过氧化氢对铬在黄棕壤中电动过程的影响

研究了在阳极池中添加过氧化氢对铬在黄棕壤中电动过程的影响。结果发现:经过约564h的电动处理后,土壤中六价铬的含量显著减少,最高去除率为91.6%,同时总铬去除率最高达39.6%。过氧化氢的存在对电流的影响不大,但明显降低了电渗流量。加入过氧化氢引起土壤中部分六价铬被还原成三价铬,降低了土壤中铬的移动性,从而使总铬的去除率减少,说明土壤中还原性物质的存在将不利于铬的去除。     

重金属-有机复合污染土壤的电动强化修复研究

许多污染场地都呈现重金属和有机污染物叠加的趋势,给修复带来了困难和挑战。以红壤为供试土壤,以铜和芘为代表性污染物,研究了添加表面活性剂羟丙基-β-环糊精（HPCD）和氧化剂H2O2对电动修复该复合污染土壤的影响,其目的是实现重金属和有机污染物的同时去除。结果表明,在所有的处理中,芘和铜都有向阴极迁移的趋势;当提高土柱的pH时降低了芘的氧化和降解,同时也阻碍了土壤中铜的迁移和去除;阳极加10%HPCD,阴极控制酸性条件pH3.5有助于土壤中污染物的解吸和迁移,芘和铜的去除率分别可达到51.3%和80.5%;由于H2O2的不稳定性,添加6%H2O2并未明显提高芘和铜的去除率。     

茶皂素对潮土重金属污染的淋洗修复作用

为了探讨茶皂素淋洗修复土壤重金属污染的可行性,该文采用振荡提取和土柱淋洗的方法,研究了茶皂素对污染土壤中重金属的去除作用。结果表明,茶皂素溶液的浓度和土壤的pH值对重金属去除率有明显影响。土柱淋洗试验中,采用质量分数7%茶皂素溶液作淋洗液,pH 5.0±0.1、土液质量体积比1：4为最佳淋洗修复条件,此时,Pb、Cd、Zn、Cu的去除率分别为6.74%、42.38%、13.07%、8.75%,去除率的大小顺序为Cd＞Zn＞Cu＞Pb。茶皂素淋洗能有效去除酸溶态和可还原态的重金属,从而大大降低了重金属的环境风险,同时说明茶皂素用于土壤重金属污染淋洗修复有较大潜力。     

石灰水对混合试剂洗脱土壤重金属淋洗效果的影响

为了探索石灰水对混合试剂(MC)洗脱后土壤中重金属的淋洗效果,对重金属污染土壤进行了盆栽淋洗试验研究。结果表明:石灰水淋洗MC洗脱土壤,淋出液中Cd、Zn、Pb和Cu浓度均显著高于去离子水淋洗MC洗脱土壤,这主要由于石灰水提高土壤pH,释放土壤所吸附的络合态重金属,这种现象在酸性污染土壤中表现更明显。对于酸性污染土壤,可采用MC+石灰水+去离子水依次进行淋洗处理,其Cd和Zn去除率与MC+去离子水+去离子水依次淋洗处理相比提高22.6%和28.8%;对于中性重金属污染土壤,两处理间重金属去除率差异不显著。石灰水淋洗可提高土壤重金属去除率,并提高土壤pH,改善MC洗脱对土壤的酸化,有利于淋洗后土壤的农业利用。     

