Chemical Fractionation Of Heavy Metals Research Articles

Mineral materials as feasible amendments to stabilize heavy metals in polluted urban soils

Four minerals, agricultural limestone (AL), rock phosphate (RP), palygorskite (PG), and calcium magnesium phosphate (CMP), were evaluated by means of chemical fractions of heavy metals in soils and concentrations of heavy metals in leachates from columns to determine their ability to stabilize heavy metals in polluted urban soils. Two urban soils (calcareous soil and acidic soil) polluted with cadmium, copper, zinc and lead were selected and amended in the laboratory with the mineral materials) for 12 months. Results indicated that application of the mineral materials reduced exchangeable metals in the sequence of Pb, Cd > Cu > Zn. The reduction of exchangeable fraction of heavy metals in the soils amended with différent mineral materials followed the sequence of CMP, PG > AL > RP. Reductions of heavy metals leached were based on comparison with cumulative totals of heavy metals eluted through 12 pore volumes from an untreated soil. The reductions of the metals eluted from the calcareous soil amended with the RP, AL, PG and CMP were 1.98%, 38.89%, 64.81% and 75.93% for Cd, 8.51%, 40.42%, 60.64% and 55.32% for Cu, 1.76%, 52.94%, 70.00% and 74.12% for Pb, and 28.42%, 52.74%, 64.38% and 49.66% for Zn. Those from the acidic soil amended with the CMP, PG, AL, and RP were 25.65%, 68.06%, 78.01% and 79.06% for Cd, 26.56%, 49.64%, 43.40% and 34.68% for Cu, 44.44%, 33.32%, 61.11% and 69.44% for Pb, and 18.46%, 43.77%, 41.98% and 40.68% for Zn. The CMP and PG treatments were superior to the AL and RP for stabilizing heavy metals in the polluted urban soils.

Distribution of Heavy Metal Contents and Chemical Fractions in Anaerobically Digested Manure Slurry

Digested slurry samples from twenty-one large-scale anaerobic digestion plants together with intensive pig and dairy farms in Jiangsu Province of China were collected and analyzed for total and dissolved concentrations of Zn, Cu and As, as well as chemical characteristics. The results showed that total concentrations of Zn, Cu and As in digested pig slurries were concentrated to <10, <5 and 0.02-0.1 mg/l, respectively; while <2 and 10-30, <1, and 0.02-0.1 mg/l, respectively, in digested dairy slurries. Lowering the dietary supply of these elements to pig and dairy would be the most effective way to control heavy metal contents in digested manure slurries. Dissolved fractions of Zn, Cu and As accounted for 1-74%, 1-33% and 2-53% of the total concentrations, respectively, in digested pig slurries; and 18-65%, 12-58% and 3-68% in digested dairy slurries. The chemical fractions of heavy metals in digested slurries were not only dependent on the total concentrations of heavy metals in raw manures but also on conditions of digestion and storage. Oxidation pond systems could significantly cripple the total contents of heavy metals in digested slurries, and the removal effect was better in multi-oxidation-pond systems than that in primary-oxidation-pond systems. However, the chemical fractions of heavy metals in digested slurries changed in a complicated manner when stored in oxidation ponds, due to the suspended solid deposition, elements reduction, as well as variations of pH values and oxidation-reduction potential.

Mobility and speciation of heavy metals in soils impacted by hazardous waste

This study describes the mobility and chemical fractionation of heavy metals (HMs) from a site impacted by auto battery slag that was generated from secondary lead smelting operations. Samples were collected from the waste pile and from the immediate surrounding soil at four depths to assess the migration and potential bioavailability of Pb, Cd, Cr, Ni and Zn. Total levels of the HMs and their fractionation were determined. The results indicate that highest levels of HMs are present in the uppermost layer with significant migration down the depth, thereby posing a threat to groundwater quality. In the fractions, the concentrations of the metals follow this sequence: Pb>Zn>Cd>Cr>Ni. The chemical fractions of Pb, Cd, Cr, Ni and Zn in the samples, expressed as mean concentrations of the sum of the individual chemical fractions, demonstrate that the HMs exist mainly in the non-residual fractions. For instance, the percentage of non-residual fractions of lead in the waste pile and the surrounding soil ranged from 48.9 to 95.6% and 69.4 to 98.3% respectively. The mobility factors of the heavy metals are significantly high indicating high potential mobility and bioavailable forms of these HMs. The high concentrations of the HMs particularly Pb in the non-residual fractions, as observed in this study, shows the impact of anthropogenic activities on enrichment of natural soil with bioavailable HMs. Consequently, there is a need to be cautious in the way waste that is generated from heavy metals projects is added to natural soil.

