Extraction Of Trace Metals Research Articles

C18 Sep-Pak extractable trace metals in waters from the Gulf of Lions

Abstract Dissolved trace-metal (Cd, Cu, Fe, Ni and Pb) interactions with C18 Sep-Pak extractable organic matter have been investigated in the Rhone mouth and in the Gulf of Lions in July 1989. Pb and Cd do not show any complexation while Ni and Fe are slightly complexed in surface waters near the Rhone mouth. Up to 40% of total dissolved Cu is complexed by the extractable organic matter in coastal waters and, in open sea waters a subsurface maximum of 64% of complexed Cu was observed, apparently linked to the maximum of primary production. Our results combined with other data on the same area suggest that in the euphotic zone of the western Mediterranean Sea, organic matter directly connected to primary production and associated degradation processes is contributing to this complexation as well as to the enrichment of colloidal fraction and the increase of the discrepancy between concentrations of dissolved organic carbon according to the method of Sugimura and Suzuki (1988) and by traditional techniques.

Preconcentration of trace metals in sea water matrix for differential pulse anodic stripping voltammetry

A preconcentration procedure with two-step extraction was proposed to be used in conjunction with differential pulse anodic stripping voltammetry (DPASV) for the determination of trace metals in sea water. The two-step extraction involved extraction of trace metals from sea water with dithiocarbamate into chloroform followed by backextraction with a Hg 2+ solution at pH 3.5, as previously reported. The aqueous solution containing simply the enriched metals and the nonreacted Hg 2+ was analysed by DPASV using a glassy carbon electrode. Anodic stripping voltammetry of the metals including Zn, Cd, Pb and Cu was conducted in the preconcentrated solution after adding 0.025 M KCl. The preconcentrated solution was observed not to cause any interference in the anodic stripping voltammetry. Besides, the Hg 2+ could be in situ utilized as the source of the mercury film coated on the glassy carbon electrode, rendering it as an efficacious working electrode. The detection limits achieved were as low as 0.004 μg/1 for Zn, 0.002 μg/1 for Cd, 0.002 μg/1 for Pb and 0.003 μg/1 for Cu in sea water by DPASV coupled with the preconcentration procedure with an enrichment factor of 20. The analytical reliability was confirmed by checking with NASS-3 (NR-A4) open ocean sea water.

Evaluation of a sequential extraction procedure for the determination of extractable trace metal contents in sediments

The determination of extractable trace metals in sediments using sequential extraction procedures has been performed in many laboratories within the last ten years in order to study environmental pathways (e.g. mobility of metals, bounding states). However, the results obtained by different laboratories could hardly be compared due to lack of harmonized schemes. Owing to the need for standardization and subsequent validation of extraction schemes for sediment analysis, the Measurements and Testing Programme (formerly BCR Programme) of the European Commission has organized a project to adopt a sequential extraction procedure that could be used as a mean of comparison of data of extractable trace metals in sediments. A scheme was designed after a series of investigations on existing schemes and tested in interlaboratory studies. This paper presents the results of two round-robin exercises on extractable trace metals using this sequential extraction protocol and describes the final version of the extraction procedure amended according to the most recent improvements.

Study of the stability of extractable trace metal contents in a river sediment using sequential extraction

Sequential extraction schemes have been used in recent years to study the environmental behaviour of trace metals present in soils and sediments. Owing to the variety of the different extraction procedures, the results obtained were not comparable as they were highly dependent on the procedure. Moreover, the lack of suitable reference materials for this type of analysis prevents quality control of the measurements. In 1987 the Community Bureau of Reference (BCR, now Measuring and Testing Programme) started a programme to harmonize the methodology and to produce certified reference materials. This paper presents the work carried out to prepare a river sediment sample to be analysed in an intercomparison exercise using a common sequential extraction scheme adopted at Sitges by a group of European experts. The studies of homogeneity and stability with time of the extractable trace metal contents in the sample are also reported.

Measurement of trace metals associated with acid volatile sulfides and pyrite in organic freshwater sediments

The efficiency of density separation and of a number of different chemical extraction methods to extract pyrite and associated trace metals from sediments having high organic matter contents were investigated. All chemical extraction methods tested were suitable for pyrite determinations but overestimated the associated trace metal (Co, Cu, Mn, Ni, Pb, and Zn) concentrations presumably due to interferences produced by simultaneous extraction of trace metals associated with organic matter. Concentrations of trace metals associated to pyrite in the bulk sediment can best be determined from the pyrite-trace metal/pyrite-Fe ratios obtained by density separation and the total concentration of pyrite in the sediment obtained by the chemical extraction methods

