Bioaccumulation of heavy metals by Phragmites australis cultivated in synthesized substrates

Accumulation of heavy metals from various oxides with adsorbed cadmium by wetland plant Phragmites australis was studied to evaluate the fate of heavy metals in the sediment of constructed wetlands. Hoagland solution was used as nutrition supply, and single metal oxide with adsorbed cadmium was applied as contaminant to study the accumulation characteristics of cadmium and the substrate metals by P. australis. After 45-d treatment, the bioaccumulation degree in root followed the order: Al(OH)₃ > Al₂O₃ > Fe₃O₄ > MnO₂ > FeOOH. Heavy metals absorbed by P. australis were largely immobilized by the roots with little translocation to aboveground parts.     

Volatilization of heavy metals during incineration of municipal solid wastes

Incineration experiments with MSW, which had been impregnated with heavy metals, were presented to obtain information on the volatilization behavior of the elements cadmium (Cd), lead (Pb), and zinc (Zn) under different conditions. Experiments were carried out in a bubbling fluid bed system connected to a customized inductively coupled plasma optical emission spectroscopy(ICP-OES) for analyzing metals in the flue gas. The results indicated that the combustion temperature, the gas atmosphere, and the chlorine content in the flue gas could affect the volatilization behavior of heavy metals. In the fluidized bed combustion, a large surface area was provided by the bed sand particles, and they may act as absorbents for the gaseous ash-forming compound. Comparer with the metals Cd and Pb, the vaporization of Zn was low. The formation of stable compounds such as ZnO.Al2O3 could greatly decrease the metals volatilization. The presence of chlorine would enhance the volatilization of heavy metals by increasing the formation of metal chlorides. However, when the oxygen content was high, the chlorinating reaction was kinetically hindered, which heavy metals release would be delayed.     

Partitioning of heavy metals in the surface sediments of Quanzhou Bay wetland and its availability to Suaeda australis

In order to investigate distributions of heavy metal pollution in Quanzhou Bay wetland, the total concentration and chemical partitioning of a number of heavy metals （Cu, Zn, Cd, Pb, Cr, Hg） in sediments of three sampling sites of Quanzhou Bay wetland and their availability to Suaeda australis were analyzed. The Geoaccumulation Index （Igeo） values reveal that the sediments of three sampling sites may all be considered as moderately contaminated for Pb and Zn, and all sediments might be strongly contaminated with cadmium. The partitioning analyses revealed the measured heavy metals in three sites are bound to the exchangeable fraction at lower concentrations. The measured metals in a considerable amount are bound to the reducible and oxidizable fractions, and a high proportion of the measured heavy metals were distributed in the residual fraction in the sediment samples. The concentrations of Cd in each chemical phase extracted from the sediments are above natural global background levels and should be further investigated because of its toxicity. Suaeda australis has different accumulation abilities for the measured heavy metals. For the root and stem, the bioaccumulation ability assessed by bioaccumulation factor （BAF） for the measured heavy metals follows the decreasing order as： Cu〉Cr〉 Zn〉Cd, Pb, Hg. In the leaf, stronger bioaccumulation ability for Hg is exhibited. The heavy metal concentrations in Suaeda australis roots have positive correlations with their available fractions, while the exchangeable fraction of Cu and Cd might have be more important to both mature plant roots and seedling roots uptake than other fractions; as for Cr, the oxidizable fraction might make a greater contribution to the plant root uptake; as for Zn, the reducible fraction might make so contribution ; and for Pb, the oxidizable fraction might make a significant contribution to the mature plant root uptake, however, the exchangeable fraction might have a significant contribution to the seedling root uptake.     