Chemical fractionation of heavy metals in airborne particulate matter (PM10) by sequential extraction procedure

In this study, a series of 36 airborne particulate matter (PM10) samples were colleted over a 1 year period at an urban area–Tirupati, India. The samples were collected on paliflex-filters using Mini-Partisol air sampler equipped with PM10 inlet. A three stage sequential extraction procedure viz. environmentally mobile, bound to carbonates and oxides and bound to silicates and organic matter, was applied to heavy metals such as Pb, Cd, Zn, and Cu in PM10 samples. The heavy metals were determined by differential pulse anodic stripping voltammetry (DPASV). The reliability and applicability of the method was checked by using, NIST Standard Reference Material (SRM 1648). Good agreement was obtained between the total concentration of studied metals after three-step leaching procedure and certified values. Speciation results shows that higher percentage of Pb and Cd are accumulated in mobile fraction, where as higher amount of Cu and Zn was found in environmentally immobile fraction. Multivariate statistical analysis has been performed for the variables to define possible sources, and the results shows that mainly two sources, particles from traffic and particles from land were identified.

Distribution and chemical fractionation of heavy metals in recent sediments from Lake Taihu, China

Distribution and chemical fractionation of heavy metals in recent sediments from Lake Taihu, China

Chemical fractionation of heavy metals in urban soils of Guangzhou, China

Knowledge of the total concentration of heavy metals is not enough to fully assess the environmental impact of urban soils. For this reason, the determination of metal speciation is important to evaluate their environment and the mobilization capacity. Sequential extraction technique proposed by the former European Community Bureau of Reference (BCR) was used to speciate Cd, Cu, Fe, Mn, Ni, Pb, and Zn in urban soils from Guangzhou into four operationally defined fractions: HOAc extractable, reducible, oxidizable, and residual. The Cu, Fe, Ni, and Zn were predominantly located in the residual fraction, Pb in the reducible fraction, and Cd and Mn within the HOAc extractable fraction. The order of Cd in each fraction was generally HOAc extractable > reducible > residual > oxidizable; Cu and Fe were residual > reducible > oxidizable > HOAc extractable; Mn was HOAc extractable > residual > reducible > oxidizable; Ni and Zn were residual > reducible > HOAc extractable > oxidizable; and Pb was reducible > residual > oxidizable > HOAc extractable. Cadmium was identified as being the most mobile of the elements, followed by Mn, Zn, Ni, Cu, Pb and Fe. Iron-Mn oxides can play an important role in binding Cd, Cu, Ni, Pb, and Zn and in decreasing their proportion associated with the residual fraction in the soils. With total concentrations of Cd, Cu, Ni, Pb, Zn, and Mn increase, these metals more easily release and may produce more negative effects on the urban environment.

Chemical fractions of heavy metals of sediments in Meiliang Bay, Lake Taihu and tracing for its pollution history

本文以梅梁湾沉积物中的重金属元素为研究对象, 利用五步连续提取的方法将梅梁湾沉积物中的重金属元素分水溶态、可交换态、碳酸盐结合态、铁锰氧化物结合态、有机物结合态和残留态六种相态。应用²¹⁰Pb、¹³⁷Cs定年法相结合, 通过对百年沉积物的连续提取及元素富集系数的分析, 得到重金属元素在不同相态中的含量随时间的变化。与历史时期人类活动相比较, 重建了自19世纪末期到2000年的人类活动影响流域环境的历史, 证实了重金属元素含量变化主要受人类活动的强度和方式制约。具明显影响的人类活动分三个时段, 其中最为严重的时段是自1977年至今。与无锡历年工业产值变化的对比分析表明, 各相态中重金属含量的相似变化记录了梅梁湾受湖湾沿岸居民的经济生产活动影响, 污染程度日益加剧, 且工业废污水中重金属主要以铁锰氧化物结合态进入太湖生态系统中。;The concentrations of heavy metals in different Chemical fractious of sediments collected from the Meiliang Bay, Lake Taihu, were measured. Sequential extraction method was used to gain the concentrations of sedi-ment-bound heavy metals in six fractions, i.e., soluble, exchangeable, bound to carbonates, bound to Fe-Mn oxides , bound to organic matter, and residual. By use of ²¹⁰Pb and ¹³⁷Cs activities to obtain age of sediments, temporal variations of heavy metals in different fractions and their enrichment factors were shown. Among them, variations of heavy metal concentration in Fe-Mn oxides fraction of the sediments can be used to reflect contaminant input by human activities. On the basis of our data, the history of catchment human activities was divided into three periods, among which the most heavily affected by human activity was from 1977 A. D. to present. By comparing the concentrations of heavy metals in Fe-Mn oxides fraction with historical industrial product values of Wuxi City, their similar trends suggest that the increasingly environmental pollution is due to a fast development of industries a-round northern Taihu region, further indicating that heavy metals was mainly as a form of bound to Fe-Mn oxides into the Lake Taihu ecosystem.

