Modeling the Fate of Metal Concentrates in Surface Water.

Metals present in concentrates are in a solid form and not bioavailable, but they can dissolve or potentially transform to more soluble forms. Transformation/dissolution (T/D) laboratory protocols have been developed to assess the importance of dissolution of sparingly soluble metal substances in the context of hazard classification, however these tests represent worst-case scenarios for metal bioavailability since attenuation mechanisms such as complexation, sorption, and transport to the sediment are not considered. A unit world model (UWM) for metals in lakes, TICKET-UWM, has been developed that considers key processes affecting metal transport, fate, and toxicity including complexation by aqueous inorganic and ligands, partitioning to DOC and POC, precipitation, and transport of dissolved metals and solids between the water column and sediment. TICKET-UWM was used to assess the fate of a metal concentrate and dissolved metal ions released from the concentrate following an instantaneous input to a generalized lake. Concentrate dissolution rates in the water column were parameterized using results from batch T/D tests for two specific concentrates containing lead (Pb), copper (Cu) and cobalt (Co). TICKET-UWM results for a generalized lake environment showed that water column concentrations of metals in the lake environment after 28 d were several orders of magnitude lower than the 28-d concentration from the T/D tests because Pb, Cu and Co partitioned to POC in the water column and were subsequently removed due to settling. Resuspension of sediment served to increase total metal in the water column, but resulting concentrations were still much lower than the 28-d concentrations from the T/D tests. Information from TICKET-UWM could be used for refining the environmental hazard profiles of metals. This article is protected by copyright. All rights reserved.