Reductive Transformation of Agrochemicals in Model Aqueous Systems: Role of Ferrous Iron SpeciationEPA Grant Number: U915172
Title: Reductive Transformation of Agrochemicals in Model Aqueous Systems: Role of Ferrous Iron Speciation
Investigators: Strathmann, Timothy J.
Institution: The Johns Hopkins University
EPA Project Officer: Carleton, James N
Project Period: September 1, 1997 through August 1, 2000
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1997) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Engineering and Environmental Chemistry , Fellowship - Civil/Environmental Engineering
The objective of this research project is to examine the abiotic reductive transformation rates of carbamate pesticides (oxamyl, methomyl, and aldicarb) in the presence of various soluble and mineral-adsorbed Fe(II) species present in aqueous-soil environments.
Kinetic experiments will be conducted in clean and sterilized anaerobic aqueous solutions to examine the potential for various Fe(II) species to reduce carbamate pesticides in anaerobic environments. Effects of Fe(II) speciation will be determined by measuring pseudo first-order rate constants for pesticide reduction in the presence of: (a) Fe(+2) alone; (b) Fe(+2) + organic ligands known to be present in soil environments (e.g., citrate and oxalate); (c) Fe(+2) + well-characterized mineral surfaces (e.g., Si, Al, and Fe-oxides); and (d) Fe(+2) + electron-transfer mediators (e.g., quinones). By varying solution conditions (e.g., pH, Fe[II] concentration, ligand concentration, and mineral loading), second-order rate constants for reduction by each Fe(II) species will be calculated. The second-order rate constants will be used to evaluate the relative importance of the various Fe(II) species for controlling agrochemical fate in the environment. Control experiments will be conducted under the same conditions (e.g., pH, buffer concentration, mineral surface) in the absence of Fe(II) to account for pesticide transformation processes not involving the Fe(II). For selected reactions, the temperature dependence of the rate constants also will be evaluated. Pesticide disappearance and product formation will be monitored by high-performance liquid chromatography with UV detection. Transformation products will be characterized by chromatographic comparison with authentic standards or from mass spectral analysis.