EVALUATION OF GEOCHEMICAL QUALITY CONTROLIN DETERMINATION OF Mn IN SOILS USING A SEQUENTIAL CHEMICAL EXTRACTION

Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo environment. One sequential chemical extraction procedure was employed here to partition various fractions of Mn in soils. The experiment was designed with quality controlling concept in order to show sampling and analytical error. Experimental results obtained on duplicate analysis of all soil samples demonstrated that the precision was less than 10%(at 95%confidence level). The accuracy was estimated by comparing the accepted total concentration of Mn in standard reference materials (SRMs) with the measured sum of the individual fractions. The recovery of Mn from SRM1 and SRM2 was 94.1%and 98.4%, respectively. The detection limit, accuracy and precision of the sequential chemical extraction procedure were discussed in detailed. All the results suggest that the trueness of the analytical method is satisfactory.

1Assessing Soil Available Potassium by Cation Exchange Membrane and Conventional Chemical Extractions

Four testing methods using canon exchange membrane (CEM), ammonium acetate, ASI (0.25 mol L-1 NaHCO3+0.01 mol L-1 EDTA +0.01 mol L-1 NH4P) and 1.0 mol L-1 boiling nitric acid, respectively, were used to evaluate soil available K. The soil K tested by CEM was significantly correlated with that by the other (conventional) methods (r2=0.43**~0.95***). The soil K tested by CEM saturated with NH4HCO3 (15 min extraction) was most closely correlated with that by the other methods (2 =0. 60***~0.95***). Potassium availability, as predicted by soil test, was comparable to actual K uptake by canola and wheat grown on the soils in growth chamber. Regression analyses showed that plant K uptake was more closely correlated with K extracted by CEM (r2=0.56***~0.81***) than that by the conventional methods (r2=0.46***~;0.81***), most closely correlsted with that by NH4HCO3-saturated CEM for 15 min (r2=0.81***), and worst correlated with that by HNO3 (r2=0.45**~0.72***).

Single and Sequential Extraction of Copper by Different Extractants from Different Peat Soil Samples of Bangladesh

A comprehensive in vitro study on single and sequential extraction methods for Cu exraction by different extractants of distinct chemical nature from some peat soils of Bangladesh was conducted to assess the pattern of metal-extractability in drying and wetting sequences. Samples were collected from peat basins of two different districts of Bangladesh (Gopalgonj and Bagerhat) and an incubation study was designed and conducted in which soils were incubated to three alternate drying and wetting cycles for 21 days. Single and sequentially extracted Cu ions in all three cycles and by all three selective extractants were compared. Maximum amount of Cu was extracted in drying days and 1M HCl extracted the largest proportion of Cu from all the soils in each incubation time. Conversely, 1M NH4Cl was the least effective extractant for extracting Cu by both single and sequential process in either day of incubation. Considerable amount of Cu was extracted by 0.005 M DTPA in dry periods. In general, single extraction was found to be more effective in extracting Cu in the alternate drying and wetting cycles from the peat soil samples except for 1M HCl in initial drying days.

Heavy Metal Remediation in AgoèNyivéLandfill Soils: Enhancing Stability through Organic Amendments

The burial of waste in developing countries, which is often carried out without respect for environmental standards, constitutes a risk of contamination of soils and even groundwater given the toxic elements they contain. The objective of this work is to carry out a study of the retention of heavy metals through the contribution of cattle manure to soil samples from the final Agoè Nyivé landfill in Lomé, Togo. Soil samples from the final landfill were taken from the surface and depth at several locations to form a composite sample. The amendment of the composite sample was carried out with bovine manure on the mock-up in the Laboratory for six months. The determination of the total contents of heavy metals by the atomic absorption spectrophotometer (SAA) on the composite sample showed high contents exceeding the thresholds recommended by the AFNOR NF U 44-041 standard. Sequential extraction on these composite samples showed that the mobile portions of lead, cadmium, copper and zinc are respectively estimated at 78.06%, 50%, 28.89% and 91.59%. The bovine manure used to amend the landfill samples presents physicochemical parameters that can contribute to rendering heavy metals immobile in the soil matrix under natural conditions. The addition of manure initially made it possible to increase the values of pH, electrical conductivity, cation exchange capacity and organic matter, which promote the retention of heavy metals. Secondly, the addition of manure made it possible to reduce the mobile portion of the heavy metals studied;from 78.06% to 14.39% for lead, from 50% to 11.52% for cadmium, from 28.89% to almost 0% for copper and from 91.15% to 80.58% for zinc. The use of cattle manure as an amendment on the composite sample was decisive in reducing the mobility of heavy metals in the polluted soils of the final landfill.