垃圾焚烧飞灰H3PO4稳定化技术及机理研究

分析了焚烧飞灰的全组分和浸出毒性,表明飞灰中含有多种重金属,其中Pb的浸出浓度为67.03mg/L,超过危险废物鉴别标准.研究了H₃PO₄投加量对飞灰稳定化效果及其环境长期稳定性的影响,结果表明:投加相当于飞灰质量8%～14%的H₃PO₄就能够有效地使焚烧飞灰无害化;8%和12%H₃PO₄稳定化飞灰都具有良好的环境稳定性;过多的H₃PO₄投加量会降低处理后飞灰对酸性环境的缓冲能力.对于12%H₃PO₄稳定化飞灰,XRD检测出Cr₂P₂O₇、ZnP₂、Pb₃P₄O₁₃、Pb₃P₂O₇、NaZnPO₄、NaPbP₃O₉、Ca₂ZnSi₂O₇等少量重金属的结晶相;SEM发现了大量独立存在的飞灰颗粒、直径约0.3～0.5μm的Pb₅(PO₄)₃Cl棒状物;CHBr₃浮选没有得到浓缩的重金属.综合分析得到:H₃PO₄是通过与强碱性飞灰之间的中和反应,激活飞灰中的重金属,改善稳定化进行的环境,并产生稳定化所需的PO₄^3-.被激活的重金属与产生的PO₄^3-在飞灰颗粒表面结合.所产生的重金属磷酸盐与SiO₂、CaCO₃、CaSO₄、KCl和NaCl等飞灰主要构成固溶相,几乎不独立存在.     

黄河三角洲不同淹水条件下芦苇和盐地碱蓬凋落物的分解与重金属归还特征

以黄河三角洲芦苇（Phragmites australis）和盐地碱蓬（Suaeda salsa）的凋落物为研究对象,研究不同淹水条件下芦苇和盐地碱蓬凋落物的分解与重金属的归还特征。结果表明：两种淹水条件下,盐地碱蓬凋落物的失重率均高于芦苇凋落物;潮汐淹水条件下芦苇和盐地碱蓬凋落物的失重率均高于短暂淹水处理。在两种淹水条件下,经过分解后芦苇凋落物中As、Cr和Cu的含量增加,潮汐淹水条件下芦苇凋落物的各金属含量均高于短期淹水处理。盐地碱蓬凋落物经过分解后,各重金属含量总体上呈上升变化趋势,潮汐淹水条件下的盐地碱蓬凋落物中As、Cu和Pb的含量均高于短期淹水处理。两种淹水条件下芦苇和盐地碱蓬凋落物中的Pb和Zn,在分解期间均发生了不同程度的释放。研究结果有助于理解潮汐作用对黄河三角洲芦苇和盐地碱蓬凋落物分解和重金属归还的影响。     

东寨港潮间带沉积物重金属环境背景值构建研究

潮间带沉积物作为重金属污染物的源和汇,对海岸带生态环境有着至关重要的影响。本文利用海南省东寨港2个柱状沉积物样品的重金属数据,结合数理统计方法,分析沉积物中Si、Al、Fe、Ca、Li、Ba、Cu、Pb、Zn、Cd、Cr和Ni等12种元素的空间分布特征,选取了归一化重金属元素,建立了东寨港潮间带沉积物各重金属环境背景线。结果表明:柱状沉积物各元素平均值含量排序为Si(以SiO₂计)>Al(以Al₂O₃计)>Fe(以Fe₂O₃计)>Ca(以CaO计)>Ba>Zn>Cr>Li>Pb>Ni>Cu>Cd,其中,SiO₂、CaO、Cu和Pb的变异系数小于10%,表现为弱变异性,其它8种元素表现为中等变异强度。各元素在垂向分布上差异明显,其中沉积物SiO₂含量最高,且随深度增加逐渐减小,30 cm以下的沉积物各重金属元素与Al、Fe、Ba、Li在垂向上的变化规律类似。选用Al作为归一化元素,构建了Al元素和重金属元素的一元线性回归方程,绝对系数R2大都在0.85以上,建立了区域重金属环境背景线。本文以东寨港作为中国南部特定类型沉积物代表,其沉积物重金属背景值构建为全国潮间带沉积物环境本底构建提供了有力补充,为潮间带区域的生态安全和环境安全提供基础数据支撑。     

