Three-stage sequential extraction procedure for metal partitioning in polluted soils and sediments

The sequential extraction procedure proposed by the Standard, Measurements and Testing program "SM&T" of the European Union has been applied to evaluate the amounts of Cr, Cu, Mn, Ni, Pb and Zn, extracted at each stage and indirectly their mobility and bioavailability in soil and sediment samples from a polluted area. Analysis of the extracts was carried out by flame atomic absorption spectrometry (FAAS). No significant matrix interferences were found except for Cr in the acetic acid and hydroxylammonium chloride extracts, which required determination by the standard additions method. Both of soils and sediments studied show similar partitioning of Mn, Ni, Cu and Cr. Mn and Ni can be considered to have significant component bound to the acido-soluble fraction, whereas, Cr and Cu occur largely in the organic and residual phases. The partitioning of Pb and Zn was different between soil and sediment. In terms of mobility and bioavailability, in soils, Ni and Mn can be regarded as moderately available followed by a lower availability of Pb while Cu, Zn and Cr have a very limited availability. In sediments, a higher availability (short-medium term) of Mn and Zn was presumed followed by a lower availability of Ni and Pb, whereas, Cu and Cr, occurring largely in the organic and residual phases, were of very limited availability.     

Distribution and speciation of metals in surface sediments of Taranto [corrected] gulf (Ionian Sea, Southern Italy)

Concentrations of metals (Al, Fe, Ti, Ni, Mn, Cr, Zn, Cu, Pb) were determined in surface sediments from Taranto gulf (Ionian Sea, Southern Italy) in order to assess the distribution and the bioavailability of metals. Total metal content and speciation of Fe, Ni, Mn, Zn, Cu and Pb were determined. Sediment cores were also sampled in some stations of particular interest. The analytical results show that metals distribution does not show significant variations in relation to depth. Metal distribution in the Taranto gulf is mainly influenced by industrial wastes from Taranto town, by rivers of the Basilicata region and by prevailing anticlockwise marine currents. These factors cause an accumulation of metals in the sediments near to the coasts of Calabria. The statistical analysis, effected by HCA and PCA methods, can be considered a good starting point in order to classify sediment samples and to locate accumulation areas. Metal speciation shows that Fe, Ni and Zn are present in sediments mainly as sulphides, Mn is present principally in an ion-exchange form or bound to carbonate, while Cu and Pb are mainly present in the fraction bounds to humic acids.     

Characterization of Metals in Surface Sediments from Xiaoyang River,Jiangsu, China

Some metal species and fractions have high affinity to anthropogenic activities, making it feasible to characterize the spatiotemporal characteristics of human-induced degradation of ecosystems. The accumulation of Fe, Mg, Mn, Zn, Cu, Cr, Ni, and Pb, their fractions, physiochemical parameters, and nutrients was evaluated in the surface sediments at 11 sites on the Xiaoyang River in urban and suburban locations in Jiangsu, China for the assessment of pollution. The sediment quality was evaluated based on sediment quality guidelines, enrichment factors, geoaccumulation index, potential ecological risk index, and risk assessment code. Principal component analysis and cluster analysis were used to identify the sources of the metals. The total concentrations of metals, enrichment factors, and geoaccumulation indices demonstrated that all sites were significantly polluted with Zn and significantly to moderately polluted by Cu, Pb, and Ni. Moreover, higher metal enrichment was present downstream through downtown Sheyang due to extensive human activities. However, the potential ecological risk indices and risk assessment codes revealed high bioavailability and toxicity of Pb in this region. These results indicated that the metal fraction showed higher susceptibility. The accuracy of the ecological risk assessment was evaluated in the river, indicating a heavy anthropogenic impact.     

Ecological risk assessment of sediment in wastewater discharging area by means of metal speciation

