Risk assessment of metals determined using remote sensing of dissolved organic carbon

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Metals can pollute the environment as a result of mining, waste and other industrial activities. To manage this pollution, water managers require tools to estimate risk of different concentrations of metals in lakes and streams. It is well established that specific water chemistry of a lake can influence the toxic effects of metals; in particular, the presence of dissolved organic matter (DOM) can decrease the toxicity of copper, nickel, lead and zinc. This effect, can quantitatively be predicted using established biotic ligand models (BLMs). For this modelling DOM is represented by the measurable quantity of dissolved organic carbon (DOC; mg C/L). Many governments recommend use of BLM approaches for establishing site-specific water quality criteria, or for risk assessment, but many local jurisdictions lack the ability to consistently and accurately measure DOC. DOC is not a routinely measured water quality parameter. Remote sensing is an active research field that might be able to address this practical data gap and help risk assessors, and water managers, to quantitatively take DOC into account when establishing metal risks for surface waters. The basis for remote sensing of DOC is that dissolved organic matter has colour (referred to as CDOM). It has not yet been demonstrated that remote sensing can accurately convert measurements of CDOM to a prediction of DOC in freshwater environments. As a proof of principle, we propose to study remote, un-impacted, lakes in Quebec using both drone- and satellite-based remote sensing methods. The estimated CDOM will be converted to DOC and ultimately, via BLM modelling, to metals risk estimates. This risk estimate will be compared to actual measured effect concentrations in samples of these same site waters. The comparison will allow us to assess the feasibility, and practicality, of remote sensing as a tool for metals, including copper, zinc, lead and nickel, risk assessment for current and future mineral extraction or waste disposal activities.