dioxins in place. Interest in the use of AC amendments as a remedial option at Superfund sites is high, but the effectiveness of AC in reducing mammalian exposure has not been demonstrated. Previously, AC amendments were shown to lower aqueous-phase dioxin concentrations and reduce bioaccumulation in simple aquatic organisms. The team has demonstrated (Boyd 2017; Sallach 2019) that AC amendments eliminate dioxin bioavailability and hence the expression of dioxin toxicity in mammals. These results support hypotheses that AC can be protective of human health, potentially saving millions in remedial costs and minimizing habitat destruction.