An extension of the transformation/dissolution protocol (T/DP) was developed and evaluated as a tool to measure the removal of metals from the water column for chronic aquatic hazard classification. The T/DP extension (T/DP‐E) consists of 2 parts: T/DP‐E part 1, to measure metal removal from the water column via binding of metals to a substrate and subsequent settling, and T/DP‐E part 2, to assess the potential for remobilization of metals following resuspension. The T/DP‐E methodology (672‐h [28‐d] removal period, 1‐h resuspension event, and 96‐h resettling period) was tested using Cu, Co, and Sr solutions in the presence of a substrate. The metal removal rates varied from rapid removal for Cu to slower rates of removal for Co and Sr. The resuspension event did not trigger any increase in dissolved Cu, Co, or Sr. Additional 96‐h experiments were conducted using dissolved Ni, Pb, Zn, and Ag and supported the conclusion that the T/DP‐E is sufficiently robust to distinguish removal rates between metals with a wide range of reactivities. The proposed method provides a means to quantify the rate of metal removal from the water column and evaluate remobilization potential in a standardized and reliable way. Environ Toxicol Chem 2019;38:2032–2042. © 2019 SETAC.

The United Nations and the European Union have developed guidelines for the assessment of long‐term (chronic) chemical environmental hazards. This approach recognizes that these hazards are often related to spillage of chemicals into freshwater environments. The goal of the present study was to examine the concept of metal ion removal from the water column in the context of hazard assessment and classification. We propose a weight‐of‐evidence approach that assesses several aspects of metals including the intrinsic properties of metals, the rate at which metals bind to particles in the water column and settle, the transformation of metals to nonavailable and nontoxic forms, and the potential for remobilization of metals from sediment. We developed a test method to quantify metal removal in aqueous systems: the extended transformation/dissolution protocol (T/DP‐E). The method is based on that of the Organisation for Economic Co‐operation and Development (OECD). The key element of the protocol extension is the addition of substrate particles (as found in nature), allowing the removal processes to occur. The present study focused on extending this test to support the assessment of metal removal from aqueous systems, equivalent to the concept of “degradability” for organic chemicals. Although the technical aspects of our proposed method are different from the OECD method for organics, its use for hazard classification is equivalent. Models were developed providing mechanistic insight into processes occurring during the T/DP‐E method. Some metals, such as copper, rapidly decreased (within 96 h) under the 70% threshold criterion, whereas others, such as strontium, did not. A variety of method variables were evaluated and optimized to allow for a reproducible, realistic hazard classification method that mimics reasonable worst‐case scenarios. We propose that this method be standardized for OECD hazard classification via round robin (ring) testing to ascertain its intra‐ and interlaboratory variability. Environ Toxicol Chem 2019;38:1839–1849. © 2019 SETAC.

The transformation/dissolution protocol (T/DP) for metals and sparingly soluble metal compounds was applied to determine the transformation/dissolution (T/D) characteristics of yellow tungsten trioxide, WO ; blue tungsten oxide, WOx, x taken as 2.9; tungsten disulphide, WS ; tungsten metal, W; 3 samples of tungsten carbide, WC; sodium tungstate, Na WO · 2H O; ammonium paratungstate (APT), (NH ) (H W O ) · 4H O; and ammonium metatungstate (AMT) (NH ) (H W O ) · 3H O. The T/D data were used to derive aquatic hazard classification outcomes under the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS) and European Union Classification, Labelling and Packaging of Substances and Mixtures (EU CLP) schemes by comparing the data with selected acute and chronic ecotoxicity reference values (ERVs) of 31 and 3.37 mg W/L, respectively. In addition to the concentration of total dissolved tungsten (W), the T/D solutions were analyzed for the concentration of the tungstate anion, because speciation can be an important factor in establishing the ecotoxicity of dissolved metals. Results show that the tungstate anion was the predominant W-bearing species in solution for all substances examined at pH 6 and 8.5. It was found that the 100 mg/L loadings of both the yellow WO and the blue WOx exceeded the 31 mg/L acute ERV, so they would classify as Acute 3-Chronic 3 under the UN GHS scheme but they would not classify under the EU CLP. An effect of pH on the reactivity of the W metal was observed with 3% and 16% W dissolution at pH 6 and 8.5, respectively. Tungsten metal would not classify under either the UN GHS or EU CLP schemes nor would the WS . The WCs were the least reactive in terms of the 1% or less dissolution of the contained W at pH 6. A critical surface area for WC was calculated. The sodium tungstate, APT and the AMT all yielded, at pH 8.5, total dissolved W concentrations that would result in UN GHS Acute 3-Chronic 3 classifications. Integr Environ Assess Manag 2018;14:498-508. © 2018 Her Majesty the Queen in Right of Canada. Integrated Environmental Assessment and Management © 2018 SETAC.

Increased temperatures and changing amounts of precipitation may alter environments, increasing the challenges faced by mines. This is a paper on topics relevant to metal mine biogeochemical environments, related waste management, element transport, and environment health south of 60° latitude. Mine waste can contain elements of interest (EOI) that may have adverse environmental and biological effects at concentrations that are higher than in undisturbed sites. Elevated concentrations of EOIs are transported by water as solutes and particles. Wind erosion also transports particles, and establishing its contribution and effects is challenging. Dispersal of EOI can be controlled at the source using water covers, geomembranes, geosynthetic clay liners, and covers with capillary barrier effects. Drainage that can be produced over a wide range of pH must be treated to meet environmental requirements. Water treatment can produce sludge that must be stored or processed. The success of these mitigation measures can be observed in the biological health of organisms at the site and vicinity. Processes responsible for EOI dissolution and transport, waste control and water management systems, and the stress experienced by biota near mines are all subject to climate change effects. Understanding and adapting to challenges from a rapidly changing environment will require cooperation between industry, government, mining communities, and scientists. Ideally, adaptation measures should correspond to temperature and precipitation projections, but this information is not always available at the relevant geographic scale. To anticipate emerging risks, it may be necessary to explore a variety of scenarios at lab and field scales, and to implement robust and flexible management techniques.

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