生物通风法修复柴油污染土壤模拟实验研究

通过生物通风技术修复不同柴油浓度污染土壤的土柱模拟实验,研究了各土柱中土壤总石油烃(total petroleum hydrocarbon,TPH)的去除规律,并对影响柴油去除效果的因素进行了分析,结果表明:①经过3个月的生物通风后,初始柴油浓度为5(柱Ⅰ)、10(柱Ⅱ)、20(柱Ⅲ)、40(柱Ⅳ)g/kg的土柱柴油去除率为ⅡⅠⅣⅢ,柱Ⅱ的修复效果最佳,半衰期为60.05天,TPH最终去除率达65.3%;②挥发和生物降解作用影响土柱中柴油的去除,由于重力引起的向下迁移作用只对柴油在土柱中的空间分布产生影响,三者共同作用决定各土柱不同取样口柴油的去除规律;③在实验过程中,各土柱土壤pH变化不大,初始柴油浓度越高土柱水分损失率越小;有效磷和速效氮含量均有所降低,柱Ⅲ降低率最大,分别为58.27%和31.87%,柱Ⅰ最小;土柱上层土壤中的酶活性要低于下层,过氧化氢酶和脱氢酶活性均呈现出先升高后降低的趋势。实验结果为研究各土柱中柴油的生物降解规律提供了依据。     

生物炭对不同酸化水平稻田土壤性质和重金属Cu、Cd有效性影响

针对南方稻田土壤酸化严重,导致养分流失有毒重金属活化,严重影响稻米质量安全的重大现实问题。以水稻秸秆和谷壳等农业废弃物为原料制备生物炭(分别记为RSC和RHC),研究不同原料生物炭对酸化土壤改良及其对重金属有效性的影响。设置3个生物炭用量(0,20,50 g/kg,分别记为CK、C1、C2),4种土壤酸化水平(pH 4.01,4.25,4.33,4.58,分别记为L1、L2、L3、L4),生物炭与重金属污染土壤共同培养60天后测定土壤pH、全氮、有机质、有效磷、速效钾和有效态Cu、Cd含量。结果表明:RSC对酸化土壤pH的改良效果明显优于RHC,且施炭量越高提高幅度越大,RSC的C2处理使4种酸度水平的土壤pH分别提高了0.68,0.97,1.29,1.71个单位。2种生物炭均能提高土壤的全氮、有效磷、速效钾和有机质含量,其中各施炭处理有机质显著提高,尤以速效钾的增幅最为显著,RSC对4种养分的提高均优于RHC。RHC对土壤有效态Cu含量无显著影响;RSC的C2较C1处理更能降低土壤中有效态Cu含量,使4种酸度水平的土壤分别降低了13.62%,6.57%,4.36%,7.88%。RHC处理的L3、L4土壤中有效态Cd含量显著降低,最大分别降低了13.79%,19.23%。RSC使4种酸度土壤有效态Cd含量最大分别降低了20.00%,25.81%,20.69%,19.23%。相关分析表明,土壤pH与有效态重金属含量呈显著负相关关系。水稻秸秆炭用于改良酸化土壤、降低重金属Cu和Cd有效性的效果更佳,且降低污染土壤中Cd的有效性较Cu好;生物炭对酸化程度越低的土壤pH和有效磷含量的提高以及有效态Cd含量的降低效果较好,而有效态Cu含量的降低效果则在酸化程度越高的土壤中表现更佳;土壤pH是生物炭调控重金属Cu、Cd有效性的主要影响因素。     

镉污染中性土壤伴矿景天修复的硫强化及其微生物效应

田间微区试验研究了施硫(S)处理对中性镉污染农田上伴矿景天镉吸取修复效率、土壤pH、有效态镉(Cd)、有效态硫以及微生物群落变化的影响。结果发现,土壤pH值随时间和硫用量的增加而显著下降,有效态镉和有效态硫随时间和硫用量的增加而显著增加。在360 g/m_²硫处理下,伴矿景天地上部镉浓度为70.9 mg/kg,较不施硫对照(38.3 mg/kg)增加85%,耕层土壤全量镉去除率为19.4%,是对照(10.5%)的1.85倍。施硫处理150天后,土壤Thiomonas和Rhodanobacter细菌相对丰度显著高于试验前土壤和对照处理。本试验结果表明,中性土壤施加适量硫磺不仅可显著提高污染土壤中镉的生物有效性,也可通过调节与硫代谢相关的功能微生物,显著增强镉的植物吸取修复效率。     

