Binding and chemical fractionation of heavy metals in typical peat matter

Laboratory batch studies were conducted to evaluate the binding capacity and the mobility of metal species bound to typical humus peat matter. The identification of phase composition of mineral fractions and functional groups in the organic matter was assessed. The results showed generally high, but different retention capacity and binding strength, suggesting distinct diversity in binding mechanisms, phases and chemical nature of binding sites, depending on the metal species and their input concentrations. In general, the binding capacity of peat for the metal ions studied follows the order: Cr(3+) > Cu(2+) > Zn(2+) > Cd(2+) and results in the decrease of pH in the same order, due to displacement of H(3)O(+) from the peat by metal ions. The highest metal enrichment occurs in fractions F1(EXC), F2(CARB), F4(MRO) and F5(OM) of different binding strength adequate to exchangeable, carbonatic, moderately reducible amorphous Fe-oxide and organic/ sulphidic fractions in soils and sediments. In relation to species distribution in peats, the prevailing part of Cr(3+) is strongly bound in oxidizable organic substrate, while Cu(2+) is highly enriched in the moderately reducible F4(MRO) and the most labile F2(EXC) fractions. Cd(2+) and Zn(2+) are predominantly bound in the labile F1(EXC) and F2(CARB) fractions. Diversity of the predominant binding phases for the studied metals suggests rather weak competition for binding sites between chromium and copper ions; the strongest competition between the sorbed metal ions is anticipated for F1(EXC) and F2(CARB) fractions.     

Online coupling of ultraviolet titanium dioxide film reactor with poly(methyl methacrylate) solid phase extraction–inductively coupled plasma mass spectrometry for speciation of trace heavy metals in freshwater

To rapidly discriminate dissolved labile and stable organic-complexed metal ions, a fully automated approach comprising a photocatalyst-assisted digestion reactor (PADR), a non-functionalized poly(methyl methacrylate) (PMMA) solid-phase extraction (SPE) column, and inductively coupled plasma-mass spectrometry (ICP-MS) instrumentation was developed. To separate labile dissolved metals from other concomitant metal complexes, a non-functionalized PMMA bead was used as the SPE adsorbent because of its selective interaction with labile metal ions. The PMMA SPE–ICP-MS hyphenated system was optimized, and its analytical reliability was confirmed by using it to analyze the certified reference material—NIST 1643e (artificial saline water). Detection limits (σ = 3, n = 7) for all analyte ions (Ni, Cu, Zn, Cd, and Pb), which ranged from 0.005 to 0.186 μg L^{− 1}, could be reached; therefore, this technique appeared uniquely suited to determining levels of trace elements in most natural freshwater samples. To determine the total quantity of dissolved metals, a new digestion reactor (PADR) was developed for online conversion of metal–organic complexes to their labile forms. Compared to conventional photolysis methods, the digestion time improved considerably and the digestion efficiency for organic substances was excellent (> 90%) in the PADR format, with a very short resident time of 10 min. After construction of the PADR–PMMA SPE–ICP-MS hyphenated system, the speciation potential of our developed method was evaluated by analyzing three intentionally contaminated water samples. Results indicated that our developed hyphenated system is effective for online determination of total, labile, and metal–humic complexes in freshwater samples and that is capable of providing representative metal speciation patterns for different aquatic systems.     

Labile rhizosphere soil solution fraction for prediction of bioavailability of heavy metals and rare earth elements to plants

A labile rhizosphere soil solution fraction has been recommended to predict the bioavailability of heavy metals and rare earth elements to plants. This method used moist rhizosphere soil in combination with a mixture of 0.01 mol L(-1) of low-molecular-weight organic acids (LMWOAs) as extractant. The extracted soil solutions were fractionated into two colloidal fractions of <0.45 microm (F(3)) and <0.2 microm (F(2)), and one truly dissolved fraction including free metal ions and inorganic and organic complexes (fractionr(0.2 microm, LMWOAs) approximately r(0.45 microm, LMWOAs). In the case of rare earth elements the good correlation was obtained for both the wheat roots and shoots. Generally, the correlation coefficients obtained by LMWAOs were better than that obtained by the first step of BCR method. Therefore, LMWAOs and F(lrss) were strongly recommended to predict the bioavailability of metals in soil pools to plants.     