铜、镉在颗粒物上吸附的结合态平衡模式

本文利用化学试剂逐级提取法测得颗粒物上各结合态吸附等温线,初步建立了沉积物和土壤对铜、镉离子吸附时包含pH和温度变量的各结合态的平衡模式,运用该模式对同类条件下的金属结合态分布及相对结合能力的变化进行了计算预测。     

还原增溶强化EGTA淋洗修复重金属污染土壤

采用还原剂调控土壤中重金属的活性,旨在强化其对乙二醇双(2-氨基乙基醚)四乙酸(EGTA)洗脱土壤重金属的洗脱效果.分析了EGTA投加量、还原剂类型、液固比、淋洗时间等对土壤重金属的影响,以及不同淋洗条件下土壤重金属浸出浓度与化学形态的差异,采用SEM-EDS和FTIR对处理前后土壤样品进行表征.结果表明,硫代硫酸钠(Na_2S_2O_3)可显著提高EGTA对重金属的洗脱率,当液固比为7.5∶1、淋洗时间为2 h、EGTA与Na_2S_2O_3投加量均为5 g·L~(-1)时,Cu、Zn、Pb和Cd洗脱率分别达85.0%、 60.7%、 88.6%和66.4%.与EGTA单独处理相比,EGTA/Na_2S_2O_3联合处理后, 4种重金属的浸出浓度均降低,Pb的降幅最大,土壤颗粒变小,团粒结构被破坏,O和Al含量减少,Si含量增加,降低了土壤矿物组分的吸附性;土壤有机质含量大幅降低,—OH振动显著减弱,配位能力较强的有机官能团减少,降低了土壤有机组分的吸附性.土壤中吸附性较强组分含量的降低是Na_2S_2O_3强化EGTA洗脱重金属的重要机制.     

原子荧光法测总悬浮颗粒物中的镉

通过选择最优消解体系,尽可能提取总悬浮颗粒物TSP滤膜上所含的重金属元素,并选定适宜的基体改进剂、仪器工作条件等,研究了用原子荧光光谱法测定TSP中重金属镉的方法。实验表明,高浓度的硼氢化钾溶液和加入一定量的焦磷酸钠能有效地排除铜、铅带来的干扰,在载流中加入含Co2＋的溶液,对镉的荧光强度有较好的增感效应,能有效提高镉的测定灵敏度和重复性。本法简单、灵敏、准确,精密度和准确度均在可靠范围内。     

稻草生物炭对土壤中Cd2+和Pb2+的吸附特性

为了探究稻草生物炭对土壤中重金属Cd2+和Pb2+的吸附机制,采用水稻秸秆在500℃下热解制备稻草生物炭,设置不同吸附时间、Na+和Ca2+离子强度、pH等影响因素,拟合稻草生物炭对重金属的吸附动力学、吸附等温线;在此基础上,采用黄沙模拟土柱试验得出稻草生物炭固定Cd2+和Pb2+的穿透曲线,着重分析比较pH和Na+离子强度对稻草生物炭吸附固定重金属的影响.结果表明:在高pH、低离子强度下,稻草生物炭对重金属的吸附效果较好;当pH为6时,稻草生物炭对Pb2+、Cd2+的吸附效率分别为92.58%、63.36%;当离子强度为10 mmol/L时,稻草生物炭对Pb2+、Cd2+的最高吸附效率分别为97.58%、68.35%;准二级动力学模型能很好地拟合稻草生物炭对Pb2+、Cd2+的吸附规律,拟合系数（R2）均大于0.995 8,表明稻草生物炭吸附速率主要由化学吸附机制决定;此外,稻草生物炭对Pb2+的吸附规律适合采用Langmuir等温吸附模型进行描述,而对Cd2+的吸附规律采用Langmuir和Freundlich等温吸附模型均能进行很好的模拟,表明稻草生物炭对Pb2+的吸附是近似单分子层吸附,而对Cd2+的吸附存在多分子层吸附.由黄沙土柱模拟试验结果得出,稻草生物炭对Pb2+和Cd2+的滞留率随着pH的升高和离子强度的降低而增强.在Pb2+和Cd2+同时存在条件下,当pH为6、离子强度为1 mmol/L、稻草生物炭按黄沙质量的0.5%投加时,稻草生物炭对土柱中Pb2+、Cd2+的滞留效果最好.研究显示,高pH对稻草生物炭吸附固定重金属起到促进作用,而高离子强度对稻草生物炭吸附固定重金属起到抑制作用.      