SEWAGE SLUDGE EFFECTS ON CHEMICAL PROPERTIES OF ACID SOILS

Field experiments were established at two locations (on an Oxisol and an Ultisol) to evaluate the effects of 0, 8, 16, and 24 metric tons ha−1 of aged municipal sewage sludge on soil properties and growth of four crop species. Soil samples taken from each plot, before sludge application and at harvest of the crops, are compared here to determine any effects of the sludge on pH, exchangeable acidity, exchangeable bases, cation and anion exchange capacity, and extractable phosphorus and trace metals. To test effects on soil properties in a more controlled environment, soil from one site was incubated with the sludge over a period of 4 months. No detrimental effects and several beneficial effects were observed. In particular, problems of soil acidity were diminished by an increase in pH and exchangeable calcium accompanied by a decrease in exchangeable acidity. Sludge applications also increased BaCl2-MgSO4 CEC, but only in the Oxisol did the sum of cations increase. Dilute acid-fluoride extractable phosphorus also increased with sludge additions accounting for 2 to 19% of added sludge P for the Ultisol and 19 to 52% of P added to the Oxisol. Increases in Mehlich-3 extractable Cu and Zn in the soils were approximately equal to the amounts of these elements added to the soil in the sludge.

Single and Sequential Extraction in Sediments and Soils

Abstract The determination of extractable trace metal contents in soils and sediments is currently performed in many laboratories to assess the bioavailable metal fraction (and related potential phyto-toxic effects) and the importance and possibility of mobilization of trace metals from polluted soil, sludge and sediment upon landfill application. Single and sequential extraction schemes are used for the assessment of the different “forms” of trace metals (e.g. “mobile/bioavailable”, “carbonate-bound” etc.). The lack of uniformity in the different extraction procedures used throughout the world does not allow the results to be compared or the procedures to be validated which has led to many criticisms in the past few years. Moreover, the lack of suitable reference materials for this type of operationally defined determinations did not enable the quality of the measurements to be controlled. Owing to the need for establishing common schemes for single and sequential extractions as well as for the improveme...

Improvement of Analytical Measurements within the BCR-Programme: Single and Sequential Extraction Procedures Applied to Soil and Sediment Analysis

Abstract The determination of extractable trace metal contents in soil and sediment, using respectively single and sequential extraction procedures, is currently performed in many laboratories to assess the bioavailable metal fraction (and related phyto-toxic effects) and the accessability to the environment (e.g. contamination of ground waters). Owing to the need for validation of the extraction schemes used and of the analytical techniques, the Community Bureau of Reference (BCR) decided to organize a project for the improvement of the quality of determinations of extractable trace metal contents in soil and sediment. The implementation of this project follows a stepwise approach involving feasibility studies, intercomparisons to detect and remove sources of errors in the application of the analytical methods, and the certification of the extractable compounds. This paper describes the organization of the work completed so far (feasibility studies and first intercomparison) and discusses its further dev...

Assessment of trace metal extraction techniques with reference to aquatic sediments

Different techniques have been employed to determine the extractability of non-residual metals from aquatic sediments. The methods classified as acid extractable, cold extractable and alkaline fusion extractable were compared on the basis of their efficiency in extracting metals responsible for pollution in streams and rivers in the Plateau state of Nigeria. The results show that optimum recovery of any metal depends on the choice of the decomposition procedure. While the cold extractable method showed affinity for most of the metals, copper and tin were optimally recovered by the acid digestion method. Generally, fusion methods gave scant metal recoveries which could be attributted to the low silicate content of the sample and volatilisation losses. In all cases the samples were quantitatively analysed by atomic absorption spectrophotometry and the error due to determination calculated as standard deviation.

Preconcentration of Trace Metals in Seawater Matrix for Inductively Coupled Plasma Atomic Emission Spectrometry

In this study, a two-step preconcentration procedure is proposed to be used in conjunction with ICP-AES for the determination of trace metals in seawater. The two-step preconcentration involves extraction of trace metals from seawater with dithiocarbamate (DTC) into chloroform followed by back-extraction with a Pd2+ solution. The extraction could concentrate the trace metals by forming a chelate with DTC with a high enrichment factor obtained with the large phase volume ratio. The back-extraction agent Pd2+ is selected because the extraction constant of Pd(DTC)2 is the largest and much higher than most of the other metal dithiocarbamates. The enrichment factor could be further enhanced at the back-extraction step with a large phase volume ratio. Finally, the aqueous solution containing simply the enriched metals and some of the nonreacted Pd2+ was taken for ICP-AES.

Trace metals in fluvial sediments of the Madeira River watershed, Amazon, Brazil

Sediment samples from 10 rivers of the Madeira River watershed, Amazon, were analyzed for major and trace element composition. Differences among river classes (white, clear and black water) were detected, in particular regarding the organic matter content, the concentration of bioelements, and the trace metals Fe, Mn, Cu and Zn. This shows that the classical differentiation of Amazon rivers based on water chemistry is also confirmed by sediments. Sequential extraction of trace metals showed that the lithogeneous and reducible fractions of sediments are the principal substrates of trace metal transport in these fluvial systems.

