Journal article
Photochemical Transformations of Dichloroacetamide Safeners
Environmental science & technology, Vol.53(12), pp.6738-6746
06/18/2019
DOI: 10.1021/acs.est.9b00861
PMID: 31117539
Abstract
Dichloroacetamide safeners are commonly added to commercial chloroacetamide herbicide formulations and widely used worldwide, but their environmental fate has garnered little scrutiny as a result of their classification as "inert" ingredients. Here, we investigated the photolysis of dichloroacetamide safeners to better understand their persistence and the nature of their transformation products in surface waters. High-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy were used to characterize photoproducts. Of the four commonly used dichloroacetamide safeners, only benoxacor undergoes direct photolysis under simulated natural sunlight ( t
∼ 10 min). Via a photoinitiated ring closure, benoxacor initially yields a monochlorinated intermediate that degrades over longer irradiation time scales to produce two fully dechlorinated diastereomers and a tautomer, which further photodegrade over several days to a structurally related aldehyde confirmed via NMR. Dichlormid, AD-67, and furilazole were more slowly degraded by indirect photolysis in the presence of the photosensitizers nitrate, nitrite, and humic acid. Reactive entities involved in these reactions are likely hydroxyl radical and singlet oxygen based on the use of selective quenchers. These safeners also directly photolyzed under higher energy ultraviolet (UV) light, suggesting their potential transformation in engineered systems using UV for disinfection. The finding that dichloroacetamide safeners can undergo photolysis in environmental systems over relevant time scales demonstrates the importance of evaluating the fate of this class of "inert" agrochemicals.
Details
- Title: Subtitle
- Photochemical Transformations of Dichloroacetamide Safeners
- Creators
- Andrew E Kral - Department of Civil & Environmental Engineering , University of Iowa , 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City , Iowa 52242 , United StatesNicholas C Pflug - Department of Chemistry , University of Iowa , E331 Chemistry Building, Iowa City , Iowa 52242 , United StatesMonica E McFadden - Department of Civil & Environmental Engineering , University of Iowa , 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City , Iowa 52242 , United StatesGregory H LeFevre - IIHR-Hydroscience & Engineering University of Iowa , 100 C. Maxwell Stanley Hydraulics Laboratory, Iowa City , Iowa 52242 , United StatesJohn D Sivey - Department of Chemistry , Towson University , 543 Smith Hall, Towson , Maryland 21252 , United StatesDavid M Cwiertny - Public Policy Center , University of Iowa , 310 South Grand Avenue , 209 South Quadrangle, Iowa City , Iowa 52242 , United States
- Resource Type
- Journal article
- Publication Details
- Environmental science & technology, Vol.53(12), pp.6738-6746
- Publisher
- United States
- DOI
- 10.1021/acs.est.9b00861
- PMID
- 31117539
- ISSN
- 0013-936X
- eISSN
- 1520-5851
- Grant note
- P30 ES005605 / NIEHS NIH HHS
- Language
- English
- Date published
- 06/18/2019
- Academic Unit
- Center for Health Effects of Environmental Contamination; Civil and Environmental Engineering; IIHR--Hydroscience and Engineering; Public Policy Center (Archive); Chemical and Biochemical Engineering
- Record Identifier
- 9983997434602771
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