Determination of trace metals in Nile River and ground water by differential pulse stripping voltammetry

The determination of trace metals in river water and ground water by DPSV is seriously disturbed by the presence of organic complexes. The influence of these substances can be eliminated by acidification of the samples with acids. Cd, Pb and Cu were determined at pH 1.1 (HNO₃ medium) and Zn, Cd, Pb and Cu at pH 2 (HCl medium), in both the Nile river and ground water. Zn was determined at pH 3.5 in HCl and pH 4.5 in HNO₃, after neutralizing the samples with NH₃/NH₄Cl buffer. Manganese could then be determined, after further addition of ammoniacal buffer solution up to pH 7.5 and 8.5. Ni and Co were determined in the adsorptive mode after formation of dimethylglyoximates at pH 9.2. The effect of pH on the stripping peaks of manganese was studied. Good agreement was observed between DPSV and AAS results for Zn, Cd, Pb, Cu and Mn, but the concentrations of Ni and Co were below the detection limits for AAS. Good agreement was obtained between DPSV results in HCl and HNO₃ for Ni and Co. The results indicate that decomposition of organic complexes by acidification with HNO₃ is better than in the case with HCl for Zn, Pb, Cu, Ni and Co, but HCl is better than HNO₃ for Cd and Mn.     

川中丘陵区铁路旁土壤重金属含量及化学形态研究

对川中丘陵区成昆铁路的三圣段、吴场段和成渝铁路的五凤段3个典型路段铁路沿线土壤重金属Cd、Zn、Cu、Pb含量及其化学形态进行了研究,并运用次生相富集系数法对重金属的潜在生态风险进行评估。结果表明:铁路沿线土壤重金属Cd、Zn、Cu、Pb含量与对照点相比都有不同程度的升高。Cd不仅具有高的含量,且化学形态主要为酸可交换态和可还原态,残渣态含量很低,其有效态比例>75%,具有很强的生物活性和可迁移性。Cu、Pb、Zn的化学形态则主要为残渣态,酸可交换态比例很小,但是Pb和Zn的可还原态和可氧化态比例较高,所以有效态比例也较高,分别为51.1%~54.9%和36.2%~50%。土壤重金属Cu在各典型路段的次生相富集系数为1.4~4.2;Zn在三圣段、吴场段2个典型路段的次生相富集系数超过3.0,均具有较大的潜在生态风险。     

Distribution of heavy metals of agricultural soils of central Greece using the modified BCR sequential extraction method

The state of heavy metal (Cd, Cu, Ni, Zn, Pb, and Cr) pollution was studied, in 440 texturally different soil profiles in Thessaly, an intensely cultivated region in Central Greece. The study was carried out in 2004 and 2005 on 220 soil samples for each year. Soil samples were classified in three soil orders: Endisols, Alfisols, and Vertisols according to the Soil Taxonomy System. The pseudo-total concentrations of heavy metals were determined by the aqua regia procedure. Heavy metals were also determined after division into four fractions by sequential extraction with (a) acetic acid (exchangeable and specifically adsorbed metals), (b) a reducing agent (bound to Fe/Mn hydroxides), (c) an oxidizing agent (bound to soil organic matter), and (d) aqua regia (bound to mineral structures, residual). The concentrations of all the metals studied were higher in the topsoil (0–30?cm) and lower in the second soil layer (30–60?cm). Concentrations of 70–82% of Cd, 39–64% of Cu, 41–69% of Ni, 29–51% of Zn, 75–89% of Pb, and 52–87% of Cr were found in the first two fractions. Cd appeared to be the most mobile of the metals studied, while Cu and Zn were found in forms associated with soil organic matter. The chemical partitioning patterns of Pb and Cr indicated that these metals are largely associated with the Fe–Mn hydroxides, while Cr was also found in the residual fractions. Significant correlations between heavy metals fractions and soil physicochemical parameters were obtained and discussed.     

