Quality survey and spatiotemporal variations of atrazine and desethylatrazine in drinking water in Quebec, Canada.

The herbicide atrazine remains in use in Canada, the United States, and several other countries, while being banned since 2003 in the European Union. A comprehensive quality survey of atrazine (ATZ) and one of its metabolites, desethylatrazine (DEA), was conducted in 2015-2018 in drinking water available to consumers in Quebec, Canada. Temporal variations of ATZ and DEA were monitored in tap water from the Montreal area for 18 consecutive months (Temporal survey 2015-2016). Within this time window, the sum of ATZ and DEA in tap water samples (n = 450) varied from 40 to 250 ng L-1 (median: 98 ng L-1). ATZ was systematically detected (100%), with a concentration range of 30-195 ng L-1 (median: 49 ng L-1) while DEA was in the range of 10-187 ng L-1 (median: 36 ng L-1). Maximum ATZ concentrations remained about 25× lower than the Canadian drinking water quality guideline (5000 ng L-1), but 48% of the samples were above that of the European Union (100 ng L-1) regarding the sum of ATZ and DEA. Trends of ATZ and DEA in drinking water were also examined across southwestern Quebec (Spatial survey 2017-2018). The sum of the two triazines in this second set of samples varied from below the method detection limit (for 33 out of the 52 surveyed municipalities) to 104 ng L-1. Apart from Montreal, locations in the southern shore of the St. Lawrence showed generally higher levels of atrazine and DEA. The highest concentrations clustered in the Montérégie region, along the St. Lawrence River (e.g., Brossard, Longueuil, Saint-Constant) and/or downstream from agricultural areas. The ATZ concentrations are suggested to have decreased compared to previous surveys, which is consistent with the decrease in the sales of active ingredients in Ontario (upstream sources) and Quebec.

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

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 vs. 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.

Evaluation of on-line concentration coupled to liquid chromatography tandem mass spectrometry for the quantification of neonicotinoids and fipronil in surface water and tap water.

A study was initiated to investigate a fast and reliable method for the determination of selected systemic insecticides in water matrixes and to evaluate potential sources of bias in their analysis. Acetamiprid, clothianidin, desnitro-imidacloprid, dinotefuran, fipronil, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam were amenable to analysis via on-line sample enrichment hyphenated to ultra-high-performance liquid chromatography tandem mass spectrometry. The selection of on-line solid-phase extraction parameters was dictated by a multicriterion desirability approach. A 2-mL on-line injection volume with a 1500 µL min-1 loading flow rate met the objectives sought in terms of chromatographic requirements, extraction efficiency, sensitivity, and precision. A total analysis time of 8 min per sample was obtained with method limits of detection in the range of 0.1-5 ng L-1 for the scope of targeted analytes. Automation at the sample concentration step yielded intraday and interday precisions in the range of 1-23 and 2-26%, respectively. Factors that could affect the whole method accuracy were further evaluated in matrix-specific experiments. The impact of the initial filtration step on analyte recovery was evaluated in ultra-pure water, tap water, and surface water. Out of the nine membranes tested, glass fiber filters and polyester filters appeared as the most appropriate materials. Sample storage stability was also investigated across the three matrix types; the targeted analytes displayed suitable stability during 28 days at either 4 °C or - 20 °C, with little deviations (± 10%) with respect to the initial T0 concentration. Method applicability was demonstrated in a range of tap water and surface water samples from the province of Québec, Canada. Results from the present survey indicated a predominance of thiamethoxam (< 0.5-10 and 3-61 ng L-1 in tap water and river water, respectively), clothianidin (< 0.5-6 and 2-88 ng L-1 in tap water and river water, respectively), and imidacloprid (< 0.1-1 and 0.8-38 ng L-1 in tap water and river water, respectively) among the targeted analytes. Graphical abstract ᅟ Development of solid-phase extraction coupled on-line to UHPLC-MS/MS for the rapid screening of systemic insecticides in water.