复合污染土壤中土霉素的吸附行为及其对土壤重金属解吸影响的研究

参考经济合作与发展组织(OECD)化学品试验导则No.106,采用批量平衡试验的方法,探讨了土霉素(Oxytetracycline,OTC)在3种土壤中的吸附解吸特性,并考察了土霉素外加量对土壤中4种代表性重金属元素(铜、锌、铅、镉)解吸量的影响。试验设置的土霉素初始浓度为0.01、0.1、1.0、5.0、10.0、25.0、50.0、100、200和400 mg L-1。结果表明:(1)存在一个土霉素特征浓度,高于或低于该浓度值时土霉素的吸附性质有所差异,且高低两个浓度范围内的数据均能用Freundlich模型与Langmuir模型较好地拟合;(2)当土霉素浓度在0~25 mg L-1之间时,能在土壤表面与重金属发生竞争吸附,且重金属解吸量随土霉素浓度的增加而增加;当土霉素浓度在25~100 mg L-1之间时,部分游离态重金属以与土霉素的络合物形式重新固定于土壤表面,土壤重金属的解吸量随土霉素浓度增加而减少;土霉素浓度高于100 mg L-1时,体系p H相对于对照有明显下降,土壤重金属的解吸量与土霉素浓度又呈正相关。     

Soil contamination with heavy metals and possibility for its remediation

The problems of changes in soil fertility under the impact of industrial contaminants and of remediation of soils polluted with heavy metals are discussed. It is shown that Fe(II) ions may serve as soil remediators. It is also shown that changes in the soil microbiological activity can be estimated by the electrochemical method from data on the potential of the biologically active iron electrode.     

Reaction kinetics of the adsorption and desorption of nickel, zinc and cadmium by goethite. I. Adsorption and diffusion of metals

The reactions of Ni, Zn and Cd with goethite were studied over a range of initial metal concentrations (10⁻⁶ to 10⁻⁴M), pH values (4 to 8), reaction times (2h to 42d) and temperatures (5 to 35°C). The adsorption of metals increased with pH, reaction time and temperature. Adsorption of Ni increased relative to Zn and Cd with increasing time and temperature. The initially rapid adsorption of metals within a few hours was followed by a much slower reaction linearly related to time^1/2, interpreted as diffusion–controlled penetration of goethite. The pH–dependent relative diffusion rates (Ni > Zn > Cd) were influenced by both affinity for goethite surfaces and by ionic radius. Diffusion coefficients of the three metals ranged from about 10⁻¹⁹to 10⁻²⁰cm²s⁻¹. The corresponding activation energies of diffusion were also calculated (Ni 35, Cd 55, Zn 90 kJ mol⁻¹). Our view about the reactions of heavy metals with goethite involves (i) adsorption of metals on external surfaces, (ii) solid–state diffusion of metals from external to internal binding sites, and (iii) metal binding and fixation at positions inside the goethite particles. The general parameters of these processes are related to the hydrolytic properties (p K values) and the ionic radii of the metals. The results show that goethite may be an efficient sink for trace metals.     

Bacterial leaching of heavy metals from sewage sludge for agricultural application

Bacterial leaching of heavy metals from sewage sludge was studied to assess the potential of agricultural application of the decontaminated sludge. Experiments were conducted in both batch processes (at 28 ?C) and continuous process (at 30 ?C) using a culture of Thiobacillus ferrooxidans and a mixted culture of Thiobacillus ferrooxidans and Thiobacillus thiooxidans. Reagent grade ferrous sulfate, spent ferrous sulfate and pyrite were used as the energy substrates. A first order kinetic model of Cu solubilization was proposed. It was shown that the processes in the continuously stirred tank reactor (CSTR) and the air lift reactor (ALR) with 20% cell recycling were more efficient than the others for metal solubilization due to a relatively large bacterial population.     

Phosphorus loss from agricultural catchments: pathways and implications for management

Abstract. The contribution non-point P sources make to the total P loading on water bodies in agricultural catchments has not been fully appreciated. Using data derived from plot scale experimental studies, and modelling approaches developed to simulate system behaviour under differing management scenarios, a fuller understanding of the processes controlling P export and transformations along non-point transport pathways can be achieved. One modelling approach which has been successfully applied to large UK catchments (50-350km² in area) is applied here to a small, 1.5 km² experimental catchment. The importance of scaling is discussed in the context of how such approaches can extrapolate the results from plot-scale experimental studies to full catchment scale. However, the scope of such models is limited, since they do not at present directly simulate the processes controlling P transport and transformation dynamics. As such, they can only simulate total P export on an annual basis, and are not capable of prediction over shorter time scales. The need for development of process-based models to help answer these questions, and for more comprehensive UK experimental studies is highlighted as a pre-requisite for the development of suitable and sustainable management strategies to reduce non-point P loading on water bodies in agricultural catchments.     