Determination of Heavy Metals in Two Regions from Kirkuk City Using Sequential Extraction

Soil is a major reservoir for heavy metals and other contamination as it possesses an ability to absorb these metals on the surface of clay minerals and bind various chemicals. These heavy metals and chemicals can exist in various forms in soil and different forces keep them bound to clay minerals and soil particles. The aim of the present work is to estimate the concentration levels of some heavy metals Zn, Cu, Pb and Cd in two sites of soil Kirkuk city. In this study the first sample was taken from inside the city of four areas around (Northern Oil Company) in Kirkuk city, while the second sample was taken from outside the city of four areas and both were randomly chosen. Sequential extraction procedure was applied to fractionate heavy metals which may help in the prediction of their mobility, bioavailability and fate of the metal contaminant. Results of sequential extraction showed that Cd and Pb were mainly bound to residual fraction, Cu was mainly bound to organic fraction and Zn was bound to Fe-Mn oxide fraction in the two sites of the study. The overall mean values obtained for the metals in the fractions gave the range: inside the city Cu (28.12 ppm), Zn (77.9 ppm), Pb (21.73 ppm) and Cd(4.21 ppm), and outside the city Cu (24.65 ppm), Zn (59.28 ppm), Pb (13.25 ppm) and Cd (2.38 ppm). The extracts were analyzed for heavy metal, using flameless-atomic absorption spectrophotometers (Flameless-AAS).

Distribution of Chemical Forms for Co, Cr, Ni and V in Typical Soils of China

Co, Ni, Cr and V in 25 typical soils of China were fractionated into exchangeable, carbonate bound (calcareous soils), Mn oxide bound, organically bound, amorphous Fe oxide bound, crystalline Fe oxide bound and residual forms using a seven-step sequential extraction procedure, so as to study the distribution of chemical forms of these metals as well as the effects of soil properties on the distribution. The results showed that most of soil Co, Ni, Cr and V were present in residual forms, and the distribution ratio averaged 48.2% for Co, 53.0% for Ni, 81.5% for Cr and 68.7% for V. The speciation of heavy metals was greatly influenced by soil physico-chemical properties and the chemistry of elements. The results also indicated that the recovery of metal elements by the sequential extraction procedure was satisfactory, with the relative difference between the sum of seven forms and the total content in soils averaging 9.5% for Co, 12.8% for Ni, 6.6% for Cr and 7.2% for V.

Use of Sequential, Single and Kinetic Extractive Schemes to Assess Cadmium (Cd) and Lead (Pb) Availability in Vietnamese Urban Soils

Modified BCR sequential extraction, single equilibrium-based EDTA extraction and kinetic fractionation were used for estimating the Pb and Cd availability in a series of soil samples from 3 sites located in urban areas of Hanoi (Vietnam). These schemes were compared to identify a simple, rapid and cheap protocol for routine estimation of Pb and Cd remobilizable fraction and the related potential risk. The comparison of these three approaches revealed their convergence in terms of mobility patterns observed for Pb and Cd. Cd was characterized by higher extractibality and mobility whatever the approach. Pb was distinguished of Cd by its high association to Feoxides, lower extractability, lower rate of desorption and then lower mobility. For this environmental scenario, EDTA single scheme at equilibrium could be suggested as the best suited and a simple protocol for determination of the labile pool of Cd and Pb. The pseudo-total concentrations of Pb and Cd are actually below the Vietnamese standard level, contrary to the results obtained by other authors for agricultural soils at other urban sites of Hanoi.

