Sorption/Desorption Kinetics and Access to Transient Reactants Photochemically Generated from Natural Dissolved Organic MatterEPA Grant Number: R825219
Title: Sorption/Desorption Kinetics and Access to Transient Reactants Photochemically Generated from Natural Dissolved Organic Matter
Investigators: Burns, Susan E.
Institution: Western Michigan University
EPA Project Officer: Hahn, Intaek
Project Period: November 1, 1996 through October 30, 2001
Project Amount: $461,023
RFA: Exploratory Research - Early Career Awards (1996) RFA Text | Recipients Lists
Research Category: Early Career Awards
In natural waters, hydrophobic association (sorption) to natural dissolved organic matter (DOM) can give sorbed contaminants access to activities of DOM-photogenerated transient reactants different from those encountered by contaminants not sorbed to DOM. Such differential access may mean that contaminants sharing the same reactivity have radically different degradation rates in natural waters. This project will determine the relationship between the equilibrium partition coefficients that describe sorption to DOM (KDOC), the kinetics of sorption to and desorption from DOM, and the access contaminants have to both hydrated electrons generated by DOM and hydroxyl radicals generated by DOM and nitrate. Measurement of KDOC and sorption/desorption kinetics for a series of compounds of environmental interest (e.g., PAHs, PCBs, pesticides) will be combined with measurements of the apparent reactivites of those compounds inside and outside of Lake Michigan DOM. The same measurements also will be made using the readily available Aldrich humic acids as a reference DOM. A purely kinetic method will be used to determine apparent access to hydroxyl radicals in solutions of DOM and DOM+nitrate. For access to hydrated electron in DOM solution, this kinetic method will be supplemented with direct, spectroscopic observation of hydrated electron consumption as an independent check on the purely kinetic method. The combined results will be incorporated into a general kinetic model relating the readily measurable KDOC to the ability of DOM to mediate the photodegradation of organic pollutants in natural waters.