喀斯特山区燃煤电厂土壤重金属污染评价

选取地处贵州省喀斯特山区的金沙电厂为研究对象,对电厂周围的表层土壤、蔬菜(莲花白)试样的重金属含量进行了测定,采用模糊数学法对土壤重金属污染进行了评价,采用富集系数法分析了莲花白对重金属的富集能力。实验结果表明:电厂周围表层土壤中Hg,As,Cd,Pb,Cu的平均含量分别达0.70,26.40,0.61,44.83,35.51 mg/kg,其中,Hg和Cd的平均含量分别为GB 15618—1995《土壤环境质量标准》中二级标准的1.40和2.03倍;电厂周围土壤受到较为严重的Hg,As,Cd污染,各个方向的重金属污染程度大小顺序为西北西东南西南东北东,总体趋势为西向大于东向;莲花白对土壤中Cd的富集作用较强,对其他重金属的富集作用较弱。     

柠檬酸淋洗去除电子垃圾污染土壤中的重金属

采用柠檬酸溶液对模拟电子垃圾污染土壤（简称污染土壤）中Cu,Pb,Cd 3种重金属进行淋洗实验,考察了柠檬酸溶液的浓度、柠檬酸溶液的pH、淋洗时间等对污染土壤中Cu,Pb,Cd的淋洗效果,探讨了柠檬酸溶液淋洗前后污染土壤中Cu,Pb,Cd 3种重金属各形态含量的变化。研究结果表明,在柠檬酸溶液的浓度0.100 mol/L、柠檬酸溶液的pH 5、淋洗时间1 440 min的适宜条件下,对污染土壤中Cu,Pb,Cd的去除率分别达到89.37%,72.11%,86.39%。柠檬酸溶液对3种重金属的去除主要是通过洗出酸可提取态（R1）和酸可还原态（R2）来实现的,每种重金属的R1和R2之和均占到其淋出总量的95%以上,而酸可氧化态（R3）和残渣态（R4）的含量淋洗前后基本无变化。     

无患子皂苷与柠檬酸协同洗脱污染土壤中镉铅

以某废弃铅锌矿区重金属污染土壤为研究对象,采用无患子皂苷与柠檬酸（CA）协同洗脱污染土壤中的Cd和Pb。以无患子果皮投加量为20 g/L所得水浸提液和浓度为0.3 mol/L的CA配制复配淋洗剂。在浸提液中添加CA后,能有效提高对土壤中Pb的去除率。在浸提液和CA的体积比为1∶3、淋洗剂pH为5、淋洗时间为12.0 h的条件下,复配淋洗剂对Cd和Pb的去除率分别为75.2%和41.6%。双常数方程和Elovich方程均可较好描述复配淋洗剂对污染土壤中Cd和Pb的淋洗过程,表明Cd和Pb的解吸主要为非均相扩散过程。复合淋洗剂能有效降低土壤中Cd的可交换态和Pb的铁锰氧化态含量,并可促进重金属形态的转变。     

典型磷矿区表层土壤重金属空间分布特征研究

以开阳磷矿区为对象,结合地统计学普通克里金插值法以及单因素分析法,研究了矿区表层土壤重金属的空间分布特征,并对其进行了污染评价。结果表明：以矿区当地土壤重金属背景值为标准,Cu,Zn,Pb,Cd,As含量均存在超标情况;5种元素含量的变异程度均为高度变异,Pb,Cd,As的变异系数远大于Cu,Zn的变异系数;土壤重金属空间分布特征为Cd,As含量在东北部的积累程度大于西南部,东北—东南方向Cu,Zn,Pb,Cd,As的富集程度远大于西北—西南方向;不同土地利用类型对重金属的积累没有显著影响,这很可能与其他因素如背景值、风向、人类干扰（如化工产业）等有关。     

复合重金属污染高岭土的电动修复

根据电子废弃物拆解场地的污染特征,以复合重金属(Cu,Cd,Pb)污染高岭土为研究对象,考察了电动技术对污染土壤的修复效果。实验结果表明:在电压梯度为1 V/cm、阳极液为自来水、阴极液为柠檬酸-柠檬酸钠缓冲液(pH=5)、靠近阴极设置活性炭渗透反应墙(PRB)的条件下电动修复96 h后,Cu,Cd,Pb的平均去除率分别可达79.93%,99.43%,39.36%;土壤的酸碱性对电动修复效果影响显著,通过在阴极添加缓冲液维持土壤偏酸性条件,有利于重金属污染物的电动去除;在靠近阴极设置活性炭PRB可富集重金属,减少阴极液的污染;迁移率大的酸可提取态重金属较易去除,残渣态重金属稳定性强,去除率较低。     