Cadmium Chemical Forms in Two Calcareous Soils Treated with Different Levels of Incubation Time and Moisture Regimes

Sequential extraction is used effectively to determine the chemical forms of heavy metals. Since few studies have been conducted in calcareous soils of Iran, the current research has been carried out to evaluate the effect of moisture regimes and incubation time on the chemical forms of cadmium in two calcareous soils. Treatments included three levels of cadmium (0, 30 and 60 mg/kg of soil as CdSo4), three incubation times (2, 4 and 8 weeks), two soils (clay and sandy clay loam) and two moisture regimes (Water-logged and Field capacity). The experiment was performed as factorial on the basis of randomized complete blocks design with two replications. At 2, 4, and 8 weeks after treatment, the Tessier et al. (1979) sequential extraction method was applied to measure the cadmium concentration in water soluble-exchangeable (WsEx.), iron and manganese oxide (Fe-MnOx.), carbonate (Car.), organic matter (Om.) and residual forms (Res.). The results showed depending on the soil texture, 68 to 72 percent of the cadmium was in water soluble-exchangeable and iron-manganese oxide forms. Flooding condition decreased the concentration of cadmium in water soluble + exchangeable form and increased the concentration of cadmium in the forms of Fe-Mn oxides, carbonate and organic matter. Concentration of cadmium in residual form was higher in clay soil. In sandy clay loam soil, water soluble-exchangeable, carbonate and organic matter forms were higher than clay soil. The iron-manganese oxides form showed no significant difference in two soils at field capacity regime. In flooding conditions, the concentration of the water soluble-exchangeable form decreased and the concentration of other forms increased. In contrast to the oxidizing conditions at the reduction conditions, no significant difference was observed in the residual and organic matter forms in two soils.

Speciation and Geochemical Behaviour of Heavy Metals in Industrial Area Soil of Mysore City, India

Soil is a major reservoir for contaminants as it possesses an ability to bind various chemicals. These chemicals can exist in various forms in soil and different forces keep them bound to soil particles. It is essential to study these interactions because the toxicity of chemicals may strongly depend on the form in which they exist in the environment. Another thing is that soil variability and some environmental properties may change in soil and cause leaching of trace toxic elements like heavy metals tightly bound to soil particles. Metals associated with urban soil are of environmental concern because of their direct and indirect effects on human health. The main purposes of this study undertaken in the Mysore city industrial zone were to identify heavy metals with dangerous environmental load and to find out of their environmental impact (Fe, Cr, Cu, Zn, and Ni). The purpose of this work was to provide information on heavy metals concentration in industrial zone soil of Mysore city, India. Soil samples were analyzed for pH, organic matter, and electrical conductivity. Total and available heavy metal concentrations were determined by AAS. In the present study, heavy metal speciation in soil sample carried out were shows that all metals were mainly associated with the oxidizable and residual fraction, which allows us to predict their mobility in the soil sample.

云南普阳煤矿新近系褐煤中稀土元素的赋存状态

目前对于褐煤中稀土元素(REY)赋存状态的研究还存在较多疑问,主要体现在两个方面:一是褐煤中REY究竟主要赋存于有机质中还是矿物质中?二是褐煤含有较多容易受到酸溶干扰的含氧官能团,在逐级化学提取实验过程中,高比例HCl提取相中的REY究竟来自于碳酸盐、磷酸盐、单硫化物等矿物还是来自于有机质?着眼于此,本文在逐级化学提取这一常规元素赋存状态研究方法的基础上,结合密度分离实验、红外光谱(FTIR)等手段,对普阳煤矿新近系褐煤中REY的赋存状态进行了系统研究。研究结果表明,普阳煤矿M2和M3煤层为极低—中灰、中高—高挥发分、中硫分褐煤,其组成矿物主要为石英、方解石、高岭石、黄铁矿。M2和M3煤层中常量元素以Al和Si为主,其REY配分模式主要为L型和N型,其中M2煤层中REY轻度富集。逐级化学提取实验结果显示M2和M3煤层中的REY主要被HCl浸取,其次被HNO3浸取,同时还有部分REY保留在残渣中,HF对煤中REY的提取率很低(一般<10%)。密度分离实验结果表明REY主要赋存于低密度组分中。红外光谱分析结果显示煤样品经HCl处理后,酚羟基、羟基等含氧官能团增多,可能是经HCl浸取后样品中与酚羟基、羟基点位结合的REY被浸出迁移所致。综合来看,普阳煤矿M2和M3煤层中的REY主要赋存于有机质中,少量赋存于硅酸盐矿物中,碳酸盐、磷酸盐、单硫化物和双硫化物也可能是部分REY的赋存载体。逐级化学提取实验过程中HCl所提取的异常高比例的REY可能主要来自于有机质。