This study was designed to evaluate the influence of wastewater discharge to the marine ecosystem after treatment plant construction. Heavy metal concentrations in sediment and bioavailability of the metals were analyzed and ecological risks were assessed using the results. Metal speciation for sediments collected in the wastewater discharging area was measured by a Shimadzu AA-680 atomic absorption spectrometer. The distribution of the metals among various geochemical phases was determined. Biological samples collected and analyzed were four species of crustacea, four species of bivalve, and seven species of fish. Exchangeable fraction of superficial sediment (0–2 cm layer) was Zn 35.09%, Ph 5.30%, Cu 0.86%, Cr 0.01% and Fe 0%. However, exchangeable fraction of deep layer sediment (15–20 cm) was not detected for all metals analyzed. Deeper sediments were found to have more residual fraction, and bioavailable phases decreased by depth, which provides an indication of the seriousness of wastewater discharge effect in this enclosed bay. The chemical concentrations observed to be associated with biological effects were sorted. The comparisons were made with regard to the potential for adverse biological effects. The potential of adverse biological effects in the sediments of wastewater discharge site was estimated as Zn 69.8%, Pb 35.8%, Cu 29.1%, and Cr 21.1%, respectively. Mullet (Mugil cephalus) among biological samples had the highest concentration of Zn in the muscle and liver organs. The bioconcentration factors (BCFs) of Zn by the mullet, mussel, oyster and crab were the highest among heavy metals determined. This result was well related to 81.6% of bioavailable phase Zn and 69.8% of adverse biological effects for the surface sediment.     

Chemical Speciation of Elements in Sediment Samples Collected at Lake Balaton

A modified sequential extraction procedure was applied to determination of the distribution of seven elements (Cd, Cu, As, Pb, Cr, Ni, Zn) in sediment samples collected at Lake Balaton. The fractions were (1) exchangeable and bound to carbonate, (2) bound to Fe/Mn oxide, (3) bound to organic matter and sulfide, and (4) acid soluble. These fractions have the advantage of providing better insight into the mechanism of association of metals with mineralogical phases of the sediments. Samples were taken in three seasons and the average concentration of the elements was calculated. Based on the results determined at 15 sampling points along the lake, it seems that Lake Balaton has not yet been polluted. Concentrations of species were below the Hungarian standard levels set for soils, and most of the elements were found in the acid-soluble fraction, indicating stable compounds in sediments. There were no significant changes in the individual seasonal concentrations of elements in this short monitoring period.     

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.     

Geochemical fractions and modeling adsorption of heavy metals into contaminated river sediments in Japan and Thailand determined by sequential leaching technique using ICP-MS

In order to provide information on the chemical processes in sediment fractions and their adsorption models, we investigated the contaminated sediments of the Sumida River in Tokyo, Japan and the Chao Phraya River in Bangkok, Thailand. Samples were leached through a sequential leaching technique to perform metal concentration analysis for the sediment fraction assessment and then samples were tested for the model adsorption of the highest level of sediments contaminated by heavy metals using the isotherm Langmuir and Freundlich equations. Metal (Pb, Cd, Zn, As, Cu, Ca, Fe, and Mn) concentration in the leached solutions was analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The pattern of geochemical fractions in both sediment samples showed the maxima leached levels of Cd (38.6 %), Ca (55.2%), and Mn (41.3%) in the soluble fraction; Pb (52.1%), and Zn (56.7%) in the reducible fraction; Cu (61.2%) in the oxidizable fraction; and As (47.1%) and Fe (55.9%) in the residual fraction. The total level fractions of Pb (62.6 ppm), Zn (240 ppm), As (27.2 ppm), Fe (16,636 ppm) and Mn (419 ppm) in the Chao Phraya River sediments were higher compared to those in the Sumida River, indicating the high anthropogenic effect in Bangkok. In the most contaminated sediments, the higher adsorption capacity of heavy metal concentrations was contributed by SiO_2, CaCO_3, and Al₂O₃ determined by the X-ray diffraction and organic contents. The model of adsorption of Cd fitted to the linear form of Langmuir’s equation with the correlation coefficients (r² = 0.94), b (0.467) and k (7137), whereas Pb, Cu, Cr, and Zn conformed to the model of the Freundlich equation.     

Environmental mobility of trace metals in sediments collected in the Lake Balaton

In environmental pollution studies on solid materials sequential extraction techniques are used for the identification of the main binding sites of trace metals. A four-step sequential extraction procedure was applied to the determination of the distribution of elements like Cd, Cu, As, Pb, Cr, Ni, Zn, Al, Fe, and Mn in sediment samples collected in the Lake Balaton. The fractions were (1) exchangeable and bound to carbonate, (2) bound to Fe/Mn oxide, (3) bound to organic matter and sulfides, and (4) acid-soluble. Elements were mainly accumulated in the stable, acid-soluble fractions. Arsenic and Cd-ions were found in low concentration (1.2–13 mg/kg and < 1 mg/kg, respectively) in the samples. Based on the results determined at 15 sampling points it can be stated that the Lake Balaton has not yet been polluted by the elements investigated.     

