Chemical partitioning of Cu,Pb and Zn in the soil profile of a semi arid dry woodland

Abstract

The chemical partitioning of Cu, Pb and Zn was examined in the soil profile of the woodland system in Keoladeo National Park, India using a five-step sequential extraction procedure (SEP). Metal partitioning was assessed in the soil up to a depth of 100cm with 25-cm intervals. The amount of metals obtained from the SEP exceeded pseudototal metal levels obtained from aqua regia digestion. The SEP results showed high preferential attachment of metals with Fe—Mn hydroxides. All the three metals showed least preferences to the exchangeable pool. The attachment of metals to the OM-S phase was also less, may be because of the low organic matter in the soil. In the case of Cu, the order of the fractions in terms of metal concentrations was Fe—Mn>RES>OM-S>CA>EXC and in the case of Pb the order was Fe—Mn>OM-S>RES>CA>EXC. Zn was different from Cu and Pb in showing higher affinity towards RES phase and the order of its concentration was RES>Fe—Mn>OM-S>EXC>CA. This suggests hydrous oxides of Fe—Mn as an important binding site for Cu and Pb, whereas silicate mineral matrix (RES phase) for Zn.     

Distribution patterns of Cd,Cu, Mn,Pb and Zn in wood fly ash emitted from domestic boilers

Abstract

Wood fuels being a renewable source of primary energy have been considered environmentally friendly. However, wood combustion in domestic boilers is a source of air pollution. The lack of a dust collection device is the reason why flue gases emit a significant load of particulate pollutants into the air, including heavy metals. The aim of this research was to assess the environmental hazard caused by both emissions of heavy metals during wood combustion in domestic boilers and their chemical forms present in fly ash.

From the various wood fuels burnt in domestic boilers, the fly ash selected for this study came from the combustion of briquettes of softwood from non-polluted areas, and from burning hardwood fuel from trees exposed to pollutants from heavy traffic. The wood fuels satisfy the quality demands determined in the EN 14961 Solid Biofuels - Fuel quality assurances. However, the concentrations of Cd, Cu, Pb and Zn in the fly ash are considerably higher than the appropriate limit values determined for soil improvers. Sequential extraction shows that Cd and Zn are associated mainly with the water leaching and carbonate fractions, regarded as mobile and bioavailable, and pose the potentially greatest hazard to the environment and human health. Cu, Mn and Pb associated with less mobile fractions may not pose a direct air quality hazard but, due to their high concentrations, medium-term and long-term effects on soils and surface and subsurface waters should be considered.     

Risk Element (As,Cd, Cu,Pb, and Zn) Contamination of Soils and Edible Vegetables in the Vicinity of Guixi Smelter,South China

Risk element (As, Cd, Cu, Pb, and Zn) contamination in soils and in two edible vegetables (Solanum melongena L. and Capsicum annum L.) was investigated in the vicinity of Guixi Smelter, South China. Soil As concentrations averaged 23.9 mg/kg. Sites near the smelter tailings recorded the highest levels of As and heavy metals in soils. The concentration order of heavy metals in soils was Cd < Pb < Zn < Cu. Cu and Cd in soils were abundant in the exchangeable and bound to carbonate fraction, while Pb and Zn were in the residual fraction, limiting their potential toxicity as pollutants. The proportions of the metals in the mobile fraction followed the order Pb < Zn < Cu < Cd. In Solanum melongena L. and Capsicum annum L., Zn concentration was the highest, followed by Cu, Cd, and Pb, different from that in soils and in the mobile fraction. Concentrations of heavy metals in the labile fractions in soils and in vegetables presented significant correlation (p < 0.05). Both of the two vegetables are not the Cu and Zn accumulators. As for Cd and As, Capsicum annum L. poses a higher risk to animal and human health than Solanum melongena L., with soil-plant transfer coefficients more than three. Root-stem is the main barrier for most of the heavy metals and As in the two vegetables, resulting in higher metal concentrations in roots relative to other plant tissues. The low stem-fruit transfer coefficients for Zn in Solanum melongena L. and for Pb in Capsicum annum L. suggested that very few of them could reach the fruits.     

Simultaneous determination of Zn,Cd, Pb,and Cu in urine of patients with blackfoot disease using anodic stripping voltammetry

Blackfoot disease (BFD) is an endemic peripheral vascular disorder resulting in gangrene of the lower extremities, especially the feet, among residents in a limited area on the southwest coast of Taiwan. In the present study, the concentrations of zinc, cadmium, lead, and copper in urine of BFD patients with matched normal controls are investigated by differential pulse anodic stripping voltammetry (DPASV) on a hanging mercury drop electrode (HMDE). The analytical results indicate that urinary copper, cadmium, and lead of the BFD patients are significantly higher than those of the controls. In addition, the patients showed a significantly lower concentration of zinc in the urine than the normal controls. The possible connection of these elements with the etiology of the disease is discussed.     

