Uptake of six heavy metals by oat as influenced by soil type and additions of cadmium,lead, zinc and copper

Summary The influence of heavy metal additions on availability and uptake of cadmium, lead, zinc, copper, manganese and iron by oat was studied. The experiments were carried out as pot experiments using sandy loam, sandy soil and organic soil. Selective extractants were used to remove metals held in different soil fractions.Lead and copper were preferently bound by organics and oxides, zinc by oxides and inorganics, and cadmium by inorganics and organics.Addition of cadmium to the soils resulted in higher cadmium concentrations in all plant parts but lower concentrations of lead, zinc, copper, manganese and iron, and the accumulation indexes of these metals were also lower when cadmium was added to the soil.Addition of cadmium plus lead, zinc and copper resulted in higher cadmium concentrations in leaves and straw of plants grown in sandy loam and sandy soil, but lower concentrations when plants were grown in organic soil as compared with the results when cadmium was added separately. The transfer of cadmium, lead, zinc and copper from soil to plant was greatest from sandy soil, and zinc and cadmium were more mobile in the plant than were lead and copper.Cadmium concentrations in leaves correlated significantly with CaCl₂ and CH₃COOH extractions in sandy loam and sandy soil and with CH₃COOH extractions in organic soil.Generally, the total metal uptake was lowest from organic soil.     

Sequestration Enhancement of Metals in Soils by Addition of Iron Oxides Recovered from Coal Mine Drainage Sites

Iron oxides recovered from abandoned coal mine drainage (AMD) sites (Lowber, Scrubgrass, and Horner) as a soil amendment were investigated in this laboratory study for their effectiveness in the stabilization of cadmium, copper, and zinc in two metal-contaminated soils. The adsorption experimental results demonstrated that all three AMD iron oxides possess significant capacity for adsorption of Cd(II), Cu(II), and Zn(II). Horner iron oxide exhibited the highest adsorption capacity. Both the adsorption and the extraction experimental results showed metal sequestration enhancement through addition of Horner iron oxide to soil (5% to 50% by weight). With soil pH of 4.5 to neutral range, AMD iron oxide addition worked best for strongly adsorbed metals such as Cu, not so well for more weakly adsorbed metals such as Cd and Zn. The more AMD iron oxide amendment added, the less the mobility of the cationic target metals. Addition of AMD iron oxide for metal sequestration was more effective for the contaminated soils with low organic content.     

Transformation of iron and manganese in rice soils under different moisture regimes and organic matter applications

Summary Transformation of iron and manganese under three different moisture regimes,viz continuous waterlogged (W₁), continuous saturated (W₂) and alternate waterlogged and saturated (W₃) and three levels of organic matterviz 0, 0.5 and 1.0% in all possible combinations was studied in four soils. The results showed that under waterlogged moisture regime there was a sharp increase in the content of water soluble plus exchangeable manganese accompanied by significant decrease in the content of reducible manganese in all the soils excepting the acidic soil which was very poor in active manganese content. The increase in respect of iron in similar form was, however, very small. The increase in the content of water soluble plus exchangeable manganese as well as iron under the continuous saturated and alternate waterlogged and saturated moisture regimes was always much lower as compared to that under the continuous waterlogged condition. Application of organic matter brought about an increase in the content of water soluble plus exchangeable manganese in all the soils excepting the lateritic one irrespective of moisture regimes but did not cause any change in the content of iron and manganese in insoluble complex. The content of water soluble plus exchangeable iron and of insoluble ferrous iron although recorded some increase due to organic matter application, the increase was not so marked in any of the soils.     

Metal distribution across different pools in the organic layer of a forest under acid deposition and its consequences for the metal dynamics