Changes on chemical fractions of heavy metals in Chilean soils amended with sewage sludge affected by a thermal impact

Forest fires are frequent in central-southern Chile; high temperatures may affect chemical fractions of heavy metals (Cu, Zn, Ni, Pb, Cd, Mo, Cr, and Mn) naturally present in soils and those coming from sewage sludge amendment. Changes in exchangeable, sorbed, organic, carbonate, and residual heavy metals fractions, evaluated by sequential extraction, were observed after heating at 400°C in 2 amended volcanic soils. Most significant heavy metals in these samples were Cu, Zn, Pb, and Ni. A significant increment in the total content of organic matter and metal ions, such as Zn and Cu, was observed in amended soils with respect to controls. In all samples, sorbed and exchangeable forms represent &lt;10% of the total amount, while organic and carbonate fractions represent 24 and 48%, respectively. The thermal treatment of amended soil samples results in a redistribution of the organic fraction, mainly into more insoluble carbonate and residual fractions such as oxides. Finally, the thermal impact is much more important on sewage sludge amended soils if a heavy metal remediation process is considered, reducing the mobility and solubility of heavy metals supported by sewage sludge, minimising leaching and promoting accumulations in surface horizons.

Accumulation and Chemical Fractionation of Heavy Metals in Andisols after a Different, 6-year Fertilization Management (8 pp)

Andisols are widespread in Japan and have some special properties such as high anion exchange capacity, low bulk density, and high organic matter content, which might influence the accumulation or chemical fractionation of heavy metals. However, few such data exist in Japanese andisols. The primary objective of this study was to investigate the distribution and chemical fractions of Cu, Zn, Ni, and Cr in the soil profiles and subsequently to assess their potential environmental hazard. Soil samples were taken from a field experiment conducted on Japanese andisols, which had received either swine compost or chemical fertilizers for 6 years. Concentrations of Cu, Zn, Ni, and Cr were determined for all of the obtained extract solutions by ICP-AES. Considerably higher total concentrations of Cu and Zn were observed in the top 20 cm layer of the compost-amended soil, relative to the unfertilized soil, while chemical fertilizers had little effect. Application of the swine compost increased the concentrations of Cu and Zn, but not Ni and Cr, in all fractions in the top 20 cm layer. The greatest increase in the organically bound fraction (OM) Cu and dilute acid-exchangeable fraction (DAEXCH) Zn was observed. This suggests that Cu and Zn are potentially bioavailable and mobile in the andisol profiles after 6-year consecutive applications of the swine compost. On the other hand, distribution of Cu, Zn, Ni and Cr among various soil fractions was generally unaffected by chemical fertilizers. We observed that 6-year consecutive applications of the swine compost led to an increase in total metals of Cu and Zn, as well as their all-chemical fractions, in the top 20 cm soil layers. Potential hazard of heavy metals, especially of Cu and Zn, as a result of the use of swine compost on andisols, must be taken into account. The long-term effect of the accumulation of heavy metals, particularly Cu and Zn, in various plant tissues and soils, as well as their potential risk to surface water via runoff and groundwater via leaching, needs to be carefully considered. Further investigations in the long-term experiments are therefore necessary.

