Metal contaminants of emerging concern in aquatic systems

Abstract

Environmental context There is potential for a range of metals being used in emerging industries to pose a risk if they reach aquatic environments. This is assessed by evaluating known environmental concentrations against available toxicity data. In most instances risks are low with current usage. Areas are identified where additional data are needed. Abstract The environmental concentrations and aquatic toxicity of a range of technology-critical metals comprising platinum group and rare earth group elements, together with gallium, germanium, indium, lithium, niobium, rhenium, tantalum, tellurium and thallium, have been reviewed to determine whether they pose a risk to aquatic ecosystem health. There is a reasonable body of toxicity data for most, but the quality is quite variable, and more data are required. Chronic toxicity EC10 or NOEC values are generally in the low mg L–1 range, far higher than the current environmental concentrations in the ng L–1 range, meaning that the existing risks to ecosystem health are extremely low. Missing are reliable toxicity data for niobium and tantalum, while confounding results for lanthanum toxicity need to be resolved. There is a likelihood that the currently low concentrations of most of these elements will increase in future years. Whether these concentrations are in bioavailable forms remains to be reliably determined. For most of the elements, measured speciation information is scarce, and unfortunately the thermodynamic data required to calculate their speciation are incomplete. In addition to this problem of uncertain speciation for some of these metals, notably those present in oxidation states of III or higher, there is also a need to explore the links between speciation and bioavailability for these higher valence metals. For circumneutral solutions, the calculated concentrations of the free metal ion tend to be very low for these metals and under such conditions the link between metal speciation and bioavailability is unclear.

Metal bioavailability in aquatic systems— beyond complexation and competition

“…Research over the past 50 years has mainly focused on the impact of high-volume base metals such as Fe, Zn, Cu, Ni and elements such as Cd and As that are present in mineral deposits. The growing world demand for rare earth elements and other technology critical elements reveals a large ecotoxicological data gap for these elements (Dang et al, 2021;Batley and Campbell, 2022). Moreover, further scrutiny of the role played by natural organic matter other than metal complexation and the effects of multiple metals other than competition are needed to provide the scientific knowledge required to build the next-generation of metal uptake/toxicity predictive models.…”

Atomic spectrometry update: review of advances in elemental speciation

“…In reviewing (121 references) metal contaminants of emerging concern in aquatic systems , Batley et al stated that for PGEs, REEs, Ga, Ge, In, Li, Ni, Rh, Ta, Te and Tl, there is a reasonable body of toxicity data for most, but the quality is quite variable, and more data are needed. 21 They noted that reliable toxicity data for Nb and Ta are missing, while the conflicting results for La toxicity need to be resolved, that for most of the elements, measured speciation information is scarce, and for those present in oxidation states of 3+ or higher, there is also a need to explore the links between speciation and bioavailability. The authors then systematically work through the analytes or groups of analytes, summarising the recent literature on (a) environmental concentrations and speciation and (b) aquatic toxicity.…”

Single and combined phytoextraction of lead and cadmium on submerged plants Potamogeton pusillus L.: removal, bioaccumulation pattern, and phytotoxicity

“…Industrialization is among the major causes of environmental degradation and contamination of surface water bodies (e.g., ponds, rivers, streams), putting ecosystems and human health at risk (Song et al 2023). Industrial wastewater is produced in large volumes and, in most cases, is discharged into the environment without being treated, releasing a wide variety of pollutants into the aquatic environment, including heavy metals and organic compounds (Batley and Campbell 2022).…”