Biochelation cartridge for the solid-phase extraction of trace metals

The characterisation and metal complexation capacities of biochelating silicas utilising hydroxamate complexation are described. Metal complexation on the silica displayed the characteristic optical properties of the free complexes in aqueous solution. Unsubstituted and N-methyl-substituted monohydroxamate silicas are compared with the biochelator, desferrioxamine immobilised on to silica; the latter displayed an over-all lower capacity as a function of pH. A trace metal cartridge utilising the biochelating silica showed good stability, pre-concentration and elution properties for a number of metals.

A quantitative method for determination of trace metal concentrations in sedimentary pyrite

Trace metals commonly undergo chemical diagenesis in anoxic sediments from association with metal oxides, organic matter, and other reactive components to coprecipitates with authigenic pyrite. Whereas this process has long been recognized as a major aspect of trace metal diagenesis, no satisfactory method for quantifying trace metal concentrations in sedimentary pyrite has been available. We present a new method, derived from the Lord technique (as described in C.J. Lord, J. Sediment. Petrol., 52: 664–666), for the quantitative extraction of trace metals from sedimentary pyrite. The new method involves the sequential leaching of sediments using 1 M HCl (reactive fraction), 10 M HF (silicate fraction) and concentrated HNO 3 (pyrite fraction). Examples are presented of the application of this new method to trace metal diagenesis in two different sedimentary marine environments: Baffin Bay, TX, and the Mississippi Delta. To establish the relation between the transfer of Fe and the trace metal of interest to the pyrite phase, the degree of pyritization (DOP) was compared with the newly introduced degree of trace metal pyritization (DTMP). Results obtained by combining these two operationally defined parameters indicate that transition metals exhibit a trend of increasing DTMP with increasing DOP, whereas DTMP values for class B metals remain essentially constant with increasing DOP levels.

The effects of variations in temperature on the extraction of trace metals from soils by selected reagents

Abstract The effects of variations in temperature on the extractability of copper, manganese, nickel, lead and zinc in soil tests were investigated by extracting five soils with five reagents at four temperatures (5, 15.5, 25.5 and 38.5 C). The results indicated a trend for metal extracted to increase with temperature, except for manganese and lead in DTPA. Nickel showed the most linear and consistent response, whereas zinc showed the most anomalous behaviour, especially in soils with elevated organic matter contents.

Selective extraction of trace metals associated with hydrous aluminum oxides

In soil/sediment analysis, subdivision of trace metal content into different categories is usually based on selective extraction schemes. To assess the disposition of metal ions bound to aluminum hydrous oxides in such schemes, suspensions of Al(OH)3gel, gibbsite, or alumina were loaded with up to 5 μ mol of Cu, Pb, Cd, or Zn ions prior to being extracted for 24 h with one of fifteen different chemical solutions. The percentage of sorbed ion retrieved varied along the reagent sequence: NaCl, CaCl2 < MgCl2, NH4NO3 < CH3COONH4, Na citrate, Na4P2O7 < EDTA, DTPA < CH3COOH, H2C2O4, HCl, HNO3. In each system, the recovery value varied with the initial surface loading (a function of sorption pH) and reflected changes in metal species form, e.g., bonded M2+, (MOH+), M(OH)2. With low loading levels up to 40% was displaced by salt solutions; with 1 to 2 μ mol sorbed, as little as 10% was displaced by acids or complex formers but this increased to ~90% with higher loadings. The relationship between sorption pH, amount sorbed, and extraction value was complex, and since in selective extraction schemes classification is based on recovery values, changes in initial retention parameters (e.g. system pH) lead to varying fractions of the different metal ions being classified as "ion exchangeable", "chemisorbed", and "incorporated in the lattice".

Determination of organically-associated trace metals in estuarine sea-water by solvent extraction and atomic-absorption spectrometry

Chloroform extraction of trace metals (Ni, Cu, Mo, Mn, Cd and Pb) in estuarine sea-water was studied at pH 8 and pH 3, on the basis that the metals would be associated with dissolved organic matter (DOM), which has recently been characterized by reversed-phase liquid chromatography. Ni, Cu, Mo and Mn were extracted more at pH 8 than at pH 3. Cd and Pb were not associated with the DOM at either pH 8 or 3. The percentage of the total dissolved trace metals in sea-water associated with DOM varied from 0 to 14%. The metals extracted into chloroform at pH 8 were assumed to be associated with neutral or weakly basic DOM while at pH 3 they could be associated with either the neutral (or weakly basic) DOM or two types of acidic DOM.

