Partitioning of Semivolatile Organic Compounds in Organic and Inorganic Aerosols: A Unified ApproachEPA Grant Number: R826771
Title: Partitioning of Semivolatile Organic Compounds in Organic and Inorganic Aerosols: A Unified Approach
Investigators: Kamens, Richard M. , Chandramouli, Bharadwaj , Strommen, Michael , Jang, Myoseon
Current Investigators: Kamens, Richard M. , Chandramouli, Bharadwaj , Jang, Myoseon
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1998 through September 30, 2001
Project Amount: $562,536
RFA: Air Pollution Chemistry and Physics (1998) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air , Safer Chemicals
The objective of this work is to provide a unified model to predict the equilibrium gas-particle (G/P) partitioning of semivolatile organic compounds (SOCs) in both organic and inorganic aerosols. To do this it is necessary to: 1) implement new models for both absorptive and adsorptive behavior of SOCs, 2) provide an experimental database to evaluate these models, and 3) demonstrate that this combined model can be used and applied to a variety of different ambient situations.
At UNC a G/P absorptive (i.e., gas-liquid) partitioning model was recently implemented which uses calculated activity coefficients to estimate phase partitioning. UNC researchers have also recently made a breakthrough on the characterization of SOC partitioning onto inorganic aerosols by developing a novel adsorptive (i.e., gas-solid) model. This new approach takes advantage of linear solvation energy relationships (LSERs) and compound polarizability. Both new techniques (gas-liquid and gas-solid) provide a dramatic improvement in predictive capability over previous models for various SOCs from different compound classes (e.g., PAHs, nitro-PAHs, alkanes, aldehydes, alkanoic acids, and methoxyphenols) and different types of aerosols (e.g., diesel soot, wood soot, secondary organic aerosols, and crustal materials). Particles used in the study will be at or below the 2.5 um 50% particle size cut point (PM2.5). By simultaneously linking models for organic and inorganic aerosols with a characterization of the different particle sources contributing to an airshed, an overall partition estimate can be obtained for almost any SOC in any atmosphere. Outdoor chamber experiments with combustion, secondary, and inorganic aerosols will be conducted to develop and validate the absorptive and adsorptive models. In all cases, effects of temperature and humidity will be addressed. Partitioning in mixtures of different types of aerosols in chambers and the ambient atmosphere will also be studied. Finally, atmospheric samples will be taken from different local airsheds in the last year of this study for the purpose of modeling real atmospheres. Partitioning predictions from the ambient samples will include chemical mass balance modeling of aerosol composition and will be compared to our measured partitioning results.
This work will provide a theoretical framework and user-friendly procedure for estimating the G/P distribution of almost any SOC, whether it be a new environmental chemical for which only chemical structural information exists, a carcinogenic compound, or an environmental endocrine disrupter.
Improvement in Risk Assessment: By improving partitioning predictions, this work will greatly reduce G/P uncertainties associated with risk-based models. Currently, these models use methodologies that have order of magnitude uncertainties associated with G/P partitioning