土壤和沉积物重金属形态分析研究进展

人类社会的发展进程导致土壤和沉积物中的重金属含量远远超过背景值,具有严重的潜在威胁隐患。然而,由于重金属的流动性、毒性以及生物累积性会对环境造成深远影响,重金属形态分析已然成为环境研究的重要一环。目前最具代表性的形态提取方法为Tessier法和BCR三步法,为标准物质研制、重金属污染评估、生态修复以及生物有效性风险等问题提供了有效解决方案,但也有着各自的局限性。总结目前常用的元素形态提取分析方法,系统对比论证,讨论重金属形态分析方法未来可能出现的问题和发展方向,以期为土壤及沉积物重金属污染研究提供思路与支撑。

土壤中重金属形态及有机物组分的电化学-质谱分析

本研究建立了一种电化学-质谱(EC-MS)法高通量分析土壤样品中的金属组分和有机物。首先,根据理化性质,将土壤样品中的金属组分和有机物组分分为水溶态、脂溶态、难溶态和可氧化态等4种形态;然后,分别采用萃取、反应、电解等方式对4种形态组分进行在线顺次提取;将提取后的组分在线传输至电喷雾电离源进行离子化,随后进行正、负离子模式检测。实际样品分析结果表明,该方法成功检测出土壤样品中多种水溶态金属盐和有机物(如Mg、Cr、Ni、Zn、Co、Cu、Al、Pb等多种水溶性金属盐,尿素及多种有机胺)、20多种脂溶态有机羧酸、以及难溶态金属盐(Mg、Ni、Cr、Pb、Co)和可氧化态(Cu、Pb)。该方法可为环境评估和环境治理提供技术支持。

基于作物Cd富集系数的土壤有效态Cd化学浸提方法筛选

土壤中镉(Cd)被作物吸收的程度及其生态风险取决于土壤中Cd的赋存形态,基于Cd有效形态的污染土壤风险评价及在此基础上制订污染土壤修复安全阈值是Cd污染农田土壤风险评价和治理亟待解决的问题。目前针对土壤中重金属有效态的化学浸提方法较多,但缺乏针对不同性质土壤中有效态Cd的普适性浸提方法已成为Cd污染土壤风险评价技术瓶颈。本研究采集了全国9个不同性质农田土壤,以水稻、小白菜和玉米为测试作物,通过外源添加方法制备Cd污染土壤,结合土壤培养和盆栽实验,测定了5种常用化学浸提方法,包括中性无机盐浸提方法(CaCl_(2)浸提法)、弱酸浸提法(HCl浸提法)、络合螯合剂浸提方法(DTPA和ETPA浸提法)和组合浸提方法(Mehlich-3(M3)浸提法)对不同性质土壤中有效态Cd浸提效果及其与作物Cd吸收的量化关系,筛选适用于不同性质土壤中有效态Cd的通用浸提方法。结果表明,不同化学浸提法提取的土壤有效态Cd含量间具有显著差异,不同浸提方法对土壤中Cd的浸提率(%)为DTPA≈EDTA≈HCl>M3≈CaCl_(2)。不同化学浸提态Cd与作物Cd吸收的相关系数间具有显著差异,基于综合相关系数方法,得出5种不同浸提态Cd与作物Cd吸收的综合相关系数为I M3=0.765,I EDTA=0.641,I DTPA=0.627,I HCl=0.606,I CaCl_(2)=0.711,M3浸提态Cd含量与不同性质土壤中水稻、小白菜和玉米植株地上部Cd相关性最高,可作为不同性质土壤中有效态Cd通用浸提方法。相关研究结果可为农田土壤中Cd有效态评价及Cd污染农田的修复提供理论依据。

