Effect of humic matter on metal adsorption onto clay materials: Testing the linear additive model

Migration of contaminants with low affinity for the aqueous phase is essentially governed by interaction with mobile carriers such as humic colloids. Their impact is, however, not sufficiently described by interaction constants alone since the humic carriers themselves are subject to a solid–liquid distribution that depends on geochemical parameters.In our study, co-adsorption of the REE terbium (as an analogue of trivalent actinides) and humic acid onto three clay materials (illite, montmorillonite, Opalinus clay) was investigated as a function of pH. ¹⁶⁰Tb(III) and ¹³¹I-labelled humic acid were employed as radiotracers, allowing experiments at very low concentrations to mimic probable conditions in the far-field of a nuclear waste repository. Humate complexation of Tb was examined by anion and cation exchange techniques, also considering competitive effects of metals leached from the clay materials.The results revealed that desorption of metals from clay barriers, occurring in consequence of acidification processes, is generally counteracted in the presence of humic matter. For all clay materials under study, adsorption of Tb was found to be enhanced in neutral and acidic systems with humic acid, which is explained by additional adsorption of humic-bound Tb.A commonly used composite approach (linear additive model) was tested for suitability in reconstructing the solid–liquid distribution of Tb in ternary systems (Tb/humic acid/clay) on the basis of data determined for binary subsystems. The model can qualitatively explain the influence of humic acid as a function of pH, but it failed to reproduce our experimental data quantitatively. It appears that the elementary processes (metal adsorption, metal–humate complexation, humic acid adsorption) cannot be considered to be independent of each other. Possible reasons are discussed.     

Spatial patterns and autocorrelation in the response of microarthropods to soil pollutants: The example of oribatid mites in an abandoned mining and smelting area

Although exogenous factors such as pollutants can act on endogenous drivers (e.g. dispersion) of populations and create spatially autocorrelated distributions, most statistical techniques assume independence of error terms. As there are no studies on metal soil pollutants and microarthropods that explicitly analyse this key issue, we completed a field study of the correlation between Oribatida and metal concentrations in litter, organic matter and soil in an attempt to account for spatial patterns of both metals and mites. The 50-m wide study area had homogenous macroscopic features, steep Pb and Cu gradients and high levels of Zn and Cd. Spatial models failed to detect metal–oribatid relationships because the observed latitudinal and longitudinal gradients in oribatid assemblages were independent of the collinear gradients in the concentration of metals. It is therefore hypothesised that other spatially variable factors (e.g. fungi, reduced macrofauna) affect oribatid assemblages, which may be influenced by metals only indirectly.     

Utilization of pulp and paper industrial wastes to remove heavy metals from metal finishing wastewater

Two pulp and paper industrial wastes, lime mud (LM) and recovery boiler ash (RB), have low moisture contents, low heavy metal contaminations and contain various carbonate compounds which contribute to a high pH. Metal finishing wastewater (MF-WW) has a low pH, high levels of TDS and high contaminations from Cr, Cu, Pb and Zn. The heavy metals from MF-WW were removed by sorption and precipitation mechanisms. LM gave better results in removing heavy metals from MF-WW than RB. At a reaction time of 45 min, the maximum removal efficiencies for Cr (93%) and Cu (99%) were obtained at 110 g L⁻¹ of LM, but at 80 g L⁻¹ for Pb (96%) and Zn (99%). Treatment with LM gives a higher sludge volume than with RB. However, the leachability of heavy metals from LM is lower. Leachability of heavy metals in the sediment for all selected treatment conditions is within government standards.     

