Mkandawire Martin, Lyubun Yelena V, Kosterin Paul V, Dudel E Gert
Dresden University of Technology, Institute of General Ecology and Environmental Protection, Pienner Strasse 8, D-01737 Tharandt, Germany.
Environ Toxicol. 2004 Feb;19(1):26-34. doi: 10.1002/tox.10148.
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 NaHAsO(4). 7H(2)O and NaAsO(3), with 0, 0.0136, 13.6, and 40 mg L(-1) KH(2)PO(4). 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 microg L(-1) As(III) compared with fronds exposed to As(V). The growth rate was stimulated when plants were exposed to 50-250 microg L(-1) of both As(III) and As(V). After exposure to 300-800 microg L(-1) growth inhibition was significantly higher for As(III) than for As(V), whereas above 800 microg 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.
在分批培养中测试了砷（As）物种对浮萍（Lemna gibba L.）的毒性以及磷酸根离子（PO₄³⁻）对砷生物有效性和吸收的影响。将浮萍暴露于六种浓度的NaHAsO₄·7H₂O和NaAsO₃中，并分别添加0、0.0136、13.6和40 mg L⁻¹的KH₂PO₄。在分批培养中，砷对浮萍的毒性与砷浓度并非呈线性关系。与暴露于五价砷（As(V)）的浮萍相比，暴露于20 - 50 μg L⁻¹三价砷（As(III)）的浮萍中，按照经合组织（OECD）和国际标准化组织/德国标准化学会（ISO/DIN）推荐的以叶状体数量计算的生长速率受到显著抑制。当植物暴露于50 - 250 μg L⁻¹的As(III)和As(V)时，生长速率受到刺激。暴露于300 - 800 μg L⁻¹时，As(III)的生长抑制作用显著高于As(V)，而在800 μg L⁻¹以上，As(V)受到的抑制作用最大。缺磷培养条件下（对于0.0136 mg L⁻¹的PO₄³⁻，As(III)和As(V)的生物累积量分别为0.98 ± 0.08和1.02 ± 0.19 g kg⁻¹），As(III)和As(V)的生物累积量显著高于富磷培养条件下（对于40 mg L⁻¹的PO₄³⁻，As(III)和As(V)的生物累积量分别为243和343 mg kg⁻¹）。暴露于As(V)的植物的吸收和累积值略高于暴露于As(III)的植物。暴露于浓度>1 mg L⁻¹的As(III)的植物与暴露于相同浓度As(V)的植物之间，生物累积量没有显著差异。这表明与培养物中的磷含量存在直接关系。毒性可能是由于在吸收过程中，由于热力学性质相近，As(V)替代PO₄³⁻被吸收，这可能改变了培养基中各成分之间的相互作用。毒性模式被解释为分批培养中物种形态变化以及在富氧环境中As(III)氧化为As(V)的表现。
