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Abstract: All the regulations that define a maximum concentration of metals in the receiving soil are based on total soil metal concentration. However, the potential toxicity of a heavy metal in the soil depends on its speciation and availability. We studied the effects of heavy metal speciation and availability on soil microorganism activities along a Cu/Zn contamination gradient. Microbial biomass and enzyme activity of soil contaminated with both Cu and Zn were investigated. The results showed that microbial biomass was negatively affected by the elevated metal levels. The microbial biomass-C (Cmic)/organic C (Corg) ratio was closely correlated to heavy metal stress. There were negative correlations between soil microbial biomass, phosphatase activity and NH4NO3 extractable heavy metals. The soil microorganism activity could be predicted using empirical models with the availability of Cu and Zn. We observed that 72% of the variation in phosphatase activity could be explained by the NH4NO3-extractable and total heavy metal concentration. By considering different monitoring approaches and different viewpoints, this set of methods applied in this study seemed sensitive to site differences and contributed to a better understanding of the effects of heavy metals on the size and activity of microorganisms in soils. The data presented demonstrate the relationship between heavy metals availability and heavy metal toxicity to soil microorganism along a contamination gradient. [Copyright &y& Elsevier]

Abstract: The role of rhizosphere bacteria in facilitating the solubility of copper (Cu) in contaminated soil and Cu accumulation in plant were studied. The bacteria strains were isolated from the rhizosphere of Elsholtzia splendens, a Cu accumulator growing on Tonglu Mountain copper mines. After the sandy soils containing 237 mg kg−1 were incubated with the bacteria strains, it was indicated that rhizosphere microbes played an important role in influencing the availability of water-soluble Cu in soils. Soils had greater concentrations of water-extractable Cu compared with axenic soils inoculated with different bacterial strains. Further evidence for bacterial facilitation of increased solubility of Cu in the soil was obtained using the antibiotic ampicillin (0.1 mg g− 1). There were 36% decreases in Cu concentration in the presence of bacterial strain MS12 and ampicillin together compared with bacterial inoculation alone. Different bacterial strains had different abilities on soil water-soluble Cu. To achieve the highest rates of plant Cu accumulation, it was necessary for bacteria to be present in the rhizosphere of E. splendens. Inoculated plants supplied with 20 μmol L− 1 CuSO4 had significantly greater concentrations of Cu in shoots and roots than uninoculated plants and bacterial strain MS2 was the most effective strain in promoting plant Cu uptake. There were 2.2-fold and 2.5-fold increases in Cu accumulation in the shoots and roots of plants inoculated with strain MS2 compared to axenic controls. Furthermore, when ampicillin and the bacterial strains were added together to the nutrient solution, the Cu concentrations in roots and shoots of ampicillin-treated plants were lower than those in inoculated plants. When ampicillin was added to the nutrient solution, Cu accumulation was inhibited by about 24–44% in shoots and 20–44% in roots. The above results provided a new insight into the phytoremediation of Cu-contaminated soil. [Copyright &y& Elsevier]

A new Ni(II) compound [Ni(bim) 2 (H 2 O) 4 ] (1,5-nds)·(H 2 O) 0.5 1 (bim = benzimidazole, 1,5-nds-Na = disodium 1,5-naphthalenedisulfonate) was readily synthesized at room temperature. Although compound 1 is only a mononuclear compound, it is extended into a 2D supermolecule layer by hydrogen bonding interactions. Hirshfeld surfaces and fingerprint maps of compound 1 crystal packing were calculated to gather information on non-covalent interactions. Photoluminescence experiments showed that 1 not only possessed good solid-state fluorescence performance but also favorable fluorescence characteristics and stability in aqueous solutions, which can be exposed to acidic and alkaline environmental conditions (pH = 1–14) for a long time. Remarkably, compound 1 displayed outstanding anti-interference properties, high sensitivity, high quenching rate, and low limit of detection (LOD) against acetylacetone (acac), MnO 4 −, and tetracycline (TET) in water media via the Turn-Off effect (LOD:7.03 μM for acac, 2.92 μM for MnO 4 − and 0.65 μM for TET). Especially, compound 1 can also be used as a rare ratiometric fluorescent probe for the detection of Ag + down to the nM level. The exceptional multi-responsive performance suggested that compound 1 could be a potential multifunctional sensor. Furthermore, possible mechanisms were systematically investigated. [Display omitted] • A new compound [Ni(bim) 2 (H 2 O) 4 ](1,5-nds)·(H 2 O) 0.5 1 with a 2D supermolecule layered structure was directly synthesized. • Compound 1 is a multifunctional fluorescent sensor. • Compound 1 can detect acetylacetone, MnO 4 − and tetracycline by the turn off effect. • Compound 1 has a low detection limit for Ag + down to the nM level. • Compound 1 possess excellent fluorescence properties and stability in acid-base solutions. [ABSTRACT FROM AUTHOR]