Acid atmospheric deposition can cause losses of metal nutrients from the organic layer of a soil. The size of these losses depend on the sizes of the different pools in which the metals are present, as these pools differ in mobility. The metal pools in an organic soil layer of a Douglas fir forest in the Netherlands subjected to acid deposition were determined by means of extractions and percolations. Na was mainly dissolved and exchangeably adsorbed, K dissolved, exchangeably adsorbed and present in the soil microbial biomass, Ca exchangeably adsorbed and present in organic precipitates, Mg exchangeably adsorbed and present in the soil biomass, and Mn exchangeably adsorbed and present in inorganic precipitates. The main part of the metals was exchangeably adsorbed. The adsorption affinity increased in the order Na < K < Mg < Mn ≈ Ca. The vertical distribution of the metals in the organic layer showed that all metals were continuously lost from the organic layer. The differences between the metals in retention and vertical distribution patterns were in agreement with their differences in deposition rate, pool distribution, and exchange affinity. Since the metals were mainly exchangeably adsorbed, and the acidifying cations dominated the atmospheric deposition, acid deposition and cation exchange must be processes that strongly affect the losses of metals from this organic soil layer. R F Huettl Section editor     

Spatial Variation and Fractionation of Bed Sediment-Borne Copper,Zinc, Lead,and Cadmium in a Stream System Affected by Acid Mine Drainage

An investigation was conducted to examine the spatial variation and fractionation of bed sediment-borne Cu, Zn, Pb, and Cd in a stream system affected by acid mine drainage. The pH had a major control on the spatial variation pattern of soluble, exchangeable, and carbonate-bound Cu, Zn, and Cd. There was a prominent concentration peak of carbonate-bound, oxide-bound, and organic-bound metals at the 29 km station, as controlled by the abundance of organic C, carbonate C, and oxides of manganese and iron. In general, the residual fraction was the dominant form for all four investigated metals. It was likely that oxide-Mn played a more important role in binding Zn and Cd than oxide-Fe did. In contrast, Cu had a higher affinity for iron hydrous oxides than for manganese oxide. Pb had a higher affinity for oxides of iron and manganese than for carbonates and organic matter. The presence of organic-bound metals in both the acidic upstream reach and non-acidic downstream reach suggests that the binding of these metals by organic matter was not markedly affected by pH, while the correspondence of organic C peak and organic-bound metal peaks at the 29 km station indicates a strong control by organic matter abundance on the quantity of organic-complexed metals.     

Influence of soil waterlogging on subsequent plant growth and trace metal content

Summary The uptake of trace metals by two plant species (French bean and maize) has been measured on two soils subjected to various waterlogging regimes. Uptake of both manganese and iron was increased due to soil waterlogging, although reoxidation of the soil affected iron more than manganese. Zinc and copper uptake was influenced by a species factor; French bean (Phaseolus vulgaris) showed preferential uptake of zinc, whereas maize (Zea mays) took up copper preferentially. Uptake of cobalt by both species was increased due to waterlogging, following the pattern of manganese.The abilities of these species to take up trace metals from soil followed the pattern predicted by selective extraction of soil for manganese, iron and cobalt, but not for zinc and copper.     

Assessment of a heavy metals‐contaminated site using sequential extraction,TCLP, and risk assessment techniques

The mobility of selected heavy metals in contaminated soil at a previous industrial site in Brisbane, Australia, was assessed using a sequential extraction technique. Copper, Pb, Zn, Cr, Fe, and Mn were extracted from the soil solution/exchangeable, carbonate, Fe and Mn oxides, and organic matter fractions. The amounts of metals adsorbed by these fractions were used as an indicator of each metal's mobility in the soil. Copper and Pb were largely adsorbed by the organic and oxide fractions, while a significant amount of Zn was extracted from the carbonate fraction. The potential mobility and biological availability of the metals in these soils is Zn > Cr = Cu ≈ Pb. Soils were also analyzed using the toxicity characteristic leaching procedure (TCLP) to determine whether the contaminated soil could be disposed of by landfilling. The leachability of all metals from the soils was very low, with metal concentrations below the allowable limits. The TCLP also showed that Zn was the most mobile metal in these soils. An environmental and health risk assessment was undertaken, and it was concluded that the site did not represent a risk despite the “total”; concentrations of some metals being up to 40 times the investigation threshold value adopted in Australia.     

Effect of algal growth on the availability of phosphorus,iron and manganese in rice soils

Summary Laboratory experiments were conducted to study the effect of algal growth on the change of (I) pH, (II) available phosphorus and (III) solubility of iron and manganese content in five waterlogged alluvial rice soils of West Bengal, India. The results showed that the algal growth initially caused an increase in the soil pH, which later declined to the original value in some of the soils. The available phosphorus content decreased upto 90 days of their growth and began to increase towards the later period of incubation. The drastic fall of water soluble plus exchaneable manganese content of the soils due to algal growth was accompanied by similar increase in reducible manganese content. No appreciable change in water soluble plus exchangeable ferrous iron content was encountered but theN-NH₄OAC(pH 3) extractable iron due to algal growth progressively decreased with the progress of the incubation period.     

