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Acute toxicity of thioarsenates to Vibrio fischeri
Author(s) -
PlanerFriedrich Britta,
Franke Doreen,
Merkel Broder,
Wallschläger Dirk
Publication year - 2008
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/07-633.1
Subject(s) - arsenite , arsenate , arsenic , toxicity , environmental chemistry , chemistry , acute toxicity , ec50 , arsenic toxicity , nuclear chemistry , biochemistry , organic chemistry , in vitro
Abstract Thioarsenic species often are the predominant arsenic species in sulfidic environments, yet little is known about their toxicity. We report to our knowledge the first determination of acute toxicity of mono‐, di‐, and trithioarsenate to the bioluminescent bacterium Vibrio fischeri , which increases with an increasing number of thio(SH)‐groups. Whereas mono‐ and dithioarsenate are much less toxic (effective analyte concentration causing a 50% decrease in luminescence [EC50], 676 and 158 mg/L, respectively), the toxicity of trithioarsenate (EC50, 14.4 mg/L) is comparable to the toxicities of arsenate and arsenite (EC50, 9.1 and 26.1 mg/L, respectively). The low toxicity of monothioarsenate is remarkable, because it has chemical properties very similar to those of arsenate. In contrast to the toxicities of arsenite and arsenate, the toxicity of thioarsenates increases with exposure time, suggesting a lack of detoxification mechanisms or a conversion of thioarsenic species into arsenic oxyanions after uptake. We determined the acute toxicity of synthetic arsenite solutions with varying sulfide concentration to V. fischeri. Arsenic speciation in these solutions was measured by ion chromatography–inductively coupled plasma–mass spectrometry, and the observed toxicity was related to the different arsenic species present. High inhibition of luminescence was observed at low and high ratios of sulfur to arsenic, in which arsenite or a mixture of di‐, tri‐, and tetrathioarsenate dominated arsenic speciation. Acute toxicity decreased at sulfur to arsenic ratios of from 1 to 10, with a minimum luminescence inhibition of 30% at a ratio of 3.5, at which concentrations of 55 mg/L of arsenite and 30 mg/L of trithioarsenate were determined. The toxicity observed under these conditions is much lower than that anticipated from the individual dose–response curves that predict each species alone already should cause 70 to 80% inhibition. The low toxicity suggests an antagonistic toxicological interaction between arsenite and trithioarsenate.