A new method for the characterisation and quantitative speciation of base metal smelter stack particulates.

Base metal smelters may be a source of particulates containing metals of environmental concern released to the atmosphere. Knowledge of the quantitative chemical speciation of particulate releases from base metal smelters will be of value in smelter emission fingerprinting, site-specific risk assessments, predictions of the behaviour of smelter stack particulates released to the environment and in resolving liability issues related to current and historic releases. Accordingly, we have developed an innovative approach comprising bulk chemical analysis, a leaching procedure, X-ray diffraction analysis and scanning electron microscopy/electron probe microanalysis characterisation in a step-wise apportioning procedure to derive the quantitative speciation of particulate samples from the stacks of three copper smelters designated as A, B and C. For the A smelter stack particulates, the major calculated percentages were 29 CuSO(4), 20 ZnSO(4).H(2)O, 13 (Cu(0.94)Zn(0.06))(2)(AsO(4))(OH), 11 PbSO(4) and four As(2)O(3). For the B smelter stack particulates, the primary calculated percentages were 20 ZnSO(4).H(2)O, 20 PbSO(4), 12 CuSO(4) and nine As(2)O(3). Finally, we calculated that the C smelter stack particulates mostly comprised 34 ZnSO(4).H(2)O, 19 (Cu(0.84)Zn(0.16))(AsO(3)OH), 11 PbSO(4), 10 As(2)O(3) and nine Zn(3)(AsO(4))(2). Between 56% and 67% by weight of the smelter stack particulates, including the As, was soluble in water. For these and other operations, the data and approach may be useful in estimating metals partitioning among water, soil and sediment, as well as predictions of the effects of the stack particulates released to the environment.

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

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.

The concept of persistence as applied to metals for aquatic hazard identification.

The criteria persistence (P), bioaccumulation (B), and toxicity (T) are applied by domestic and international regulators and modelers to the hazard identification of chemical substances, including metals and metalloids, that may present harm to the environment. In this paper, we critically examine the literature to determine the weight of evidence for the application of water column partition half-times as a surrogate for the persistence criterion in the aquatic hazard identification of metals and metal compounds. Dissolved metals such as Fe, Mn, Cu, Pb, Co, Cs, Hg, and Zn, as well as the metalloids As and Se, tend to partition from the water column by adsorption onto sinking particulates, with reported and calculated partition half-times in the range 4 to 30 d, with outliers of 0.07 and 280 d. Within freshwater lakes, values of t1/2 for the transition metals Cr, Mn, Fe, Co, and Cu averaged about 10 d, while those for the nontransition metals Sr, Zn, Cs, and Hg and the metalloids As and Se varied up to 55 d. These data are consistent with the well-established complexing properties of the transition metals, which are significantly greater compared to the nontransition metals and the metalloids. While the considerable variations in the literature at present preclude the use of metal partition half-times in aquatic hazard identification, the surrogate for the persistence criterion could be the partition half-time of the bioavailable fraction of the total dissolved metal concentration as determined in a laboratory protocol under standardized conditions.

Inverse relationship between bioconcentration factor and exposure concentration for metals: implications for hazard assessment of metals in the aquatic environment.

The bioconcentration factor (BCF) and bioaccumulation factor (BAF) are used as the criteria for bioaccumulation in the context of identifying and classifying substances that are hazardous to the aquatic environment. The BCF/BAF criteria, while developed as surrogates for chronic toxicity and/or biomagnification of anthropogenic organic substances, are applied to all substances including metals. This work examines the theoretical and experimental basis for the use of BCF/BAF in the hazard assessment of Zn, Cd, Cu, Pb, Ni, and Ag. As well, BCF/BAFs for Hg (methyl and inorganic forms) and hexachlorobenzene (HCB) were evaluated. The BCF/BAF data for Zn, Cd, Cu, Pb, Ni, and Ag were characterized by extreme variability in mean BCF/BAF values and a clear inverse relationship between BCF/BAF and aqueous exposure. The high variability persisted when even when data were limited to an exposure range where chronic toxicity would be expected. Mean BCF/BAF values for Hg were also variable, but the inverse relationship was equivocal, in contrast with HCB, which conformed to the BCF model. This study illustrates that the BCF/BAF criteria, as currently applied, are inappropriate for the hazard identification and classification of metals. Furthermore, using BCF and BAF data leads to conclusions that are inconsistent with the toxicological data, as values are highest (indicating hazard) at low exposure concentrations and are lowest (indicating no hazard) at high exposure concentrations, where impacts are likely. Bioconcentration and bioaccumulation factors do not distinguish between essential mineral nutrient, normal background metal bioaccumulation, the adaptive capabilities of animals to vary uptake and elimination within the spectrum of exposure regimes, nor the specific ability to sequester, detoxify, and store internalized metal from metal uptake that results in adverse effect. An alternative to BCF, the accumulation factor (ACF), for metals was assessed and, while providing an improvement, it did not provide a complete solution. A bioaccumulation criterion for the hazard identification of metals is required, and work directed at linking chronic toxicity and bioaccumulation may provide some solutions.

