Lumped Chemical Approach for Fate and Transport Modeling of Organic Pollutant MixturesEPA Grant Number: R829355
Title: Lumped Chemical Approach for Fate and Transport Modeling of Organic Pollutant Mixtures
Investigators: Reardon, Kenneth F. , Shackelford, Charles D. , DuTeau, Nancy M.
Current Investigators: Reardon, Kenneth F. , Shackelford, Charles D. , Pruden, Amy
Institution: Colorado State University
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 2001 through September 30, 2004 (Extended to January 31, 2006)
Project Amount: $721,695
RFA: Complex Chemical Mixtures (2000) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management , Safer Chemicals
Accurate risk assessment and effective risk management rely upon knowledge of contaminant transport and fate. While this is a difficult task for single chemicals, it is much more challenging for mixtures. The primary goal of this research project is to evaluate a promising method for modeling the transport and fate of organic chemical mixtures: the use of lumping analysis to group chemicals into "pseudocompounds", which are then modeled in place of the original mixture components. The user of this method has the flexibility to choose their desired position on the tradeoff between simplicity and accuracy. Specific chemicals can easily be isolated from groups. A secondary goal is to evaluate microbial community changes and changes in biodegradation rates along the flow path of a model aquifer system (soil column). The primary hypotheses of this research are: (1) The lumped chemical approach can successfully be used with models of transport and fate in aquifer environments, and (2) The microbial community will be different at different points along the flow path, and these changes will be significant for models of the biodegradation rate. Four objectives will be addressed to test these hypotheses: (1) Expand/refine our previous lumped chemical model for biodegradation kinetics, (2) Determine mixture transport properties, (3) Evaluate mixture transport and fate in soil columns, and (4) Develop lumped chemical modeling for the transport and fate of the organic chemical mixture.
To carefully establish the utility of lumped chemical modeling, the research outlined in this proposal uses a model system of a 13-chemical mixture (benzene, toluene, ethylbenzene, chlorobenzene, o- and m-xylene, o- and m-cresol, phenol, naphthalene, diethyl and dibutyl phthalate and phenanthrene), a stable microbial community, and a set of model soils. The work consists of two kinds of experiments (suspended cell batch cultivations and soil column tests) and mathematical modeling/simulation. The experimental results will guide the development of the lumped chemical model, and some of the Objective 3 data will be reserved for validation of the model. The research will be performed by a multidisciplinary team of engineers and scientists.
This project will demonstrate the effectiveness and utility of the lumped chemical approach for contaminant transport and fate modeling, a potentially powerful tool that would improve risk assessment and facilitate risk management. In addition, our work will suggest useful strategies for forming pseudocompounds and for model development in an imperfectly lumpable system. This project will produce knowledge on the changes in a microbial community with time during batch biodegradation and distance in soil column tests, as well as knowledge about mixture effects on sorption and transport of organics and the impact of soil composition on those effects.