Recent atmospheric lead deposition recorded in an ombrotrophic peat bog of Great Hinggan Mountains, Northeast China, from Pb and Cs dating

Radioactive markers are useful in dating lead deposition patterns from industrialization in peat archive. Peat cores were collected in an ombrotrophic peat bog in the Great Hinggan Mountains in Northeast China in September 2008 and dated using ²¹⁰Pb and ¹³⁷Cs radiometric techniques. The mosses in both cores were examined systematically for dry bulk density, water and ash content. Lead also was measured using atomic emission spectroscopy with inductively coupled plasma (ICP-AES). Both patterned peat profiles were preserved well without evident anthropogenic disturbance. Unsupported ²¹⁰Pb and ¹³⁷Cs decreased with the depth in both of the two sample cores. The ²¹⁰Pb chronologies were established using the constant rate of supply model (CRS) and are in good agreement with the ¹³⁷Cs time marker. Recent atmospheric ²¹⁰Pb flux in Great Hinggan Mountains peat bog was estimated to be 337 Bq m⁻² y⁻¹, which is consistent with published data for the region. Lead deposition rate in this region was also derived from these two peat cores and ranged from 24.6 to 55.8 mg m⁻² y⁻¹ with a range of Pb concentration of 14-262 μg g⁻¹. The Pb deposition patterns were consistent with increasing industrialization over the last 135-170 y, with a peak of production and coal burning in the last 50 y in Northeast China. This work presents a first estimation of atmospheric Pb deposition rate in peatlands in China and suggests an increasing trend of environmental pollution due to anthropogenic contaminants in the atmosphere. More attention should be paid to current local pollution problems, and society should take actions to seek a balance between economic development and environmental protection.     

Performance investigation of a single-stage metal hydride heat transformer

This article presents the performance analysis of a single-stage metal hydride-based heat transformer (SS-MHHT) working with three different alloy pairs, namely LaNi_4.6Al_0.4/MmNi_4.15Fe_0.85, LaNi_4.61Mn_0.26Al_0.13/La_0.6Y_0.4Ni_4.8-Mn_0.2, and Zr_0.9Ti_0.1Cr_0.9Fe_1.1/Zr_0.9Ti_0.1Cr_0.6-Fe_1.4. The performances of the SS-MHHT are predicted by solving the conjugate heat and mass (hydrogen) transfer equations in cylindrical coordinates. The effects of various parameters such as heat output (T_H), heat input (T_M), and heat sink (T_L) temperatures on the coefficient of performance (COP_HT), specific heating power (SHP) and second law efficiency (η_E) are presented. The effects of overall heat transfer coefficient and mass ratio on the coefficient of performance (COP_HT) and specific heating power (SHP) are also presented. Numerical results are compared with the experimental data reported in the literature, and a good agreement is found between them. The maximum COP_HT of 0.436 and SHP of 54 W/kg are obtained for LaNi_4.61Mn_0.26Al_0.13/La_0.6Y_0.4Ni_4.8-Mn_0.2 pair. For a given operating temperatures of T_M = 358 K and T_L = 298 K, the maximum temperature lift of about 50 K is predicted for Zr_0.9Ti_0.1Cr_0.9Fe_1.1 /Zr_0.9Ti_0.1Cr_0.6Fe_1.4 pair.     

Assessment of a process to degrade metal working fluids using Pseudomonas stutzeri CECT 930 and indigenous microbial consortia

The development of a novel biological process to treat metal working fluids (MWFs)-containing effluents at bioreactor scale was pursued in this work. The bacteria Pseudomonas stutzeri CECT 930 was investigated for the first time as an alternative agent for MWF degradation. An adequate medium design and mixing and aeration system, as well as an appropriate microorganism proved to be crucial for reaching high levels of degradation by P. stutzeri and by an indigenous consortium (about 70% and 50% of reduction in total petroleum hydrocarbon content in less than 2 wk, respectively). Additionally, as there is no information in literature trying to kinetically characterize an MWF-polluted effluent degradation process, all the experimental data were fitted to logistic and Luedeking and Piret models, that allowed to elucidate the growth-associated character of the biodegradation process.     

