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The present study investigated the biochemical response of aquatic plant Wolffia arrhiza (Lemnaceae) treated with lead (Pb) and cadmium (Cd) at a range of concentrations from 1 to 1000 microM. W. arrhiza has been identified as good scavenger of heavy metals from aqueous solution. Pb and Cd accumulation was found to be increased in a concentration- and duration-dependent manner. However, the highest biosorption of heavy metals was found in plants exposed to low levels (10 microM) of Cd and Pb in the nutrient medium. In observing the response to heavy-metal stress, we noted inhibited plant growth and decreased photosynthetic pigments, monosaccharides, and proteins. In addition, Cd was found to be more toxic to plants than Pb. Heavy metals also induced oxidative damage as evidenced by increased lipid peroxidation and hydrogen peroxide levels. In contrast, the deleterious effects resulting from the cellular oxidative state can be alleviated by enzymatic (catalase, ascorbate peroxidase, nicotinamide dinucleotide [NADH] peroxidase) and nonenzymatic (ascorbate, glutathione) antioxidant mechanisms activated in W. arrhiza plants exposed to Cd and Pb, especially at 10 microM. These results suggest that W. arrhiza is a promising bioindicator of heavy-metal toxicity.

Green unicellular alga Acutodesmus obliquus (Turpin) Hegewald et Hanagata (SAG strain no. 276-6) (Chlorophyceae) was used for determination of phytotoxicity of lead (Pb) at the range of concentrations 0.01-500 μM during 7 days of culture. The accumulation of Pb in algal cells was found to be increased in a concentration- and duration-dependent manner. The highest Pb uptake value was obtained in response to 500 μM Pb on the seventh day of cultivation. The decrease in the number and the size of cells and the contents of selected primary metabolites (photosynthetic pigments, monosaccharides, and proteins) in A. obliquus cells were observed under Pb stress. Heavy metal stimulated also formation of reactive oxygen species (hydrogen peroxide) and oxidative damage as evidenced by increased lipid peroxidation. On the other hand, the deleterious effects of Pb resulting from the cellular oxidative state can be alleviated by enzymatic (superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase) and non-enzymatic (ascorbate, glutathione) antioxidant systems. These results suggest that A. obliquus is a promising bioindicator of heavy metal toxicity in aquatic environment, and it has been identified as good scavenger of Pb from aqueous solution.

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A multi-commutation flow analysis system using on-line solid phase extraction and flame atomic absorption spectrometric detection (MCFA-FAAS) was developed for the study of chromium speciation in sewage samples.