Inputs, source apportionment, and transboundary transport of pesticides and other polar organic contaminants along the lower Red River, Manitoba, Canada

Abstract

The Red River originates in the U.S., drains into Lake Winnipeg, and is a significant pathway for nutrients. We investigate its role as a source for pesticides, pharmaceuticals, per- and polyfluoroalkyl substances (PFASs), and microbes bearing antibiotic resistance genes (ARGs). We delineate agricultural, urban, and rural land-use for organic contaminants to determine the extent of chemical transboundary riverine fluxes, and characterize levels and trends of organic contaminants and ARGs between spring and fall 2014 and 2015. The herbicide atrazine peaked at over 500 ng/L (14-day time-weighted average) near the border, indicating that the U.S. represents the major source into Canada from the Red River. Neonicotinoid insecticides had relatively constant concentrations, suggesting more widespread agricultural use in both countries. Pesticide concentrations were greatest post-application in June and July. Mass loadings of pesticides over the sampling periods, from the river to Lake Winnipeg, ranged from approximately 800 kg of atrazine, to 120 kg of thiamethoxam and clothianidin, to 40 kg of imidacloprid. Exposure distributions for atrazine exceeded benchmark water quality guidelines for protection of aquatic life (0.2% probability of exceeding chronic benchmark) with no exceedances for neonicotinoids. Seven pharmaceuticals were detected, mostly at low ng/L levels downstream of the City of Winnipeg wastewater treatment plant. Carbamazepine, the only pharmaceutical detected consistently at all sites, contributed on average 20 kg each year into Lake Winnipeg. While minor inputs were observed all along the river, city inputs represented the greatest source of pharmaceuticals to the river. Both PFASs and ARGs were observed consistently and ubiquitously, indicative of an anthropogenically-influenced system with no indications of any single point-source signature. While transboundary flux from the U.S. was an important source of pesticides to the Red River, especially for atrazine, observed concentrations of all measured contaminants suggest that known aquatic toxicological risk is minimal.

Spatio-Temporal Patterns of Crops and Agrochemicals in Canada Over 35 Years

“…Fertilizers, in the form of nitrogen (N) and phosphorus (P), are responsible for impaired water quality through eutrophication of lakes and rivers (Michalak et al, 2013;Lassaletta et al, 2014;Bunting et al, 2016), groundwater contamination (Burow et al, 2010), and greenhouse gas production (Park et al, 2012). Similarly, frequent pesticide applications have been related to the occurrence of a wide range of pesticides in lakes (Struger et al, 2017;Metcalfe et al, 2018), rivers (Challis et al, 2018), wetlands (Main et al, 2014), and air (Yao et al, 2006). Several pesticide groups (e.g., the neonicotinoid insecticides) are known to adversly affect non-target species in terrestrial and aquatic ecosystems (Goulson, 2014;Morrissey et al, 2015).…”

Neonicotinoids: Spreading, Translocation and Aquatic Toxicity

“…According to a study on Red River, Canada [51] neonicotinoids had relatively constant concentrations, suggesting a more widespread agricultural use both in the US and Canada. The maximum values for the three neonicotinoid insecticides TMX, CLO and IMI ranged 14.1-31.7 ng/L with mean concentrations over the two-year study <8 ng/L.…”

Development and Calibration of the Polar Organic Chemical Integrative Sampler (POCIS) for Neonicotinoid Pesticides

“…In recent years, various passive samplers have been devised for monitoring neonicotinoid pesticides in aquatic environments; these include Chemcatcher (Schäfer et al 2008; Sánchez-Bayo and Hyne 2014), a silicone rubber rod (Martin et al 2018), and the polar organic chemical integrative sampler (POCIS;Ahrens et al 2015;Challis et al 2018;Sultana et al 2018;Noro et al 2019;Xiong et al 2019). The collected amounts for Chemcatcher increased linearly for 20 d (Sánchez-Bayo and Hyne 2014).…”

“…The sampling rate (R s ) of the silicone rubber rod has been relatively low, at 0.04 mL/d at a flow rate of 5 cm/s (Martin et al 2018). The POCIS sampler has been used for field tests (Challis et al 2018;Sultana et al 2018;Xiong et al 2019), even though the linear range was relatively short, 3 to 14 d (Noro et al 2019), or the collected amount increased nonlinearly for 26 d of deployment (Ahrens et al 2015).…”