改良剂对土壤锌铬及养分有效性的影响

选用5种不同类型的改良剂,对锌铬复合污染的土壤进行试验,分析了不同改良剂对土壤养分及重金属有效态含量的影响.结果表明:各改良剂的施入均改变了土壤pH,其中,过磷酸钙、麦秆及油菜秆降低了土壤pH值,石灰及兔粪提高了土壤pH值.5种改良剂均显著降低了土壤中的锌、铬有效态含量,其中,麦秆(高浓度)处理的土壤有效态锌含量最低,为20.00 mg/kg,较对照降低了53.25%;石灰(高浓度)处理的土壤有效态铬含量最低,为3.18 mg/kg,较对照降低了60.15%.除过磷酸钙和石灰降低了土壤速效钾含量之外,各改良剂处理均显著提高了土壤速效氮、磷、钾含量,其中,兔粪(高浓度)处理的土壤碱解氮含量最大,为124.56 mg/kg,比对照提高了41.51%;过磷酸钙(高浓度)处理的土壤速效磷含量最大,为42 mg/kg,较对照提高了133.33%;麦秆(高浓度)处理的土壤速效钾含量最大,为211.56 mg/kg,较对照提高了136.88%.     

植物间作体系根际修复土壤多氯联苯的效应

以大豆、黑麦草和南瓜为材料,运用盆栽实验,通过3种植物的单作和间作对多氯联苯污染土壤的根际修复效应进行了研究。结果表明,植物不同种植方式均对根际土壤中PCB浓度的降解有促进作用,其中植物单作的去除率比CK提高了10.4%～17.0%,植物间作的去除率比CK提高18.4%～23.9%。南瓜-大豆体系中的大豆根的蓄积浓度显著差异高于其他处理,而与大豆南瓜间作方式下黑麦草根蓄积浓度均比其单作显著提高,大豆-南瓜和南瓜-黑麦草间作系统中的大豆和黑麦草根中PCB蓄积浓度也显著提高（P〈0.05）。各处理间根际土壤的pH、Eh、电导率的差异性规律性不大。相关分析结果表明,根际土壤PCB去除率与植物吸收量呈显著正相关,而与pH、Eh和电导率没有达到显著相关。     

碳酸钙改性滑石施加量对土壤重金属铬的形态影响研究

通过将碳酸钙与滑石按照摩尔比2∶1混合后,在马弗炉中1150℃焙烧2 h后得到改性滑石,然后利用XRD、FTIR和BET对其进行系统表征,最后通过土壤培育实验探讨碳酸钙改性滑石不同施加量(添加量分别为0%、0.5%、1%、2%、3%和4%)对土壤铬形态动态影响效应。结果表明:碳酸钙改性滑石主要物相组成为Ca2Mg(Si2O7)和少量的Ca3Mg(SiO4)2,疏松多孔,平均孔径为18.809 nm,通过FTIR可以观测到明显的特征峰Si-O-Si,改性滑石有效硅含量高达19.09%。施加该材料在土壤中可以通过形成硅酸盐络合物来改变土壤铬的形态,有助于降低土壤中重金属铬的可交换态含量,最大降低幅度能够达到60%以上,并且对碳酸盐结合态有着明显的降低效果,但对铁锰氧化物结合态的影响不大,对于有机物结合态含量同样有着降低的效果。在第60天的时候,施加量为0.5%时,土壤中铬的残渣态含量增加了15%。过量的施加该材料会导致土壤的pH变成强碱性,因此适当的施加该材料有助于改变重金属铬在土壤中的存在形态,有助于降低铬的生物有效性,从而可以治理重金属污染。     

