乙醇对过硫酸盐氧化地下水中苯系物的影响

过硫酸盐已经被广泛用于土壤和地下水有机污染物的原位化学氧化修复。随着乙醇汽油的推广,乙醇汽油引起的地下水污染问题越来越严重,因此有必要去除该类污染物。前人研究乙醇汽油污染修复多数停留在自然修复技术,为了进一步探究去除地下水中乙醇汽油更为有效的技术手段,深入了解乙醇对降解苯系物（BTEX）存在的潜在风险,需要研究使用新的修复方法。文章通过批实验探索了过硫酸盐氧化法对乙醇汽油污染地下水的修复效果,以及Fe2+活化和过硫酸盐添加方式变化对乙醇汽油中苯系物（BTEX）和乙醇的去除影响。结果表明:活化后的过硫酸盐能够有效去除地下水中的BTEX,但会抑制BTEX的生物降解作用;当有乙醇存在时,过硫酸盐能够优先氧化BTEX,其去除速率明显高于乙醇,这与单纯生物降解作用相反。在过硫酸盐投注总量一定时,分批添加更有利于BTEX的去除,但对乙醇去除没有明显促进作用。该研究为过硫酸盐原位化学氧化技术在地下水乙醇汽油污染修复中的应用提供了重要参考。     

酚污染地下水化学氧化修复技术进展

酚类化合物属于优先控制的有机污染物之一,开展酚污染地下水原位修复方法的研究具有重要的现实意义。化学氧化是目前处理酚污染地下水的有效方法,常用的化学氧化方法包括:Fenton氧化过硫酸钠活化氧化臭氧氧化。本文系统综述了修复酚污染地下水各种氧化技术的机理影响因素修复效果适用范围优缺点,并提出在低渗透性土层深度污染时,化学氧化、增溶淋洗、电动修复技术的联合是发展方向。     

膨润土负载纳米铁镍同步修复地下水中三氯乙烯和六价铬复合污染

纳米零价铁原位注射修复地下水污染是近年发展的新技术,以往研究多侧重于单一目标污染物的去除效果及作用机理,但是地下水多种污染物共存问题不容忽视。本文针对典型污染物三氯乙烯TCE和六价铬Cr(Ⅵ),运用合成的活性高、稳定性强的膨润土负载纳米铁镍(B-Fe/Ni)开展修复实验,研究B-Fe/Ni对TCE和Cr(Ⅵ)共存复合污染的修复效果及其作用机制。通过一步法合成B-Fe/Ni,对TCE和不同浓度Cr(Ⅵ)混合污染的去除进行试验研究,对反应前后的样品B-Fe/Ni进行表征,并跟踪反应过程中TCE和Cr(Ⅵ)的浓度变化。结果表明:B-Fe/Ni同步去除水中TCE和Cr(Ⅵ)快速高效,50 mg/L Cr(Ⅵ)在2 h内能被B-Fe/Ni (1 g/L)完全去除而不受共存TCE(0. 1 mmol/L)的影响,然而TCE降解速率会随共存Cr(Ⅵ)的浓度(0、10、30、50 mg/L)增大而降低。经透射电镜-电子能谱及X射线光电子能谱表征验证,这是由于B-Fe/Ni与Cr(Ⅵ)快速反应,生成部分Fe-Cr共沉淀会覆盖B-Fe/Ni表面的活性位点,抑制了TCE的降解,但通过分析TCE降解产物可知,B-Fe/Ni同样能对TCE完全脱氯。因此,B-Fe/Ni适用于地下水复合污染修复,实际应用时需考虑多种污染物共存的相互影响,选择适宜试剂用量和注射方式,这对纳米零价铁修复技术的发展具有重要理论意义和应用参考价值。     

原位淋洗技术修复石油类污染土壤的研究进展

随着石油的大量开采使用,污染土壤问题也越来越严重,如何修复石油污染土壤成为了人们研究的重点也是难点之一。原位淋洗修复方法不需要对污染土壤进行挖掘,能适用于大面积修复。但是,由于天然场地地质条件的复杂性和现今技术水平的限制,该方法还没有广泛的应用于实际修复之中。文章对原位淋洗修复技术的作用机理、适用范围和国内外研究现状做了介绍,探讨了天然含水层的非均质性对该技术修复效果的影响,介绍了3种原位淋洗修复强化技术,并对原位淋洗技术的未来进行了展望。     

