Experimental Assessment of Using Soluble Humic Substances for Remediation of Heavy Metal Polluted Soils

Since heavy metals are nondegradable and strongly bonded in soils, remediation of heavy metal polluted soils by extraction is difficult and current extraction techniques require harsh chemicals such as ethylenediaminetetraacetic acid (EDTA). However, use of EDTA is environmentally problematic because of costs, persistence, toxicity and deterioration of soil structure. Therefore, the potential of soluble natural humic substances (HS) to extract heavy metals from contaminated soils is tested as an environmentally friendly substitute for EDTA. A strongly polluted, calcareous urban soil (CRC soil) and a moderately polluted agricultural soil (CUP soil) were extracted at neutral pH in batch mode by three HS solutions from beech and Norway spruce litter (Beech-HS and Spruce-HS) and processed cow slurry (Bio-HS), all containing 25 mM dissolved organic carbon (DOC). After 10 extractions with a solution to soil ratio of 5:1 (L/kg), 8% to 39% of the total Cd, Cu, Ni and Pb soil contents, lowest for Ni and highest for Cu/Pb, were extracted. Natural and processed HS samples had comparable capacities to extract the heavy metals. A comparison of 100 mM DOC of Bio-HS and EDTA as extractants for Cu from the CRC soil showed extraction of 67% by EDTA and 41% by Bio-HS, indicating somewhat higher efficiency of EDTA than of HS. Sequential extraction of the CRC soil after Bio-HS and EDTA extraction showed removal of exchangeable, carbonate- and metal oxide-bound Cu but also of some residual Cu. It is therefore concluded that HS appears to be an attractive and promising alternative to EDTA as remediation agent for heavy metal polluted soils provided cheap HS of good quality is easily available.     

Ni2+对不同发育阶段斜纹夜蛾虫体血淋巴能量物质的影响

研究了饲料中不同浓度的Ni2+(140mg/kg)对连续3个世代斜纹夜蛾Spodoptera litura Fabricius6龄末幼虫、蛹和成虫血淋巴中能量物质总糖、蛋白质和脂肪含量及血淋巴中热量值的影响。结果表明,Ni2+胁迫1个世代,6龄末幼虫、蛹和成虫血淋巴中的总糖含量均低于对照,而血淋巴中的蛋白质含量则在低浓度Ni2+胁迫下增高,在高浓度Ni2+胁迫下降低;只有受120mg/kg Ni2+胁迫的6龄末幼虫血淋巴的脂肪含量高于对照,而蛹和成虫血淋巴中的脂肪含量及热量值均低于对照。在Ni2+胁迫的第2、3代,6龄末幼虫、蛹和成虫血淋巴中的总糖、蛋白含量和热量值与饲料中Ni2+浓度的反应关系均表现为低浓度Ni2+胁迫增加而高浓度Ni2+胁迫降低的趋势;然而,血淋巴中的脂肪含量随饲料中Ni2+浓度的增加而降低。因此,重金属Ni2+对S.litura能量物质的影响与虫体内能量物质的种类和虫体的发育阶段有一定的关联。     

Antibody suppression by zinc and nickel

Rats were treated with zinc chloride and with nickel acetate 2 weeks prior to immunization withE. coli bacteriophageT-1; antibody titers to bacteriophageT-1 were reduced 500–2600-fold in metal-treated rats compared to titers found in untreated control animals. Examination of the effect of metal treatment on lymphocyte blastogenesis revealed a significant reduction in the number of blast cells in the spleens of metal-treated rats.     

On the rate limiting step in downhill transport via the LacY permease of Escherichia coli

Strains of Escherichia coli K12 were constructed for the specific purpose of evaluating the inducibility of the influx mechanism controlled by the lacY gene. These strains are heteromerodiploids characterized by a high and relatively constant level of β-D-galactosidase which is not affected significantly by induction of the Lac operon. These properties were obtained by introducing episomal lacI⁺,O^c,Z⁺,Y^? genes into the cells. In these merodiploids the rate of o-nitrophenyl-β-D-galactopyranoside (ONPG) hydrolysis of extracted cells is 50-times that of intact cells. This difference indicates that the rate limiting step in the ONPG hydrolysis by intact cells is influx. Using a set of merodiploids with and without the LacY transport system, we were able to demonstrate a specific induction of ONPG influx. However, the increase in influx due to induction was only 3.5-fold as compared to the 40-fold increase observed when the LacY permease was measured by intracellular accumulation of [¹⁴C] TMG.     