Bioavailability and mobility of heavy metals in soil in vicinity of a coal mine from Huaibei,China

This study investigated the concentrations of Co, Cr, Cu, Mn, Ni, Pb and Zn in surface soil and corn cob samples collected from agricultural fields near a coal mine from Huaibei, China. Meanwhile, the mobility and availability of heavy metals in soil samples were evaluated by a modified three-step The European Community Bureau of Reference (BCR) sequential extraction procedure. The total concentrations of metals in soil pose no ecological threats to the local plants. Transfer factors of essential metals, Cu and Zn, as well as those of non-essential metal Pb, were higher than those of the remained metals. The results of BCR fractionation analysis revealed that the acid soluble, reducible and oxidizable fractions of the Mn, Pb and Zn were higher than those of the residual fraction, suggesting that these elements may be more bioavailable. The pH and organic matter contents of soil were significant parameters affecting speciation of metals in soil samples. Hierarchical cluster analysis indicated significant correlations between metal levels in corn grains and more available (acid soluble and reducible) fractions in soil, indicating that heavy metals in the first two fractions were more available for corn crops. The elevated mobility and bioavailability of Pb in soil are of great concern in the study area.     

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.     

Estimation of Cd,Pb, and Zn Bioavailability in Smelter-Contaminated Soils by a Sequential Extraction Procedure

Chemical fractionation methods may be capable of providing an inexpensive estimate of contaminant bioavailability and risk in smelter-contaminated soil. In this study, the relationship between metal fractionation and methods used to estimate bioavailability of these metal contaminants in soil was evaluated. The Potentially BioAvailable Sequential Extraction (PBASE) was used for Cd, Pb, and Zn fractionation in 12 soils contaminated from Pb and Zn mining and smelting activities. The PBASE procedure is a four-step sequential extraction: extraction 1 (E1) is 0.5 M Ca(NO₃)₂, E2 is 1.0 M NaOAc, E3 is 0.1 M Na₂EDTA, and E4 is 4 M HNO₃. Metal bioavailability for two human exposure pathways, plant uptake (phytoavailability) and incidental ingestion (gastrointestinal, Gl, availability), was estimated using a lettuce (Lactuca sativa L.) bioassay and the in vitro-Gl Physiologically Based Extraction Test(PBET). Metal in the PBASE E1 fraction was correlated with lettuce Cd (P < 0.001) and Zn (P < 0.05) and was the best predictor of Cd and Zn phytoavailability. Only total metal content or the sum of all PBASE fractions, ΣE_1–4, were correlated (P < 0.001) with PBET gastric phase for Pb. The sum of the first two PBASE fractions, ΣE_1–2, was strongly correlated (P < 0.001) with Pb extracted by the PBET intestinal phase. The PBASE extraction method can provide information on Cd and Zn phytoavailability and Gl availability of Pb in smelter-contaminated soils.     

Time evolution of Pb(II) speciation in Pampa soil fractions

Abstract

Soil pollution by heavy metals, particularly lead, is an important environmental concern; the bioavailability of such pollutants is strongly dependent on their chemical form. Here, the speciation of Pb(II) in soil fractions as a function of time shortly after its incorporation is studied, using a selective sequential extraction method. The sample came from an Argentinean Pampas region and was extensively characterised, including Rietveld analysis of the silt+clay fraction XRD pattern to find the major mineral components. Experiments were run twice, once in the winter and once in the summer. The results show different speciation time profiles in both cases, showing faster changes in winter due to the higher water content. The summer experiment corresponds to an earlier stage in the speciation profile evolution compared with winter. The soluble/exchangeable fraction decreases with time in summer but shows a lower and constant value in the winter. A high proportion is found to be adsorbed onto the stable (aluminosilicates+quartz) mineral fraction. The results strongly suggest that, even at a short time following soil pollution with Pb, a high proportion is adsorbed onto the mineral fraction, with only a low fraction being bioavailable. The most stable (mineral incorporated) form is observed to increase with time. Soil water content appears to be more important than temperature in determining the differences between the two.     