Copper and Chromium Electrodialytic Migration in CCA-Treated Timber Waste

Chromated copper arsenate (CCA)-treated timber waste is hazardous for the environment due to the leakage of copper, chromium as well as arsenic to the soil and the groundwater. The study concentrates on electrodialytic removal of copper and chromium and their migration behavior in the wood chips and sawdust matrix in an applied electric field. The method is based on the movement of the charged particles in the electric field, enhanced by incubation with oxalic acid (2.5% w/w) and various placement of the contaminated waste in the electrodialytic cell area to analyze the distribution of chemicals in the proposed matrix. The method was tested in laboratory scale experiments where the CCA contaminated wood chips and clean sawdust were placed in various places of the cell, i.e., adjacent to the cathode and anode compartments and in the mid-section of the cell. The duration of each experiment was 14 days and the current was kept constant at 40 mA. During the electrodialytic treatment negative copper and chromium compounds were mostly found in the anolyte or accumulated in the anion-exchange membrane. The amount of positive compounds found in the catholyte is negligible. The placement of contaminated chips close to the anode and cathode showed that copper and chromium moved towards the positively charged anode. If placed in the mid section of the cell, significant amount of contaminants remained bound to the wood matrix or slightly migrated towards the anode. To predict the formation of copper and chromium species at certain pH and Eh, the computer-modeling program MTDATA to generate Pourbaix diagrams was used.     

均匀电场下两株多环芳烃降解菌在土壤中的迁移及电动注入

采用电动注入装置,研究了枯草芽孢杆菌和白腐真菌在均匀电场作用下在土壤中的迁移特征,以及这两种微生物电动注入的效果。结果表明,枯草芽孢杆菌和白腐真菌可通过电泳和电渗两种作用在电场下迁移,电泳起主导作用,微生物向阳极迁移为主。在所研究土壤中,微生物的迁移速率分别为：枯草芽孢杆菌13.5cm·d-1,白腐真菌18.0cm·d-1。采用循环混合电解液可使土壤中pH值保持中性,有利于提高微生物的存活。相比于定期变换电场方向,保持电场单向运行可使微生物在土壤中分布更均匀。     

土壤电动修复中电极切换对土壤微生物群落的影响

通过细菌计数和Biolog方法,研究了在3.0V·cm^-1的电压梯度下,不同电场切换周期（24h、5h、10min和1min）对土壤微生物群落的影响。结果表明,电压梯度为3.0V·cm^-1的电场作用能够促进土壤微生物的活性,但会轻微地降低土壤微生物功能多样性,电场切换不能改变这种电场对微生物群落的影响;长时间的电场处理下,电极反应对微生物数量和功能多样性损害严重,切换电场电极能有效消除电极效应,电场电极切换周期≤5h时,可保护电极附近土壤微生物多样性,当切换周期≤10min时,不仅可保护土壤微生物多样性,而且可以保护微生物数量。研究结果说明了电场电极切换能有效降低电极反应对微生物群落的影响,揭示了电场电极切换对土壤微生物群落影响的规律,为电场电极切换方法在污染土壤电动强化生物修复技术中的深化和应用提供理论依据。     

Chromium Removal from Modjo Tannery Wastewater Using Moringa stenopetala Seed Powder as an Adsorbent

An electrokinetic technique was used to remediate As-, Cu-, and Pb-contaminated paddy soil in a real field on a pilot scale. A hexagonal electrode placement with one anode at the center and six cathodes at the vertices of the hexagon was installed in the field. After operation for 4 weeks, the average removal of Pb was 64.9 % in the top layer (0–0.4 m), 81.2 % in the middle layer (0.4–0.8 m), and 66.9 % in the bottom layer (0.8–1.2 m). The removal of As was 28.2 % in the top layer, 43.2 % in the middle layer, and 24.5 % in the bottom layer. The removal of Cu was 17.7 % in the middle layer and was not observed in the other layers. The relatively high removal of Pb might come from the more labile fraction of Pb in soil compared to As and Cu. However, the circulation of anolyte using an alkaline solution to enhance removal of As failed because the electrolyte leaked between the anode and surrounding soil. Effective circulation might enhance the performance of the electrokinetic process.     

