Ecotoxicity tests were performed with fish, invertebrates, and algae to investigate the effect of water quality parameters on Mn toxicity. Models were developed to describe the effects of Mn as a function of water quality. Calcium (Ca) has a protective effect on Mn toxicity for both fish and invertebrates, and magnesium (Mg) also provides a protective effect for invertebrates. Protons have a protective effect on Mn toxicity to algae. The models derived are consistent with models of the toxicity of other metals to aquatic organisms in that divalent cations can act as competitors to Mn toxicity in fish and invertebrates, and protons act as competitors to Mn toxicity in algae. The selected models are able to predict Mn toxicity to the test organisms to within a factor of 2 in most cases. Under low-pH conditions invertebrates are the most sensitive taxa, and under high-pH conditions algae are most sensitive. The point at which algae become more sensitive than invertebrates depends on the Ca concentration and occurs at higher pH when Ca concentrations are low, because of the sensitivity of invertebrates under these conditions. Dissolved organic carbon concentrations have very little effect on the toxicity of Mn to aquatic organisms.

Purpose To support the needs of downstream users of zircon sand and other industry stakeholders, the Zircon Industry Association (ZIA) conducted an industry-wide life cycle assessment (LCA) with the aim to quantify the potential environmental impacts of zircon sand production, from mining to the separation of zircon sand (zirconium silicate or ZrSiO 4). This novel work presents the first, globally representative LCA dataset using primary data from industry. The study conforms to relevant ISO standards and is backed up by an independent critical review. Methods Data from ZIA member companies representing 10 sites for the reference year 2015 were collected. In total, more than 77% of global zircon sand production was covered in this study. All relevant mining routes (i.e. wet and dry mining) were considered in the investigation, as well as all major concentration and separation plants in major zircon sand-producing regions of the world (i.e. Australia, South Africa, Kenya, Senegal and the USA). As it is common practise in the metal and mining industry, mass allocations were applied with regard to by-products (Santero and Hendry, Int J Life Cycle Assess 21:1543-1553, Santero and Hendry 2016) where economic allocation is only applied if high-valued metals like PGMs are separated with a process flow. A sensitivity analysis was used to understand the relevance of the major contributing effect of the life cycle impact assessment (LCIA) results, power consumption. Results and discussion It was shown that mining is the main contributor to all impact categories (between 65 and 90% compared with the mineral separation plant). For example, primary energy demand (PED) and global warming potential (GWP) contribute 76% and 70%, respectively, to the production of 1 kg of zircon sand. PED for 1 kg of zircon sand is calculated to be 4 MJ, whereas the GWP is 0.32 kg CO 2 equivalent per kg of zircon sand. The main influencing factor in the mining process is electricity consumption. Conclusions In conformity with relevant ISO standards, and backed up by a critical review, this LCA quantified the potential environmental impacts associated with the production of the zircon sand (ZrSiO 4). With this study, a sound dataset for downstream users of zircon sand has been provided. It is the first LCA dataset of the ZIA.

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