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 25xlower 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 Monteregie 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. (C) 2019 Elsevier B.V. All rights reserved.