Thematic minireview series: Metals in Biology 2012

Metals are present in about one-half of the protein structures available and also have critical roles in nucleic acid biochemistry. This prologue introduces the fourth of the Thematic Minireview Series on Metals in Biology, which deals with several topics involving iron, manganese, copper, and other metals. The six minireviews discuss metal transport and intracellular homeostasis, including chaperones and siderophores, maturation of the diiron active sites in hydrogenases, the balance between manganese and iron, and copper homeostasis relevant to pathogens.     

菌根植物根际环境对污染土壤中Cu、Zn、Pb、Cd形态的影响

采用根垫法和连续形态分析技术,分析了生长在污灌土壤中菌根小麦和无菌根小麦根际Ｃｕ、Ｚｎ、Ｐｂ、Ｃｄ的形态分布和变化趋势。结果表明,下对照土壤相比,菌根际土壤中交换态Ｃｕ含量显著增加,交换态Ｃｄ呈减少的趋势;与非菌根际相比,Ｃｕ、Ｚｎ、Ｐｂ的有机结合态在菌根根际中显著增加,而４种测定金属２的碳酸盐态和铁锰氧化态都没有显著改变,该结果表明,植物根系能影响根际中金属形态的变化,且菌根比无菌根的影响程度大     

Distributions of pH and chemical components in Mizorogaike, a pond with a floating-mat bog

Distribution patterns of pH and concentrations of chemical components were studied in Mizorogaike, a pond with a floating-mat bog, which is naturally acidified by the Sphagnum community. Considering the distribution of pH, sampling sites were selected on the floating mat (two sites), beneath the floating mat (one site), in the open water around the floating mat (two sites), and at the mouths of inflows (two sites). Monthly observations from April 1994 through March 1995 revealed that the distribution patterns of chemical components could be classified into three groups according to their pH dependence: (1) concentrations of dissolved organic carbon, organic phosphorus, aluminum, iron, and manganese increase with decrease in pH; (2) concentrations of dissolved orthophosphate and silicon increase with increase in pH; (3) concentrations of suspended particulate aluminum, iron, manganese, phosphorus, and silicon do not depend on the pH. Thus in Mizorogaike, the distribution of dissolved components depends on the pH.     

Redox conditions and iron chemistry in highland swamps of Burundi

Iron toxicity is a major soil constraint to rice (Oryza sative L.) cropping in highland swamps of Burundi. These swamps have a wide range of carbon content. This study aims at determining the influence of carbon content and redox conditions on the release of iron from Fe-bearing minerals. The pe-pH pairs distribution and oxalate dissolution data strongly suggest a control of Fe²⁺ activity by a pool of poorly crystallized ferric oxides. Flooding results in high values of KCl-extractable Fe (up to 22 cmolc kg^-1) being released from that pool. The iron release is positively correlated with organic matter. On the other hand, highly organic, peaty soils have large CEC and their adsorbed Fe fraction remains relatively low. As the exchangeable Fe fraction has previously been correlated with Fe toxicity to rice, we may conclude that very organic (> 25% C), peaty soils exhibit a lower Fe toxicity hazard than soils with intermediate carbon content (10–25%).     

Transport and distribution of trace elements and other selected inorganic constituents by suspended particulates in the Salton Sea Basin, California, 2001

