Pesticides in the Red River and its Tributaries in Southern Manitoba ...

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186 RAWN ET AL. Table 1. Effective drainage area of the tributaries on the Canadian side of the Red River (Agriculture Canada 1996) River Drainage area (km2) Assiniboine LaSalle Morris Pembina Rat Roseau Seine Red at Emerson Red at Ste. Agathe Red at Selkirk the border, the Red River also passes through primarily agricultural land along its 635 km length (Tornes and Brigham 1994). Between the U.S./Canada border and its mouth at Lake Winnipeg, seven main tributaries contribute to the flow of the Red River. The majority of the land in southern Manitoba is used for agricultural activity. Crops from this region are primarily grains and cereals. Corn is grown in the southern region of the basin, but only in limited amounts as the Red River passes increasingly northward. Phenoxyacid (e.g., 2,4-D [(2,4-dich1orophenoxy)acetic acid]), dinitroaniline (e.g., trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine]) and phenolic herbicides (e.g., bromoxynil [3,5-dibromo-4-hydroxybenzonitrile]) are most commonly used on these crops (Table 2). 2,4-D was the most frequently detected herbicide in surface waters of Manitoba, and MCPA [(4-chloro-2-methy1phenoxy)acetic acid] was found in Manitoba river systems at higher concentrations than in surface waters from the other prairie provinces, based on water quality monitoring data for a 30year period of record (Currie and Williamson 1995). Based on estimates of areas treated (Tomes and Brigham 1994) and typical application rates, greater than 1.7 million kg of 2,4-D and 1.4 million kg of MCPA are applied annually within the U.S. part of the drainage basin. Dinitroaniline products are widely used on the U.S. side of the Red River drainage basin where in excess of 1.8 million kg of trifluralin alone are applied annually. In comparison, approximately 900,000 kg of phenoxyacid herbicides and 165,000 kg of trifluralin were applied annually in southern Manitoba (Agriculture Canada, unpublished data). Approximately 135,000 kg of atrazine 16-chloro-N-ethyl-N'- (1-methyl ethyl)-1,3,5-triazine-2,4-diazine] and 146,000 kg of alachlor [2-chloro-2',6'-dimethyl-N-(methoxymethyl)acetanilide] are applied annually on the U.S. side of the Red River drainage basin (Tomes and
PFSTICIDES IN THE RED RIVER 187 Table 2. Pesticide recovery from spiked water samples, method detection limits and classification of individual pesticides Pesticide Recovery (%I Method detection (N=6) limit (ng/L) Classification -- Alachlor Atrazine Bromoxynil Chlorpyrifos Chlorthal dimethyl (Dacthal/DCPA) Cyanazine 2,4-D Dichlorprop Diclofop Ethalfluralin MCPA Metolachlor Terbuthylazine Triallate Triclopyr Trifluralin Acetanilide Triazine Phenolic (benzonitrile) Organophosphate Benzoic acid Triazine Phenoxyacid Phenoxy acid Phenoxyacid Dinitroaniline Phenoxyacid Acetanilide Triazine Carbamate Phenox yacid Dinitroaniline Brigham 1994). In Manitoba, however, the use of atrazine is limited (11,700 kg), due to the minor production of corn, and alachlor is not reg- istered for use in Canada. Despite low uses of atrazine, this chemical was detected frequently in Manitoba rivers (Currie and Williamson 1995): Loadings of neutral, persistent herbicides, such as atrazine and alachlor, have been widely determined for rivers in the U.S. midwest and Great Lakes region (Larson et al. 1995; Schottler et al. 1994; Glotfelty et al. 1990; Frank and Logan 1988). In comparison, while the phenoxyacid herbicides are widely used on cereals and grains and are frequently detected in river systems, loading estimates for these compounds are rare in the literature (Currie and Williamson 1995; Morgensen and Spliid 1995; Berryrnan and Giroux 1994; Frank and Logan 1988). The primary objective of this study was to determine seasonal concentrations and mass loadings of commonly used pesticides in the Red River and its tributaries. Additionally, we wanted to determine if a rela- tionship existed between regional pesticide use and concentrations and loadings of major neutral, phenoxyacid and phenolic pesticide contami- nants in these river systems. Based on work in the Red River previously reported by U.S. Geological Survey, Environment Canada and Manitoba Environment (Currie and Williamson 1995; Tomes and Brigham 1994), we selected 16 pesticides (15 herbicides and one insecticide) for analysis. Pesticide loadings in the Red River at the Canadian border were deter-
Page 1 and 2: Water Qual. Res. 1. Canada, 1999 Vo
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Page 9 and 10: 0 ~ m o + h m ~ o m + o m m a m + m
Page 11 and 12: Table 3. (continued) Triallate Tric
Page 13 and 14: Table 3. (continued) 2,4-D Dichlorp
Page 15 and 16: Red River at Selkirk N=33 Alachlor
Page 17 and 18: PESTICIDES IN THE RED RIVER 199 Wit
Page 19 and 20: 2001 Red at Ste. Agathe PESTICIDES
Page 21 and 22: 20 1994 - GAtrazine l4 -- 0 Chlorpy
Page 23 and 24: PE~~ICIDES IN THE RED RIVER 205 Tab
Page 25 and 26: PESTICIDES N THE RED RIVER 207 area
Page 27 and 28: &blc 7. Seasonal discharge (m3) of
Page 29 and 30: Dakota and Minnesota, in the southe
Page 31 and 32: atrazine's greater persistence in s
Page 33 and 34: PESTICIDES IN THE RED RIVER 215 chl
Page 35 and 36: PESTICIDES IN THE RED RIVER 217 Win
Page 37: PFSTICIDES IN THE RED RIVER 219 Env

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