Relationships between fractionations of Pb, Cd, Cu, Zn and Ni and soil properties in urban soils of Changchun, China

An extensive soil investigation was conducted in different domains of Changchun to disclose the fractionations of Pb, Cu, Cd, Zn and Ni in urban soils. Meanwhile correlation analysis and multiple stepwise regressions were used to define relationships between soil properties and metal fractions and the chief factors influencing the fractionation of heavy metals in the soils. The results showed that Pb, Ni and Cu were mainly associated with the residual and organic forms; most of Cd was concentrated in the residual and exchangeable fractions. Zn in residual and carbonate fraction was the highest. The activities of the heavy metals probably declined in the following order: Cd, Zn, Pb, Cu and Ni. The chemical fractions of heavy metals in different domains in Changchun City were of significantly spatial heterogeneity. Soil properties had different influences on the chemical fractions of heavy metals to some extent and the main factors influencing Cd, Zn, Pb, Cu and Ni fractionation and transformation were apparently different.

Total concentrations and fractions of Cd, Cr, Pb, Cu, Ni and Zn in sewage sludge from municipal and industrial wastewater treatment plants

Heavy metals are one of the important factors that affect the final disposal of sewage sludge. In this paper, the metal mobility and bioavailability of heavy metals in sewage sludge were studied by using Community Bureau of Reference (BCR) sequential extraction procedure to get more information for the reasonable disposal of sludge. Sewage sludge was collected from five municipal wastewater treatment plants and three industrial wastewater treatment plants. The sludge was examined for and the total concentrations and different chemical fractions of Cd, Cr, Pb, Cu, Ni and Zn. The total metal concentrations of heavy metals in sludge varied greatly. The contents of Zn and Cu were the highest, followed by then Cr, Ni and Pb and the content of Cd was the least. There was no significant difference in total metal concentration between municipal and industrial wastewater treatment plants. Fractions extracted by the BCR sequential procedure were acid soluble/exchangeable, reducible and oxidizable fraction. Sludge pH was found to have profound effect on the chemical fractions of heavy metals. Acidic sludges (Xiamen and Jinlin Petrochemical Group Co., wastewater treatment plant) had higher proportion of the acid soluble/exchangeable fractions than in neutral sludge. In neutral sludges, Pb and Cr were principally distributed in between the oxidizable fraction and the residual fraction; Cu was in the oxidizable fraction; Cd mainly in the residual fraction in municipal wastewater treatment plants and had high percentage of acid soluble/exchangeable and reducible fractions in industrial wastewater treatment plants; Ni and Zn had higher percentage in the acid soluble/exchangeable and the oxidizable fraction.

Relationship of chemical fractions of heavy metals with microbial and enzyme activities in sludge and ash-amended acid lateritic soil from India

The influence of metals, Cd, Cr, Cu, Ni, Pb and Zn, on the microbial biomass and enzyme activities of an amended acid lateritic soil were investigated under field conditions receiving a one-time application of 52 t ha−1 of sludge, coal ash and their mixtures at 1:3, 1:1 and 3:1 proportions, and including control and chemical fertilizer treatment at crop-specific recommended doses. Paddies and peanuts were grown in the experimental plots and soil was sampled twice after 6 months and 1 year after amendment application. The heavy metals in the soil were fractionated using sequential extraction and the increments in their concentrations in amended soil with respect to the control were determined. Concentrations of Cd, Ni and Zn were determined to have increased in their mobile fractions and were more pronounced in soil collected during the second sampling, which was associated with a decrease in soil organic carbon. The size of the microbial biomass carbon and the soil enzyme activities increased with the addition of an amendment and was highest at equal proportions of coal ash and sludge. Further increase in the proportion of sludge resulted in a significant decrease in biomass carbon. Simple correlation revealed significant and strong negative relations of mobile fractions of Cd and Ni with the ratio between microbial biomass C and organic carbon in soil, while the organic carbon content and the pH were positively correlated. The microbial activities were determined to be sensitive to the concentrations of some heavy metals in mobile fractions and therefore indicated possibilities of being useful as indicators for evaluation of toxic effects of sludge-borne metals on soil organisms.

Chemical fractionation of heavy metals in soils around oil installations, Assam

The chemical fractionation of lead, cobalt, chromium, nickel, zinc, cadmium and copper in soils around Lakwa oil field, Assam, India was studied using a sequential extraction method. It is evident from the study that the residual fraction is the most important phase for the seven heavy metals under study. Among non-residual fractions metals are mostly associated with the Fe–Mn oxides fraction. The association of heavy metals with organic matter was observed in the following order: copper> cadmium> zinc> lead. The concentration of Pb in the carbonate fraction for both the seasons is higher compared with other metals, which may pose environmental problems due to its highly toxic nature. The comparatively low concentration of metals in the exchangeable fraction indicates low bioavailability. Correlations between physicochemical parameters and metal fractions of soil do not show consistent behaviour. The local mean values of metals when compared with the accepted values of normal abundance and geochemical background, indicates two to four fold increases in this area. However, the values are within the range of normal abundance. As well as from natural soil geochemical behaviour, anthropogenic influence might have a close bearing on the association of metals with the soil system in the studied area.