Ultrasound-Assisted Extraction for the Evaluation of Element Mobility in Bottom Sediment Collected at Mining and Smelting Pb–Zn Ores Area in Poland

The current BCR procedure for metal fractionation recommended by the Standard Measurement and Testing Programme requires rather time-consuming sample pretreatment. Ultrasonic energy seems to be an attractive alternative for leaching metal from solid samples into a liquid extractant phase. This study aims at optimizing ultrasonic extraction in order to replace the BCR method of leaching using acetic acid and to apply the procedure of assessing element mobility in bottom sediment rich in moderately soluble carbonate minerals. The application of ICP-MS allowed the determination of As, Cd, Cr, Cu, Pb, Ni, Tl and Zn in extracts, in a wide range of concentration without any special treatment. Finally, 40’min extraction in an ultrasonic bath was proposed for evaluation of the mobile fraction of As, Cd, Cr, Cu, Pb and Zn as an assessment of environmental risk. The recovery of the ultrasound-assisted extraction in comparison to the shake-filter method, as applied in the common BCR procedure, was slightly higher than 100% for As, Cr and Pb, reasonably high (about 70%) for Cd, Zn and Cd, but did not exceed 21% for Tl. Also, the mobility and extractability (relative mobility) of the studied elements from sediment collected over one year were compares. According to the results obtained after 40’min of ultrasound-assisted extraction it can be concluded that mobility did not change over one year for Cr, Cu, As, Cd, Ni and Tl, but noticeable differences for Zn and Pb were observed. The total content of all studied elements was almost the same in samples taken in the years 2003 and 2004, respectively.     

耐高盐碱蓬对湿地土壤中金属元素的富集特征研究

基于秦皇岛滨海湿地人工种植耐高盐碱蓬修复工程试验,通过分析湿地土壤沉积物及耐高盐碱蓬中不同金属元素的含量与变化,研究了耐高盐碱蓬对金属元素的富集特征。结果显示:湿地沉积物中Fe、Mn、Cr、Pb和Zn的浓度较高,分别为8 210. 94、110. 04、8. 78、8. 25、10. 95 mg/kg,Cd的浓度最低,平均值为0. 022 mg/kg,湿地试验区土壤中同一金属元素变异程度较小,分布较均匀。碱蓬体内重金属含量根据采集地点的不同有差异,但与各站位中土壤的重金属分布特征存在正相关性;其中碱蓬内Fe、Mn、Zn、Cu的平均含量相对较高,且Fe、Mn、Ni、Cu、As、Cd、Pb元素在碱蓬根中的平均含量高于茎叶,而Cr在茎中的平均含量最高,Zn和Mo在叶中的含量最高。碱蓬的根、茎、叶对Cd的富集效果最好,其次为Mo、Cu,对Fe、Mn、Zn、As和Pb的富集效果相对较差,说明碱蓬对沉积物中不同金属元素的富集移出率存在差异。金属元素在碱蓬中的转移系数研究表明,Mo、Zn、Cd和Mn等元素可由根部转移到叶中,而Fe、Ni、Pb、As和Cu等金属元素固定在根部,该研究可为利用碱蓬修复湿地重金属污染提供理论基础。     

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。     

Evaluation of heavy metal and elemental composition of particles in suspended matter of the Upper Course of the Lerma River

The metal distribution of Cr, Mn, Fe, Cu, Zn, and Pb, and the elemental composition, morphology and relative abundance of particles have been evaluated in suspended matter of the Upper Course of the Lerma River in Mexico. The metal concentrations in the suspended matter decrease in the sequence: Fe > Mn > Zn > Cu = Cr > Pb. The Fe and Mn concentrations in the suspended matter are produced principally by natural contributions whereas the Cu, Zn, Cr, and Pb concentrations are produced principally by anthropogenic contributions. In general, the particle groups decrease in the following sequence: aluminosilicate > silica > sulphur > metals > calcium > manganese > iron > calcium carbonate.     