巯基改性蒙脱石对中国北方中碱性农田土壤镉钝化效果研究

农田土壤重金属污染是影响中国农产品环境质量安全的主要因素。钝化材料是修复农田重金属污染土壤的关键材料,研究开发出高效土壤重金属钝化材料,对于修复重金属污染农田和保障农产品食用安全非常重要。本文以蒙脱石为原材料,将巯基基团负载在其表面或层间制备巯基改性蒙脱石,借助X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和傅里叶红外光谱(FTIR)等技术表征巯基改性蒙脱石的特性,并开展室内土培试验,采用二乙三胺五乙酸浸提-火焰原子吸收分光光度法分析土壤镉的有效态,通过Tessier修正顺序七步提取法分析土壤镉的赋存形态。结果表明:蒙脱石经巯基改性后不仅新增了C-H、S-H共价键,而且增强了-OH和C=O化学键的活性,能与Cd2+发生巯基及羟基配位吸附。供试土壤添加巯基改性蒙脱石后,由于巯基配位吸附作用使土壤离子交换态镉转化为铁锰氧化物结合态,而增强的羟基配位吸附作用使其转化为碳酸盐结合态,结果使土壤中镉的赋存形态发生显著改变,离子交换态大幅减少,作物根系可吸收的土壤有效镉显著降低。添加1%、3%、5%巯基改性蒙脱石后,土壤有效镉分别降低21.92%、69.11%、82.90%;而作为对照组添加1%、3%、5%蒙脱石仅分别降低3.37%、1.80%、6.71%。蒙脱石经巯基改性后对土壤镉的钝化效果得到显著提升,土壤有效镉的降低幅度有随巯基改性蒙脱石添加量增加而提高的趋势。巯基改性蒙脱石对中国北方中碱性农田土壤镉的钝化效果显著,具有一定的参考应用价值。

Effects of long-term phosphorus fertilization and straw incorporation on phosphorus fractions in subtropical paddy soil

Study on soil phosphorus（P） fraction is an important aspect in probing the mechanisms of soil P accumulation in farmland and mitigating its losing risk to the environment. We used a sequential extraction method to evaluate the impacts of long-term fertilization and straw incorporation on inorganic, organic, and residual P（Pi, Po, and Pre） fractions in the plow layer（0–20 cm） of acidic paddy soil in southern China. The experiment comprised of six treatments：（i） no fertilizer control（CK）;（ii） straw incorporation and green manure（SG）;（iii） nitrogen and P fertilizer（NP）;（iv） NP＋SG;（v） NP＋K fertilizer（NPK）; and（vi） NPK＋SG. The results showed that, compared to the initial total soil P content（TSP, 600 mg kg^–1 in 1990）, long-term（20 years） combined continuous P fertilizer and SG significantly increased P accumulation（by 13–20%） while single fertilization（39.3 kg P ha^–1 yr^–1） could maintain soil P status at the most. The average soil P fractions comprised of extractable Pi, Po, and Pre by 51.7, 33.4, and 14.9% in total soil P, respectively. With comparison of no fertilizer addition（CK）, long-term single fertilization significantly（P〈0.05） increased the accumulation of Na HCO3^–, Na OH^–, and HCl^– extractable Pi fractions accounting for two- to three-fold, while SG increased the accumulation of Na HCO3^– and Na OH^– extractable Piand Po accounting for 12–60%. Though the mobilization of Pre fractions was not significant（P〉0.05）, our data indicate that SG may partially substitute for fertilizer P input and minimizing soil P accumulation and subsequent environmental risk in the subtropical paddy soil.

