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

Abstract

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 microg 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 (DT(50)) 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 DT(50), 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.

Effects of a herbicide mixture on primary and bacterial productivity in four prairie wetlands with varying salinities: An enclosure approach

“…The target concentration or the expected environmental concentration (EEC) of each herbicide in the treatment enclosures was based on 100% direct overspray of herbicide at recommended field application rate on a 0.5-m deep wetland (Cessna et al, 2006). Assuming minimal herbicide concentrations in the wetland when the overspray occurs, the resulting EEC due to overspray should represent a maximum exposure scenario for aquatic flora and fauna.…”

Adsorption and desorption characteristics of monosulfuron in Chinese soils

“…Sulfonylurea herbicides are widely applied in the controlling of several broad-leaved weeds and some grasses in a variety of crops due to their low application rates (3-40 g ha −1 ) and good crop selectivity [1][2]. However, these remained chemicals are highly phytotoxic to some rotational plants at only 1% or even less of the originally applied amount, resulting in growth inhibitions of certain rotational crops or fruit trees [1,[3][4].…”

Chemical Analysis of Pesticides Using GC/MS, GC/MS/MS, and LC/MS/MS

“…As a general rule the choice of positive or negative mode depends upon polarity and acidity of analytes and sample matrix impacts. In general, ESI-is more sensitive for phenoxyacid herbicides and their transformation products (Raina and Etter, 2010;Koppen et al, 1998;Dijkman et al, 2001) and chloroacetanilide transformation products; ESI+ for sulfonylureas, phenylureas, N-methylcarbamates, organophosphorus pesticides (Cessna et al, 2006;Degenhardt et al, 2010;Hernandez et al, 2006;Steen et al, 1999;Raina and Sun, 2008); APCI+ for triazines (Dagnac et al, 2005;Jeannot et al, 2000); and APCI+ or ESI+ for chloroacetanilides (Dagnac et al, 2005;Ferrer et al, 2007;Banerjee et al, 2009 …”