土壤中重金属铊的分级提取形态分析法研究

以自然高铊污染土壤为样品, 对BCR标准分级提取形态分析法中争议较大的HAc和NH2OH·HCl提取剂pH、提取剂浓度和提取体系温度对土壤中相应形态Tl提取量的影响进行了研究。实验发现标准条件的HAc提取体系可有效提取土壤中可交换态的Tl, 而标准的NH2OH·HCl提取体系不能有效提取土壤中易还原态的Tl。根据实验结果, 对标准BCR法进行如下改进: NH2OH·HCl提取剂pH由2.0酸化至1.5, 提取剂浓度由0.1mol/L增至0.5 mol/L, 提取体系温度由室温(28℃)增至60℃; 其他提取条件不变。     

化学提取方法快速评估污染土壤中生物可消化性铅

为建立一种简单的方法鉴定污染土壤中的铅在消化系统中被人体消化吸收的潜力（即生物可消化性或生物可接受性）,采用连续提取法和7种单一化学提取法比较研究了13个污染土壤中铅的化学形态及其可提取性,以模拟胃液提取法为参比,选择和比较了7种化学提取剂,包括：CaCl2稀盐、NH4OAc、DTPA—TEA、Mehlich Ⅰ、Mehlich Ⅲ、草酸铵缓冲液和盐酸羟铵溶液。结果表明,土壤中铅的平均提取率由高至低依次为：草酸铵缓冲液,盐酸羟铵溶液,MehlichⅠ、MehlichⅢ,DTPA—TEA,NH4OAc,CaCl2相关分析表明,氧化物结合态铅是污染土壤中生物可消化铅的主要组分,用盐酸羟铵溶液提取的铅可很好地表征污染土壤中铅的生物可消化性,其提取量与模拟胃液提取的铅接近,两者之间具有显著的相关性。     

土壤中氟的化学形态分析方法研究

氟是一种与健康密切相关的必需微量元素,人体对氟的摄入不足或过量都可能会引发健康问题。查明土壤中氟的赋存形态,对了解氟的生物有效性、迁移转化规律及预防氟缺乏或过剩可能导致的生态环境和健康问题具有重要意义。通过讨论,将氟的形态划分为水溶态、吸附态、氧化结合态和固定态。重点研究了固液比、超声时间、超声温度对水溶态氟的提取影响,确定了固液比为1:10、超声时间为30min以及超声温度为25±5℃为最佳提取条件,并在此条件下,开展了弱酸(H2C2O4)、弱碱(NaHCO3)提取剂的先后顺序和不同浓度NH3OHCl-C2H4O2提取液对吸附态氟及氧化结合态氟提取效果的影响。结果表明,土壤的pH对提取吸附态的氟有一定的影响,确定了以酸性土壤使用先碱后酸、碱性土壤使用先酸后碱为吸附态氟的提取顺序;得出了使用0.25mol/L浓度的NH3OHCl - C2H4O2提取液会使氧化结合态氟的提取率更高的结论。所使用的方法精密度RSD/%在3.58% ~ 22.8%之间,准确度RD%在0.42% ~ 10.5%之间,回收率在81.0% ~ 99.2%范围内,均优于区域生态地球化学评价(DZ/T 0289-2015)规范的要求。该方法简单有效,并易于控制,可为研究氟在土壤中的迁移转化提供科学依据。     

涡旋提取-电感耦合等离子体发射光谱(ICP-OES)法测定酸性和中性土壤中交换性盐基总量

传统的土壤交换性盐基总量检测方法前处理过程复杂,检测时间长,建立涡旋提取-电感耦合等离子体发射光谱(ICP-OES)法,大大提高了检测效率。采用涡旋提取中性和酸性土壤中交换性盐基总量,结合电感耦合等离子发射光谱仪（ICP-OES）同时测定土壤提取液中交换性盐基总量钙镁钠钾含量。通过考察土液比,涡旋时间,涡旋转速以及方法的精密度和准确度。结果表明,最佳涡旋条件为土液比为1:50,涡旋时间为20 min,涡旋速度为1500 r/min。利用ICP-OES测定国家标准物质RMH-A275、RMH-A274和GBW07458a（ ASA-7a）土壤提取液中交换性盐基总量钙镁钠钾含量,各元素测定结果均在标准值范围内,相对标准偏差均小于2 %,交换性钙镁钠钾的方法检出限分别为0.048 cmol/kg、0.035 cmol/kg、0.038cmol/kg和0.072 cmol/kg。应用该方法检测20份耕地实际土壤样品,与国标法相比,交换性盐基总量钙镁钠钾的测定值相对误差均小于2 %,满足土壤样品分析检测的要求。该方法操作简便、试剂用量少,准确度和精密度好,适用于大批量生态地球化学评价土壤样品中交换性盐基总量钙镁钾钠的测定。     