重金属污染土壤生物毒性的发光菌法测定及评价

向土壤中人为投加重金属污染物,制备了重金属含量不同的一系列污染土壤,对土壤重金属浸提条件进行了探究,并应用明亮发光杆菌T3（Photobacterium phosphoreum T3）对单一Cu、Cd和Pb污染及Cu-Cd和Cu-Pb复合重金属污染土壤的生物毒性进行了测定。实验结果表明,土壤重金属的最佳浸提剂为0.1 mol/L HCl溶液,最佳浸提时间为2.0 h。在单一重金属污染条件下：Cu表现出低浓度促进生长、高浓度抑制生长的双重生物效应,而Cd和Pb则表现出浓度与生物毒性的正相关性;3种重金属污染土壤的毒性强弱顺序为Cd>Pb>Cu。在复合重金属污染条件下,由于重金属之间的相互作用,污染土壤的生物毒性增强。     

气化炉渣的重金属浸出特性及化学形态分析

分别采用硫酸硝酸法、水平振荡法和醋酸缓冲溶液法制取气化炉渣的浸出液，考察了不同提取方式对浸出液中重金属质量浓度的影响。采用改进BCR连续提取法对气化炉渣中的重金属Cr，Zn，Cu，Pb，Ni，As，Cd的化学形态进行了分析。实验结果表明：煤气化工艺中的气化炉渣属第Ⅰ类一般工业固体废物;在3种提取方式中，醋酸缓冲溶液法的重金属浸出种类最多，且浸出量最大;Cd和Cr对环境具有较高的潜在危害性，Cu次之，Zn，Pb，Ni，As主要以残渣态形式存在，对环境的直接危害性较低。     

电石渣脱硫运行存在问题的探讨

石灰石—石膏湿法脱硫技术是我国燃煤电厂烟气脱硫的首选工艺,以电石渣代替石灰石进行烟气脱硫,可以达到废物利用、循环经济的目的。分析了以电石渣为脱硫剂时,系统运行存在的问题,并提出相关建议。     

硫酸锰渣污染土壤中重金属的形态分布及生物活性

测定了硫酸锰渣污染土壤中Cu,Zn,Cd,Pb,Mn的总量和各形态含量.结果表明重金属总量远超过环境背景值和土壤环境二级标准.重金属各形态分布特征:Cu,有机态>残渣态>铁锰氧化态>碳酸盐态>可交换态;Zn,残渣态>铁锰氧化态>有机态>碳酸盐态>可交换态;Cd,铁锰氧化态>可交换态>碳酸盐态>残渣态>有机态;Pb,铁锰氧化态>残渣态>有机态>碳酸盐态>可交换态;Mn,铁锰氧化态>残渣态>可交换态>有机态>碳酸盐态.重金属的生物可利用性系数和迁移系数均为Cd>Mn>Pb>Cu>Zn.     

电动力修复铅镉复合污染土壤

采用电动力修复技术处理Pb、Cd复合污染土壤,考察了柠檬酸和乙二胺四乙酸二钠（EDTA）作为电解液对棕壤（ZR）和红壤（HR）两种我国典型壤质中Pb、Cd去除效果的影响。实验结果表明：在电压梯度为2 V/cm,修复时间为4 d的条件下,ZR的最佳电解液为EDTA,Pb、Cd平均去除率为13.2%和17.8%,HR的最佳电解液为柠檬酸,Pb、Cd的平均去除率为20.0%和33.8%;延长修复时间至10 d能显著提高HR中Pb、Cd的去除率,电解液为柠檬酸时Cd平均去除率达91.1%,电解液为EDTA时Pb平均去除率达63.2%,修复后土壤中Cd和Pb含量均低于建筑用地土壤污染风险筛选值。综合考虑能耗及修复效果,EDTA是高效且经济的修复电解液。     

Heavy metal speciation in various types of fly ash from municipal solid waste incinerator

