Natural and anthropogenic lead in soils and vegetables around Guiyang city, southwest China: a Pb isotopic approach.

Soils, vegetables and rainwaters from three vegetable production bases in the Guiyang area, southwest China, were analyzed for Pb concentrations and isotope compositions to trace its sources in the vegetables and soils. Lead isotopic compositions were not distinguishable between yellow soils and calcareous soils, but distinguishable among sampling sites. The highest (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios were found for rainwaters (0.8547-0.8593 and 2.098-2.109, respectively), and the lowest for soils (0.7173-0.8246 and 1.766-2.048, respectively). The (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios increased in vegetables in the order of roots

[Evaluation of phytoavailability of zinc and cadmium in contaminated soils by a short sequential extraction procedure].

Cultivated soils and maize samples from heavy metal contaminated locations affected by zinc smelting activities were collected in Hezhang County, Guizhou Province. Chemical fractions of zinc and cadmium (extracted by 0.01 mol x L(-1) CaCl2 and 0.005 mol x L(-1) DTPA) were evaluated by using a short three-step sequential extraction procedure. Results showed that Zn and Cd in soil were dominated by residual fraction, while the CaCl2 extractable and DTPA extractable fraction are only accounted for 0.63%, 3.91% for Zn, and 10.94%, 10.13% for Cd, respectively. Correlation analyses demonstrated that soil CaCl2 extractable metals were not correlated with maize metal concentrations, whereas the DTPA extractable fraction, residual fraction and total Zn and Cd concentrations were correlated significantly with the metal concentrations in maize roots, stems and leaves. These results indicated that CaCl2 extractable fraction may not pay important role on metal phytoavailability in the studied soils. While DTPA extractable fraction and total metal concentrations can be employed to evaluate metals phytoavailability.