超声波提取-原子吸收光谱法测定油区土壤中重金属的含量

优化了超声波辅助提取土壤中重金属的条件,建立了原子吸收光谱法测定土壤中Cd、Cr、Cu、Ni、Pb和Zn的方法.各元素的线性关系良好(r=0.9991～0.9998),检出限为0.002～0.013 mg/L,相对标准偏差(RSD)为1.4％～5.8％,加标回收率为92.0％～110％.在优化的超声提取条件下分析标准物质GBW07439,并与湿法消解结果相比较,两种方法的测定值与参考值均相符,但超声提取法速度较快、安全性较好、污染小、试剂消耗少、残渣少.利用该方法分析辽河油田周边土壤中重金属含量,采用单因子污染指数法和内梅罗综合污染指数法评价了土壤受重金属污染的程度.     

超声提取-改进BCR法测定PM_(2.5)中6种重金属元素的化学形态

应用改进的BCR法对大气微颗粒物(PM2.5)进行分析,用超声法代替原来的机械振荡法,对所采得的微颗粒物样品中6种重金属元素(铜、锌、铅、镉、镍、铬)的4种化学形态(酸可交换态F1,可还原态F2,可氧化态F3及残渣态F4)进行分别提取,所得各形态溶液中的金属元素含量用电感耦合等离子体质谱法测定。结果表明:超声提取法的提取时间仅为30min(对F1及F2)和20min(对F3),而原方法需16h;而且超声提取的效率较高,是原方法的89.5%~133%;6种元素的化学形态测定结果的相对标准偏差(n=8)均小于25%。此外,样品中的元素形态总量(ng·m-3)与元素全量(ng·m-3)之间的偏差在-30.7%~-11.5%之间。     

改进BCR法在活性污泥样品重金属形态分析中的应用

利用改进的BCR三步顺序提取法研究了活性污泥中重金属的形态分布。所研究的可提取态包括可交换态,还原态-铁锰氧化物结合态和氧化态-有机物和硫化物结合态。这三态的含量之和加上残渣态的含量与各重金属的总量进行了比较。利用ICP-MS测定了活性污泥提取液以及残渣态中Cr,Mn,Co,Ni,Cu,Zn,As,Cd,Pb的含量。实验表明,采用改进的BCR法可以用来分析活性污泥样品中的金属形态。     

改进的BCR连续提取法-电感耦合等离子体质谱法分析水泥基底泥固化材料中重金属形态

为测定水泥基河道底泥固化材料中4种重金属元素(Pb、Cu、Cr、Zn)的形态,作如下试验:将普通硅酸盐水泥与河道底泥按质量比2∶8进行混合,并注装于模具中干燥成型后,于湿度95%,温度为(20±0.5)℃条件下的养护箱内分别湿式养护3,7,14,28,45,60d,制得一系列固化材料样品。作为分析用样品,须将固化块样破碎至通过75μm孔径的网筛并充分混匀。测定上述样品中重金属元素总量时,取此经破碎的样品0.100g,用硝酸3 mL,过氧化氢1 mL和氢氟酸1mL进行微波消解。所得消解液于150℃加热蒸发赶酸,冷却后加水溶解并定容为50.0mL。用电感耦合等离子体质谱法(ICP-MS)测定此溶液中4种重金属元素的含量。另取0.800g样品,按改进的BCR连续提取法先后分离出上述4种重金属元素的4种结合形态,依次为酸可提取态(F1)、可还原态(F2)、可氧化态(F3)和残渣态(F4)。分离所得4种形态的样品溶液用ICP-MS分别测定其中重金属元素的含量。在ICP-MS分析中,用Sc、Ge、In和Bi作为内标,以校正响应信号的变化和消除仪器的漂移及基体效应。试验结果表明,所用方法具有较好的准确度和精密度。根据改进的BCR连续提取法分离后,ICP-MS的分析结果得到了固化过程中4种重金属元素迁移性变化的特征和规律。     

土壤中铅的含量及其化学形态分析

对广州市黄埔港区所取土壤中铅的化学形态分析进行了研究。采用含不同组分提取剂的连续提取程序对1 g土壤进行提取,使之分成8种形态的铅,并用火焰原子吸收光谱法(FAAS)对每种提取所得的形态中的铅进行了测定。另在一份试样中直接测定其总铅量,对提取剂的组成及其溶液的浓度及提取操作条件进行了研究和优化,对FAAS测定方法的仪器工作条件作了说明。试验结果表明,所取试样中大部分铅以稳定的结合形态存在,以可交换态和碳酸盐结合态存在的铅仅达6%,总铅量随土壤深度的增加而减少。FAAS测定方法的灵敏度和检出限依次为0.007 mg.L-1及0.01 mg.L-1,分析和测定了4个试样中8种形态的铅量,其加和量为147.9 mg.kg-1,与直接测得的总铅量(159.9 mg.kg-1)之间的偏差小于10%。     

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.     