Fate of mercury in flue gas desulfurization gypsum determined by Temperature Programmed Decomposition and Sequential Chemical Extraction

A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition（TPD） and Sequential Chemical Extraction（SCE） were applied to FGD gypsum to identify the Hg species in it. The FGD gypsum samples were collected from seven coal-fired power plants in China, with Hg concentrations ranging from 0.19 to 3.27 μg/g. A series of pure Hg compounds were used as reference materials in TPD experiments and the results revealed that the decomposition temperatures of different Hg compounds increase in the order of Hg_2Cl_2〈 HgCl_2〈 black HgS 〈 Hg_2SO_4〈 red HgS 〈 HgO 〈 HgSO_4. The Hg compounds existing in FGD gypsums identified by TPD included HgCl_2, Hg_2Cl_2, Hg_2SO_4, black HgS and red HgS, of which mercury sulfides were the primary compounds. The results of SCE indicated that Hg was mainly distributed in the strongly complexed phase. The low Hg content in FGD gypsum increases the ambiguity of assigning extraction fractions to certain Hg species by SCE. The fact that the primary compounds in FGD gypsum are HgS phases leads the leaching of Hg in the natural environment to be quite low, but a considerable amount of Hg may be released during the industrial heating process.

Removal of Heavy Metal from Contaminated Soil with Chelating Agents

Removal of copper and nickel by the addition of the biodegradable chelating agent, chitosan and ethylenediamine tetraacetic acid (EDTA), was investigated, alongside the reaction of a reference compound sodium citrate for comparison. The artificial-contaminated soils were used in this study. The experiments showed that the extraction ability for copper and nickel from the contaminated soil decreased as follows: chitosan > EDTA > sodium citrate. The pH value of the eluents is the key to control the extraction, especially to chitosan solution. It was evident that the chitosan solution was the most efficient when the pH value was 3 - 3.5, the rate of extraction of copper being 43.36% and of nickel being 37.07%. And the best match of concentration and liquid/solid was 0.3 g/L and 10 mL/g.

Sequential extraction of Cs and Sr from Ain Oussera soils around Es-Salam research reactor facility

Four types of undisturbed soil in Ain Oussera region around the Es-Salam reactor facility,located in the south of Algiers, Algeria, at about 200 km, were artificially contaminated for one year with stable CsCl and SrCl2 in order to simulate an accidental release of these elements. This study was performed using sequential extraction procedure based on Shultz method and containing six fractions. The selectivity of the extraction protocol was confirmed by analyzing some elements（Ca, C, Fe, Mn, Si and Al） designed as indicators of the targeted phases. The obtained results showed an acceptable reproducibility, in view of the coefficients of variation that were in most cases less than 15%. The results revealed a clear proportional correlation between the extracted Cs and Sr in fractions for each soil and some of soils physicochemical properties. Organic matter appears to play an important role in the soil retention, particularly for Cs where the extracted percentage exceeds to 30% in whole soils. In contrast, strontium expresses a remarkable affinity for the fraction bound to carbonates. The obtained data also indicate that the availability of Cs in the four soils is less important compared to Sr availability. This is illustrated by the higher value of extracted Sr in the easily extractible phase, including the water-soluble and the exchangeable fraction.

Application of ultrasonic to speciation analysis of heavy metals in soil

In order to reduce the operation time and improve the extraction efficiency, ultrasonic energy by means of ultrasonic bath was used to the modified Tessier sequential extraction for speciation analysis of heavy metals in soil. Extractable contents of Cu, Fe, Mn, Ni, Pb and Zn were measured by atomic absorption spectroscopy(AAS). The merit of the ultrasonic extraction(UE) applied to the modified Tessier method is not only that the operation time for the first 4 fractions was reduced from ca.18 h to 8 h, comparing with conventional extraction(CE), but also the extraction efficiency was higher. The results for both of UE and CE were consistent. The extractable Cu, Ni and Zn in the sample No.1 were mainly associated with the third fraction(Fe-Mn oxides fraction), and fourth fraction(organic matter fraction) in the sample No.2. The extractable Fe and Mn were all mainly associated with the third fraction, and Pb the fourth fraction in both of the samples. The effects of concentration of hydroxylamine chloride on the capability for the extraction of studied metals were also studied.