Increased focus on the development and application of bioavailability-based metal water quality guideline values requires increased understanding of the influence of water chemistry on metal bioavailability and toxicity. Development of empirical models, such as multiple linear regression models, requires the assessment of the influence of individual water quality parameters as toxicity-modifying factors. The present study investigated the effect of pH on the lability and toxicity of zinc (Zn) to a tropical green microalga (Chlorella sp.). Zinc speciation and lability were explored using the Windermere Humic Aqueous Model (WHAM7), ultrafiltration, and diffusive gradients in thin films (DGT). Zinc toxicity increased significantly with increasing pH from 6.7 to 8.3, with 50% growth inhibition effect concentrations decreasing from 185 to 53 µg l -1 across the pH range. Linear relationships between DGT-labile Zn and dissolved Zn did not vary across the tested pH range, nor did the linear relationship between dissolved (<0.45 µm) and ultrafiltered (<3 kDa) Zn. Our findings show that Zn toxicity to this freshwater alga is altered as a function of pH across environmentally realistic pH ranges and that these toxicity changes could not be explained by Zn speciation and lability as measured by DGT and WHAM7.

Environmental context. Having appropriate and robust models used for developing water quality guidelines is critical for sound environmental management. Methods used to validate models have only been demonstrated appropriate for a small portion of data types used in these models. This study has found that models using certain data types would be more appropriately validated using alternative evaluation criteria. This study serves as an important reference for developing and evaluating robust models.

No abstract

The geographical shift of nickel mining to small island countries of the Southeast Asia and Melanesia region has produced a need to assess the environmental risk associated with increased sediment nickel exposure to benthic estuarine/marine biota. Chemical measurements of nickel concentration and potential bioavailability, including the use of diffusive gradients in thin films (DGT), were compared to effects on 10‐d reproduction of the epibenthic estuarine/marine amphipod Melita plumulosa in nickel‐spiked sediments and field‐contaminated sediments with different characteristics. The 10% effect concentrations (EC10s) for amphipod reproduction ranged from 280 to 690 mg/kg total recoverable nickel, from 110 to 380 mg/kg dilute acid–extractable nickel, and from 34 to 87 μg Ni/m2/h DGT‐labile nickel flux. Nickel bioavailability was lower in sediments with greater total organic carbon, clay content, and percentage of fine particles. Measurements of DGT‐labile nickel flux at the sediment–water interface integrated exposure to nickel from porewater, overlying water, and ingested sediment exposure pathways and were found to have the strongest relationship with the biological response. At most, there was a 29% reduction in 10‐d M. plumulosa reproduction relative to the control when exposed to nickel from field‐contaminated sediments collected from nickel laterite mining regions of New Caledonia. The DGT technique can be used as a complementary tool to measure the bioavailability of nickel in estuarine/marine sediments, especially sediments that are in nickel laterite mining regions where there are no or few toxicity data available for determining biological effects on local species. Based on the combined data set of the 3 nickel‐spiked sediments a DGT‐labile nickel EC10 threshold of 50 (30–69) μg Ni/m2/h was determined. Environ Toxicol Chem 2021;40:1266–1278. © 2020 SETAC

Zinc is an essential element for aquatic organisms, however, activities such as mining and refining, as well as zinc’s ubiquitous role in modern society can contribute to elevated environmental concentrations...

No abstract

Anthropogenic activities in Antarctica have led to contamination of terrestrial sites, and soils in ice‐free areas have elevated concentrations of metals, particularly around current and historic research stations. Effective management of Antarctic contaminated sites depends on the assessment of risks to a representative range of native terrestrial species. Bdelloid rotifers are an abundant and biodiverse component of Antarctic limnoterrestrial communities and play a key role in nutrient cycling in Antarctic ecosystems. The present study investigates the toxicity of five metals (cadmium, copper, nickel, lead, and zinc) to the endemic bdelloid rotifer Adineta editae, both singly and in metal mixtures. Based on the concentrations tested, zinc was the most toxic metal to survival with a 7‐day median lethal concentration (LC50) of 344 µg Zn/L, followed by cadmium with a 7‐day LC50 of 1542 µg Cd/L. Rotifers showed high sensitivity using cryptobiosis (chemobiosis) as a sublethal behavioral endpoint. Chemobiosis was triggered in A. editae at low metal concentrations (e.g., 6 µg/L Pb) and is likely a protective mechanism and survival strategy to minimize exposure to stressful conditions. Lead and copper were most toxic to rotifer behavior, with 4‐day median effect concentrations (EC50s) of 18 and 27 µg/L, respectively, followed by zinc and cadmium (4‐day EC50 values of 52 and 245 µg/L, respectively). The response of rotifers to the metal mixtures was antagonistic, with less toxicity observed than was predicted by the model developed from the single‐metal exposure data. The present study provides evidence that this bdelloid rotifer represents a relatively sensitive microinvertebrate species to metals and is recommended for use in contaminant risk assessments in Antarctica. Environ Toxicol Chem 2023;42:1409–1419. © 2023 SETAC

No abstract