Metal Speciation Service
Metal speciation has recently come to the forefront in assessing metal toxicity, because not all metal species are bioavailable to aquatic organisms. It is generally accepted that the free metal ion is considered the most toxic metal species. Chemical equilibrium modelling, (e.g., MINEQL+) has become a powerful tool used to predict free metal ion concentrations under site-specific conditions, such as in an effluent or a receiving water. The degree of influence, of site water quality parameters on metal speciation, can also be determined (i.e., dissolved organic carbon, hardness, alkalinity, and pH).
Another model, which takes metal speciation one step further, is called the Biotic Ligand Model and has been developed to predict metal toxicity thresholds (i.e., LC5Os). This model has recently made its way into a requirement under a mine's Certificate of Approval by the Ontario Ministry of the Environment.
AquaTox has used the toxicity predictions and metal speciation simulations in: Toxicity Identification and Evaluation (TIE) procedures in mining effluents, generating site-specific aquatic criteria, and evaluating the use of EDTA, a metal chelator, as a wastewater treatment option for the Mining industry.