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

This article focuses on using real-time electrical conductivity (EC) data from autonomous sensors as a surrogate to estimate aqueous total selenium (TSe) concentrations in McClean Lake, a boreal lake in Saskatchewan, Canada, receiving treated effluent from a uranium mill. The study validated the accuracy of EC sensors and established a strong correlation between EC and TSe, enabling the derivation of a site-specific aqueous Se threshold of 0.7 µg/L, which is below current Canadian and U.S. guideline values. Selenium concentrations in periphyton and benthic macroinvertebrates were measured to identify areas of potential bioaccumulation and toxicity, with the highest Se levels found near the effluent diffuser, indicating localized ecological risk. The findings highlight the utility of autonomous sensor technology for continuous monitoring of Se exposure in aquatic ecosystems with complex effluent mixing, while emphasizing that site-specific calibration is necessary before applying this approach elsewhere.