The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is used in aquatic systems as a treatment for invasive Eurasian watermilfoil. However, the degradation rate and resulting lifetime of 2,4-D can vary widely, with complete degradation in Wisconsin lakes ranging from 70 to 150 days. This variability may increase the risk for off-target effects to fish and aquatic plants due to unintended long exposure times. We used a combination of laboratory and field-based studies to investigate the dominant mechanisms of degradation of 2,4-D in aquatic systems. Microbial and photochemical degradation were individually assessed using laboratory-based microcosms and irradiation studies, respectively. Additionally, field campaigns were conducted in six lakes to quantify 2,4-D loss following whole-lake herbicide treatments. Initial results suggest sediment microbial communities are instrumental to 2,4-D degradation at the sediment water interface. Furthermore, previous treatment of a lake with 2,4-D can shorten the lag time between initial 2,4-D exposure and the start of degradation, likely due to selection pressures favoring 2,4-D degraders. Irradiation studies show that 2,4-D is primarily susceptible to indirect photochemical degradation in the presence of sunlight. Additionally, the primary metabolites from microbial degradation undergo relatively rapid photodegradation, suggesting that both bacterial degradation and photodegradation contribute to the transformation of 2,4-D and its major products in aquatic systems. These results will be used to determine environmentally relevant 2,4-D degradation mechanisms to optimize the application of 2,4-D and support decision making related to whole-lake herbicide treatments.

New insights to the degradation of 2,4-dichlorophenoxyacetic acid when applied to whole-lake treatments

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.