Transformation/dissolution examination of antimony and antimony compounds with speciation of the transformation/dissolution solutions.

Speciation is held to be a key factor in controlling the ecotoxicity of metals in solution. Using the United Nations transformation/dissolution protocol (T/DP) for metals and sparingly soluble metal compounds, we have examined the transformation/dissolution (T/D) characteristics in terms of the concentrations of total dissolved Sb at pH 6 and 8.5 in 1, 10, and 100 mg/L loadings over 7 d as well as the concentrations of Sb(III) and Sb(V) at the 1 mg/L loadings over 28 d, of sodium hexahydroxoantimonate (NaSb(OH)(6)), antimony metal (Sb), antimony trioxide (Sb(2) O(3)), antimony sulfide (Sb(2) S(3)), sodium antimonate (NaSbO(3)), antimony tris(ethylene glycolate) (Sb(2) (C(2) H(4) O(2) )(3)), antimony trichloride (SbCl(3)), antimony triacetate (Sb(CH(3) COO)(3)), and antimony pentoxide (Sb(2) O(5) ). We also measured the concentrations of the dissolved Sb(III) and Sb(V) species at the 1 mg/L loadings. Because of complexing, the trivalent organic Sb compounds exhibited little or no oxidation of Sb(III) to Sb(V). However, oxidation of Sb(III) to Sb(V) was evident for the trivalent inorganic Sb compounds. Conversely, with pentavalent Sb compounds, there was no reduction of Sb(V) to Sb(III). Based on the percentage of Sb in the compound dissolved or metal reacted at 28 d and 1 mg/L loadings, the solubility rankings at pH 6 are NaSb(OH)(6) > Sb(CH(3) COO)(3) > Sb metal > Sb(2) (C(2) H(4) O(2))(3) > Sb(2) S(3) > Sb(2) O(3) > NaSbO(3) ≈ SbCl(3) > Sb(2) O(5). For pH 8.5 the order is NaSb(OH)(6) > Sb(CH(3) COO)(3) > Sb metal > Sb(2) (C(2) H(4) O(2) )(3) > SbCl(3) > Sb(2) O(3) > Sb(2) S(3) > NaSbO(3) > Sb(2) O(5) . We provide worked examples of how the T/D data have been used to derive hazard classification proposals for Sb metal and these selected compounds for submission to the European Chemicals Agency under the Registration, Evaluation, Authorization and Restriction of CHemicals (REACH) legislation.

A new approach to the hazard classification of alloys based on transformation/dissolution.

Most of the metals produced for commercial application enter into service as alloys which, together with metals and all other chemicals in commerce, are subject to a hazard identification and classification initiative now being implemented in a number of jurisdictions worldwide, including the European Union Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) initiative, effective 1 June 2007. This initiative has considerable implications for environmental protection and market access. While a method for the hazard identification and classification of metals is available in the recently developed United Nations (UN) guidance document on the Globally Harmonized System of Hazard Classification and Labelling (GHS), an approach for alloys has yet to be formulated. Within the GHS, a transformation/dissolution protocol (T/ DP) for metals and sparingly soluble metal compounds is provided as a standard laboratory method for measuring the rate and extent of the release of metals into aqueous media from metal-bearing substances. By comparison with ecotoxicity reference data, T/D data can be used to derive UN GHS classification proposals. In this study we applied the T/DP for the 1st time to several economically important metals and alloys: iron powder, nickel powder, copper powder, and the alloys Fe-2Cu-0.6C (copper = 2%, carbon = 0.6%), Fe-2Ni-0.6C, Stainless Steel 304, Monel, brass, Inconel, and nickel-silver. The iron and copper powders and the iron and nickel powders had been sintered to produce the Fe-2Me-0.6C (Me = copper or nickel) alloys which made them essentially resistant to reaction with the aqueous media, so they would not classify under the GHS, although their component copper and nickel metal powders would. Forming a protective passivating film, chromium in the Stainless Steel 304 and Inconel alloys protected them from reaction with the aqueous media, so that their metal releases were minimal and would not result in GHS classification. For the other alloys, we developed a new critical surface area-toxic units (CSA-TU) approach to derive their GHS classification proposals. The CSA-TU approach can be readily applied to other multicomponent alloy systems, without the need to arbitrarily select a particular component among several as the determinant of toxicity. This paper shows how regulatory obligations, such as those mandated by REACH, can be met with a laboratory-based CSA-TU method for deriving hazard classification proposals for alloys, linking to attendant environmental protection management decisions. Drawing on T/D data derived from laboratory testing of the alloy itself, the CSA-TU approach can be applied to establish scientifically defensible decisions on hazard classification proposals for an alloy of interest. The resulting decisions can then be incorporated into environmental management measures in such jurisdictions as the European Union. Based on an approach developed specifically for alloys, the hazard classification decisions can be regarded as relevant, credible, and protective of the environment. Since alloys are usually more resistant to chemical attack than their components, this approach is a considerable improvement over the possibility provided for in the GHS of calculating a hazard classification level for an alloy from the classification levels of its components.