Sampling method and season influence selenium dynamics at the base of a boreal lake food chain.

Few studies have investigated the potential influence of sampling method and season on Se bioaccumulation at the base of the aquatic food chain. In particular, the effects of low water temperature associated with prolonged ice-cover periods on Se uptake by periphyton and further transfer to benthic macroinvertebrates (BMI) have been overlooked. Such information is crucial to help improve Se modelling and risk assessment at sites receiving continuous Se inputs. To date, this seems to be the first study to address these research questions. Here, we examined potential differences related to sampling methods (artificial substrates vs. grab samples) and seasons (summer vs. winter) on Se dynamics in the benthic food chain of a boreal lake (McClean Lake) receiving continuous low-level Se input from a Saskatchewan uranium milling operation. During summer 2019, water, sediment grab samples and artificial substrates were sampled from 8 sites with varying mill-treated effluent exposure. In winter 2021, water and sediment grab samples were sampled at 4 locations in McClean Lake. Water, sediment, and biological samples were subsequently analyzed for total Se concentrations. Enrichment functions (EF) in periphyton and trophic transfer factors (TTF) in BMI were calculated for both sampling methods and seasons. Periphyton collected with artificial substrates (Hester-Dendy samplers and glass plates) exhibited significantly higher mean Se concentrations (2.4 ± 1.5 µg/g d.w) than periphyton collected from the surface of sediment grab samples (1.1 ± 1.3 µg/g d.w). Selenium concentrations in periphyton sampled in winter (3.5 ± 1.0 µg/g d.w) were significantly greater than summer (1.1 ± 1.3 µg/g d.w). Nevertheless, Se bioaccumulation in BMI was similar between seasons, possibly suggesting that invertebrates are not actively feeding in winter. Further investigations are necessary to verify if peak Se bioaccumulation in BMI takes place in spring, coinciding with the reproductive and developmental windows of some fish species.

Ecological risk assessment (ERA) based on contaminated groundwater to predict potential impacts to a wetland ecosystem.

To assess the ecological risk resulting from an accidental gasoline spill upstream from a wetland, groundwater and sediment sampling was carried out during two campaigns at the 48th and 52nd months after the spill had occurred. In total, 21 groundwater monitoring wells in the affected area were sampled plus an additional reference well located upstream from the accident location. Seven sediment sampling points were selected inside the wetland, plus a reference point upstream from the accident. Physicochemical parameters, BTEX (benzene, toluene, ethylbenzene, m-xylene, p-xylene and o-xylene) and metal concentrations were analysed to estimate the chemical risk. Acute (Allivibrio fischeri, Daphnia similis, Hyalella azteca) and chronic (Artemia salina and Desmodesmus subspicatus) toxicity assays were performed with groundwater and sediments elutriate to determine the ecotoxicological risk. Results from groundwater indicated an extreme chemical level of risk in14 out of 21 monitoring wells. These 14 wells also exhibited free-phase gasoline and lead (Pb) concentrations above the threshold values adopted by this study. The presence of Pb, however, could not be associated with the gasoline accident. High acute and chronic toxicities were reported for the majority of wells. Conversely, the risks associated with the sediments were considered low in most sampling points, and the ecotoxicity found could not be related to the presence of gasoline. Groundwater flow modelling results have evidenced the migration of the contamination plume towards the wetland. Thus, to prevent contamination from reaching the protected area, more effective groundwater clean-up techniques are still required.

Environmental risk assessment of psychoactive drugs in the aquatic environment.

The consumption of psychoactive pharmaceuticals has increased worldwide, and wastewater treatment plants are not able to eliminate them from the effluent. An extensive review was carried out to assess the environmental risk (ERA model) based on secondary data about potential impacts on non-target organisms of seven psychoactive drugs consumed worldwide (alprazolam, bromazepam, citalopram, clonazepam, diazepam, lorazepam, and oxazepam). Risk quotients (RQs) were calculated according to the European Medicines Agency (EMA) on ERA of Medicinal Products For Human Use based on (i) the predicted and measured environmental concentrations (PEC and MEC, respectively) of the psychoactive drug in surface water, groundwater, and wastewater effluent and (ii) the predicted no-effect concentration (PNEC) derived from ecotoxicological assays or ECOSAR software. Furthermore, this study reviews and discusses non-standardized ecotoxicity assays, such as sublethal and behavioral effects on different organisms. In total, 903 MEC entries of psychoactive drugs and 162 data on ecotoxicological assays were gathered from the literature survey addressing behavioral effects (115), acute/chronic effects (35), and sublethal effects (12). Citalopram and diazepam were the only substances that are likely to pose an environmental risk (RQ > 1) to surface waters. Even though there is considerable amount of data on behavioral effects of psychoactive drugs to aquatic species, results are currently not integrated into the EMA risk assessment framework. The large amount of data on psychoactive drug concentrations and effects on non-target organisms collected, interpreted, and discussed in the present study should be used as a baseline for future improvement of ERA strategies.