淋洗法修复铬渣污染场地实验研究

铬渣污染场地已经列为我国土壤污染重点治理对象,急需修复铬渣污染土壤的关键技术。本文通过室内模拟实验,采用振荡淋洗的方法研究了水、EDTA、EDDS、柠檬酸、草酸、盐酸、磷酸、环糊精和十二烷基苯磺酸钠等淋洗剂对铬渣污染场地Cr的淋洗效果,探讨了淋洗剂浓度、淋洗时间、土水比、淋洗次数等对淋洗效果的影响,并研究了不同淋洗剂复合对Cr的淋洗效果以及不同浓度柠檬酸淋洗前后重金属形态的变化。结果表明：水、EDTA、EDDS、环糊精和十二烷基苯磺酸钠对Cr的去除率较低,柠檬酸在浓度为0.5mol·L-1、土水比1：20、反应时间为24h、淋洗次数为2次的条件下可以达到最佳淋洗效果,Cr的去除率可达到82.8%;SDBS、EDTA与柠檬酸单独组合顺序或者混合淋洗,都没有增加柠檬酸对Cr的去除率。重金属形态分析表明,柠檬酸淋洗有效地改变了Cr的形态从而达到较高的修复效果。当柠檬酸浓度小于0.25mol·L-1时,对铬的去除主要以C（rⅥ）为主;当柠檬酸浓度大于0.25mol·L-1时,对铬的去除主要以C（rⅢ）为主。本文的研究结果为异位淋洗修复铬渣污染土壤提供理论依据。     

陡坡林地加速侵蚀的水动力学及能耗机制研究

利用野外原位模拟降雨试验,对陡坡林地加速侵蚀下的薄层水流水力学参数和能耗特征进行了研究。结果表明,林地原状延缓径流作用显著,流速维持在0.05～0.09m/s,加速侵蚀后流速均增加,且自上坡面至下坡面有增大的趋势。原状林地处理的雷诺数(Re)为160.8,属于层流;加速侵蚀后坡面Re显著增加,处于层流与紊流之间的过渡流状态。与原状相比,去除枯枝落叶层和除地上部分处理的Re分别增加了114.9%～245.1%和322.2%～1 012.9%,阻力系数(f)分别减少了5.2%～90.6%和42.6%～270.3%;除枯枝落叶层处理的中下段和下段弗汝德数(Fr)均大于1,为急流,坡上和中上段Fr均小于1,为缓流。翻耕处理的径流流速减缓,Re减小;Fr在坡中上、中下段、下段增加了181.6%～72.3%,f减少了41.3%～66.8%,坡上Fr减少了67.3%,但f表现为增加。在降雨初期动能较低,随降雨历时增加呈缓慢上升,最后趋于稳定,且径流势能远大于径流动能。坡面除枯枝落叶层、除地上部分和翻耕加速侵蚀后,坡面能耗增大,侵蚀量与能耗相关性较好。     

A simple and inexpensive method for chromium speciation in soil extracts

Abstract

Chromium (Cr) appears in two stable forms in nature as Cr(III) and Cr(VI). Hexavalent chromium (CrO₄ ^2‐; Cr₂O₇ ^2‐) is very toxic and carcinogenic, while inorganic Cr(III), however, is essential for mammals. Only two methods, atomic absorption and inductively coupled plasma atomic emission (ICP) spectrometry, provide information on the total amount of Cr in a test solution. This is the reason that several efforts have been made with regard to Cr speciation. Either an acidic or a basic activated aluminum oxide and a reversed phase C‐18 column or an ion exchanger column are used for the separation of chromium(III) from chromium(VI) in FIA and HPLC analyses. In our experiments, acidic‐activated aluminum oxide was used for separation. This alumina was placed into a silicon tube and connected to an ICP spectrometer between the nebulizer and peristaltic pump. The average grain size of the alumina was large enough that the solution could be pumped through the micro column. Acidic‐activated aluminum oxide in the 2.0 to 8.0 pH range adsorbs the chromate anion but not the Cr(III) cation. During this stage, the Cr(III) content of a sample is measurable. The adsorbed chromate can be eluted with a strong acid. The height or area of the elution peak can be used for the calibration of Cr(VI). Detection limits of 4 μg/kg and 0.5 μg/kg were obtained for Cr(III) and Cr(VI), respectively. The effects of sulphate and phosphate anions on the surface of the alumina on chromate adsorption were also evaluated. This method was used for the measurement of Cr(VI) concentration by 0.01M CaCl₂ extraction of soil.     