利用网格采样法比较潮间带沉积物不同粒度区域重金属含量特征

采用网格采样法,在渤海湾潮间带泥质区、泥沙过渡区和粉沙区分别以10 m和1 m为间隔,采集了384个表层沉积物样品,对Al、Fe、Ti、Mn、Ba、Sr、Zn、Cr、Ni、Cu 10种重金属含量特征进行研究,对比了潮间带不同粒度沉积物中重金属的蓄积特征.结果表明,10种重金属在淤泥、泥沙混合、粉沙3种研究区的总含量分别为147.37、98.68和94.27 g·kg-1,粒度变化造成重金属含量的显著分异;除Ba、Sr倾向在富含长石的粗颗粒区富集外,多数重金属元素呈现细颗粒区富集倾向;Sr含量受粒度变化影响最大,而Cr、Ti含量受粒度变化影响相对较小.     

羟基镁铝复合物对于水体中镉的去除研究

近年来,由于受到各种工业废水和固体废弃物的影响,使得水体中的重金属含量不断上升,镉污染就是受关注度较高的一种重金属污染,居民若长期食用含镉稻米或含镉水,会引发骨痛病,严重时还会危害人体生命健康。羟基镁铝复合物是在强化混凝过程中形成的,是一种较好的复合材料,能够有效去除水体中的镉。本次主要研究这种材料对于Cd离子的去除效果,可以得出如下结论：pH、混凝剂Al13是较关键的影响因素,这些因素均影响着羟基镁铝复合物的形成情况以及其对于Cd离子的去除效果。通过一些表征说明,镁铝复合物的形态呈无定形,比表面积较大,成分也较复杂,并且在一定pH保证下,聚合度较高的Al13形成复合物的颗粒较大,对于Cd离子的去除起到积极的促进作用。     

青霉菌和镰刀菌对重金属Cd~(2+)、Cu~(2+)、Zn~(2+)和Pb~(2+)的吸附特性

研究了青霉菌和镰刀菌对重金属Cd2+、Cu2+、Zn2+和Pb2+的吸附特性,探讨了复合重金属和不同培养基对菌株吸附能力的影响.同时,采用察氏液体培养基(CDM)和马铃薯葡萄糖培养基(PDB)接种菌株,对不同种类和浓度的重金属进行吸附实验.结果表明,青霉菌和镰刀菌对Cd2+、Cu2+和Zn2+的吸附率随金属浓度的升高而下降,吸附量随金属浓度的增加先增大后减小;当浓度增加到较高值(300mg·L-1)时,Pb2+的吸附率开始下降,吸附量先逐渐增加后变化不大.菌丝体对重金属的吸附能力表现出一定的差异性,对Pb2+的吸附率和吸附量明显高于其他3种金属,CDM培养青霉菌对300mg·L-1Pb2+的最大吸附量达到34.80mg·g-1.多种重金属的复合抑制了菌丝体对重金属离子的吸附.不同菌丝体对复合重金属的吸附量差异性较大,PDB培养混合菌体对重金属离子的吸附率和吸附量均较大,并有明显的促进作用.CDM培养菌丝体对Pb2+的吸附量均高于PDB培养菌丝体.     