Complexation as the most important factor in the fate and transport of heavy metals in the Dnieper water bodies

The results of long-term investigations of the concentrations of dissolved forms of some heavy metals (Mn, Cu, Zn, Pb, Cr, Cd) and their species in the water of the Dnieper reservoirs and the Dnieper-Bug estuary are considered. Chemiluminescent methods, anodic stripping voltammetry, membrane filtration, ion-exchange, and gel-permeation chromatography were used for study of the speciation of the metals. It has been found that binding of heavy metals into complexes with dissolved organic matter (DOM) is the dominant factor of their stabilization in solution. The molecular weight distribution of organic metal complexes and their chemical nature, as well as the potential complexing ability of DOM were investigated. Humic substances, particularly fulvic acids, play a major role in the complexation. These ligands bind from 45 to 80% of metals in the form of organic complexes. Metal complex compounds of relatively low molecular weight (<5 kDa) predominated in the organic complexes.     

An Electrochemical Study of the Interactions Between Trace Metals and Humic Substances in Freshwaters by Anodic Stripping Voltammetry with a Thin Mercury Film Rotating Disk Electrode

An improved theoretical approach to Anodic Stripping Voltammetry with a Thin Mercury Film Rotating Disk Electrode for elucidating the nature of the interactions of Pb(II), Cd(II) and Zn(II) with humic substances in model solutions of Laurentian fulvic acid, and of Pb(II), Cd(II), Zn(II) and Cu(II) in freshwaters, is presented. Conditional stability constants of Pb(II), Cd(II) and Zn(II) complexes decreased with the ionic potential (z²/r) and increased with softness of the metal ion, indicating strong affinity of soft, polarizable donor ligands on humic substances for softer metal ions, resulting in an appreciable covalent character in electrostatic bonding between the metals and humic substances.     

贵阳污灌区菜地土壤团聚体中有机碳和重金属的含量特征及相关性分析

以贵阳某污灌区菜地土壤为研究对象,分别采用微波消解-电感耦合等离子体质谱(ICP-MS)法和水合热重铬酸钾氧化分光光度法分析不同粒径土壤团聚体中重金属和有机碳的含量特征,并对有机碳和重金属的相关性进行分析。结果表明,以2mm粒径团聚体的含量为最高,约占75%。Cu、Zn、Cd和Pb在0.25～0.5mm粒径团聚体中含量最高,Cr在5～8mm粒径团聚体中含量最高,As在不同粒径团聚体中的含量变化不大,重金属含量随土层深度增大而减小。土壤重金属富集因子表现为CuPbCdZnCrAs,Cu、Zn、Cd和Pb在0.25～0.5mm粒径团聚体中分布因子最高,而在5～8mm粒径团聚体中重金属的质量负载因子最大。土壤有机碳含量随团聚体粒径的增大表现为先增大后减小,不同粒径团聚体中Cu、Cd、Pb和As含量与有机碳含量均呈显著正相关(p0.05)。污灌区菜地土壤Cr、As在5～8mm粒径团聚体中富集现象显著,Cu、Zn、Cd、Pb在0.25～0.5mm粒径团聚体中均表现出显著的富集特征。6种重金属在5～8mm粒径团聚体中的质量负载因子均为最高,表明6种重金属在5～8mm粒径团聚体中的贡献最大。     

用溶出伏安法测定蛋白胨细胞生长液中易变形态铜

采用阳极阶梯溶出伏安法 ,测定了蛋白胨细胞生长液中的易变形态铜 ,并获得了总铜量中易变形态的摩尔分数以及易变形态的表观稳定常数。通过使用交换介质法 ,较好消除了由于蛋白胨细胞生长液中各种氨基酸或其它组分吸附在汞膜表面而引起的干扰     

Determination of the labile species of zinc by anodic stripping staircase voltammetry, with special reference to correlation with the toxicity to tetrahymena