Analysis of heavy metals in road-deposited sediments

Road-deposited sediments were analysed for heavy metal concentrations at three different landuses (residential, industrial, commercial) in Queensland State, Australia. The sediments were collected using a domestic vacuum cleaner which was proven to be highly efficient in collecting sub-micron particles. Five particle sizes were analysed separately for eight heavy metal elements (Zn, Fe, Pb, Cd, Cu, Cr, Al and Mn). At all sites, the maximum concentration of the heavy metals occurred in the 0.45-75 μm particle size range, which conventional street cleaning services do not remove efficiently. Multicriteria decision making methods (MCDM), PROMETHEE and GAIA, were employed in the data analysis. PROMETHEE, a non-parametric ranking analysis procedure, was used to rank the metal contents of the sediments sampled at each site. The most polluted site and particle size range were the industrial site and the 0.45-75 μm range, respectively. Although the industrial site displayed the highest metal concentrations, the highest heavy metal loading coincided with the highest sediment load, which occurred at the commercial site. GAIA, a special form of principal component analysis, was applied to determine correlations between the heavy metals and particle size ranges and also to assess possible correlation with total organic carbon (TOC). The GAIA-planes revealed that irrespective of the site, most of the heavy metals are adsorbed to sediments below 150 μm. A weak correlation was found between Zn, Mn and TOC at the commercial site. This could lead to higher bioavailability of these metals through complexation reactions with the organic species in the sediments.     

Trace metal contents in certified reference sediments determined by nitric acid digestion and atomic absorption spectrometry

The trace metal (Cd, Cu, Pb, Zn, Fe) contents of certified reference sediments BCSS-1, MESS-1, SRM 1645 river sediment and SRM 1646 estuarine sediment) were determined by nitric acid digestion at 140°C without silicate lattice dissolution. All the metals studied except iron were completely recovered by this digestion method. About 20% of the iron was not recovered under the given conditions. The trace metal contents in SRM 1645 were also examined by using the hydroxylammonium chloride/acetic acid leaching procedure.     

Metals in water and surface sediments from Henan reaches of the Yellow River, China

The concentrations of Cd, Cr, Cu, Ni, Pb and Zn were determined in the water and surface sediments from the Henan reaches of the Yellow River. Twenty-three sampling sites along the Yellow River and its tributaries were selected. Generally, metal concentrations were found to decrease in sequences of Zn > Cu > Pb > Cr > Ni > Cd in water and Zn > Cr > Pb > Ni > Cu > Cd in sediments. High levels of metal concentration were determined at a few stations of the river and its tributaries, such as Yiluo River, Si River and Qin River. The pollution of the Yellow River by Cd, Cr, Cu, Ni, Pb and Zn can be regarded as much higher compared to the background values, US EPA criteria (1999) and China water quality criteria (2002). For sediments, metal levels except Pb did not significantly exceed the average shale levels and backgrounds in several countries including China. Data analysis manifests that positive correlations were found between Cu, Ni and Zn in water, and Pb, Ni, Zn and Cr in sediments. The Pearson correlation coefficient analysis and Cluster analysis were provided to assess the possible contamination sources. The results indicate a general appearance of serious pollution along the banks of the Yellow River. The wastewaters discharged by the mine plants, smelter plants, power plants, battery plants, tannery plants, etc., and sewage inputs from the cities along the river banks may be the sources of metals.     

Sediment Assessment of the Pchelina Reservoir,Bulgaria

The temporal dynamics of anthropogenic impacts on the Pchelina Reservoir is assessed based on chemical element analysis of three sediment cores at a depth of about 100–130 cm below the surface water. The ¹³⁷Cs activity is measured to identify the layers corresponding to the 1986 Chernobyl accident. The obtained dating of sediment cores gives an average sedimentation rate of 0.44 cm/year in the Pchelina Reservoir. The elements’ depth profiles (Ti, Mn, Fe, Zn, Cr, Ni, Cu, Mo, Sn, Sb, Pb, Co, Cd, Ce, Tl, Bi, Gd, La, Th and U_nat) outline the Struma River as the main anthropogenic source for Pchelina Reservoir sediments. The principal component analysis reveals two groups of chemical elements connected with the anthropogenic impacts. The first group of chemical elements (Mn, Fe, Cr, Ni, Cu, Mo, Sn, Sb and Co) has increasing time trends in the Struma sediment core and no trend or decreasing ones at the Pchelina sampling core. The behavior of these elements is determined by the change of the profile of the industry in the Pernik town during the 1990s. The second group of elements (Zn, Pb, Cd, Bi and U_nat) has increasing time trends in Struma and Pchelina sediment cores. The increased concentrations of these elements during the whole investigated period have led to moderate enrichments for Pb and U_nat, and significant enrichments for Zn and Cd at the Pchelina sampling site. The moderately contaminated, according to the geoaccumulation indexes, Pchelina Reservoir surface sediment samples have low ecotoxicity.     