Chemical fractionation of heavy metals in a soil amended with repeated sewage sludge application

A sequential extraction method (KNO3, NaOH, Na2-EDTA, HNO3) was used to determine the soil fraction of Zn, Cd, Cu, Ni, Pb, and Cr in different plots treated with sewage sludges. The sludges were applied to cropland from 1983 to 1991. Soil samples were collected after the 1st and 5th-year of the last sludge application. Sludge applications increased the INOR-fraction for Zn, Cd, and Cu. Cu was the only element found in the EXCH-fraction. Pb and Cr were found mainly in the RES-fraction. Ni was found in the INOR and OM-fractions. All the metals increased in the more resistant fractions. Sewage sludge applications changed the metals distribution of the soil and this effect has continued for at least 5 years.

Binding and chemical fractionation of heavy metals in typical peat matter

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

Retention and distribution of heavy metals in mangrove soils receiving wastewater

The distribution and chemical fractionation of heavy metals retained in mangrove soils receiving wastewater were examined by soil column leaching experiments. The columns, filled with mangrove soils collected from two swamps in Hong Kong and the People's Republic of China, were irrigated three times a week for 150 days with synthetic wastewater containing 4 mg l −1 Cu, 20 mg l −1 Zn, 20 mg l −1 Mn and 0.4 mg l −1 Cd. Soil columns leached with artificial seawater (without any heavy metals) were used as the control. At the end of the leaching experiments, soil samples from each column were divided into five layers according to its depth viz. 0–1, 1–3, 3–5, 5–10 and > 10 cm, and analyzed for total and extractable heavy metal content. The fractionation of heavy metals in the surface soil samples (0–1 cm) was investigated by the sequential extraction technique. In both types of mangrove soils, the surface layer (0–1 cm) of the columns receiving wastewater had significantly higher concentrations of total Cu, Cd, Mn and Zn than the control. Concentrations declined significantly with soil depth. The proportion of exchangeable heavy metals in soils receiving wastewater was significantly higher than that found in the control, about 30% of the total heavy metals accumulated in the soil masses of the treated columns were extracted by ammonium acetate at pH 4. The sequential extraction results show that in native mangrove soils (the soils without any treatment), the major portion of Cu, Zn, Mn and Cd was associated with the residual and precipitated fractions with very low concentrations in more labile phases. However, in mangrove soils receiving wastewater, a significantly higher percentage of Mn, Zn and Cd was found in the water-soluble and exchangeable fractions. Copper appeared to be more strongly adsorbed in mangrove soils than the other heavy metals. In general, heavy metal accumulation in the surface mangrove soils collected in Hong Kong was higher than those in the PRC, although the metals in the latter soil type were more strongly bound. These findings suggest that whether the heavy metal retained in managrove soils becomes a secondary source or a permanent sink would depend on the kinds of heavy metals and also the types of mangrove soils.

Chemical Fractionation of Heavy Metals in Anoxic Estuarine and Coastal Sediments

Chemical extraction experiments for estimating characteristic particulate binding forms of heavy metals in anoxic marine and freshwater sediments were carried out under both the presence and absence of atmospheric oxygen during the analytical procedure. Storage methods including aeration of anoxic sediments do not preserve the initial fractionation patterns of heavy metals and may both increase (Ni, Pb, Cu, Zn, Cd) and decrease (Fe, Mn) their mobility. Elutriate tests of methanogenic freshwater sediments from Hamburg harbour basins show that metals with increased carbonatic fractions (Fe, Hn) and those with predominantly sulphidic/organic fractions (Zn, Cu, Cd) are particularly sensitive to sample aeration. Transformations of oxidizable Ni (11%), Zn (62%), and Cd (67%) predominantly lead to easily reducible associations. Drying of the sediments decreases the proportion of the sulphidic/organic fraction of the metals to a stronger degree. Oxidized Zn and Cd is then found even in the least stable exchangeable fraction. If pretreatment of sediment samples is done adequately the chemical leaching approach may provide information on diagenetic effects and reaction kinetics, which influence the mobility of contaminants in highly complex matrices.