In order to examine the transport of contaminants associated with river-derived suspended particles in the Salton Sea, California, large volume water samples were collected in transects established along the three major rivers emptying into the Salton Sea in fall 2001. Rivers in this area carry significant aqueous and particulate contaminant loads derived from irrigation water associated with the extensive agricultural activity, as well as wastewater from small and large municipalities. A variety of inorganic constituents, including trace metals, nutrients, and organic carbon were analyzed on suspended material isolated from water samples collected at upriver, near-shore, and off-shore sites established on the Alamo, New, and Whitewater rivers. Concentration patterns showed expected trends, with river-borne metals becoming diluted by organic-rich algal particles of lacustrine origin in off-shore stations. More soluble metals, such as cadmium, copper, and zinc showed a more even distribution between sites in the rivers and off-shore in the lake basin. General distributional trends of trace elements between particulate and aqueous forms were discerned by combining metal concentration data for particulates from this study with historical aqueous metals data. Highly insoluble trace metals, such as iron and aluminum, occurred almost entirely in the particulate phase, while major cations and approximately 95% of selenium were transported in the soluble phase. Evidence for greater reducing conditions in the New compared to the Alamo River was provided by the greater proportion of reduced (soluble) manganese in the New River. Evidence of bioconcentration of selenium and arsenic within the lake by algae was provided by calculating “enrichment” concentration ratios from metal concentrations on the algal-derived particulate samples and the off-shore sites. Guest editor: S. H. Hurlbert The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife and People, 1905–2005, held in San Diego, California, USA, March 2005 Roy A. Schroeder—Retired.     

Protein metalation in biology

Inorganic metals supplement the chemical repertoire of organic molecules, especially proteins. This requires the correct metals to associate with proteins at metalation. Protein mismetalation typically occurs when excesses of unbound metals compete for a binding site ex vivo. However, in biology, excesses of metal-binding sites typically compete for limiting amounts of exchangeable metals. Here, we summarise mechanisms of metal homeostasis that sustain optimal metal availabilities in biology. We describe recent progress to understand metalation by comparing the strength of metal binding to a protein versus the strength of binding to competing sites inside cells.     

Effects of added manganic and ferric oxides on sulfate reduction and sulfide oxidation in intertidal sediments

Abstract Freshly precipitated iron or manganese oxides were added to surface sediments from a salt marsh and from the intertidal region of Lowes Cove, Maine. In the presence of added manganese, sulfate was formed under anoxic conditions, suggesting a manganese dependent sulfide oxidation. Sulfate formation was not observed with iron additions. Sulfate reduction was substantially but not completely inhibited by either metal oxide, even though both were added at levels well in excess though both were added at levels well in excess of natural concentrations. Manganese-catalysed sulfide oxidation was further documented using a combination of radiolabel, metal oxide, and inhibitor additions, Results from this study suggested that losses of radiolabelled sulfide could result in underestimates of gross sulfate reduction rates in the presence of significant manganic oxide concentrations. In addition, manganic oxides may facilitate the anaerobic regeneration of sulfate from sulfides.     

Effect of calcium carbonate and organic matter on the growth and concentration of iron and manganese in sorghum (Sorghum bicolor)

Summary The effect of CaCO₃ and organic matter on the availability of iron and manganese was studied on sorghum (Sorghum bicolor). Addition of calcium carbonate caused significant decrease in dry matter and grain yield. But yields tended to increase with the addition of organic matter at the rate of 15 t/ha. The iron concentration decreased with the addition of CaCO₃ at all the stages of crop growth. Like iron, concentration of manganese also decreased with the increase in added CaCO₃. Organic matter increased the iron concentration both at seedling and flowering stage. The concentration of manganese was, however, dependent on the stage of the crop.     

Phytotoxicity and distribution of copper in tropical soil amended with sewage sludge and copper sulfate

Abstract

A greenhouse experiment was conducted to evaluate phytotoxicity and distribution of Cu in a tropical soil amended with sewage sludge (Sw) and copper sulfate (CuSO₄.5H₂O). Samples of a clay soil from the State of Paraná, Brazil were collected at depth of 0–20; 20–40 and 40–60 cm, and brought to the laboratory to be properly accommodated in experimental units (PVC tubes). The Cu treatments were performed by the application of Sw (10 t ha-¹) amended with Cu (SB-T), and by CuSO₄. H₂O (WB-T). Lettuce plants were cultivated in the amended soil in order to predict the toxicity of the Cu. The experiment was conducted for 70 days, and then the lettuce plants and soil samples were collected for analysis. A sequential method was used to separate soil Cu into following fractions: exchangeable, amorphous iron oxide bound, crystalline iron oxide bound, organic matter bound and residual bound. The experimental results showed that Fe, Zn, K, P, Cu and organic matter amounts of the soil increased with the treatment SB-T. The toxic phyto-available Cu content in the soil for the lettuce plants was 80.00 mg kg^-1. A percolation study showed that the Cu contents were larger for the first 20 cm of depth, indicating that the metal was not transported down the soil profile. The Cu content of different fractions declined in an order residual > amorphous iron oxide > crystalline iron oxide > organic matter > exchangeable, regardless of treatment performed. Additionally, the Cu contents added from treatments were determined mainly in amorphous iron oxide fraction.     

