The Effect of Major Ions and Dissolved Organic Matter on Complexation and Toxicity of Dissolved Thallium to Daphnia magna

Abstract

Thallium (Tl) is a trace element associated with base metal mining and processing, but little is known regarding how its toxicity is influenced by water chemistry. In the present study, the 48‐h median lethal concentration (LC50) of Tl to Daphnia magna was determined in a standard laboratory water, and toxicity was reassessed under conditions of varying cation (Ca2+, K+, Na+), anion (Cl–, HCO–3), and dissolved organic matter (DOM) concentrations. The calculated 48‐h LC50 of 1.86 mg Tl/L was consistent with previous work on Tl toxicity to D. magna. At the 48‐h LC50 concentration, changes in water chemistry had no statistically significant effect on mortality, although there was a trend toward lower Tl toxicity with elevated water K+. Test waters containing 10 mM CaCl2 did not support control survival. The measurement of Tl complexation with DOM using asymmetric flow field flow fractionation confirmed the outcomes of biogeochemical speciation modeling: Tl speciation was relatively unaffected by water chemistry, and the majority of Tl remained in the ionic form across all treatments. These data indicate that Tl toxicity is largely independent of speciation, a property that will greatly simplify risk assessments for this metal in freshwaters. Environ Toxicol Chem 2019;38:2472–2479. © 2019 SETAC

Effects of Acute and Subchronic Waterborne Thallium Exposure on Ionoregulatory Enzyme Activity and Oxidative Stress in Rainbow Trout (Oncorhynchus mykiss)

“…Details of exposure water Tl concentrations have been previously reported in Table 1 of Nagel et al (2023). Briefly, acute exposure measured values (mean ± SD, n = 6) of 0.11 ± 0.01, 0.87 ± 0.01, 2004 ± 73, and 4200 ± 196 µg L –1 were recorded for nominal exposure concentrations of 0, 0.8, 2135, and 4270 µg L –1 .…”

“…Rainbow trout (size 19–55 g) were exposed to Tl, as described in Nagel et al (2023). Briefly, individual fish ( n = 8 per exposure concentration) were held in 8‐L glass aquaria containing 4 L of dechlorinated facility water.…”

“…The water sampling regime and analysis of water Tl occurred exactly as detailed in Nagel et al (2023). Details of these protocols can also, however, be found in the accompanying Supporting Information.…”

“…Analyses were conducted to assess the relationship between branchial NKA activity and the previously published Tl gill burden data for these same fish from Nagel et al (2023). Analyses were performed using a simple linear regression, where NKA activity was plotted against Tl burden for acute and subchronic data sets.…”

Accumulation of Thallium in Rainbow Trout (Oncorhynchus mykiss) Following Acute and Subchronic Waterborne Exposure

“…This has also been shown experimentally, with several studies noting that Tl does not bind MT (Caron et al, 2017; Rosabal et al, 2016). Similarly, Tl speciation in freshwater is dominated by the free Tl + ion and the formation of complexes in the presence of dissolved organic matter (a complex organic molecule containing thiol groups) is negligible (Nagel et al, 2019). This supports the idea that MT is unlikely to play an important role in the accumulation of Tl in the gill or, indeed, other tissues.…”