Transformation/dissolution characteristics of a nickel matte and nickel concentrates for acute and chronic hazard...

For the purposes of aquatic hazard classification under the United Nations Globally Harmonized System of Classification (UNGHS), we have examined the transformation/dissolution (T/D) characteristics of a Ni matte and 4 Ni concentrates at pH 6 using the United Nations (UN) Transformation/Dissolution Protocol (T/DP) for metals and sparingly soluble metal compounds. Among the analytes Ni, Co, and Cu, Ni was released into the T/D solutions in the highest concentrations and was thus the main driver in establishing the hazard classification. We applied an extrapolation-scaling approach to obtain concentrations of total dissolved Ni at low loadings of 0.1 and 0.01 mg/L for derivation of chronic classification outcomes in the European Union (EU) classification, labeling, and packaging (CLP) scheme. The T/D data would classify the Ni matte as Acute 2-Chronic 2 under the Globally Harmonized System (GHS) scheme, and Chronic 1 under the EU CLP. Three of the 4 Ni concentrates would classify as GHS Acute 2-Chronic 2 and EU CLP Chronic 2, whereas the 4th would classify as GHS Acute 3-Chronic 3 and EU CLP Chronic 3. In applying the critical surface area (CSA) approach to the Ni concentrates, acute and chronic hazard classification outcomes were the same as those derived from direct application of the T/D data to the GHS and EU schemes. Such agreement provided confidence that the CSA approach could yield scientifically defensible acute and chronic hazard classification outcomes.