Solubility and uptake of heavy metals from a Swedish soil

Samples of the surface layer (Ap) and of grass, collected from: (1) grass ley fertilized in the normal way; (2) permanent pasture fertilized in the normal way; and (3) permanent pasture treated with large amounts of sewage sludge five years earlier, were analysed for Mn, Zn, Cu, Cr, Co, Ni, Pb, and Cd.The soil samples were extracted with: (1) distilled water saturated with CO₂; (2) 1 M neutral ammonium acetate; (3) ammonium acetate + acetic acid, pH 4.75; and (4) 2 M nitric acid on a waterbath. The efficiency of these extractants differed greatly and, in relative values, was: 1 for H₂O + CO₂, 3.4 for NH₄OAc, 20.7 for NH₄OAc + HOAc, and 343 for 2 M HNO_3- The dissolving effects of the extractants differed markedly with the kind of element.Grass from the field treated with sewage sludge showed much higher contents of Mn and Zn and somewhat higher contents of Cu and Pb than grass from the untreated field. The levels of Cr, Co, Ni, and Cd were practically uninfluenced by the treatment. Grass from a field close to a highway accumulated large amounts of air-borne Pb and Cd during the summer.It is concluded that the total contents of heavy metals in soils have only limited importance for the uptake by plants. Weak extractants therefore give better information about the plant-available amounts in soils.     

青海倒淌河末端沉积物中重金属含量及其指示意义

对青海湖流域倒淌河末端沉积物样品中As、Cd、Pb、V、Cr、Mn、Ni、Cu、Zn等9种重金属元素的含量进行了分析测定,并评估了其污染程度。结果表明:无论在横向还是纵向上,所分析重金属元素含量均低于青海湖土壤背景值、青海省土壤平均值和土壤环境质量一级标准值,潜在生态风险因子均低于40,多风险因子指数均低于65;样品中As、Cd、As富集系数基本为1~2,其它重金属元素富集系数基本小于1。倒淌河末端沉积物尚未出现重金属污染,但该流域确实存在重金属的人为排放,而且在近代排放更为显著。虽然经过沉积和植物吸收,倒淌河河水流至其末端时重金属元素依然未完全被净化干净,主要体现在As、Cd、Pb上,应限制它们进入环境     

Standards for the contents of heavy metals and metalloids in soils

In line with the present-day ecological and toxicological data obtained by Dutch ecologists, heavy metals/metalloids form the following succession according to their hazard degree in soils: Se > Tl > Sb > Cd > V > Hg > Ni > Cu > Cr > As > Ba. This sequence substantially differs from the succession of heavy elements presented in the general toxicological GOST (State Norms and Standards) 17.4.1.02-8, which considers As, Cd, Hg, Se, Pb, and Zn to be strongly hazardous elements, whereas Co, Ni, Mo, Sb, and Cr to be moderately hazardous. As compared to the general toxicological approach, the hazard of lead, zinc, and cobalt is lower in soils, and that of vanadium, antimony, and barium is higher. The new sequence also differs from that of the metal hazard in soils according to the Russian standard on the maximal permissible concentration of mobile metal forms (MPC_mob): Cu > Ni > Co > Cr > Zn. Neither an MPC_mob nor an APC_mob has been adopted for strongly hazardous thallium, selenium, and vanadium in Russia. The content of heavy metals in contaminated soils is very unevenly studied: 11 of them, i.e., Cu, Zn, Pb, Ni, Cd, Cr, As, Mn, Co, Hg, and Se, are better known, while the rest, much worse, although there are dangerous elements (Ba, V, Tl) among them.     

Aqueous release of heavy metals from two sewage sludges

Two anaerobically digested sewage sludges, one of relatively low and the other of relatively high heavy metal content, were extracted several times with water to determine the levels of Cu, Zn, and Cd that would be readily available for transport in the soil water if these sludges were applied to land. Generally, the quantity of metal released in the aqueous extracts was between 1 to 7% of the total content with Cu and Zn being released to a greater extent than Cd. The porportion of relatively mobile, non-cationic heavy metals in the aqueous extract differed in the two sludges and ranged from < 1% for Zn and Cd in one sludge to 56.2% for Cd in the other sludge.[/P ]     

Effects of crystallinity of goethite: II. Rates of sorption and desorption of phosphate