Trace metal speciation in coastal and off-shore sediments from Ross Sea (Antarctica)

The information on total metal concentration in sediments is not sufficient to assess the metal behaviour in the environment, while speciation studies are more effective in estimating environmental impact of contaminated sediments. Concerning metal distribution in Antarctic marine sediments, several studies reported total or extractable (by means of a unique reagent) content, but only few publications dealt with metal speciation.This work presents the total content and speciation pattern of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in 12 cm sediment cores, sampled both in coastal and off-shore sites of the Ross Sea shelf area, within the framework of the Italian National Antarctic Programme (PNRA). The total content results of metals are comparable with the background values and the speciation highlights good environmental quality of the studied areas. Only Cd and Pb, in fact, are present in significative amount in non residual phases (acid-extractable and reducible, respectively).     

Geochemical variability of copper and iron in Oman Margin sediments

An analysis of the geochemical distribution of selected trace metals among various geochemical phases of the sediments in the Oman Margin was carried out using a sequential extraction technique. The present study showed that most Cu in abyssal sediment is associated with only oxidisable mainly organic and sulphide bound metals with insignificant bound to exchangeable, carbonates, easily/moderately reducible fraction. The preservation of Cu in the sediments indicates the importance of primary production and upwelling in the overlying waters and an organic flux in the sedimentary deposition of open-ocean environments. The early diagenetically formed oxidisable mainly organic and sulphide fraction are not degraded and results in a pronounced association of Cu with organic fraction in the sediments of the Oman continental margin. The strong correlation between Cu, TOC and Fe oxides associated with the oxidisable fraction in one of the core indicates that it is likely to be the presence of sulphides.     

Senio river ecosystem: characterization and distribution of inorganic species in water and sediments

Analytical results are reported for the determination of inorganic species in water and sediments sampled in the Senio river ecosystem. The species determined are Cu, Pb, Cd, Zn, Co, Cr, Ni, Fe, Mn, Hg, F-, Cl-, Br, NO3-, SO4-, Na+, K+, Ca++, Mg++, NH4+ in integrated water, and Cu, Pb, Cd, Zn, Co, Cr, Ni, Fe, Mn, Hg in sediments. For all the elements, in addition to detection limits, precision and accuracy are given: the former, expressed as relative standard deviation (sr), and the latter, expressed as relative error (e), were good, being in all cases lower than 6%. Limitedly to Cu, Pb, Cd and Zn a critical comparison with voltammetric measurements is also discussed.     

Comparison of three sequential extraction procedures used to study trace metal distribution in an acidic sandy soil

On an acid sandy soil contaminated with trace metals (Fe, Mn, Cu, Pb and Zn), three sequential extraction procedures were compared to determine the efficiency of the reagents used and the effects of the step order on the fractionation of metal species. In all cases, a magnesium nitrate solution (MgNIT) was previously used to extract exchangeable forms. In the first procedure (I), the next extraction step was performed with sodium acetate buffer (NaOAc), as used on calcareous soils, to dissolve active calcium carbonate. Then trace metals bound to different forms of oxi-hydroxides (NH(2)OH, TAMOx and TAMAs fractions) were extracted before organic matter/sulfide oxidation with hydrogen peroxide at pH 2.0 in nitric acid medium (OMHyd). Finally, residual bound metals (RESID) in each procedure were extracted with a nitric-hydrofluoric-perchloric acid mixture. The second procedure (II) was the same as I, but without the NaOAc step, because of the absence of carbonate in the study soil. In procedure III, the NaOAc step was omitted and the oxidizable organic/sulfide fraction was extracted with sodium hypochlorite at pH 8.5 (OMOCl) before the reducible fractions. This study first showed that NaOAc may remove considerable amounts of metals (especially Mn and Zn) in other forms than exchangeable ones. Procedures II and III give similar results for Fe, Mn and Zn forms, which were mainly found in fractions of inorganic soil components, but not for Cu and Pb. Copper distribution was affected by the position of the oxidation step in the sequence. In procedure II, where the oxidation step (OMHyd) ended the sequence, Cu was mainly recovered in the TAMOx fraction. However, in procedure III, where the oxidation step (OMOCl) preceded the NH(2)OH, TAMOx and TAMAs steps, Cu was found in both OMOCl and TAMOx fractions. Lead distribution varied with oxidation reagent: it was partly removed in the OMHyd fraction of procedures I and II, and to a much lower extent in the OMOCl fraction of procedure III, probably due to the alkaline pH of the reagent in the latter case.