DOI

10.17077/etd.f5ku19pc

Document Type

Thesis

Date of Degree

Spring 2018

Degree Name

MS (Master of Science)

Degree In

Civil and Environmental Engineering

First Advisor

Cwiertny, David M.

First Committee Member

LeFevre, Greg

Second Committee Member

Lehmler, Hans-Joachim

Abstract

Safeners are widely used ingredients in commercial herbicide formulations, but their environmental fate has garnered relatively little scrutiny because of their classification as “inert” by the US EPA. Here, we investigated the photolysis of one popular class of safeners, dichloroacetamides, to better understand their persistence and formation potential for bioactive transformation products in surface waters. Of four commonly used dichloracetamide safeners only benoxacor underwent direct photolysis. Benoxacor had a half-life of 7.7 min when irradiated at pH 7, thus photolysis will likely be an important fate pathway in surface waters. Other dichloroacetamide safeners AD-67, dichlormid, and furilazole, while resistant to direct photolysis, were slowly degraded by indirect photolysis pathways in the presence of common photosensitizers including nitrate, nitrite, and humic acids. Half-lives of these compounds were greater than 8 hours. Reactive entities involved in these reactions are likely •OH and 1O2 as verified by selective quenchers, such as isopropanol (•OH) and sodium bromate (1O2). Where possible, we identified photoproducts using NMR and high-resolution mass spectrometry. Only benoxacor photolysis yielded detectable and identifiable transformation products. These products were generally more polar, and were entirely dechlorinated through photolysis, suggesting they are likely to have limited bioactivity relative to benoxacor.

Pages

xii, 102 pages

Bibliography

Includes bibliographical references (pages 100-102).

Copyright

Copyright © 2018 Andrew Kral

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