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As the biogeochemical cycling of S in soil is closely associated with the mobility and bioavailability of heavy metals, in this study, we investigated the influence of S fertilization (S and SO) in paddy soils on rice growth, iron plaque formation over root surface, and Cu speciation of rice rhizosphere soil under flooding conditions. The dry weight and height of rice plants increased significantly after S fertilization, indicating that S fertilization of Cu-contaminated paddy soils can enhance rice growth. Sulfur fertilization (less than 500 mg/kg) promoted the formation of iron plaque, thus sequestering a large amount of Cu on root surface and decreasing the bioavailability of Cu by inducing transformation of Cu bioavailable fractions (exchangeable, carbonate oxides, or iron and manganese oxide bound to Cu) to Cu bound to organic matter. Copper K-edge X-ray absorption near-edge structure (XANES) revealed that S fertilization increased the percentage of Cu present as CuS and Cu-cysteine in rice rhizosphere soil, thus reducing Cu mobility. As Cu concentration in rice plants decreased and the biomass of rice plants increased after S fertilization, it can be suggested that S fertilization may be an effective approach for managing Cu-contaminated paddy soils. [ABSTRACT FROM AUTHOR]

The concentrations, leachability and vertical distributions of chromium (Cr) and other metal elements were determined in soil and the level was also determined in groundwater and surface water around an abandoned chromate chemical plant located in Hangzhou, China. The results showed that Cr, Pb, Zn, Cd, Cu, Hg and As heavily polluted the surface soil and groundwater. However, the surface water from a river near the abandoned chemical plant was not heavily polluted by the aforementioned heavy metals. The leachability of metals was not uniform within different sampling points. The highest concentrations of Cr (170.18 mg/L) and Cr(VI) (130.59 mg/L) in the soil leaching solution were recorded at a depth of 0-20 cm at the warehouse in the center of the plant. However, the attenuation of heavy metals (Cr, Pb, Zn, Cd and Hg) toward the vertical distribution was fast with increasing depth. Our results suggest that the multi-element pollution in soil and water may pose a drastic risk to the environment and human health surrounding those abandoned chemical plants in China and other developing countries with fast urbanization. [ABSTRACT FROM AUTHOR]

Elsholtzia splendens is a well-known Cu-tolerant plant; yet, the impact of Cu-contaminated soil on bacterial community in its rhizosphere is not known. We studied the spatial variability of bacteria in the rhizosphere using Cu-contaminated soil with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and real-time PCR. In the uncontaminated soil, the content of the dissolved organic carbon (DOC) and bacterial diversity gradually increased in the rhizosphere soil along the root growth direction (from the interface zone to the meristematic zone), while for the Cu-contaminated soil, the highest DOC content and the strongest potential bioavailability of Cu were found in the interface zone, which also had the lowest bacteria diversity. Bacteria diversity was positively correlated with DOC in the uncontaminated soil ( p < 0.01) but not in the contaminated soil. Compared with uncontaminated soil, some species such as Firmicutes only existed in the rhizosphere of contaminated soil, while the very small amount (if any) of some species exists such as Deinococcus- Thermus, indicating that the contaminated environment altered the bacterial composition. Moreover, spatial variation of the bacterial community was found among different soil zones. Real-time PCR confirmed the spatial variation via the gene expression of flagellin ( fliC) and chemotaxis gene ( cheA). The spatial characteristics of cheA expression were consistent with that of DOC and bacterial diversity. In conclusion, we demonstrated that the spatial variation of the bacterial community in the rhizosphere was present, independent of Cu contamination. DOC and Cu toxicity may affect specific gene expressions such as fliC and cheA, resulting in bacterial spatial variation. [ABSTRACT FROM AUTHOR]