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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]

Lead concentrations in roots, stems and leaves of accumulating and non-accumulating ecotypes of Sedum alfredii (Hance) were studied through a hydroponic experiment with different Pb concentrations supplied as Pb(NO3)2. Lead concentrations in leaves and stems of the accumulating ecotype were 4–9 times and 3–5 times those of the non-accumulating ecotype, and Pb-accumulated amounts in stems and leaves of the accumulating ecotype were 4–9 times and 8–11 times higher than those of the non-accumulating ecotype, respectively. The results indicated that the accumulating ecotype had better ability to transport Pb from roots to shoots. The subcellular distributions of Pb in the root, stem and leaf tissues were studied using sucrose differential centrifugation. Approximately 50% of Pb contents was found to be associated with the cell wall fraction in stems of the accumulating ecotype and the percentage increased to 80% both in roots and leaves, no matter when plants were grown with different levels of Pb. The results indicated that the distribution of Pb on cell walls of the accumulating ecotype could mainly account for the high tolerance to Pb. [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]

Abstract: A pot experiment and a sandy culture experiment grown with three vegetable crops of Chinese cabbage (B. chinensis L., cv. ZaoShu 5), winter greens (B. var. rosularis Tsen et Lee, cv. Shang-Hai-Qing) and celery (A. graveolens L. var. dulce DC., cv. Qing-Qin) were conducted, respectively. The initial soil and four incubated soils with different extractable Cd (0.15, 0.89, 1.38, 1.84 and 2.30 mg Cd/kg soil) were used for the pot experiment. Five treatments were designed (0, 0. 0625, 0. 125, 0.250 and 0.500 mg Cd/L) in nutrient solution in the sandy culture experiment. Each treatment in pot and sandy culture experiments was trireplicated. The objectives of the study were to examine Cd accumulation in edible parts of selected vegetable crops, its correlation with Cd concentrations in vegetable garden soil or in nutrient solution, and evaluate the criteria of Cd pollution in vegetable garden soil and in nutrient solution based on the hygienic limit of Cd in vegetables. Cadmium concentrations in edible parts of the three selected vegetable crops were as follows: 0.01--0.15 mg/kg fresh weight for Chinese cabbage, O. 02--0.17 mg/kg fresh weight for winter greens, and 0.02--0.24 mg/kg fresh weight for celery in the pot experiment, and 0.1--0.4 mg/kg fresh weight for Chinese cabbage, 0.1--1.4 mg/kg fresh weight for winter greens, and 0.05--0.5 mg/kg fresh weight for celery in the pot experiment(except no-Cd treatment). The order of the three test vegetable crops for cadmium accumulation in the edible parts was celery > winter greens > Chinese cabbage in both the pot experiment and the sandy culture experiment. Cadmium accumulation in edible parts or roots of the vegetable crops increased with increasing of cadmium concentration in the medium(soil or nutrient solution). And cadmium concentrations in edible parts of the test vegetable crops were significantly linearly related to the Cd levels in the growth media (soil and nutrient solution). Based on the... [ABSTRACT FROM AUTHOR]

Abstract: A field experiment located in Taihu Lake Basin of China was conducted, by application of urea or a mixture of urea with manure, to elucidate the interception of nitrogen (N) export in a typical rice field through “zero-drainage water management” combined with sound irrigation, rainfall forecasting and field drying. N concentrations in floodwater rapidly declined before the first event of field drying after three split fertilizations, and subsequently tended to return to the background level. Before the first field drying, total particulate nitrogen (TPN) was the predominant N form in floodwater of plots with no N input, dissolved inorganic nitrogen (DIN) on plots that received urea only, and dissolved organic nitrogen (DON) on plots treated with the mixture of urea and manure. Thereafter TPN became the major form. No N export was found from the rice field, but total nitrogen (TN) of 15.8 kg/hm2 was remained, mainly due to soil N sorption. The results recommended the zero-drainage water management for full-scale areas for minimizing N export. [Copyright &y& Elsevier]