焚烧飞灰卫生填埋共处置的螯合稳定化技术研究

对4种垃圾焚烧飞灰的性质进行了分析,其主要元素以Si、Ca、Al、Cl等为主,此外还含有相当数量的重金属如Pb、Zn、Cu、Cr、Cd等,存在很大的环境风险.而飞灰进入卫生填埋场进行共处置是现实可行的出路,为保证共处置的安全性,针对共处置情景制订的浸出毒性浸出方法提高了浸取液酸强度(0.3 mol·L-1,以H 计),此浸出方法已于2007-05-01日开始执行.采用二硫代氨基甲酸盐(dithiocarbamate)类螯合剂对焚烧飞灰进行了稳定化处理工艺实验,结果表明,DTC类螯合剂通过螯合反应作用于飞灰中的重金属,当DTC类螯合剂投加量为3%(质量分数)时,4种飞灰中重金属的浸出值均能达到在卫生填埋场和垃圾进行共处置的要求.     

A porous biochar supported nanoscale zero-valent iron material highly efficient for the simultaneous remediation of cadmium and lead contaminated soil

Risk associated with heavy metals in soil has been received widespread attention.In this study,a porous biochar supported nanoscale zero-valent iron（BC-nZVI） was applied to immobilize cadmium（Cd） and lead（Pb） in clayey soil.Experiment results indicated that the immobilization of Cd or Pb by BC-nZVI process was better than that of BC or nZVI process,and about 80% of heavy metals immobilization was obtained in BC-nZVI process.Addition of BC-nZVI could increase soil pH and organic matter（SOM）.Cd or...     

磺胺二甲基嘧啶对镉在针铁矿上吸附行为的影响

环境中抗生素与重金属的共存会使各自在土壤中的迁移转化和生态效应变得更为复杂,为了准确评估磺胺二甲基嘧啶(SMT)与重金属镉复合污染下的环境风险,采用紫外光谱法,研究了中性条件下磺胺二甲基嘧啶与镉的络合特性;采用批量振荡吸附平衡法,研究了SMT存在的条件下针铁矿对镉的吸附特性.结果表明:SMT与镉有一定的络合能力,络合常数log K值为-3.31;针铁矿对SMT和镉都有一定的吸附作用;在SMT存在条件下,针铁矿对镉的吸附容量明显增强,这可能是由于SMT改变了针铁矿表面带电情况,红外结果表明在吸附过程中形成了针铁矿-SMT-镉三元络合物.因此,在评估抗生素与重金属复合污染的环境影响时,需要考虑到污染物之间的协同效应.     

贵州砂页岩母质黄壤镉吸附及表面络合模型研究

重金属在土壤中的吸附行为受土壤表面酸碱性质的影响. 贵州酸性黄壤镉(Cd)污染形势严峻,研究黄壤中Cd的吸附特征及形态变化对镉的防控和治理具有重要意义. 本文以贵州省百花湖镇不同深度的砂页岩母质黄壤为供试土壤,基于连续酸碱电位滴定试验,利用1-site/2-pK_a表面络合模型(SCM),探讨土壤表面酸碱性质;基于不同pH下黄壤Cd吸附试验,运用SCM模拟Cd的吸附行为及其形态分布;同时解析黄壤组成与表面酸碱性质的相关性. 结果表明:①SCM计算所得腐质层(0~45 cm)、淋溶层(>45~57 cm)、淀积层(>57~81 cm)、风化层(>81~110 cm)、母质层(>110~183 cm)土壤表面位点浓度(H_s)随深度的增加大致呈下降趋势,各层H_s分别为0.120、0.090、0.097、0.056、0.055 mol/L,而电荷零点(pH_pzc,SCM)变化趋势与之相反,分别为4.83、4.71、4.61、4.96、4.98,pH_pzc,SCM与试验测定数据(pH_pzc,M)接近且变化趋势一致,说明1-site/2-pK_a SCM适用于黄壤的表面酸碱性质研究. ②Cd吸附试验表明,随pH的增加,Cd从溶解态逐渐转向吸附态,并在pH=7附近达到完全吸附;SCM拟合得到的不同pH下Cd的溶解态和吸附态浓度与吸附试验数据吻合良好(相关系数R≥0.995),且Cd的吸附行为与不同pH下黄壤表面位点3种形态(≡SOH₂+、≡SOH、≡SO?)分布的模拟结果一致,≡SOH₂+、≡SO?分别为pHpzc、pH>pH_pzc时的主要形态,揭示了黄壤表面酸碱性质对Cd吸附行为的影响机制,进一步说明SCM适用于描述Cd随土壤pH变化的吸附特征. ③相关性分析表明,有机质、游离氧化铁对H_s起主要作用,不同深度土壤的电荷零点(pH_pzc)则主要由土壤中的黏土矿物、石英等无机胶体控制. 研究显示,利用1-site/2-pK_a SCM可以准确描述贵州省酸性黄壤的表面酸碱性质以及Cd的吸附特征及其形态分布,可为重金属在土壤中的迁移转化行为研究提供新思路.      