An ultrastructural study of iron and manganese deposition associated with extracellular polymers of pedomicrobium-like budding bacteria

Morphological characteristics of two Pedomicrobium-like budding bacteria are described. A structured surface layer was regularly observed on strain 868. Ruthenium red- and Alcian blue-staining polymers were found on both strains.When either strain was grown in the presence of iron or manganese, the corresponding oxides accumulated on their surfaces. In thin sections iron oxides appeared as fine threads, arrays of particles or dense coatings, depending on the source of iron. Manganese oxides appeared as branching filaments or convoluted ribbons. Both metal oxides stained with ruthenium red. Extraction of the oxides followed by ruthenium red staining revealed that polyanionic polymers previously deposited on the cells were associated with the metals.Treatment of cultures with glutaraldehyde, HgCl₂, or heat, inhibited manganese but not iron deposition, suggesting that iron oxides accumulated by passive, non-biological processes. Manganese oxides apparently accumulated under control of a biological manganese-oxidizing factor. Incomplete inhibition of manganese deposition observed in cell suspensions suggested that, if the oxidizing factor was an enzyme, it was unusually stable.Based on these results, possible mechanisms of iron and manganese deposition in association with extracellular polymers are suggested.     

Operationally determined chemical speciation of barium and chromium in drilling fluid wastes by sequential extraction

ABSTRACT

A study has been conducted to determine the influence of pH on the speciation and distribution of barium and chromium in drilling mud. Samples in equilibrium under controlled conditions were subjected to sequential extraction procedure to fractionate the heavy metals into the designated forms of exchangeable, adsorbed, organically bound, carbonate and residual phases. This provides an insight into the potential availability of the heavy metals for possible release into groundwaters and/or surface waters. The major portion of both the metals studied was found in the carbonate and residual forms with the relative distribution depending on the pH. Generally, decreasing pH caused a shift from the residual form towards the carbonate or organic forms of metals. The occurrence of metals in more stable organic, carbonate and residual forms in drilling mud, coupled with no significant release to the aqueous phase upon varying the pH indicates the resistance of these metals to remobilisation from drilling mud.     

Sludge-Derived Cu and Zn in a Humic-Gley Soil: Effect of Dissolved Metal-Organic Matter Complexes on Sorption and Partitioning

A sequential extraction scheme was combined with sorption isotherm analysis in order to investigate sorption of sewage sludge-derived Cu and Zn to the A-horizon of a humic-gley soil as a whole, and to the operationally defined exchangeable (1?M MgCl₂), carbonate (1?M NaOAc), Fe/Mn oxide (0.04?M NH₂OH.HCl), and organic (0.02?M HNO₃+30% H₂O₂) soil fractions. Sorption parameters were compared for a sample of sludge leachate (with 97.4% of Cu and 63.2% of Zn present as dissolved metal-organic matter complexes, as calculated by geochemical modeling involving MINTEQA2 and verified using an ion exchange resin method) with that of a reference solution exhibiting the same chemical characteristics as the leachate, except for the presence of dissolved organic material. Dissolved metal-organic matter complexes were found to significantly (P<0.05) depress sorption to the bulk soil and each fraction. The greatest depression of Cu and Zn sorption was observed for the exchangeable, carbonate, and Fe/Mn oxide fractions, while the organic fraction of the soil was the least affected. This reflects a greater affinity for the exchangeable, carbonate, and Fe/Mn oxide fractions by the free divalent metal (Cu²⁺, Zn²⁺), with sorption by these fractions attributed to cation exchange, chemisorption, and co-precipitation processes. The sorption characteristics of the organic fraction indicated that Cu and Zn sorption by soil organic matter mostly involved dissolved metal-organic matter complexes. This may be attributed to hydrophobic interactions between nonpolar regions of the dissolved metal-organic matter complexes and solid-phase soil organic matter.