The influence of water hardness on copper (Cu) toxicity in Daphnia magna was studied using gene expression analysis. Exposing D. magna to Cu in water with increasing levels of hardness decreased the acute toxicity. Hardness did not affect the predicted Cu complexation. After 24 h, D. magna showed an increased level of genes related to metal homeostasis (mt) following exposure to 25 μg Cu/L in hard water. Daphnids in soft and medium water responded to 25 μg Cu/L by upregulation of antioxidant defense and mt genes, revealing oxidative stress as a mechanism of Cu toxicity in D. magna. D. magna exposed to 25 μg Cu/L in soft water did not survive for 96 h. In contrast, those exposed to 25 μg Cu/L in medium and hard water survived for 96 h with significantly higher levels of mt genes. The genes related to oxidative damage (heat shock protein and glutathione S-transferase) in these groups did not deviate from control levels, indicating the protective effect of hardness. Metallothionein genes were upregulated at 17 μg Cu/L at both 24 h and 96 h. The expression of catalase and ferritin increased in this group in soft and hard water at 96 h. The protective effect of hardness (in the tested range) on survival was also observed at a concentration of 25 μg/L. The results suggest metallothionein (A and B), catalase, and ferritin genes, as potential biomarkers for copper exposure in D. magna regardless of hardness.

Metals and metalloids in aquatic environments are a result of anthropogenic activities as well as of natural events. Many investigations have been carried out focusing on certain remote or polluted areas. The present project intended to obtain a more widespread picture of elements in fresh and salt surface water. For this purpose, samples were collected from 22 countries and three continents. These were analyzed for 29 elements, covering potentially toxic elements but also saline elements, by inductively coupled plasma mass spectrometry. Statistical analysis of the obtained results showed significant differences between countries as well as between water types: Alkali metals and earth alkaline metals contributed most to the distinction of water types. The results from this study were consistent with data from the literature regarding fresh water from different locations. Al, As, Cd, Co, Mo, Ni, Se, Ni, and U correlated with the geographic provenience of the samples. A correlation analysis, which also included three perfluorinated alkyl substances from a previous study, showed a correlation between the organic contaminants and V and As.

Crumb rubber, derived from recycled tyres, has been used as a sustainable, low-cost infill material. However, growing evidence suggests that tyre crumb rubber leachates can be highly toxic, underscoring the need for comprehensive risk assessments of different types of rubber and the development of safer alternatives. This study evaluated the acute toxicity of leachates from various infill materials, including black recycled tyre rubbers, coloured thermoplastic rubbers, and a mineral-based material ("Bioflex"), on key models of marine plankton. Specifically, we determined the effects of micronised crumb rubber leachates on the microalga Rhodomonas salina, embryos and nauplii of the copepod Acartia tonsa, and early developmental stages of the sea urchin Arbacia lixula. We also evaluated the toxicity of leachates extracted using an organic solvent compared to those obtained using filtered seawater, using R. salina as a model organism. Toxicity varied significantly among rubber types, with EC₅₀ values ranging from 22.1mgL^-1 to >1505mgL^-1, depending on the organism, and biological endpoint. One of the tested tyre rubber crumbs consistently exhibited high toxicity across all test species, with EC₅₀ values as low as 50mgL^-1 for specific life stages. Among thermoplastic rubbers, green crumb rubber also showed high toxicity towards R. salina, with an EC₅₀ of 25.7mgL^-1. In contrast, the mineral-based material was only toxic to the early stages of A. lixula, exhibiting relatively low toxicity (EC₅₀ = 2305mgL^-1). In most cases, the toxicity of seawater-based leachates was comparable to that of solvent-based extracts, indicating that most toxic compounds affecting R. salina are water-soluble. Metal analysis revealed that the mineral-based material contained lower concentrations of toxic metals, such as zinc, and lower levels of polycyclic aromatic hydrocarbons than the other rubbers. This may partially explain its reduced toxicity to plankton. Our findings demonstrate that leachates from recycled crumb rubber and thermoplastic rubbers are toxic to marine plankton, although the effects are species-specific and dependent on the material composition. Our results also suggest that mineral-based infill materials (e.g., "Bioflex") are ecologically safer alternatives to rubbers. Overall, this study indicates that leachate pollution from recycled tyre rubber and thermoplastic rubber particles poses a potential risk to the pelagic food web, highlighting the importance of restricting or banning their use in areas near sensitive aquatic environments.

A black substance exuding from fractures was observed in 2012 in Ytterby mine, Sweden, and identified in 2017 as birnessite with the composition M_x[Mn(III,IV)]₂O₄∙(H₂O)_n. M is usually calcium and sodium, with x around 0.5. The Ytterby birnessite is unique, with M being calcium, magnesium, and also rare earth elements (REEs) constituting up to 2% of the total metal content. The biogenic origin of the birnessite was established in 2018. Analysis of the microbial processes leading to the birnessite formation and the REE enrichment has continued since then. The process is fast and dynamic, as indicated by the depletion of manganese and of REE and other metals in the fracture water during the passage over the precipitation zone in the mine tunnel. Studies of the exchangeability of metals in the structure are the main objective of the present program. Exposure to solutions of sodium, calcium, lanthanum, and iron led to exchanges and altered distribution of the metals in the birnessite, however, generating phases with almost identical structures after the exchanges, and no new mineral phases were detected. Exchangeability was more efficient for trivalent elements (REE) over divalent (calcium) and monovalent (sodium) elements of a similar size (ionic radii 90–100 pm).