Anodic stripping staircase voltammetry (ASSV) has been tested as a method to determine the concentration of “free” ions and very labile complexes of zinc. These species are thought to be primarily responsible for the toxic effect of zinc on the ciliated protozoan Tetrahymena pyriformis. ASSV and toxicological experiments were performed in an inorganic salt medium and the effects of Cu interference were studied. Even though the ASSV results were encumbered with problems, the results agreed well with the toxicological effects. In contrast, calculations based on the solubility product of Zn₃ (PO₄)₂·4H₂O could lead to erroneous results because kinetic and other effects result in very slow precipitation of zinc phosphate at the concentration levels in the salt medium used. In this medium there is a dose-dependent effect of zinc on Tetrahymena which is in agreement with the ASSV data, which indicate that all the zinc is in a labile form. The study emphasizes the importance of using experimental determinations in preference to theoretical models, which may predict quite erroneous results.     

Metal-ion-coordinating properties of the dinucleotide 2'-deoxyguanylyl(5'-->3')-2'-deoxy-5'-guanylate (d(pGpG)3-): isomeric equilibria including macrochelated complexes relevant for nucleic acids

The interaction between divalent metal ions and nucleic acids is well known, yet knowledge about the strength of binding of labile metal ions at the various sites is very scarce. We have therefore studied the stabilities of complexes formed between the nucleic acid model d(pGpG) and the essential metal ions Mg2+ and Zn2+ as well as with the generally toxic ions Cd2+ and Pb2+ by potentiometric pH titrations; all four ions are of relevance in ribozyme chemistry. A comparison of the present results with earlier data obtained for M(pUpU)- complexes allows the conclusion that phosphate-bound Mg2+ and Cd2+ form macrochelates by interaction with N7, whereas the also phosphate-coordinated Pb2+ forms a 10-membered chelate with the neighboring phosphate diester bridge. Zn2+ forms both types of chelates with formation degrees of about 91% and 2.4% for Zn[d(pGpG)]cl/N7 and Zn[d(pGpG)]-cl/PO, respectively; the open form with Zn2+ bound only to the terminal phosphate group, Zn[d(pGpG)]-op, amounts to about 6.8 %. The various intramolecular equilibria have also been quantified for the other metal ions. Zn2+, Cu2+, and Cd2+ also form macrochelates in the monoprotonated M[H;d(pGpG)] species (the proton being at the terminal phosphate group), that is, the metal ion at N7 interacts to some extent with the P(O)2(OH)- group. Thus, this study demonstrates that the coordinating properties of the various metal ions toward a pGpG unit in a nucleic acid differ: Mg2+, Zn2+, and Cd2+ have a significant tendency to bridge the distance between N7 and the phosphate group of a (d)GMP unit, although to various extents, whereas Pb2+ (and possibly Ca2+) prefer a pure phosphate coordination.     

Metals in surface water of Ukraine: the migration forms,features of distribution between the abiotic components of aquatic ecosystems,and potential bioavailability

We have generalized the results of long-term studies of coexisting forms of a series of metals (Al, Fe, Mn, Zn, Cu, Cr, Pb, Mo, Cd, and V) in surface water bodies of Ukraine, differing in the hydrological regime and the water chemical composition (rivers, reservoirs, lakes, and ponds). The studied metals content has ranged widely, the concentrations of aluminum, iron, and manganese being typically the highest, and the concentration of molybdenum, vanadium, and cadmium being typically the lowest. The ratio between the suspended and the dissolved forms of the metals has been established. Iron and aluminum migrate mostly as part of the suspended matter, whereas the other metals mainly migrate in the dissolved state. The dissolved manganese form predominates in the water bodies under anaerobic conditions. Copper and molybdenum are present almost always in the dissolved state, regardless of the water body type. The data on the relative content of the labile metal fraction (potentially toxic to aquatic organisms) are reported. The relatively low content of this fraction has been found to be majorly owing to the metal ions complexing with natural organic ligands. The humic compounds, the most widespread group of natural organic compounds, play the primary role in the complexation. Even metals with variable oxidation state (Cr, Mo, and V) are found mainly in the form of anionic complexes with the humic substances. Carbohydrates are also involved in the metals binding in the highly bioproductive water bodies, thus increasing the mass fraction of the neutral complexes during the summer and autumn periods. The molecular weight distribution of anionic metal complexes has been discussed; the substantial part of the metals constitutes the compounds with the molecular weight of below 5.0 kDa.     