Kinetic Study of the Effect of pH on Hexavalent and Trivalent Chromium Removal from Aqueous Solution by <Emphasis Type="Italic">Cupressus lusitanica</Emphasis> Bark

Solution pH is among the most important parameters that influence heavy metal biosorption. This work presents a kinetic study of the effects of pH on chromium biosorption onto Cupressus lusitanica Mill bark from aqueous Cr(VI) or Cr(III) solutions and proposes a mechanism of adsorption. At all assayed contact times, the optimum pH for chromium biosorption from the Cr(III) solution was 5.0; in contrast, optimum pH for chromium biosorption from the Cr(VI) solution varied depending on contact time. The kinetic models that satisfactorily described the chromium biosorption processes from the Cr(III) and Cr(VI) solutions were the Elovich and pseudo second-order models, respectively. Diffuse reflectance infrared Fourier transform spectroscopy studies suggest that phenolic compounds present on C. lusitanica Mill bark play an important role in chromium biosorption from the Cr(III) solution. On the other hand, chromium biosorption from the Cr(VI) solution involved carboxyl groups produced on the bark by redox reactions between oxygen-containing groups and Cr(VI), and these were in turn responsible for the biosorption of Cr(III) produced by Cr(VI) reduction.     

Removal of Heavy Metals from Soils using Enhanced Electrokinetic Soil Processing

In order to remediate contaminated land, a new process of electrokinetic purging of heavy metals from saturated soil is examined by laboratory experiments. Electrokinetic soil remediation is one of the most promising soil decontamination processes as it has high removal efficiency and time-effectiveness in low permeability soils such as clay. Being combined with several mechanisms-electromigration, electroosmosis, diffusion and electrolysis of water, electrokinetic soil processing can remove non-polar organics as well as ionic contaminants. This study suggests that the removal efficiencies for Pb and Cd are significantly influencedby applied voltage and current, type of purging solutions, soilpH, permeability and zeta potential of soil. The removal efficiencies for Pb and Cd were 75–85% for the kaolinite soil and 50–70% for the tailing soil over the duration of 4 days. For heavy metals, their adsorption capacities on the soil surface and mobilities in soil have significant effects on the removal efficiency.     

Cosolvent-enhanced Desorption and Transport of Heavy Metals and Organic Contaminants in Soils during Electrokinetic Remediation

Numerous sites are contaminated with both heavy metals and polycyclic aromatic hydrocarbons (PAHs) and the technologies to treat such mixed contaminants are very limited. Electrokinetic remediation has the potential to remediate mixed contaminants in soils, including low permeability soils; however, the efficiency of this technology depends on the extracting solution employed. Previous studies on electrokinetic remediation have focused on the removal of heavy metals and organic compounds when they exist individually in clayey soils. In the present study, the feasibility of using cosolvents to enhance the electrokinetic removal of PAHs from clayey soils in the presence of heavy metals is investigated. A series of laboratory electrokinetic experiments was conducted using kaolin soil spiked with phenanthrene and nickel at concentrations of 500 mg/kg each to simulate typical field mixed contamination. Experiments were performed using n-butylamine (cosolvent) at concentrations of 10 and 20% and deionized water, each mixed with 0.01 M NaOH solution and circulated at the anode to maintain alkaline conditions. A periodic voltage gradient of 2 VDC/cm in cycles of 5 days on and 2 days off was applied in all the tests. During the initial stages when the soil pH was low, nickel existed as a cation and electromigrated towards the cathode. However, as the soil pH increased due to hydroxyl ions generated at the cathode and also flushing of high pH n-butylamine solution from the anode, nickel precipitated with no further migration. Phenanthrene was found migrating towards the cathode in proportion to the concentration of n-butylamine. The extent of phenanthrene removal was found to depend on both the electroosmotic flow and the concentration of n-butylamine, but the presence of nickel did not influence the transport and removal of phenanthrene.