Eight samples of goethite ranging in surface area from 18 to 132 m² g^-1 were mixed with phosphate at a range of pH values for periods which ranged from 0·5 h to 6 weeks. The sample with a surface area of 18 m² g^-1 had been hydrothermally treated to improve its crystallinity. Its rate of reaction with phosphate depended on pH but was complete within a day. Its maximum observed reaction was close to the theoretical maximum for surface adsorption of 2·5 μmol m^?2. For the other samples, phosphate continued to react for up to 3 weeks and exceeded the value of 2·5 μmole m^?2. The duration and extent of the reaction depended on the crystallinity of the goethite. The results were closely described by a model in which the phosphate ions were initially adsorbed on to charged external surfaces. The phosphate ions then diffused into the particles. This was closely described using equations for diffusion into a cylinder. Samples of goethite which had been loaded with phosphate dissolved more slowly in HCl, and had a longer lag phase, than phosphate-free goethite. For the hydrothermally treated goethite, HCl removed much of the phosphate when only a small proportion of the iron had been dissolved. For a poorly crystallized goethite, it was necessary to dissolve much more of the iron to obtain a similar removal of phosphate. Brief treatment with NaOH removed most of the phosphate from the hydrothermally treated goethite but only half the phosphate from a poorly crystallized goethite. These results are consistent with the idea that phosphate ions were not only bound on external surface sites but had also penetrated into meso- and micro-pores between the domains of the goethite crystals and were then adsorbed on internal surface sites. This penetration tied the domains together more firmly thus increasing the lag phase for dissolution. Differences between sites for phosphate adsorption are therefore caused mainly by their location on either external or internal sites. Models that ignore this are incomplete.     

Effect of porosity of goethite on the sorption of six heavy metal ions

Seven different samples of goethite with differing crystallinity were prepared and the rate of reaction of six metal ions was measured for up to 4 weeks. The ions used were: Cu²⁺, Pb²⁺, Cd²⁺, Mn²⁺, Ni²⁺ and Cr³⁺. For Cu, decreasing goethite crystallinity, and therefore increasing porosity, increased the rate of reaction. In contrast, for Pb there was no effect. Hydrothermal treatment, which was used to induce ‘healing’ in one of the goethites, did not prevent the continuing reaction. It decreased the rate of reaction for Cu, Mn and Cd, but had no effect on Ni and Cr. This suggests that the main route for Ni and Cr is not via pores, but by lattice diffusion. The presence of silicate in the goethite decreased the reaction of Mn and Cd. We suggest that silicate decreased the spaces between goethite domains and that these spaces are the pathways largely used by these two ions. These observations show that metallic cations differ amongst themselves, and differ from anions such as phosphate, in the pathways they follow when they penetrate materials such as goethite subsequent to an initial adsorption reaction.     

Immobilization of heavy metals in soils amended by nanoparticulate zeolitic tuff: Sorption‐desorption of cadmium

Immobilization of Cd in contaminated soil is a technique to improve soil quality. Zeolites are potentially useful additives to bind heavy metals. This study examines the influence of decreasing the grain size of raw zeolitic tuff to the nano‐range on Cd sorption‐desorption isotherms in a sandy soil. The aim was to evaluate the feasibility of using nanoparticulate zeolitic tuff as a sequestering agent for Cd in soil. Sorption and desorption of Cd on zeolitic nanotuff was investigated in batch experiments. The sandy soil was amended with zeolitic nanotuff, synthetic Al oxide nanoparticles, or raw zeolitic tuff. After a 48 h sorption step, three desorption steps were induced using the sequential dilution method. The measured sorption‐desorption data were adequately described by the Freundlich equation. A nonlinear two‐stage one‐rate model matched well with measured Cd sorption‐desorption isotherms of zeolitic nanotuff, raw zeolitic tuff, Al oxide nanoparticle, and control soil. The batch experiments demonstrated the strong influence of pH on Cd sorption. Zeta‐potential measurements of zeolitic nanotuff indicated that electrostatic interaction was important for sorption. Soil amended with zeolitic nanotuff showed the lowest hysteresis index based on the differences obtained from sorption‐desorption isotherms regarding the amount of Cd sorbed. The index decreased with increasing metal concentration. For soil amended with nanoparticulate zeolitic tuff, the estimated Freundlich coefficient was 4 orders of magnitude higher than in the control soil and 2 orders of magnitude higher than the soil amended with raw zeolitic tuff. In addition, this sorbent decreased the amount of Cd released after three desorption steps by up to 12 and 7 times compared to the control soil and the soil amended with raw zeolitic tuff, respectively. The effect on Cd sorption of grinding the raw zeolitic tuff to the nanorange was considerably more pronounced than the effect of raw zeolitic tuff.     