Heavy Metals (Cd,Cu, Ni,Pb, and Zn) Fractionation in River Sediments,Hamedan, Western Iran

Five heavy metals (Cd, Cu, Ni, Pb, and Zn) in river sediments from Abshineh River, Hamedan, western Iran, were fractionated by a sequential extraction procedure. Cu, Ni, Pb, and Zn existed in sediments mainly in residual fraction (mean 92%, 86%, 77%, and 65%, respectively), whereas Cd occurred mostly as organic matter (mean 41%) and exchangeable (mean 25%) fractions. The mean percent of mobile fraction of Cd, Cu, Ni, Pb, and Zn in contaminated sediments was 25, 13, 4, 24, and 10, respectively, which suggests that the mobility and bioavailability of the five metals in sediments probably decline in the following order: Cd = Pb > Cu > Zn > Ni. The metal levels were also evaluated according to the contamination factor, which revealed significant anthropogenic pollution of Cd and Pb.     

The distribution and bioavailability of Cd and Zn in cultivated soil of Henan Province

Abstract

Concentrations of surface soil Zn and Cd from agricultural areas of the Henan Province were measured. About 234 soil samples were collected. Total metal analyses, sequential chemical fractionation which were divided into seven fractions according to the method of the Geological Survey Technical Standard (DD2005-03) set by the China Geological Survey were carried out on the samples. Total Cd and Zn concentrations of the topsoil were 0.1909 (0.1–0.549) and 63.07 (33.3–344.3) mg kg^?1 respectively. Compared with the values permitted in China’s control standards for soil (GB 15618–1995) and background value in Henan Province, the soil samples showed high levels of Cd. The soil organic carbon has a significantly positive correlation with Cd and Zn concentration in the soil. Significant positive correlation between pH and Cd, Zn concentration was observed. On average, the order of Cd in each fraction was exchangeable, (27.3%)>weakly bound to organic matter; (22.7%)>strongly bound to organic matter; (16.4%)>residual; (15.1%)>carbonate; (12.1%)>Fe/Mn oxide bound; (4.5%)>water soluble; (2.0%), Zn was residual; (66.3%)>Fe/Mn oxide bound; (10.9%)> weakly bound to organic matter; (9.4%)> exchangeable; (6.0%)> strongly bound to organic matter; (3.9%)> carbonate (2.9%)> water soluble (0.6%). The accuracy of the sequential extraction was judged by the relative error (RE). RE for Cd ranged from 0 to 45% with a mean of 16.3%. RE for Zn ranged from 0.1 to 11.4% with a mean of 3.4%. On average, bioavailability index (BI) for Cd and Zn was 39.1% and 9.0% respectively. The mobility of the elements in the order Cd> Zn corresponds with the plant-availability of individual elements. Comparisons between activities of Cd²⁺ and Zn²⁺ calculated by Sauve semi-mechanistic equations and that of the water soluble fractions were demonstrated. The activities of Cd²⁺ and Zn²⁺ calculated by the semi-empirical equation are lower than its water soluble fraction.     

Arsenic contamination of soils and sediments from tailings in the vicinity of Myungbong Au mine,Korea

Abstract

Geochemical characteristics of As contamination in the Myungbong gold mine area in Korea were investigated, and the mine tailings were found to contain high concentrations of As (2,500–6,420 mg/kg). The mine tailings are an obvious candidate for the source of contamination in the study area. From the sequential, and oxalate, extraction analyses the majority of the As in the tailings was found to be associated with Fe oxides produced when sulfide minerals are oxidised. Mineralogical examinations showed the formation of poorly crystalline Fe oxides on a rim of pyrite, onto which the As was retained. The sediments of two ponds affected by the tailings also contained significant levels of As. High concentrations of dissolved As were also found in pond and stream waters. It has been suggested that the mobility of the As was increased by the reductive dissolution of Fe oxides under reducing conditions in the pond. Agricultural fields, located beneath the tailing dumps, have been contaminated by the continuous use of contaminated stream water and groundwater for irrigation.     

Relationship of Soil Properties to Fractionation of Pb and Zn in Soil and Their Uptake into Plantago lanceolata

