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Phytoremediation is becoming an established technology for environmental clean-up and protection. Hyperaccumulator plants are potential tools to remove excess metals from contaminated soils. As an efficient operational routine technology, phytoextraction requires a better knowledge of tolerance and accumulation for excess metals by particular plants. Based on the vegetation survey, a new zinc (Zn)-accumulating ecotype of Sedum alfredii Hance naturally-growing in an old Zn/lead (Pb) mining region in Quzhou City (29°17′ N, 118°56′ E) and a non-Zn-accumulating ecotype of Sedum alfredii Hance in the suburb of Hangzhou City (30°06′ N, 120°12′ E), Zhejiang province were found. To identify Zn tolerance and accumulation characteristics of the two ecotypes of Sedum alfredii Hance, a solution culture experiment was carried out with four treatments: 0.0325 (CK), 20, 80, 160 mg Zn L−1 in the basic nutrient solution. The biomass of root, stem and leaf for the ecotype of Sedum alfredii from Zn/Pb mining area, as well as of leaf of non-Zn-accumulating ecotype of Sedum alfredii, expressed as dry weight, were not significantly different among the treatments after 12 days. However, the biomass of root and stem for non-Zn-accumulating ecotype of Sedum alfredii in treatments with 80 and 160 mg Zn L−1 were significantly lower than that of the control treatment (CK). The results indicated that Zn concentrations in leaves, stems and roots of the test plants increased significantly with increasing Zn concentration in the nutrient solution. Zn concentrations in leaves and stems of the ecotype from Zn/Pb mining area were 25–34 and 7–48 fold higher than those in leaves and stems of the non-Zn-accumulating ecotype. The amounts of Zn accumulated in shoots (leaves and stem) of the ecotype from Zn/Pb mining area in 20, 80 and 160 mg Zn L−1 treatments were significantly larger than those of the non-Zn-accumulating ecotype. As the Zn concentrations on the dry weight in leaves and stems of the ecotype from Zn/Pb mining area were 16,740 and 19,567 mg kg−1 in the 80 mg Zn L−1 treatment, this ecotype can be regarded as a Zn hyperaccumulator. [ABSTRACT FROM AUTHOR]

Copper pollution in soils is widespread° and its accumulation in crop products could pose a risk on human health. In this paper, bioavailability of added copper (Cu) and critical Cu concentrations in a vegetable garden soil was evaluated for Chinese cabbage (Brassica chinensis L.), pakchoi (Brassica chinensis L.), and celery (Apiumg graveolens L. var. dulce DC) based on human dietary toxicity. The availability of added Cu in the soil decreased with incubation time, and had minimal change after 10-12 weeks. After incubated for 12 weeks, about 60% of added Cu was not extractable by DTPA. The same crops were also grown in sand culture to determine their responses to solution Cu. Shoot growth was significantly inhibited at Cu concentrations above 10 mg kg[sup -1] in the solution or above 150 mg kg[sup -1] (DTPA-Cu) in the soil. The sensitivity of the crops to Cu toxicity differed among the three vegetable crops. Copper concentration in shoots and edible parts varied with Cu supply levels and type of the vegetables. Negative correlations (r= -0.90-0.99**) were noted between Cu concentration in shoots and fresh matter yields, but Cu concentrations in the edible parts were positively correlated with available and total Cu in the soil (r= 0.91-0.99**). The critical tissue Cu concentrations at 10% shoot DM reduction were 19.4, 5.5, 30.9 mg kg[sup -1] for Chinese cabbage, pakchoi, and celery, respectively. Based on the threshold of human dietary toxicity for Cu (10 mg kg[sup -1]), the critical concentrations of total and available Cu in the soil were 430 and 269 mg kg[sup -1] for pakchoi, 608 and 313 mg kg [sup -1] for celery, and 835 and 339 mg kg-1 for Chinese cabbage, respectively. [ABSTRACT FROM AUTHOR]