The utilization of modified BCR three-step sequential extraction procedure for the fractionation of Cd, Cr, Cu, Ni, Pb and Zn in soil reference materials of different origins

A modified three-step sequential extraction procedure for the fractionation of heavy metals, proposed by the Commission of the European Communities Bureau of Reference (BCR) has been applied to the Slovak reference materials of soils (soil orthic luvisols, soil rendzina and soil eutric cambisol), which represent pedologically different types of soils in Slovakia. Analyses were carried out by flame or electrothermal atomic absorption spectrometry (FAAS or ETAAS). The fractions extracted were: exchangeable (extraction step 1), reducible-iron/manganese oxides (extraction step 2), oxidizable-organic matter and sulfides (extraction step 3). The sum of the element contents in the three fractions plus aqua-regia extractable content of the residue was compared to the aqua-regia extractable content of the elements in the origin soils. The accuracy obtained by comparing the determined contents of the elements with certified values, using BCR CRM 701, certified for the extractable contents (mass fractions) of Cd, Cr, Cu, Ni, Pb and Zn in sediment following a modified BCR-three step sequential extraction procedure, was found to be satisfactory.     

Three-step extraction procedure for determination of heavy metals availability to vegetables

A three-step sequential extraction procedure was used to determine the concentration of heavy metal speciation forms in soil. The procedure allows one to identify the pool of heavy metals that can be potentially mobilised under changes in soil pH value or redox potential. It has been shown that similar portions of heavy metals are present in reducible, oxidisable and residual fractions. It was found that soil chemical properties significantly affected the distribution of heavy metals among different fractions and their uptake by vegetables. Cadmium was a dominant element which occurred in the exchangeable fraction—the most bioavailable and potentially toxic.     

Ultrasound and microwave-assisted extraction of metals from sediment: a comparison with the BCR procedure

In this paper we investigate alternatives to mechanical stirring for the extraction of the mobile fraction of metals from sediment, and analyze whether these techniques can reduce extraction time and improve reproducibility. We compare the quantities of metal extracted from BCR601 and BCR701 certified sediments using ultrasound bath, microwave-assisted extraction and the first step in the certified BCR sequential extraction procedure. Some environmentally important not-certified metals such as As, Mn, Co, Fe and Al have been included in this study. In the case of microwave-assisted extraction, we compare tests in which samples are exposed to constant, low power irradiation with tests using pulsed high power.

In the tests using the ultrasound bath, less metal was extracted than with the other extractive techniques and standard deviations were comparable to those obtained with the BCR procedure; in assays using microwaves at constant power, extraction efficiencies were different for different metals and for different reference materials and, in some cases, standard deviations were higher than those for the reference method. In contrast, tests with microwaves and constant temperature produced encouraging results: R.S.D.s lay in the 2–4% range, both for certified and not-certified metals; these values are very low compared to those for the reference method. Extraction efficiencies for certified metals were close to 100% for Cd, Zn, Cu and Ni and around 80% for Pb and Cr.     

Sequential extraction for the speciation of some heavy metals in soils

The five step sequential extraction for speciation of copper and nickel originally designed for sediments has been applied to soil samples. The extractant solutions were: 1 mol/l ammonium acetate, 1 mol/l hydroxylammonium chloride in 25% acetic acid (1∶1), 0.1 mol/l hydrochlorid acid, 0.5 mol/l sodium hydroxide and 8 mol/l nitric acid. The residue was decomposed by HF and HNO₃. Using this procedure the metal fraction bound to the organic matter can be distinguished. The concentrations of analytes were determined in the soil extracts by FAAS and ETAAS. Accuracy was assessed by comparing the sum of the contents of copper and nickel in soil extracts with the total certified values of CRMs of soils. The overall recovery values for nickel was 84–105% and for copper 105–114%.     

Fractionation studies of mercury in soils and sediments: A review of the chemical reagents used for mercury extraction

Mercury in contaminated soils and sediments could be extracted by various chemical reagents in order to determine the different mercury species and partitions, providing useful information of toxicology, bioavailability and biogeochemical reactivity. Unfortunately, at present, neither specific extractants nor standard protocols exist for the isolation of particular mercury species. Although there has been considerable research focused on reagents for extracting mercury species, there is still little consensus. Thus, workers are advised to select the most appropriate reagent based on the nature of their sample, and to take all possible steps to validate the analyses performed. Therefore, the aim of this paper is to review the current reagents used for determining total mercury and its speciation as well as fractionation such as methylmercury, ethylmercury, elemental mercury, mercury sulphide and organically bound mercury by supposed selective (one reagent) and sequential (several reagents) extractions. The gathering information presented here bring to light the need for standard protocol for which the used chemical reagents should take into account the particular chemistry of mercury associated with specific properties of soil and sediment. Beside this required scheme, appropriate reference materials are also demanded.     