Fly ash (FA) from municipal solid waste incinerators has been known as hazardous waste, which is mostly because of the high content of heavy metal and dioxins. Besides the content, the form of the heavy metals in fly ash is also very important, because it is tightly related with the leaching behavior of fly ash in diverse circumstances. To evaluate the environment potential risk of fly ash, the Tessier chemical extraction method was adopted. In this study, four kinds of fly ash were examined, one sample from China (CFA) and the other three from Japan (RFA, CaFA and NaFA). Five metal elements were detected and they were Ni, Cr, Cd, Pb, and Cu. The result of total heavy metals’ concentration showed CFA has the lowest content. As to the Tessier chemical extraction experiments, the results show that Cd, Pb, and Cu have higher leaching risk in the environment than other heavy metals. The result of leaching test experiment showed that the more exchangeable speciation of Cd, Cr and Pb in FA, the more it could leach out in natural environment.     

Characteristics of element distributions in an MSW ash melting treatment system

Thermal treatment of municipal solid waste (MSW) has become a common practice in waste volume reduction and resource recovery. For the utilization of molten slag for construction materials and metal recovery, it is important to understand the behavior of heavy metals in the melting process. In this study, the correlation between the contents of elements in feed materials and MSW molten slag and their distributions in the ash melting process, including metal residues, are investigated. The hazardous metal contents in the molten slag were significantly related to the contents of metals in the feed materials. Therefore, the separation of products containing these metals in waste materials could be an effective means of producing environmentally safe molten slag with a low hazardous metals content. The distribution ratios of elements in the ash melting process were also determined. The elements Zn and Pb were found to have a distribution ratio of over 60% in fly ash from the melting furnace and the contents of these metals were also high; therefore, Zn and Pb could be potential target metals for recycling from fly ash from the melting furnace. Meanwhile, Cu, Ni, Mo, Sn, and Sb were found to have distribution ratios of over 60% in the metal residue. Therefore, metal residue could be a good resource for these metals, as the contents of Cu, Ni, Mo, Sn, and Sb in metal residue are higher than those in other output materials.     

Leaching behavior of heavy metals from municipal solid waste incineration bottom ash and its geochemical modeling

With the increase in the number of municipal solid waste incineration (MSWI) plants constructed in China recently, great attention has been paid to the heavy metal leaching toxicity of MSWI residues. In this study, the effects of various parameters, including extractant, leaching time, liquid-to-solid ratio, leachate pH, and heavy metal content, on the release properties of Cd, Cr, Cu, Ni, Pb, and Zn from MSWI bottom ash were investigated. Partial least-squares analysis was employed to highlight the interrelationships between the factors and response variables. Both experimental research and geochemical modeling using Visual MINTEQ software were conducted to study the pH-dependent leaching behavior of these metals in fresh and weathered bottom ash, considering precipitation/dissolution and surface complexation reactions (adsorption by hydrous ferric oxide and amorphous aluminum oxide/hydroxide). The results showed that leachate pH was the predominant factor influencing heavy metal leachability. The leaching of Cu, Pb, and Zn was mainly controlled by precipitation/dissolution reactions, whereas surface complexation had some effect on the leaching of Cr, Cd, and Ni for certain pH ranges. The modeling results aggreed well with the experimental results. Part of this work was presented at the Fourth International Conference on Combustion, Incineration/Pyrolysis and Emission Control (i-CIPEC)     

Characterization of a thermal power plant air heater washing waste: a case study from Iran.

In Iran most of the electricity is generated by thermal power plants. As a result of fuel oil burning in winter time, the air heaters of the boilers have to be washed and cleaned frequently. The wastewater originating from air heater washing is then treated in an effluent treatment plant by chemical precipitation followed by dewatering of the sludge produced. The resulting waste is classified as specific industrial waste that should be characterized in detail under the Waste Management Act of Iran. The quantity of this waste produced in the studied power plant is about 20 tonnes year(-1). In the present investigation, the first to be carried out in Iran, seven composite samples of dewatered sludge from air heater washing wastewater treatment were subjected to investigation of the physical properties, chemical composition and leaching properties. The most likely pollutants that were of concern in this study were heavy and other hazardous metals (Cd, Co, Cr, Mn, Ni, Pb, Zn and V). The results revealed that mean pH, wet and dry density and moisture content of the waste were 6.31, 1532 kg m(-30, 1879 kg m(-3) and 15.35%, respectively. Magnetite, SiO2, P2O5, CaO, Al2O3 and MgO were the main constituents of the waste with a weight percentage order of 68.88, 5.91, 3.39, 2.64, 2.59 and 1.76%, respectively. The toxicity characteristic leaching procedure test results for some heavy and other hazardous metals showed that mean elemental concentrations of Cd, Co, Cr, Mn, Ni, Pb, V and Zn in leachate were 0.06, 1.55, 5.49, 36.32, 209.10, 0.58, 314.06 and 24.84 mg L(-1), respectively. According to the Waste Management Act of Iran this waste should be classified as hazardous and should be disposed of in accordance with hazardous waste disposal regulations.     

