Redox Status and Degradation Kinetics of Representative Triazine and Urea Herbicides in Soil-Water SystemsEPA Grant Number: R824008
Title: Redox Status and Degradation Kinetics of Representative Triazine and Urea Herbicides in Soil-Water Systems
Investigators: Jayaweera, Gamani R. , Biggar, James W. , Spurlock, Frank
Current Investigators: Jayaweera, Gamani R. , Biggar, James W. , Rolston, Dennis E. , Spurlock, Frank
Institution: University of California - Davis
EPA Project Officer: Hiscock, Michael
Project Period: October 1, 1995 through September 1, 1998
Project Amount: $350,653
RFA: Exploratory Research - Chemistry and Physics of Water (1995) RFA Text | Recipients Lists
Research Category: Water , Land and Waste Management , Engineering and Environmental Chemistry
Description:This project is designed to evaluate the significance of soil redox status in the transformations of two model herbicide compounds, atrazine (s-triazine) and diuron (substituted phenylurea), which are being used extensively in the United States and have been detected in both surface and groundwater systems. This project specifically proposes to evaluate: (a) significance of sequential environmental changes in redox conditions on the transformations of atrazine and diuron transient redox conditions of aerobic-anaerobic-aerobic transition, (b) fate of atrazine and diuron under alternate electron acceptors steady state redox conditions at denitrifying (nitrate reducing), manganese reducing, iron reducing, sulfidogenic (sulfate reducing) and methanogenic (carbon dioxide reducing) conditions, (c) role of acclimation in atrazine and diuron transformations, (d) role of soluble organic carbon in influencing microbial degradation of these herbicides, (e) the decoupling of microbial and chemical transformation processes of these compounds, (f) the transformation pathways of atrazine and diuron under various environmental redox conditions, and (g) estimate the half-lives of atrazine and diuron under redox conditions.
These studies will be conducted using a flow-through system, which has been developed recently to evaluate chemical transformations under both steady state and transient state redox conditions.
This research will evaluate the relative importance of anaerobic and aerobic degradation on the fate of atrazine and diuron in soils and aquifers and contribute to the solution of groundwater contamination problems in many parts of the United States. The degradation studies that will be conducted during an aerobic-anaerobic-aerobic transition will provide information on the real world situations in vadose zone and aquifers. The quantitative information from this study can be incorporated into existing computer models to improve the prediction capabilities of the fate of herbicides under aerobic and anaerobic environments. The understanding of atrazine and diuron degradation pathways under transient and steady state redox conditions associated with improvements in the herbicide fate models may lead the regulatory agencies, environmentalists and agriculturists to develop field strategies to control the entry of these widely used herbicides into ground and surface water systems to preserve the quality of the environment.