Risk assessment of heavy metal contaminated soil in the vicinity of a lead/zinc mine

Heavy metal contamination of soils through anthropogenic activities is a widespread and serious problem confronting scientists and regulators throughout the world. In this study we investigated the distribution, chemical species and availability of lead, zinc, cadmium and copper in nine surface（0 to 20 cm） soils from near an abandoned lead/zinc mine tailings located in Shaoxing, Zhejiang, China. Total heavy metal contents ranged from 5271 to 16369 mg/kg for Pb, 387 to 1221 mg/kg for Zn, 3.0 to 9.3 mg/kg for Cd and 65 to 206 mg/kg for Cu. In general, all heavy metals exceeded China National Standards for Soil Environmental Quality of Heavy Metals by a factor of 3-65 times. Comparison of the heavy metal concentrations（Pb, Zn, Cd and Cu） with clay content revealed a strongly significant relationship while significant relationship（ P 〈 0.001 ） was also obtained between Cd ＋ Zn and Pb ＋ Cu. Solid phase speciation of the soils using Tessier procedure showed that the heavy metals were distributed in the order： residual 〉〉 organically complexed-Fe-Mn oxides occluded 〉 carbonate bound 〉 exchangeable 〉 water soluble. In the organic matter fraction, the ratio of Pb（29.1% ） to its total concentration in the soils was higher than those of Zn（4.70% ）, Cd（3.16% ） and Cu（9.50% ）. The percentages of the water soluble and the exchangeable fractions of Pb（1.80% ） and Cd（2.74% ） were markedly greater than those of Zn（0.10% ） and Cu（0.15% ）, suggesting that Pb and Cd are relatively more mobile and hence more toxic in the contaminated soils. Strongly significant relationships between H20-Pb, H20-Zn and H20-Cu, strong positive correlations between H20-Pb, H20-Zn, H20-Cu and organic matter in soil were found. The content of H20-Pb, H20-Zn, H20-Cu was negatively correlated with pH values. The similar negative relationships between pH values and exchangeable heavy metals were also recorded. It is suggested that increasing soil pH or liming the soil could decrease bioavailability of heavy metals in the soil.     

酸雨、土壤酸化与森林衰亡

本文主要综述酸雨通过土壤酸化导致森林衰亡方面的国外最新研究进展。对于森林衰亡的原因目前主要有几种假说:综合胁迫;土壤的酸化——铝毒害;气态污染物（SO2,O3）;酸雨——镁亏缺和过量营养物铵/氮沉降等。这些假说都有一定的事实依据,并直接或间接涉及酸雨问题。酸雨在很大程度上是通过土壤——植物系统间接危害森林的。长期持续的酸雨输入导致土壤酸度升高,减少可利用态磷,降低有机质的分解速率,抑制氮的矿化作用;土壤酸度升高使钙、镁等离子易被淋失造成营养元素亏缺,溶出铝和某些重金属离子毒害植物。      

Removal of heavy metals through adsorption using sand

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