Hydrochemical Regime of the Kiliya Delta of the Danube River in Retrospective and Modern Conditions: II. Metal Content and Speciation

Past and present data on the concentration and speciation of metals (Al, Fe, Cu, Zn, Pb, Cr, Cd, Mo, Ni) in the Kiliya Danube delta have been generalized, and variations in their concentrations have been compared. It has been shown that the highest pollution of the Danube lower reach has occurred from the second half of 1980s to the first half of 1990s due to intensive anthropogenic impact on the river delta ecosystem. Subsequently, decrease of the metal concentration was observed as a result of industrial crisis in the late 1990s–early 2000s. The major part of metals is transferred by water flow in the form of suspended solids, which is related to their relatively high content in water of the Kiliya part of the Danube delta. The results of studying dissolved metal species, in particular the ratio of the labile fraction that is potentially toxic to hydrobionts and complexes with dissolved organic matter, have been discussed. Data on the distribution of metals among complexes with dissolved organic substances of different chemical natures and molecular weights are given. Humic substances have been shown to contribute most to the complexation. Compounds with molecular weights of 1 to 5 and less than 1 kDa constitute the major part of anionic metal complexes with humic substances.     

Synthesis and spectral studies of macrocyclic Pb(Ⅱ), Zn(Ⅱ), Cd(II)and La(Ⅲ) complexes derived from 1,4-bis(3-aminopropoxy)butane with metal nitrate and salicylaldehyde derivatives

Eight new macrocyclic complexes were synthesized by template reaction of 1,4-bis(3-aminopropoxy)butane with metal nitrate and 1,3-bis(2-forrnylphenyl)propane or 1,4-bis(2-formylphenyl)butane and their structures were proposed on the basis of elemental analysis, FTIR, UV-vis, molar conductivity measurements, 1H NMR and mass spectra. The metals to ligand molar ratios of the complexes were found to be 1:1. The complexes are 1:2 electrolytes for Pb(II), Zn(II) and Cd(II) complexes and 1:3 electrolytes for La(lIl) as shown by their molar conductivities (Am) in DMSO at 10-3 tool L-l. Due to the existence of free ions in these complexes,such complexes are electrically conductive. The configurations of La(Ⅲ) and Pb(U) were proposed to probably octahedral and Zn(II) and Cd(II) complexes were proposed to probably tetrahedral.     

Evaluation of "labile" metal in sediments by use of ion-exchange resins

The metal content of a series of contaminated sediments has been determined by equilibrating ion-exchange resins of different types (held in porous cages) with aqueous suspensions of the sediments. H(+)-form exchangers took up high proportions of the Cu, Pb, Zn and Cd contents with recoveries depending on whether the acid functional groups were strong. Na(+)-form exchangers took up a smaller, loosely bound, labile fraction. The metal ions held on the exchangers were back-extracted into 0.05M EDTA and determined by flame AAS. Dissolution of sediment components led to the exchangers also taking up large amounts of Ca, Mg, Fe and Al. The exchange-resin technique provides an alternative means of subdividing the metal content of sediments into different "labile" or "available" fractions. Possible advantages include minimal re-adsorption of released metal ions by the sediment phases, retention of only "labile" species (ions or complexes), and a transfer mechanism which may resemble the action of plant roots more closely than chemical extractant processes do.     

