Magnitude and persistence of herbicide residues in farm dugouts and ponds in the Canadian prairies

Abstract

Abstract-Farm ponds or dugout waters were monitored for residues of seven major herbicides used in the Canadian prairies from fall of 1987 to spring of 1989. The frequencies of confirmed detection of herbicides in water samples, depending on the time of sampling, in decreasing order were: 2,4-dichlorophenoxyacetic acid (2,4-D; 93-100%), diclofop (46-95%), bromoxynil (50-85%), 4-chloro-2-methyl-phenoxyacetic acid (MCPA; 33-70%), triallate (28-63%), dicamba (17-55%), and trifluralin (0-18%). The corresponding frequencies of quantifiable residues (Ն0.05 g/L) were lower, ranging from 75 to 86% for 2,4-D to 0 to 7% for dicamba. Median residues in all water samples were near or below the quantification limits of 0.05 g/L. Maximum residues varied widely and were (g/L): trifluralin (not detectable [ND]-0.11), bromoxynil (0.27-0.33), dicamba (ND-11.2), triallate (0.05-0.87), MCPA (0.12-1.97), 2,4-D (0.64-2.67), and diclofop (0.27-3.47). Maximum residues were seasonal and declined to near or below detection limits by the following sampling time. Median values were two to three orders of magnitude less than the corresponding maximum allowable concentration and interim maximum allowable concentration guidelines for drinking water in Canada and the United States. Maximum values were also less than these guidelines. Only the maximum values for residues of MCPA and 2,4-D approached the guidelines for these herbicides in water used for irrigation.

Environmental Fate of Trifluralin

“…Highest sustained residues of trifluralin in surface bodies of water would be expected in farm ponds or dugouts that receive runoff from the surrounding treated fields as well as atmospheric deposits, especially during and following the application period. Grover et al (1997) monitored residues of seven herbicides, including trifluralin, in waters of farm ponds across four soil regions in Saskatchewan. Water samples were collected before herbicide spraying season in spring, in July following herbicide applications, and before freeze-up in fall.…”

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

“…The pesticides are transported to the wetlands via spray drift, atmospheric deposition, surface runoff, and ground water flow (Grover et al, 1988;Waite et al, 1992). As a result, they are frequently detected in prairie surface waters across this region such as wetlands (Main et al, 2014;Donald et al, 1999Donald et al, , 2001Waite et al, 2002Waite et al, , 2004, lakes (Donald and Syrgiannis, 1995), farm dugouts (Cessna and Elliott, 2004;Grover et al, 1997), and drinking water reservoirs (Donald et al, 2007). The seven herbicides most frequently detected in prairie drinking water reservoirs were: 2,4-D [(2,4-dichlorophenoxy)acetic acid], MCPA [(4-chloro-2-methylphenoxy)acetic acid], dicamba [3,6-dichloro-2-methoxybenzoic acid], clopyralid [3,6-dichloropyridine-2-carboxylic acid], dichlorprop [2-(2,4-dichlorophenoxy)propanoic acid], mecoprop [2-(4-chloro-2-methylphenoxy)propanoic acid], and bromoxynil [3,5-dibromo-4-hydroxybenzonitrile] (Donald et al, 2007).…”

Dehalogenation of the Herbicides Bromoxynil (3,5-Dibromo-4-Hydroxybenzonitrile) and Ioxynil (3,5-Diiodino-4-Hydroxybenzonitrile) by Desulfitobacterium chlororespirans

“…The need for a comprehensive understanding of bromoxynil degradation is indicated by the toxicity associated with bromoxynil (classified as a group C possible human carcinogen and considered to be developmentally toxic [46]), along with reports of its off-site movement in wind-eroded sediment (23) and in waters (17,28,31) associated with agricultural areas. Detectable levels of bromoxynil in blood plasma were found in 19.3% of the rural residents tested in Saskatchewan, Canada, even though bromoxynil application in the region had not occurred for 5 months (40).…”