Toxicity of arsenic species to <i>Lemna gibba</i> L. and the influence of phosphate on arsenic bioavailability: Fid-Bau Portal

Toxicity of arsenic species to Lemna gibba L. and the influence of phosphate on arsenic bioavailability

Mkandawire, Martin / Lyubun, Yelena V. / Kosterin, Paul V. / Dudel, E. Gert

10.1002/tox.10148.abs

The toxicity of arsenic (As) species to Lemna gibba L. and the influence of PO $_{4}^{3−}$ on As bioavailability and uptake were tested in batch culture. L. gibba were exposed to six test concentrations of NaHAsO₄ · 7H₂O and NaAsO₃, with 0, 0.0136, 13.6, and 40 mg L⁻¹ KH₂PO₄. In batch culture As toxicity to L. gibba did not relate linearly to As concentration. The growth rate, related to frond number as recommended by OECD and ISO/DIN, was significantly inhibited in fronds exposed to 20–50 μg L⁻¹ As(III) compared with fronds exposed to As(V). The growth rate was stimulated when plants were exposed to 50–250 μg L⁻¹ of both As(III) and As(V). After exposure to 300–800 μg L⁻¹ growth inhibition was significantly higher for As(III) than for As(V), whereas above 800 μg L⁻¹ As(V) was inhibited the most. The bioaccumulation of As(III) and As(V) was significantly higher for P‐deficient cultures (0.98 ± 0.08 and 1.02 ± 0.19 g kg⁻¹, respectively for 0.0136 mg L⁻¹ PO $_{4}^{3−}$ ) than for P‐sufficient cultures (243 and 343 mg kg⁻¹ for 40 mg L⁻¹, respectively). Plants exposed to As(V) had uptake and accumulation values slightly higher than did plants exposed to As(III). No significant differences in bioaccumulation were found between plants exposed to a concentration of As(III) >1 mg L⁻¹ and those exposed to As(V) at the same concentration. This indicates a direct relationship to P content in the culture. Toxicity may result from the uptake of As(V) instead of PO $_{4}^{3−}$ as a result of ion competition during uptake because of close thermodynamic properties, which may change the interaction among components in the media. The toxicity pattern is interpreted as a manifestation of changing speciation in the batch culture and of the oxidation of As(III) to As(V) in an oxygen‐rich environment. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 26–34, 2004.