Effect of organic colloids on ASV signals of Cd, Pb and Cu

The effect of organic colloids, such as humic and fulvic acids, on the ASV signals of Cd, Pb and Cu in acetate-buffer media has been investigated. Owing to their ability to adsorb metal ions, or form complexes (some sparingly soluble), the presence of the organic acids caused the magnitude of the signal peaks to decrease, the effect increasing with increase in organic acid: metal-ion ratio, and pH (from 5 to 8). Analysis before and after nitration through a 0.45-mum membrane indicated that most of the Cd retained was labile; in the Pb and Cu system less than half of the sorbed metal ion was labile, though a further fraction was displaced in the presence of Chelex 100 resin. The magnitude of the interference effect varied with the molarity of the medium and the presence of diverse anions (e.g. chloride, bromide) in the system. Cu displayed the most anomalous behaviour, with the stripping peak tending to broaden and split, particularly in the presence of humic acids. This behaviour was enhanced when the contact time with the preformed Hg film before the deposition/stripping cycle was increased above 5-10 min. This effect has been attributed to reduction (and subsequent oxidation) of Cu-humate species adsorbed on the mercury film.     

添加不同塑料与污泥混合热解对生物炭中重金属的影响

利用高温管式炉开展城市污泥（SS）与四种塑料（PE、PP、PS和PVC）混合热解实验,分别得到四种生物炭（SSC_PE、SSC_PP、SSC_PS和SSC_PVC）,研究了生物炭中重金属（Cr、Mn、Ni、Cu、Zn、As、Cd和Pb）含量、残余率、BCR形态和TCLP浸出毒性特征,并开展潜在生态风险评估。结果表明,添加不同塑料与污泥混合热解能够降低除Cd以外重金属的残余率。与污泥单独热解所得生物炭（SSC）相比,添加PE、PP和PS能够促进生物炭中的重金属向相对稳定态（F3+F4）转化,实现固化稳定;添加PVC仅对生物炭中Cr和As有固化稳定作用,对其他重金属有明显活化作用。四种生物炭中的重金属浸出量低于GB5085.3-2007浸出毒性鉴别标准规定的限值,生态风险均明显地降低至轻微风险水平,表明添加PE、PP、PS和PVC与污泥混合热解所得生物炭的应用不会带来新的环境风险,这为污泥与废塑料协同处置工艺提供了良好的理论支撑。     

Study of the Contents and Speciation of Heavy Metals in River sediments By Factor Analysis

Abstract

Heavy metals Zn, Cd, Pb, Cu, Ni and Co from two spanish river sediments have been determined by voltammetric techniques, along with % CaCO₃ and % organic matter, and the whole data set examined by means of Factor Analysis, finding a different behaviour of the metals in each river.

Heavy metal speciation in the sediments was carried out by using the Tessier's scheme: Zn and Pb were mainly associated to ‘reducible phases’, Cd and Cu bound to ‘organic matter and sulphides’, and Ni and Co were distributed between the above fractions. The ‘residual’ metals were used as pollution indicators from the rivers, finding a similar behaviour to other industrialized river systems.     

煎煮对几种特色南药中重金属元素含量和形态影响

考察了几种特色南药中重金属(Cd,Cr,Cu,Fe,Mn,Ni,Pb,Sr,Zn)的含量状况,并采用形态连续萃取法分析重金属在药材中的形态分布,研究了药材煎煮时药材中重金属的释放及煎煮过程对药材中重金属形态分布的影响。结果表明,几种南药中Cr,Pb,Zn的含量较高,且巴戟天中的重金属总量高于限量标准;原药材中Cr,Cu,Mn,Ni,Pb和Zn主要存在于有机态和残留态,Fe和Sr主要存在于残留态。煎煮使南药中大量重金属迁移到药汤中;药汤中Cu,Mn,Cr,Pb和Zn主要来自于其在药材中的可交换态、碳酸盐结合态和有机态,而药汤中Sr,Ni和Fe不仅包含其非残留态,更多来自于它们的残留态。为减少药汤中重金属,对于Cu,Mn,Cr,Pb和Zn既要控制在药材中的总量,且需降低它们在药材中的非残留态含量;对于Fe,Ni和Sr则主要是控制其在药材中的总量。