HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cessna, A. J. Articles by Headley, J. V. Search for Related Content PubMed PubMed Citation Articles by Cessna, A. J. Articles by Headley, J. V. Agricola Articles by Cessna, A. J. Articles by Headley, J. V. Related Collections Agricultural Pesticides Pesticides Organic Compounds

TECHNICAL REPORTS

Organic Compounds in the Environment

Persistence of the Sulfonylurea Herbicides Thifensulfuron-Methyl, Ethametsulfuron-Methyl, and Metsulfuron-Methyl in Farm Dugouts (Ponds)

^a Environment Canada, 300-2365 Albert St., Regina, SK, Canada S4P 4K1
^b National Water Research Institute, 11 Innovation Blvd, Saskatoon, SK, Canada S7N 3H5

^* Corresponding author (allan.cessna{at}ec.gc.ca)

Received for publication December 16, 2005. Sulfonylurea herbicides are applied at relatively low rates (3 to 40 g ha^–1) to control weeds in a variety of crops across the Canadian prairies. Because of their high phytotoxicity and the likelihood of their transport in surface runoff, there is concern about their possible impact to aquatic ecosystems. Little is known, however, about their persistence and behavior in aquatic ecosystems. To assess persistence in aquatic ecosystems, three prairie farm dugouts (ponds) were fortified with either thifensulfuron-methyl {methyl 3-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]-2-thiophenecarboxylate}, ethametsulfuron-methyl {methyl 2-[[[[[4-ethoxy-6-(methylamino)-1,3,5-triazin-2-yl]amino]carbonyl]amino]sulfonyl]benzoate} or metsulfuron-methyl {methyl 2-[[[[(4-methoxy-6-methyl-1,3,5-triazinyl)amino]carbonyl]amino]sulfonyl]benzoate}. The decreasing order of persistence of environmentally relevant concentrations (1 to 4.6 µg L^–1) of these herbicides in dugout water over the June to October period was metsulfuron-methyl>ethametsulfuron-methyl>thifensulfuron-methyl. The corresponding dissipation half-lives (DT₅₀) of 84, 30, and 16 d, respectively, are in the same relative order as the recropping intervals for these herbicides. Thifensulfuron-methyl showed a biphasic dissipation with slower dissipation during the winter months. In contrast, the dissipation of metsulfuron-methyl, the sulfonylurea herbicide with the longest DT₅₀, was somewhat enhanced under winter conditions. One of the major routes of sulfonylurea herbicide dissipation was removal from the water column when dugout water was lost during hydrological discharge. The relatively long persistence of these herbicides in water indicates that partitioning into sediments was minimal, the sulfonylurea and methyl ester linkages in these compounds were resistant to hydrolysis in weakly alkaline waters, and that microbial and photolytic degradation in dugout waters were slow.

Abbreviations: HPLC, high performance liquid chromatography • LC, liquid chromatography • MS-MS, tandem mass spectrometry • ESI, electrospray ionization • MRM, multiple reaction monitoring