Feasibility of a counter-current extraction procedure for the removal of heavy metals from contaminated soils

Effective remediation and sanitation technologies for soils contaminated with heavy metals are limited. We investigated the feasibility of a counter-current metal extraction procedure for the removal of selected heavy metals (Cd, Cu, Ph, and Zn) from two contaminated soils. The process involved a decarbonation (removal of carbonates), acid solubilisation, washing, and liming step. Results from batch equilibration experiments simulating the counter-current process showed more than 85% of the Cd present to be removed. Removal efficiencies for Cu and Pb were limited to approximately 15%, this mainly due to resorption of these elements during the decarbonation step. As most Zn was found to be present in a more difficult acid-extractable solid phase, its extractability accounted for only 25%. While reaction (pH) conditions of both decarbonation and solubilisation determined removal efficiencies, washing the extracted soil with deionized water only slightly increased the amount of metals removed. Metal distribution among solid phases — exchangeable, carbonate, reducible, organically bound, and residual — was affected by the different treatments. The amount of metals contained in the exchangeable and residual fractions determined their extractability. Except for Cu, the reducible and organically bound fractions were less important. After solubilisation 13 to 70% of the metals were present in an exchangeable solid phase. This implicates that washing the solubilized soil with a salt may increase the extractability of metals, especially for Zn and Pb. Based on our results the process is critically evaluated and possibilities for optimization formulated.     

Observations and modelling of the reactions of 10 metals with goethite: adsorption and diffusion processes

A sample of goethite was mixed for periods which ranged from 2 hours to 8 weeks with solutions of dilute nitrate salts of Pb, Hg, Cd, Zn, Cu, Ni, Co, Mn, Cr and Al. The amount of sorption after each period was measured for an appropriate pH range for each metal. The sorption behaviour was characterized both by using characteristics of the sorption curves such as the pH at which half of the added metal was sorbed (pH₅₀) and by fitting a model in which sorption was mainly characterized by an affinity constant and by a diffusion constant. Initial sorption, whether characterized by the pH₅₀ or by the affinity constant, was closely correlated with the appropriate dissociation constants of the metals. The greater the affinity of the metals for hydroxide ions, the greater their affinity for the goethite surface. The metals differed in the rate at which they continued to react with the goethite. Lead had the slowest continuing reaction, cobalt the fastest. The continuing reaction was due to diffusion into the particles. It was characterized by the fitted diffusion constant and by the change with time in the pH₅₀. For seven of the eight divalent metals, these were correlated with the ionic radius of the metals: the larger the radius, the slower the reaction. For Al and Cr, rates were slower than would be expected from the ionic radii and we suggest this shows that these ions react as the larger M(OH)²⁺ ions. The behaviour of Ni was consistent with oxidation of the surface species and diffusion of Ni(OH)²⁺ ions. The continuing reaction was similar to that observed when metal ions react with soils and suggests that their reaction with iron oxides is important in soils. The results also show that studies in which sorption is measured at only one period of reaction are incomplete and the application of equilibrium models to such results is misleading.     

Selective removal of heavy metals from contaminated kaolin by chelators

The competitive desorption/dissolution of kaolin-adsorbed heavy metal mixtures and mixtures of adsorbed Cd with Mg and/or Ca by four chelators (NTA, EDTA, EGTA, and DCyTA) was investigated. Metals were adsorbed on kaolin at pH 7 and the effects of chelator type and concentration on the extent of metal dissolution was studied at a solution pH of 10. EGTA addition. EGTA was the most effective chelator in selectively removing Cd from kaolin in the presence of adsorbed alkaline-earth metals. Approximately 90% of the adsorbed Ca and Mg were retained on the kaolin until almost all (> 80%) of the cadmium was dissolved by EGTA chelator. NTA was the least effective chelator in selectively dissolving Cd from kaolin contaminated with both Cd and Ca (≈ 45% of the adsorbed Cd could not be removed). All four chelators exhibited some desorption/dissolution selectivity for Cd, Cu, and Pb adsorbed on kaolin. When the concentration of chelator in solution was insufficient to dissolve all adsorbed metals, the observed metal ordering for chelation and dissolution was Cd > Cu > Pb (for EGTA), Cd > Pb > Cu (for EDTA and DCyTA), and Cu > Cd > Pb (for NTA).     

