Duke University
Project 5
Title:Fate, Transport, and Exposure Risk of Superfund Chemicals
PI: Andrew Schuler, Ph.D.
Repeated detection of polar and ionogenic organic contaminants (P/IOCs) on the 1997 CERCLA Priority List of HAzardous Substances in surface and ground water and knowledge of their potential toxicity and carcinogenicity emphasizes the urgency for an improved understanding of contaminant fate and transport at the field scale. The interrelationship between the chemical structure of a contaminant and its environmental behavior is relatively well established for recalcitrant hydrophobic organic contaminants (HOCs) at the laboratory scale, while similar relationships for polar/ionogenic contaminants are being developed. The utility of these relationships at the field scale is limited by the spatial variability in subsurface composition and physico-chemical properties. Furthermore, the risk of organic contaminant exposure to humans and wildlife precludes the intentinal release of these contaminants into the natural environment for purposes of understanding field scale fate and transport processes. Hence, it is important to understand the environmental behavior of conservative and sorbing innocuous tracers (or surrogates) that may be intentionally released into the field for research purposes. Structural similarity between Rhodamine WT (and EPA approved fluorescent dye) and several polar/ionogenic contaminants warrants a study of the environmental behaviour of polar/ionogenic contaminants and RWT on both the laboratory and the field scale. Furthermore, extensions of field scale transport of RWT to previously established environmental behavior of HOCs (DDT/DDE, dieldrin, kepone, PCB#126, benzo[a]pyrene, investigated in Projects 2,3, & 4) can also be explored.
Graduate Student Ryan Fimmen with the HPLC
instrument used to analyze content of field samples.
The Specific Aims of this project are:
1. To conduct a multi-scale physico-chemical characterization of the surface and subsurface in and around two North Carolina Superfund field sites.
2. To identify abiotic interfacial processes expected to attenuate or mobilize the test contaminants and Rhodamine WT (together referred to as solutes) within representative subsurface matrices.
3. To conduct laboratory scale (mass) transport studies of Rhodamine WT (RWT), lithium, bromide, and test contaminants in representative subsurface matrices.
4. To employ inverse modeling in laboratory column studies to estimate the physico-chemical properties of the subsurface and the parameters describing equilibrium and non-equilibrium interfacial processes.
5. To relate the observed similarities and differences in the
environmental behavior of RWT and the test contaminants to the compounds’
physical-chemical properties and to molecular and spatial physico-chemical
variability of the subsurface environments.
6. To test existing models and formulate new forward and inverse mathematical models that describe the fate and transport of RWT and Superfund chemicals at the two sites.
7. To obtain a field scale characterization of solute transport by conducting field injection tests of RWT at the Superfund sites.
8. To utilize field data on RWT as a vehicle to upscale laboratory scale data on the test contaminants to the field scale.
9. To formulate a field-scale stochastic fate and transport model for Superfund chemicals to estimate concentration exceedence probabilities in ground and surface waters, and translate these probabilities to human and wildlife exposure risk.