The influence of Nickel on population dynamics and on some demographic parameters of Daphnia magna

Daphnia magna was cultured with two different techniques at sublethal nickel concentrations from 0 up to 200 µg Ni l^-1. The results of the experiments run with cohorts of single individuals in static cultures were compared with the results obtained with populations held in flow through cultures. The most sensitive demographic parameters in cohorts were life span, the total number of progeny and the achievable maximum body length. The investigated nickel concentrations lowered the mean animal density in populations. Size class distribution was affected and the oscillation of the percentage of ovigorous adults increased with increasing nickel concentrations. In 200 µg Ni l^-1 one population extincted. Individuals in static cultures exposed to the same nickel concentration produced at least two neonates. Both employed techniques are discussed.     

Hazard and risk assessment of human exposure to toxic metals using in vitro digestion assay

Clean-up targets for toxic metals require that the site be “fit for purpose”. This means that targets are set with respect to defined receptors that reflect intended land-use. In this study, the likely threat of human exposure to toxic metals has been evaluated by simulating the human digestion process in vitro. The effects of key attributes (i.e. sample fraction size, pH, K_d and total metal concentrations) on the bioavailability of Cu and Ni were also investigated. Total metal concentration was the key explanatory factor for Cu and Ni bioavailability. A comparative ranking of metal concentrations in the context of tolerable daily intakes for Cu and Ni confirmed that the pH has the greatest impact on metals bioavailability. Rapid screening of key attributes and total toxic metal doses can reveal the relative hazard imposed on human, and this approach should be considered when defining threshold values for human protection.     

Fate of aluminium and nickel in soil. Evaluation through lysimeters under laboratory conditions

ABSTRACT

Nanomaterials (Nms) applications and environmental deposition are continuously increasing. Aluminum (Al) and nickel (Ni) fate in soil, both from gamma alumina-based Nms and as chloride salts were evaluted through lysimeters. After 85 days of treatment, which included irrigation and collection of eluates, the soil of each lysimeter was divided into four sections. The metal concentration was analyzed in eluates, soil samples, and extracts. Al and iron (Fe) present in soil eluted from Control lysimeter. Al from Nms suspension treatment was quantified in the eluates since 30 days on. Ni eluted upon solid salt deposition on top of one device. These results indicate that Al and Ni applied under certain conditions on soil, could leach and reach groundwater. The total concentration and bioavailability (extractable metals) of Al and Fe in soils showed similar patterns. Ni was retained only in the soil of devices treated with chloride salts. Bioavailability % results were of concern for Ni under certain conditions of treatment: 15.57% and 11.08% in two chloride salt-treated lysimeters versus 0.55% and 0.47% of those in control and treated with Nms lysimeters. Conducting studies with different kinds of soil and longer treatment periods should be useful to understand Nms-metals fate in the environment. The results presented here constitute important evidences both for significant metal release from Nms and elution and for considerable Ni bioavailability, after deposition on soil in the form of Nms or as a chloride salt, respectively. Then, possible toxic effects could occur through exposure of aquatic and terrestrial organisms.     

Simulation of Adsorbate-Induced Surface Reconstruction

Abstract

Adsorbed atomic monolayers of atoms such as carbon and nitrogen can cause substantial reconstructions of a nickel {001} surface. In this simulation we combine an atomic-orbital-based calculation of electronic structure with an empirical pair-wise repulsive potential to model the covalent part of the total energy. For 0.5 monolayer coverage by the adsorbate, the surface metal layer relaxes into a p(2 × 2) structure, with transverse displacements of about 0.4 Å. At the same time these displaced surface nickel atoms ride up above second layer nickels, with a vertical displcement of about 0.4 Å. The covalent contribution to the relaxation energy comes out at about 2.0 eV per carbon atom and 1.4eV per nitrogen atom, of which the reconstruction contributes about 0.3eV.