The toxicity of sulfur to microtox® from acetonitrile extracts of contaminated sediments

Abstract

Toxicity bioassays of solvent extracts of sediments are used to evaluate the toxicological effects of extracted hydrophobic organic contaminants. However, this type of bioassay assesses the toxicity of all extracted compounds, natural or anthropogenic. Sediment extracts are typically subjected to cleanup procedures before chemical analysis to remove interfering, coextracted substances. This study evaluated the effect of cleanup procedures on the toxicity of acetonitrile extracts of contaminated sediments by using the Microtox® bioluminescence bioassay. Extract cleanup significantly reduced toxicity of most extracts when copper powder was added to remove coextracted sulfur. Microtox was shown to be highly sensitive (EC50 of 24.7‐35.8 μg/L) to elemental sulfur dissolved in several organic solvents. Toxicity tests utilizing solvent extracts of sediments must take into account the toxic effects of coextracted sulfur on bioassay organisms to accurately assess the environmental impacts of extracted hydrophobic contaminants.

Confirmation of elemental sulfur toxicity in the Microtox® assay during organic extracts assessment of freshwater sediments

“…The algal test was the least sensitive (EC50/96 h Ͼ 1,000 g S/ L), followed by the D. magna test (EC50/48 h of 802.9 g S/L) and the Microtox test (EC50/15 min of 11.9 g S/L). The bacterium used in the Microtox assay was clearly the species most sensitive to elemental sulfur dissolved in DMSO, and the measured EC50 is in good agreement with that reported by Jacobs et al [22].…”

“…Furthermore, Jacobs et al [22], using a cleanup procedure that combines C 18 columns and copper, concluded that the elemental sulfur in organic extracts of sediments can be toxic in the Microtox assay. As sulfur concentrations were not measured in the aforementioned paper, its results still must be verified.…”

“…Elemental sulfur, which represents approximately 1% of total sulfur in the sediment of eutrophic lakes [18], is reported to be soluble in many of the organic solvents used to prepare Microtox extracts, such as acetone [19] or hexane [20]. An analysis of the published data [21,22] reveals that the elemental sulfur dissolved in different organic solvents is highly toxic for V.…”

Toxicity Assessment by Microtox® in Sediments, Pore Waters and Sediment Saline Elutriates in the Gulf of Gdansk (Baltic Sea)

“…4. These findings are in agreement with several authors who found sediment toxicity related to low redox levels and high levels of sulfides and elemental sulfur generally present in anoxic sediments [6,33,48,49]. High pore water ammonia concentrations can also be inhibitory for Vibrio fischeri bacteria [35].…”

Toxicity of elemental sulfur in sediments

“…A form of cyclic S was shown to be toxic in a bacterial lumines-8 cence test, both tested as pure compound and from extracts of sediments in accordance with a previous Ž . report Jacobs et al, 1992 . The sulfur dominated the acute toxicity in extracts of the two sediments and Ž probably also in the tests of whole sediments Svenson .…”