Comparative bioaccumulation kinetics of trace elements in Mediterranean marine sponges

While marine organisms such as bivalves, seagrasses and macroalgae are commonly used as biomonitors for the environment pollution assessment, widely distributed sponges received little attention as potential helpful species for monitoring programmes. In this study, the trace element and radionuclide bioaccumulation and retention capacities of some marine sponges were estimated in a species-comparative study using radiotracers technique. Six Mediterranean species were exposed to background dissolved concentrations of ^110mAg, ²⁴¹Am, ¹⁰⁹Cd, ⁶⁰Co, ¹³⁴Cs, ⁵⁴Mn, ⁷⁵Se and ⁶⁵Zn allowing the assessment of the uptake and depuration kinetics for selected elements. Globally, massive demosponges Agelas oroides, Chondrosia reniformis and Ircinia variabilis displayed higher concentration factor (CF) than the erectile ones (Acanthella acuta, Cymbaxinella damicornis, Cymbaxinella verrucosa) at the end of exposure, suggesting that the morphology is a key factor in the metal bioaccumulation efficiency. Considering this observation, two exceptions were noted: (1) A. acuta reached the highest CF for ^110mAg and strongly retained the accumulated metal without significant Ag loss when placed in depuration conditions and (2) C. reniformis did not accumulate Se as much as A. oroides and I. variabilis. These results suggest that peculiar metal uptake properties in sponges could be driven by specific metabolites or contrasting biosilification processes between species, respectively. This study demonstrated that sponges could be considered as valuable candidate for biomonitoring metal contamination but also that there is a need to experimentally highlight metal-dependant characteristic among species.     

Determination of the effect of operating cost uncertainty on mining project evaluation

Mining projects are complex businesses that demand constant risk assessment. This is because several kinds of uncertainties influence the value of a mine project, typically. These uncertainties may be classified as exploration uncertainties, economic uncertainties and engineering uncertainties. The evaluation of a mine project under these uncertainties is a complicated job, which may lead to making a wrong decision by managers and stockholders. Therefore, at first, the engineers must recognize the mining uncertainties before carrying out the project evaluation. The economic uncertainties are the most important factors, which may affect the project evaluation. Among the mentioned uncertainties, the operating cost uncertainty is an important and effective factor, which is ignored to a certain extent.     

二甲基二硫代氨基甲酸钠处理锌冶炼含镉废水

以二甲基二硫代氨基甲酸钠(福美钠)作为脱镉螯合剂,以聚合氯化铝作为絮凝剂,脱除含镉废水中的Cd2+。在考察福美钠加入量、搅拌时间、聚合氯化铝加入量、沉淀时间等工艺条件对Cd2+脱除效果影响的单因素实验的基础上,采用正交实验对工艺参数进行进一步优化。实验结果表明:在福美钠加入量为1.0 g/L、搅拌时间为20 min、聚合氯化铝加入量为0.2 g/L、沉淀时间为5 h的最佳工艺条件下,采用福美钠处理初始Cd2+质量浓度为100 mg/L的锌冶炼含镉废水,剩余Cd2+质量浓度降至0.008 mg/L,Cd2+去除率为99.99%,处理后的废水达到GB8978—1996《污水综合排放标准》。     

Microtubule integrity and cell viability under metal (Cu,Ni and Cr) stress in the seagrass Cymodocea nodosa

The effects of increasing Cu, Ni and Cr concentrations (0.5, 5, 10, 20 and 40 mg L⁻¹) on microtubule organization and the viability of leaf cells of the seagrass Cymodocea nodosa for 13 consecutive days were investigated under laboratory conditions. Increased oblique microtubule orientation, microtubule depolymerization at the 5–40 mg L⁻¹ Ni treatments after 3 d of exposure, and a complete microtubule depolymerization at all Ni treatments after 5 d were observed. Cu depolymerised microtubules after three to 7 d of exposure, while Cr caused an extensive microtubule bundling after 9 or 11 d of exposure, depending on metal dosage. Fluorescence intensity measurements further consolidated the above phenomena. Cell death, occurring at later time than microtubule disturbance, was also observed at all Cu and Ni treatments and at the 10–40 mg L⁻¹ Cr treatments and adding to the above quantification of the number of dead cells clearly showed that only a portion of the cell population studied died. The data presented, being the first assessment of microtubule disturbance in seagrasses, indicate that microtubules in seagrass leaf cells could be used as a valuable and early marker of metal-induced stress in biomonitoring programmes.