Soil samples (0 to 5?cm) from 30 locations in the Celje region, Slovenia, an area that has been subjected to severe industrial emissions of Pb and Zn, were analyzed for selected soil properties and subjected to a six-step sequential extraction of Pb and Zn. Phyto-available forms of heavy metals: soluble in soil solution and exchangeable from soil colloids to soil solution together accounted for 0 to 1.68% of Pb and 0 to 40.8% of total soil Zn. Most of the Pb and Zn was found to reside in less labile forms bound to carbonate (2.04 to 43.5% Pb, 3.9 to 35.1% Zn), bound to Fe and Mn oxides (0 to 16.1% Pb, 1.4 to 25.4% Zn), bound to organic matter (35.8 to 71.1% Pb, 14.8 to 56.2% Zn), and in the residual fraction (10.4 to 53.4% Pb, 14.2 to 75.3% Zn). Factor analysis and stepwise multiple regression revealed that the concentration of Pb in the proposed indicator plant, narrow leaf plantain (Plantago lanceolata) did not correlate with the measured soil properties, Pb fractionation in soil, and total soil Pb. Plant uptake of Zn, however, significantly correlated with soil pH and with the share of phyto-available forms of Zn in the soil (R² = 86.9). A statistically significant correlation (P<0.01) was found between the fractions of Pb and Zn carbonates and soil organic matter content (R² = 90.6 and 90.9, respectively); the fraction of Pb bound to organic matter and soil organic matter content (R² = 90.6); the residual fraction of Pb and total Pb content in soil (R² = 95.7); the fraction of Zn bound to Fe an Mn oxides, the fraction of Zn bound to organic matter, the residual fraction of Zn and total Zn content in soil (R² = 75.9, 93.2, and 87.4, respectively). Soil texture, pH, and cation exchange capacity did not affect the relative proportions of Pb and Zn forms in soil.     

Effects of organic amendments on Cd, Zn and Cu bioavailability in soil with repeated phytoremediation by Sedum plumbizincicola

Organic materials with different functional groups can be used to enhance metal bioavailability. Traditional organic materials (rice straw and clover) and ethylenediamine disuccinic acid (EDDS) were applied to enhance metal uptake from polluted soil by Sedum plumbizincicola after repeated phytoextraction. Changes in pH, dissolved organic carbon (DOC) and metal concentrations were determined in the soil solution after EDDS application. Amendment of the soil with ground rice straw or ground clove resulted in higher concentrations of Cd only (by factors of 1.92 and 1.71 respectively) in S. plumbizincicola compared to control soil. Treatment with 3 mmol kg(-1) EDDS increased all the metals studied by factors of 60.4, 1.67, and 0.27 for Cu, Cd, and Zn, respectively. EDDS significantly increased soil solution DOC and pH and increased soil plant-available metals above the amounts that the plants could take up, resulting in high soil concentrations of soluble metals and high risk of ground water contamination. After repeated phytoremediation of metal contaminated soils the efficiency of metal removal declines as the concentrations of bioavailable metal fractions decline. Traditional organic materials can therefore be much more effective and environmentally friendly amendments than EDDS in enhancing phytoremediation efficiency of Cd contaminated soil     

重金属Cd、Zn、Cu、Pb对土壤微生物和酶活性的影响

采用室内培养实验(25℃),研究了不同培养时间下重金属Cd、Zn、Cu、Pb(浓度分别为50,800,400,800mg.kg-1)污染对土壤微生物和酶活性的影响。结果表明,土壤蔗糖酶、过氧化氢酶和脱氢酶活性随着培养时间的增加而显著下降,在培养20d的时候达到最小值,然后酶活性缓慢升高。Cu对脲酶活性以及Cd对酸性磷酸酶和脲酶活性的抑制作用随时间增加而增加。土壤微生物生物量碳、细菌、真菌和放线菌数量随培养时间的增加均表现出先降低后升高的变化趋势。Cd和Cu对微生物生物量氮的抑制作用则随着培养时间的增加而增强,在培养30d时微生物生物量氮到达最低值,分别较培养10天减少了12.6%和16.5%。     

Distribution of Toxic Trace Metals Zn,Cd, Pb,and Cu in Tirupati Soils,India

The concentrations of toxic trace metals in the soil samples collected from Tirupati, India, have been determined using differential pulse anodic stripping voltammetry (DPASV). The total metal concentrations of the soils in the study area were in the following ranges: 19.5 to 23.6 mg of Zn, 0.032 to 0.036 mg of Cd, 15.8 to 18.9 mg of Pb, and 19.0 to 23.4 mg of Cu per kg soil. Analysis of standard reference material IAEA-SOIL-5 indicates good accuracy. Recoveries were nearly quantitative for all elements studied. Comparison of the average metal concentration levels with world averages indicates an elevated value for Pb. The applicability of this method was crosschecked with AAS and the results were in good agreement.     

