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Widespread occurrence and spatial distribution of glyphosate, atrazine, and neonicotinoids pesticides in the St. Lawrence and tributary rivers

Montiel-León, J. M. et Munoz, G. et Vo Duy, S. et Do, D.T. et Vaudreuil, M.-A. et Goeury, K. et Guillemette, F. et Amyot, M. et Sauvé, S. (2019). Widespread occurrence and spatial distribution of glyphosate, atrazine, and neonicotinoids pesticides in the St. Lawrence and tributary rivers. Environmental Pollution , 250 . p. 29-39. DOI: DOI: 10.1016/j.envpol.2019.03.125.

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Résumé

The occurrence and spatial distribution of selected pesticides were investigated along a 200-km reach of the St. Lawrence River (SLR) and tributaries in Quebec, Canada. Surface water samples (n = 68) were collected in the summer 2017 and analyzed for glyphosate, atrazine (ATZ), 8 systemic insecticides (acetamiprid, clothianidin, dinotefuran, fipronil, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam) and some metabolites. Overall, 99% of the surface water samples were positive to at least one of the targeted pesticides. The most recurrent compounds were glyphosate (detection frequency: 84%), ATZ (82%), thiamethoxam (59%), desethylatrazine (DEA: 47%), and clothianidin (46%). Glyphosate displayed variable levels (4–3,000 ng L-1 ), with higher concentrations in south tributaries (e.g., Nicolet and Yamaska). In positive samples, the sum of ATZ and DEA varied between 5 and 860 ng L−1 , and the sum of 6 priority neonicotinoids between 1.5 and 115 ng L−1 . From Repentigny to the Sorel Islands, the spatial distribution of pesticides within the St. Lawrence River was governed by the different upstream sources (i.e., Great Lakes Ottawa River) due to the limited mixing of the different water masses. Cross-sectional patterns revealed higher concentrations of glyphosate and neonicotinoids in the north portions of transects, while the middle and south portions showed higher levels of atrazine. In Lake St. Pierre and further downstream, cross-sections revealed higher levels of the targeted pesticides near the southern portions of the SLR. This may be due to the higher contributions from south shore tributaries impacted by major agricultural areas, compared to north shore tributaries with forest land and less cropland use. Surface water samples were compliant with guidelines for the protection of aquatic life (chronic effects) for glyphosate and atrazine. However, 31% of the samples were found to surpass the guideline value of 8.3 ng L-1 for the sum of six priority neonicotinoids. Glyphosate, atrazine, and neonicotinoid pesticides showed systematic spatial patterns along a 200 km reach of the St. Lawrence River and tributaries, in relation with their agricultural sources.

Type de document: Article scientifique
Statut du texte intégral: Autre
Mots-clés libres: Pesticides survey, Surface water, St. Lawrence River, Glyphosate, Atrazine, Neonicotinoid insecticides.
Sujets: 6. Milieu humain > 6.5. Urbanisation
8. Impacts et monitoring > 8.1. Qualité de l’eau
Date de dépôt: 31 oct. 2019 15:46
Dernière modification: 31 oct. 2019 18:44
URI: http://belsp.uqtr.ca/id/eprint/1438

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