Laboratory study on the leaching potential of spent alkaline batteries

Four different leaching tests were carried out with spent alkaline batteries as an attempt to quantify the environmental potential burdens associated with landfilling. The tests were performed in columns filled up with batteries either entire or cross-cut, using either deionized water or nitric acid solution as leachant. In a first set of tests, the NEN 7343 standard procedure was followed, with leachant circulating in open circuit from bottom to top through columns. These tests were extended to another leaching step where leachant percolated the columns in a closed loop process.Leachate solutions were periodically sampled and pH, conductivity, density, redox potential, sulphates, chlorides and heavy metals (As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Tl and Zn) were determined in the samples.The results showed that the total amount of substances leached in tests with cross-cut batteries was higher than with entire ones; zinc and sulphates were the substances found the most in the leachate solutions. In general, the amount of substances dissolved in open circuit is higher than in closed loop due to the effect of solution saturation and the absence of fresh solution addition.Results were compared with metal contents in the batteries and with legal limits for acceptance in landfill (Decision 2003/33/CE and Decree-Law 152/2002). None of the metals were meaningfully dissolved comparatively to its content in the batteries, except Hg. Despite the differences in the experiment procedure used and the one stated in the legislation (mixing, contact time and granulometry), the comparison of results obtained with cross-cut batteries using deionized water with legal limits showed that batteries studied could be considered hazardous waste.     

The influence of pH on the leaching behaviour of inorganic components from municipal solid waste APC residues

The influence of pH on the leaching behaviour of air pollution control (APC) residues produced in municipal solid waste incineration (MSWI) is addressed in this study. The residue is considered hazardous waste, and in accordance with their chemical properties, the leaching of contaminants into the environment is the main concern. Several leaching tests can be used for research studies or regulatory purposes, where a wide variety of conditions may be tested. Our work deals mainly with the leaching behaviour of toxic heavy metals (Pb, Cd, Zn, Cr, Ni, Cu) and inorganics associated with soluble salts (Na, K, Ca, Cl). The main goal is to obtain an overview of the leachability of APC residues produced in a Portuguese MSWI process. Among the different variables that may have influence on the leaching behaviour, pH of the leachant solution is the most important one, and was evaluated through pH static tests. The acid neutralization capacity (ANC) of the residue was also determined, which is in the range of 6.2–6.8 meq g^?1 (for pH = 7) and 10.1–11.6 meq g^?1 (for pH = 4). The analysis of the leaching behaviour is particularly important when the leaching is solubility controlled. The amphoteric behaviour of some elements was observed, namely for Pb and Zn, which is characterized through high solubilization at low and high pH and moderate or low solubility at neutral or moderate high pH. The solubility curves for Pb, Cd, Zn, Cr, Ni and Cu as a function of pH were obtained, which are very useful for predicting the leaching behaviour in different scenarios. The solubility of K and Na reveals to be nearly independent of the solution pH and the released amount is mainly availability-controlled. Moreover, the pH static test showed that Cl^? is the most pH-independent species. The APC residue turns out to be a hazardous waste because of the high leaching of lead and chloride. On the other hand, leaching of elements like cadmium, nickel and copper is limited by the high pH of the residue, and as long as the waste keeps its ANC, the risk of mobilization of these elements is low.     