Effect of Sequence in Extraction of Trace Metals from Soils

AbstractWhile many workers have utilized various reagents for sequential extraction of soil trace metals, few studies have examined the order of extraction for key steps in the sequential procedure. In this study, several sequences involving both adsorbed and structural (occluded) metal extractants were evaluated to determine the most appropriate sequential methodology for extracting different forms of Cu, Fe, and Mn. For “specifically adsorbed” metals, Pb(NO3)2 and CH3COOH were used. The results showed that the former reagent extracted less Cu, Mn, and Fe and was probably more specific in replacing metals covalently bound to adsorption sites. Lead nitrate was therefore placed before CH3COOH extraction in the sequence. Chao's NH2OH·HCl reagent and K4P2O7, used for Mn oxide and organic metal removal, respectively, were found to solubilize significantly different amounts of Cu and Mn depending on sequence, with K4P2O7 extracting more metal when used first. As NH2OH·HCl has little effect on organic metals, it should be used before K4P2O7. Noncrystalline and crystalline Fe compounds are solubilized next, using a variety of reagents, and residual (silicate lattice) metals are dissolved in the final step. A nine‐step sequential method is proposed to characterize trace metals in agricultural, polluted, and waste‐amended soils.

Effects of flow rate and pretreatment on the extraction of trace metals from estuarine and coastal seawater by Chelex-100

During the extraction of previously acidified estuarine samples, altered organic material still retains some capacity to inhibit the extraction of trace metals by Chelex-100. Previous studies have indicated that heating or UV oxidation of samples reduces the capacity of this organic matter to inhibit the extraction of trace metals by Chelex-100. The results of this study using recently collected samples indicate that decreasing the flow rate to 0.2 mL min/sup -1/ is also an effective means of increasing the retention of trace metals by Chelex-100. Additional benefits of the slow-flow column extraction method include improvements in precision and the elimination of pretreatment procedures that could cause contamination or reduce the extractability of Fe. Aged acidified samples require heating of the sample prior to extraction. Controlled contamination can be minimized for most metals by preextraction of the buffer solution. 21 references, 1 figure, 2 tables.

Trace Metal Chemistry in Arid‐Zone Field Soils Amended with Sewage Sludge: III. Effect of Time on the Extraction of Trace Metals

AbstractThe surface horizons of two arid‐zone field soils that either had received amendments of composted sewage sludge annually since 1975, or had received amendments of liquid sludge between 1976 and 1978, were fractionated by sequential extraction for 4 years annually, beginning in 1979, to compare the solid‐phase forms of Ni, Cu, Zn, Cd, and Pb. The total concentration of each trace metal in the soils continually receiving composted sludge increased with time, whereas the total concentration of the metals in the soil that had received liquid sludge until 1978 did not increase with time. Regardless of the time variation of total metal concentration, the percentages of the metals in either the EDTA (ethylenedinitrilote‐traacetic acid)‐extractable fraction or the HNO3‐extractable fraction often tended to increase with time in the soils. This trend was more evident in the lighter‐textured field soil receiving composted sludge. It was concluded that the observed increase in EDTA‐extractable trace metals with time could be the result of the formation of trace metal carbonates accompanying the gradual mineralization of the organic matter in the applied sludge in the soil environment.

An investigation of methods commonly used for the selective removal and characterization of trace metals in sediments

The characterization of solid phase-associated transition metals is important in understanding solid—seawater interactions. This has proven to be a difficult problem because of the complex nature of most sediments and suspended particulate matter. Many chemical techniques have been proposed to describe sedimentary metal phases. Most rely on characterizing equivalent chemical reactivities from the various metal phases rather than the characterization of the actual physical phases with which the metals are associated. In this study, several of the most widely used trace metal extraction techniques are compared for many of the most commonly measured transition metals using a variety of naturally occurring major marine sediment types. All solid concentrations are normalized to total metal values as obtained by neutron activation and X-ray fluorescence analyses. One weak, four intermediate strength, and two strong metal extraction methods were studied individually. The weak method had the lowest degree of extraction efficiency, but dissolved all solid carbonate phases. Its probable inability to retain released metals quantitatively in solution is a major problem. Three of the four intermediate methods are similar. The other and simplest of the four methods (0.5 N HCl), released much lower amounts of most metals studied when compared to these other three. It cannot be classified as a weak method, however, as it does attack some moderately resistant solid phases. Only one of the other three intermediate methods (a reducing acetic acid solution), was relatively free from analytical difficulties and it is preferred for this reason. The two strong extraction methods are quite similar, with neither yielding total metal concentrations. A five-step sequential extraction scheme was also evaluated. The results were generally quite good, both with regard to metal phase fractionation and overall total extraction of available metals. Based on the results of this study, a sequential extraction scheme is a useful method for characterizing solid phase-associated transition metals.