Bioremediation of heavy metals from municipal sewage by cyanobacteria and its effects on growth and some metabolites of Beta vulgaris

The present research was done to study the ability of cyanobacterial species for removing heavy metals from sewage. As well, to estimate the growth and some metabolites of Beta vulgaris irrigated with sewage treated by cyanobacterial species. The best removal results were obtained by Anabaena oryzae compared to the other studied cyanobacteria. Whereas A. oryzae showed high removal efficiency for cadmium (Cd²⁺) followed by lead (Pb²⁺), zinc (Zn²⁺), iron (Fe²⁺), copper (Cu²⁺) and manganese (Mn²⁺) (88.5, 83.1, 68.8, 62.0, 55.2 and 42.4%, respectively). Irrigation of plants by untreated or treated sewage generally caused stimulation in the total proteins, proline, carbohydrates and ascorbic acid. B. vulgaris grown in soil irrigated with untreated sewage showed maximum catalase, peroxidase activity, hydrogen peroxide (H₂O₂) and lipid peroxidation compared to the other treatments. The heavy metals availability was relatively low in the plant irrigated with treated sewage by cyanobacterial species, so the antioxidants requirement was low and hence the induction of antioxidants was lower compared to the plant irrigated with untreated sewage.     

三峡水库蓄水对消落带土壤重金属的影响

河岸带土壤重金属已成为国内外研究的热点问题之一。随着水库蓄水,长江水流速度降低,水体稀释扩散能力下降,水体中污染物浓度增加,水库大面积长时期淹水容易造成污染物在土壤中滞留时间加长[5],此外,水库两岸排放的污染物也将在水流缓慢的消落带富集。另外,水库大     

Elimination of heavy metals from process waters of the bioleaching process by electrolysis

2 Conclusions  The investigations into the membrane electrolysis cell show that electrochemical metal separation from bioleaching process waters can represent a practical alternative for metal separation by alcalization, Coal and platinized titanium material exhibit good anodic resistance at the current densities tested. By contrast, high-grade steel and to some extent lead anodes were dissolved and are hence unsuitable for this purpose. However, for practical application, suitable ways are required to discharge the precipitates containing heavy metals deposited on the electrodes from the electrolysis cell and to prevent membrane clogging. Regarding the main components zinc, manganese, and nickel, the combination electrodes proved to be suitable for eliminating the heavy metals from the aqueous phase. Another way of treating diluted process waters containing sulphuric acidic and heavy metals is to concentrate the sulphuric acid in the anode region and to precipitate the heavy metals in the cathode region. The sulphuric acid recovered could then be returned to the leaching process, hence avoiding wastewater.     

Leaching of heavy metals from sewage sludge through coastal plain soils

Abstract

Three types of sewage sludge are applied to the surface of soil columns of Coastal Plain soils and leached with distilled water. The Zn concentrations in leachate samples from a Sassafras loamy sand soil loaded with an industrial sludge increased with sludge loading rate. All leachate samples contained very low concentrations of Cd, Cr and Cu. Hazardous amounts of Cd, Cr, Cu and Zn would not be leached to the groundwater when recommended rates of the tested sludges are applied to Coastal Plain soils under most conditions.     

砷-重金属复合污染土壤稳定化材料研究进展

我国土壤重金属污染现状十分严峻,多金属复合污染,尤其是砷-重金属复合污染普遍存在,治理难度大。土壤中累积的多金属污染物严重威胁土壤健康、农产品安全与人居环境安全。因此,多金属复合污染土壤修复是土壤污染治理和风险防控的重要命题。固化/稳定化技术是我国最为广泛使用的污染土壤修复技术,通过投加稳定化材料,降低多金属污染物在土壤中的可迁移性与生物有效性,从而实现多金属污染物暴露途径的有效阻断。对砷-重金属型复合污染土壤的稳定化作用机理进行了详细阐述并梳理了应对砷-重金属复合污染土壤的新型修复材料。砷与其它重金属的协同稳定化主要通过表面络合与沉淀作用实现。富含铁、钙元素的材料对这种类型土壤的稳定化具有优异的作用效果。砷-重金属协同稳定化材料的修复效果取决于稳定化材料的类型、复合污染物的种类、材料施用量、土壤条件（如pH,氧化还原电位、阳离子交换量等）,其中pH和土壤可溶性有机质含量对稳定化效果有显著的影响。本文发现,功能化生物质复合材料、工业固废基材料、改性复配天然矿物等绿色修复材料是近年来研究的热点。未来的研究亟须考虑砷与重金属污染物协同稳定剂的长效性,以及通过大田试验验证新型材料的应用潜能。