Mercury and lead: Assessing the toxic effects on growth and metal accumulation by Lemna minor

Lemna minor L. was used to investigate the toxic effects of Pb and Hg either alone or in various binary mixtures under the static test conditions. A full-strength Jacob culture medium was used for the long-term cultivation of duckweeds and the experiments. Tests were run for 4 and 7 days. The EC₅₀ values for Pb was estimated as 6.8±0.2 mg L⁻¹ and 5.5±0.1 mg L⁻¹ for a 4 and a 7-day test periods, respectively. Hg was much more toxic than Pb with the EC₅₀ of 0.64±0.03 mg L⁻¹ (4 days) and 0.48±0.02 mg L⁻¹ (7 days). The amounts of Pb uptake by the plants were determined by atomic absorption spectrometer (AAS). The cold vapor AAS-technique (CV-AAS) was used for Hg determination. The interactive effect between Pb and Hg on growth was evaluated as additive on the basis of statistical data analysis. However, an antagonistic interaction was observed on the metal accumulation efficiency.