Characteristics of ashes from different locations at the MSW incinerator equipped with various air pollution control devices

The characteristics of ashes from different locations at a municipal solid waste incinerator (MSWI) equipped with a water spray tower (WST) as a cooling system, and a spray dryer adsorber (SDA), a bag filter (BF) and a selective catalytic reactor (SCR) as air pollution control devices (APCD) was investigated to provide the basic data for further treatment of ashes. A commercial MSWI with a capacity of 100 tons per day was selected. Ash was sampled from different locations during the normal operation of the MSWI and was analyzed to obtain chemical composition, basicity, metal contents and leaching behavior of heavy metals. Basicity and pH of ash showed a broad range between 0.08-9.07 and 3.5-12.3, respectively. Some major inorganics in ash were identified and could affect the basicity. This could be one of the factors to determine further treatment means. Partitioning of hazardous heavy metals such as Pb, Cu, Cr, Hg and Cd was investigated. Large portions of Hg and Cd were emitted from the furnace while over 90% of Pb, Cu and Cr remained in bottom ash. However 54% of Hg was captured by WST and 41% by SDA/BF and 3.6% was emitted through the stack, while 81.5% of Cd was captured by SDA/BF. From the analysis data of various metal contents in ash and leach analysis, such capturing of metal was confirmed and some heavy metals found to be easily released from ash. Based on the overall characteristics of ash in different locations at the MSWI during the investigation, some considerations and suggestions for determining the appropriate treatment methods of ash were made as conclusions.     

Sb release characteristics of the solid waste produced in antimony mining smelting process

Sb release characteristics of blast furnace slag, mining waste rock and tailing sand were investigated in static immersion and dynamic leaching test. These three kinds of waste samples were collected from the antimony mine in Lengshuijiang, China, produced in mining smelting process. Effects of solid/liquid ratio, sample size and pH of leaching solution on Sb release characteristics were inspected based on the analysis of scanning electron microscope, pH and EC of leachate. The optimal parameters for Sb leaching of each sample were analyzed. For blast furnace slag and mining waste rock, Sb release contents increased along with the decline of solid/liquid ratio. The maximum accumulative release contents were 42.13, 34.26 mg/kg at the solid/liquid ratio of 1:20. While Sb release content for tailing sand decreased first and then increased with the reduction of solid/liquid ratio. When the solid/liquid ratio was 1:5, the accumulative Sb release content reached the most (24.30 mg/kg). Sb release content of mining waste rock increased with the drop of leaching solution pH, with the highest accumulative release content of 26.01 mg/kg at pH 2.0. Sb release contents of blast furnace slag and tailing sand showed positive correlation with the variation of leaching solution pH. The maximum accumulative release contents of these two samples were 215.91 and 147.83 mg/kg, respectively, when leaching solution pH was 7.0. In summary, Sb release capacity of the three samples in descending order was tailing sand, blast furnace slag and mining waste rock. pH and EC of the leachate in dynamic test varied independently with the initial pH of leaching solution while showing close relationship with mineral hydrolysis in the waste.     

Metal leachability, heavy metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls in fly and bottom ashes of a medical waste incineration facility

Medical waste from hospitals and other healthcare institutions has become an imperative environmental and public safety problem. Medical waste in Greece has become one of the most urgent environmental problems, because there are 14,000 tons produced annually, of which only a small proportion is incinerated. In the prefecture of Attica there is only one modern municipal medical waste incinerator (started 2004) burning selected infectious hospital waste (5-6 tons day(-1)). Fly and bottom residues (ashes) are collected and stored temporarily in barrels. High values of metal leachability prohibit the landfilling of these ashes, as imposed by EU directives. In the present study we determined quantitatively the heavy metals and other elements in the fly and bottom ashes of the medical waste incinerator, by inductively coupled plasma emission spectrometry (ICP) and by energy dispersive X-ray analysis (EDAX). Heavy metals, which are very toxic, such as Pb, Cd, Ni, Cr, Cu and Zn were found in high concentrations in both fly and bottom ashes. Metal leachability of fly and bottom ashes by water and kerosene was measured by ICP and the results showed that toxic metals in both ashes, such as Pb, Cr, Cd, Cu and Zn, have high leaching values. These values indicate that metals can become soluble and mobile if ash is deposited in landfills, thus restricting their burial according to EU regulations. Analysis of polychlorinated biphenyls and polycyclic aromatic hydrocarbons in fly and bottom ashes showed that their concentrations were very low. This is the first known study in Greece and the results showed that incineration of medical waste can be very effective in minimizing the most hazardous and infectious health-care waste. The presence of toxic metals with high leachability values remains an important draw back of incineration of medical waste and various methods of treating these residues to diminish leaching are been considered at present to overcome this serious technical problem.