Application of autonomous sensor technology to estimate selenium exposure and a site‐specific selenium threshold in a Canadian boreal lake

Abstract

There is an increasing trend in the use of real-time sensor technology to remotely monitor aquatic ecosystems. Commercially available probes, however, are currently not able to measure aqueous selenium (Se) concentrations. Because of the well-described bioaccumulation potential and associated toxicity of Se in oviparous vertebrates, it is crucial to monitor Se concentrations at sites receiving continuous effluent Se input. This study aimed to estimate Se concentrations in a boreal lake (McClean Lake) downstream from a Saskatchewan uranium mill using real-time electrical conductivity (EC) data measured by autonomous sensors. Additionally, this study aimed to derive a site-specific total aqueous Se (TSe) threshold based on Se concentrations in periphyton and benthic macroinvertebrates sampled from the same lake. To characterize effluent distribution within the lake, eight Smart Water (Libelium) sensor units were programmed to report EC and temperature for five and seven consecutive weeks in 2018 and 2019, respectively. In parallel, periphyton and benthic macroinvertebrates were sampled with Hester-Dendy's artificial substrate samplers (n = 4) at the same sites and subsequently analyzed for Se concentrations. Electrical conductivity was measured with a handheld field meter for sensor data validation and adjusted to the median lake water temperature (13 °C) registered for the deployment periods. Results demonstrated good accuracy of sensor readings relative to handheld field meter readings and the successful use of real-time EC in estimating TSe exposure (r = 0.87; r 2 = 0.84). Linear regression equations derived for Se in detritivores versus Se in periphyton and Se in periphyton versus sensor-estimated TSe were used to estimate a site-specific TSe threshold of 0.7 µg/L (±0.2). Moreover, mean Se concentrations in periphyton (16.7 ± 4.4 µg/g dry weight [d.w.]) and benthic detritivores (6.0 ± 0.4 µg/g d.w.) from one of the exposure sites helped identify an area with potential for high Se bioaccumulation and toxicity in aquatic organisms in McClean Lake.

Laboratory and In situ Selenium Bioaccumulation Assessment in the Benthic Macroinvertebrates Hyalella azteca and Chironomus dilutus

“…The goal of this study was to assess Se bioaccumulation in two model benthic macroinvertebrates, H. azteca and C. dilutus, under known exposure duration conditions. Thereby, this study also aimed to clarify results from earlier eld studies in which arti cial substrates were used to sample BMI in a boreal lake (McClean Lake) downstream from a uranium milling and mining operations in northern Canada (Mendes et al 2022a(Mendes et al , 2022b(Mendes et al , 2023 in press). To address this goal, two Se bioaccumulation studies were conducted to investigate Se bioaccumulation in H. azteca and the potential effect of biological competition in co-exposure with C. dilutus.…”

“…The previous on-site studies showed that diluted e uent distribution in McClean Lake E.B. is heterogeneous (Mendes et al 2022a) and varies depending on a season (AREVA 2016a).…”

On Robustness of the Explanatory Power of Machine Learning Models

“…Before deployment at Lake Miwasin, a similar WSN methodology was tested in Canadian lakes to delineate effluent exposure downstream of a Uranium Mill region (Cupe-Flores et al, 2022) and to estimate selenium (Se) exposure using a site-specific threshold value (Peixoto Mendes et al, 2023). In Lake Miwasin, deployment spanned from September 18 th to October 10 th in 2020; and from June 21 st to October 16 th in 2021.…”

New technologies as decision aids for the advancement of ecological risk assessment

“…Exposure characterization describes the magnitude and spatial and temporal patterns of exposure to stressors (e.g., contaminants) shown in the conceptual model. To this end, autonomous sensor technology has been adapted to estimate exposure levels from pollutants such as metals in lakes associated with adverse effects (Peixoto Mendes et al, 2023). Some of the advantages of this technology include their wireless, remote, ubiquity, and real-time capabilities (Randhawa et al, 2017), which can lead to data collection from remote or hazardous sites.…”

“…As the affordability and accuracy of commercial sensors increase, their deployment and application also increase in monitoring activities and site identification (Randhawa et al, 2017). For example, real‐time electrical conductivity data from autonomous sensors have been shown to be a good surrogate for total aqueous selenium levels in a Canadian boreal lake and for identifying key monitoring locations (Peixoto Mendes et al, 2023). Autonomous sensors can not only be deployed to measure water‐quality parameters, but also, they can generate exposure estimates of levels of contaminants on a case‐by‐case basis, as shown for metals in aquatic ecosystems.…”