农作物体内铅,镉,铜的化学形态研究

本文报道了农作物体内重金属存在的化学形态。用逐步提取法分析了生长在污染土壤上的水稻、小麦的根与叶。结果表明,在两种作物中,根部的铅以活性较低的醋酸可提取态与盐酸可提取态占优势,而叶中的铅以盐酸可提取态占优势。不论根部或叶部,在各种形态镉中,以氯化钠可提取镉所占比例较高,作用较重要。作物体内的铜活性较强,根部以乙醇可提取态占优势,叶中以水提取态占优势。各种结合形态的重金属迁移能力、毒性效应有显著差异。作物体内重金属化学形态特征与其表观毒性效应有密切联系。     

Distribution of Cd, Pb, Zn, Mo, and S in juvenile and mature Brassica napus L. var. napus

The study was conducted at three locations in the Savinjska region of Slovenia, where soil is contaminated with heavy metals due to the zinc industry (Cinkarna Celje). In Ponikva the soil to a depth of 30 cm contains 0.8 mg kg(-1) Cd, 32.2 mg kg(-1) Pb, and 86 mg Zn kg(-1), in Medlog 1.4 mg kg(-1) Cd, 37.4 mg kg(-1) Pb, and 115 mg kg(-1) Zn and in Skofja vas 10.9 mg kg(-1) Cd, 239.7 mg kg(-1) Pb, and 1356 mg kg(-1) Zn. The pH at the selected sites was between 7.3 and 7.6. In the beginning of September 2006 two hybrids of Brassica napus L. var. napus, PR45 D01 and PR46 W31 suitable for production of biodiesel obtained from Pioneer Seeds Holding GmbH, were sown. After 96 days juvenile and after 277 days mature plants were collected. Parts of plants (root, shoot and seed) were separated and Cd, Pb, Zn, Mo, and S determined by ultra-trace ICP-MS. We compared the uptake of Cd, Pb, Zn, Mo and S in different parts of juvenile and mature plants of the two different hybrids, TF (translocation factor), BAF (bioaccumulation factor), and PP (phytoextraction potential) were calculated. The mature hybrid PR46 W31 had higher shoot/root ratio and higher PP for metals (Cd, Pb, and Zn) and lower PP for the micronutrient (Mo) and macronutrient (S) on the polluted site. The study demonstrated the potential use of oilseed rape on multiply polluted soils for production of 1st and 2nd generation biofuels. The potential restoration of degraded land could also disburden the use of agricultural land.     

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     

Soil pH Effects on Uptake of Cd and Zn by Thlaspi caerulescens

For phytoextraction to be successful and viable in environmental remediation, strategies that can optimize plant uptake must be identified. Thlaspi caerulescens is an important hyperaccumulator of Cd and Zn, whether adjusting soil pH is an efficient way to enhance metal uptake by T. caerulescens must by clarified. This study used two soils differing in levels of Cd and Zn, which were adjusted to six different pH levels. Thlaspi caerulescens tissue metal concentrations and 0.1 M Sr(NO₃)₂ extractable soil metal concentrations were measured. The soluble metal form of both Cd and Zn was greatly increased with decreasing pH. Lowering pH significantly influenced plant metal uptake. For the high metal soil, highest plant biomass was at the lowest soil pH (4.74). The highest shoot metal concentration was at the second lowest pH (5.27). For low metal soil, due to low pH induced Al and Mn toxicity, both plant growth and metal uptake was greatest at intermediate pH levels. The extraordinary Cd phytoextraction ability of T. caerulescens was further demonstrated in this experiment. In the optimum pH treatments, Thlaspi caerulescens extracted 40% and 36% of total Cd in the low and high metal soils, respectively, with just one planting. Overall, decreasing pH is an effective strategy to enhance phytoextraction. But different soils had various responses to acidification treatment and a different optimum pH may exist. This pH should be identified to avoid unnecessarily extreme acidification of soils.     

Leaching of Cd,Zn, Pb,and Cu in Packed and Undisturbed Columns of Soils Affected by the Spill from a Pyrite Mine in the South of Spain

A study has been made of the leaching of Cd, Zn, Pb, and Cu in three representative soils within the zone affected by the spill from a pyrite mine in Aznalcollar (Sevilla, Spain) employing packed soil columns. According to the breakthrough and cumulative leaching curves, the relative mobilities of the different toxic elements in the columns are as follows: Cd> Zn> Cu> Pb. The effect of leaching on the distribution of metals as a function of depth using intact soil cores was also studied. The results showed that the soils themselves have a good capacity for immobilizing the soluble fraction of the elements from the spilled mud. This capacity varied as follows: clayey soil with a high carbonate content > clayey soil with a moderate carbonate content > sandy-clay loam soil with a low carbonate content. However, sandy soils with a low carbonate content could pose a risk to groundwater if initial contamination was high. These results could be considered during the evaluation of remedial technologies for the immobilization of soil metals.