A 3D numerical modeling of the links between hydrodynamics, dissolved oxygen, and water temperature of a northern rural-urban shallow lake with two distinct basins.

A 3D hydrodynamic model (EFDC) was applied to simulate dissolved oxygen (DO) and temperature (T) (two crucial parameters impacting water quality) throughout Lake St. Charles, a rural-urban shallow lake located North of Quebec City, Canada. Model outputs of T and DO corroborate observations at five monitoring stations within the lake. Simulated results indicated annual cycles of turnovers and stratifications and different behaviors for the deep and shallow basins. For the simulated years, the deep basin was stratified in summer and winter, while the shallow basin was mostly mixed throughout the year. The lake heat budget indicates that during summer with a long retention time, the thermal structure of the lake is principally controlled by net radiation, latent, and sensible heat fluxes. For the rest of the year, the inflow (from the main tributary, the Des Hurons River) and outflow are the main drivers of the lake's thermal structure.

Spatial and temporal variability of contaminants of emerging concern in a drinking water source.

The spatial-temporal behaviour of contaminants of emerging concern (CECs) are not well-documented in drinking water sources, including in Quebec, Canada. In this study, a set of seven contaminants, which are more frequently reported in water sources, were monitored from May 2016 to August 2017 at ten locations within an urbanized watershed (lakes and rivers) in Quebec, Canada. Samples were collected between a wastewater plant discharge (upstream) and the intake of a drinking water plant (downstream). The results showed that three (acetaminophen, salicylic acid, caffeine) out of seven CECs were consistently detected at a range of up to a few hundred ng L-1 at all sampling stations throughout the sampling period with a detection frequency between 51% and 94%. Upstream of two wastewater plant discharge locations, six CECs were measured above the detection limit compared to other locations where only three CECs (acetaminophen, salicylic acid, caffeine) were detected. Most of the CEC concentrations were higher (a few ng L-1) during late winter in comparison with the summer, in both years 2016 and 2017. The results highlight that the wastewater effluents and septic system effluents are significant sources of CECs that are released into the surface water. Moreover, the results help to identify the spatio-temporal patterns, which is a crucial element to understand the fate of CECs in water sources submitted to extreme weather conditions during the year. This research also provides baseline data for CEC occurrence at different points across lakes, rivers, and tributaries which will be useful for future ecotoxicological studies.

Probabilistic framework for assessing ecological risk of Contaminants of Emerging Concern: Application to a Canadian lake system.

Contaminants of Emerging Concern (CECs) in natural water pose risks to ecosystems. The concentration of CECs varies spatially and temporally, and their estimated ecotoxicities differ widely by toxicological studies. This study extensively reviewed literature on ecological risk assessment and proposed a probabilistic framework for assessing ecological risk and its uncertainties (aleatory and epistemic). The framework integrated Adverse Outcome Pathway in risk assessment and was applied to a Canadian lake system for seven CECs: salicylic acid, acetaminophen, caffeine, carbamazepine, ibuprofen, drospirenone, and sulfamethoxazole. Altogether 264 water samples were collected and analyzed from 15 sites May 2016 to September 2017. Phytoplankton, zooplankton, and fish were also sampled and analyzed. The results show ecological risk estimates (Risk Quotient, RQ) varied considerably indicating a range of uncertainty. Based on the conservative estimate, the central tendency estimate of the ecological risk of mixture compounds was medium (RQ = 0.6) including drospirenone. However, the reasonably maximum estimate of the risk was high (RQ = 1.4) for mixture compounds including drospirenone. The high risk is primarily due to drospirenone as its individual risk was high (RQ = 1.1) to fish. The specific site and time of high drospirenone exposure was identified for implementing control measures. Classification of ecotoxicity values based on environmental parameters such as climate and water quality, can reduce uncertainty in the risk estimate.

Tracking domestic wastewater and road de-icing salt in a municipal drinking water reservoir: Acesulfame and chloride as co-tracers.

Developing strategies to identify the origins of contaminants in watersheds is crucial for source water protection. The use of multiple tracers improves the ability to identify contamination events originating from various land use activities. The objective of this study was to evaluate the use of acesulfame and chloride as co-tracers to represent the impact of pollution originating from wastewater and road de-icing on water quality in a municipal drinking water source. The study included a two-year sampling and water quality analysis program in numerous locations within a drinking water reservoir comprising a lake (upstream) and a river (downstream) which supply raw water to a municipal water treatment plant. Results showed that the spatial variability of acesulfame and chloride within the watershed of the lake-river systems depends on the location of contaminant sources, mainly municipal wastewater and septic tank discharges (for acesulfame) and the presence of small tributaries of the lake and river (for chloride). Temporal variability of the tracers under study differed according to the sampling location and was mainly affected by seasonal conditions. Correlation analyses between the two tracers in lake and river waters (in terms of concentrations and loads) made it possible to pinpoint the probable origins of contamination. The assessment of the spatio-temporal variability of these co-tracers within the lake-river watersheds allowed for the delineation of priority intervention zones as a decision-making tool for municipal authorities in improving drinking water source protection.

Occurrence and seasonality of raw and drinking water contaminants of emerging interest in five water facilities.

The goal of this work was to investigate the occurrence of contaminants of emerging interest (CEI) in source surface water (SW; river water) and drinking water (DW; tap water) from five drinking water treatment plants (DWTPs) in the Province of Québec, Canada. A total of 28 sampling campaigns were conducted to collect SW and DW samples from each DWTP from June 2016 to July 2017. The seven targeted CEI, including acetaminophen, salicylic acid, caffeine, carbamazepine, ibuprofen, sulfamethoxazole and drospirenone, were analyzed using solid-phase extraction-ultra pressure liquid chromatography-mass spectrometry (SPE-UPLC-MS/MS) for all collected water samples. The selected CEI were detected in all SW and DW samples, with the exception of drospirenone, which occurred in amounts that were below the limit of detection in one DWTP in June and July 2016. In all the SW samples, caffeine was detected and had the highest median concentration range (12.3-91.0 ng/L), followed by acetaminophen (7.9-85.0 ng/L) and salicylic acid (21.6-39.0 ng/L). In the DW samples, salicylic acid was detected and had the highest median concentration range (20.5-50 ng/L), followed by caffeine (5.2-21.8 ng/L), and acetaminophen (5.0-7.7 ng/L). Carbamazepine, ibuprofen, and sulfamethoxazole primarily occurred in amounts between the limit of detection and limit of quantification in SW and occurred below the limit of detection in DW. All the DWTPs exhibited a similar trend in the removal of CEI, which include acetaminophen (≤97.6%), followed by caffeine (71.0-86.5%) and salicylic acid (<50.0%). Varying levels of efficiencies were observed among the removal strategies for CEI under study, which were mainly associated with the contaminant concentration in SW in the case of acetaminophen, and with the treatment processes in the case of caffeine and salicylic acid.