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A glasshouse pot experiment was conducted to study the effects of phytoextraction bySedum plumbizincicolaand application of rapeseed cake (RSC) on heavy metal accumulation by a subsequent rice(Oryza sativa L.)crop in a contaminated paddy soil collected from east China. After phytoextraction byS. plumbizincicolathe soil and brown rice Cd concentrations effectively declined. After phytoextraction, RSC application reduced brown rice Cd concentrations in the subsequent rice crop to 0.23–0.28 mg kg−1, almost down to the standard limit (0.2 mg kg−1). After phytoextraction and then application of RSC, the soil solution pH, dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations increased during early stages of rice growth resulting directly and indirectly in lowering the bioavailability of the heavy metals. Thus the grain yield of the subsequent rice crop increased and the heavy metals in the brown rice declined significantly. In this contaminated acid soil, growing the hyperaccumulatorS. plumbizincicolaand rice in rotation together with RSC application may therefore be regarded as a viable strategy for safe grain production and bioremediation. [ABSTRACT FROM PUBLISHER]

Abstract: Phosphate is ubiquitous in the environment. However, its impact on sorption of hydrophobic organic compounds in soils has received little attention. Some effects of phosphate on phenanthrene sorption were investigated in this study using two Chinese soils with contrasting properties. The presence of phosphate significantly decreased the capacity and increased the nonlinearity of phenanthrene sorption in the soils, and this sorption-inhibiting effect was more significant at high phosphate concentration. The influence of phosphate on phenanthrene sorption in the soils was governed by the release of dissolved organic carbon (DOC), particularly higher-molecular-weight and highly aromatic DOC, which tended to be enhanced in the presence of phosphate (p <0.01) as evidenced by size exclusion chromatography and specific UV absorbance analysis. Atomic force microscopy and ζ potential analysis reveal that the ringed microaggregates of DOC were disrupted into larger condensed microaggregates and the solid interfaces tended to be more hydrophilic in the presence of phosphate which also inhibited the accumulation of phenanthrene in the soils. This study for the first time points to an important role of phosphate in the sorption of phenanthrene in soils and provides substantial evidence for the mechanisms involved using a combination of microscopic and chromatographic techniques. [ABSTRACT FROM AUTHOR]