Selenate and selenite uptake, accumulation and toxicity in Lemna minuta

The kinetics of Se uptake and toxicity toLemnawere studied over a period of 14 days of exposure to Se(IV) or Se(VI). The growth ofLemnastopped immediately after exposure to 5.0 mg/L of Se(IV) or Se(VI). The content of chlorophyll and phaeopigments ofLemnaexposed to 5.0 mg/L of Se(IV) was two to three times less than in the control after 3 d exposure.Lemnatook up Se rapidly within the first 3 d. The Se content inLemnaalong with the exposure time fitted well the two-compartment and the hyperbolic model, which demonstrates that the mechanism of Se(IV) and Se(VI) uptake inLemnais not only through passive diffusion, but also through other processes such as ion channel proteins or transporters. The kinetic bioconcentration factors (BCFs) were 231 and 42 for 0.5 mg/L Se(IV) and Se(VI) exposure, respectively. The uptake rate ofLemnareached 263 mg/kg/d and 28 mg/kg/d in the Se(IV) and Se(VI) treatments, respectively. This study showed that Se(IV) has a faster accumulation rate than Se(VI), but a higher toxicity, indicatingLemnacould be a good candidate to remove Se(IV) from water, producing Se-enriched biomass which may eventually also be considered for use as Se-enriched feed supplement or fertilizer.