Chemical speciation of trace metals in fine airborne particles: advances in operational performance of a new sequential extraction scheme

A speciation method of inorganic metal compounds in airborne particulate matter based on selective sequential extractions is described. The sequential leaching procedure was perfected for improvement of performance at different stages of scheme. The loss of fine particles during the leaching procedure was the main source of error that was assessed and corrected. Loss of sample volume due to the heating steps and due to the absorption on filter material was also a difficulty to solve. New experimental conditions were optimized for the operational scheme to remove the different sources of loss. Microwave assistance with an optimum programme as a heating system, filtration of extractable solutions, and the use of internal standards were the main contributions.     

Chemical speciation and contamination assessment of Zn and Cd by sequential extraction in surface sediment of Klang River, Malaysia

The concentration and chemical speciation of Cd and Zn as well as total organic carbon (TOC) were studied in surface sediments from 21 stations along Klang River. Sequential extraction technique (SET) was applied to assess the four (exchangeable, acid-reducible, oxidisable-organic and residual) fractions in surface sediment. And also, to obtain an overall classification of cadmium and zinc pollution in this area. This investigation was the first study on the basis of the chemical speciation of Cd and Zn in surface sediments of the Klang River. The total concentrations of metals were ranged (0.60–2.26 µg g^{− 1}) for Cd and (33.26–268.24 µg g^{− 1}) for Zn. The chemical speciation of Cd and Zn in most sampling stations were in the order of residual > acid-reducible > oxidisable-organic > exchangeable, and it showed that the Zn in Klang River surface sediments existed in the nonresistant fractions, whilst Cd existed in the resistant fraction. The degree of surface sediments contamination was determined for individual contamination factors (ICF) and global contamination factor (GCF). The result of ICF and GCF values showed that those stations located vicinity of municipal area had high potential risk to fauna and flora of the Klang River. The relationship between the concentration of cadmium and zinc at the oxidation-organic fraction with TOC in surface sediment was identified. The results showed that TOC had a positive function to complex with Cd and Zn in the surface sediment of Klang River.     

Occurrence and chemical speciation analysis of organotin compounds in the environment: A review

Environmental concerns regarding organotin compounds have increased remarkably in the past 20 years, due in large part to the use of these compounds as active components in antifouling paints [mainly tributyltin (TBT)] and pesticide formulations [mainly triphenyltin (TPhT)]. Their direct introduction into the environment, their bio-accumulation and the high toxicity of these compounds towards “non-target” organisms (for example: oysters and mussels) causes environmental and economic damage around the world. As a consequence, the presence and absence of organotin compounds is currently monitored in a range of environmental matrices (e.g., water, sediment and shellfish) to examine the utility of controls meant to regulate the level of contamination as required in some EC Directives and the Water Framework Directive 2000/60/EC. To evaluate the environmental distribution and fate of these compounds and to determine the effectives of legal provisions adopted by a number of countries, a variety of analytical methods have been developed for organotin determination in the environment. Most of these methods include different steps such as extraction, derivatisation and clean up. The aim of the present review is to evaluate the environmental distribution, fate and chemical speciation of organotin compounds in the environment.     

Study of partitioning and dynamics of metals in contaminated soil using modified four-step BCR sequential extraction procedure

The modified four-step BCR sequential extraction procedure (exchangeable and weak acid available species, reducible, oxidisable and residual fractions) was used to examine the distribution of As, Cd, Cr, Cu, Pb, and Zn with soil depth in an area (Baia Mare — Bozanta, Romania) with both high natural level of elements considered as toxic and historical pollution resulting from nonferrous metallurgy. The BCR approach proved a high metal input of anthropogenic origin down to 40 cm, while at lower depths the naturally elevated metal content must be considered. Results of the partitioning study and XRD analysis of solid matrix showed the greatest potential for chemical remobilisation of Cd, Zn, and Cu in weak acidic medium as well as their affinity for the oxidisable fraction (organic matter/sulphide). The tendency of Cr, Pb, and As to be immobilised as residual or reducible species on Fe-Mn oxides was evident. Although the partitioning of As in chemically inactive forms such as scorodite (FeAsO₄ · 2H₂O) soluble under reducible conditions and beudantite (PbFe₃(AsO₄)(SO₄)(OH)₂)), a residual species soluble in acid media, chemical mobilisation from soil in groundwater was confirmed. Dynamic processes of metal retention in soil under different conditions, namely acidic, reducing or oxidisable, were predicted from the Pearsonșs correlation analysis of element species with soil characteristics and components such as Fe, Mn, organic matter content, pH, and total element content, respectively. At the moment of the study, soil and groundwater in the area were found to be polluted with As, Cd, Cu, Pb and Zn. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.