电化学循环井驱动模拟含水层化学氧化降解三氯乙烯

传统原位化学氧化地下水修复技术存在氧化剂迁移距离短和利用率低等问题。本研究在双井循环模式促进传质的基础上,通过注水井中的地下水电解原位提供O₂和H₂,配合乙二胺四乙酸(ethylenediamine tetraacetic acid,EDTA)络合溶解出含水层Fe(Ⅱ),活化O₂产生羟基自由基(•OH),实现地下水三氯乙烯(TCE)的氧化降解。在填充了砂土和黏土互层的二维砂槽中,设置电流为0.2 A、流速为72 cm/d、初始TCE浓度为3 mg/L,经过9 d的连续通电处理后,TCE浓度降低到1 mg/L,降解率达到67%。通电前投加0.5 mmol/L EDTA,经过1 d水流循环后含水层中溶解态Fe(Ⅱ)浓度从02 mg/L增加到414 mg/L,黏土区域较高。通电过程中,循环井促进O₂、Fe(Ⅱ)-EDTA和TCE的有效接触与反应,使TCE氧化降解。通电初期,黏土区域Fe(Ⅱ)氧化速率、TCE降解速率较周围慢,后期差异逐渐减小。未通电时加入醋酸钠可促进Fe(Ⅲ)还原,使含水层中铁循环利用。该修复过程通过循环井提升了氧化剂迁移距离,使用源于含水层的Fe(Ⅱ)-EDTA和稳定性较好的O₂提高了氧化剂利用率,有望应用于有机污染地下水修复。     

钒污染土壤地下水的修复技术研究进展

钒是典型的氧化还原敏感元素,其在地壳中储量丰富,又是现代工业中性能优异的催化剂.由于地质风化作用及密集的开采、冶炼、应用等人类活动,导致土壤地下水钒污染日益严重,引起研究者的广泛关注.从物理法、化学法和生物法3个方面,综述了土壤地下水钒污染修复技术的最新研究进展.物理法主要包括改土法和电解法,化学法主要包括化学淋洗、化学吸附及化学还原固定,生物法主要包括植物修复和微生物修复.同时展望了钒污染土壤地下水修复技术的发展趋势,为后续研究提供参考.     

电化学循环井耦合氧化 -还原降解地下水中三氯乙烯

三氯乙烯（TCE）是一种地下水中常见的有机污染物,传统的地下水循环井修复技术虽然有效但耗时长,且需配套地面处理。文章研发了一种电化学循环井耦合修复体系,以期通过顺序化学氧化 -还原作用高效快速降解地下水中TCE。以地下水循环井为基础,通过抽水井中的地下水电解,原位提供O2和H2,投加Fe（Ⅱ） -EDTA络合物活化O2产生羟基自由基氧化降解TCE,进而利用钯催化剂催化剩余的H2还原降解TCE。在二维砂槽模拟含水层中评价了该体系的运行效果,含水层中初始TCE浓度为7.50 mg/L,经过13天的连续通电处理后,TCE浓度降低到1.65 mg/L,降解率达到78%。处理后Cl-浓度相应增加118.20 μmol/L,接近于TCE降解量（44.50 μmol/L）的3倍,证明TCE近乎完全脱氯。运行过程中,TCE平均降解速率由0~5 d的0.90 mg/(L·d) 降低到9~13 d的0.10 mg/(L·d),氧化降解主要发生在前期阶段,钯催化还原效率较为稳定,后期两种过程降解效率都逐渐下降,主要原因是溶解态Fe（Ⅱ）浓度减少以及钯催化剂活性降低。该耦合修复体系是基于地下水循环井技术的改进,其氧化 -还原作用机理有望实现地下水中多种不同有机污染物的降解。     

某废弃煤矿有机污染场地地下水修复治理中试研究

某废弃煤矿竖井经倾倒有机废液,导致环境污染事件,造成巷道及采空区内地下水污染。本文结合场地实际情况,选取倾倒竖井(事故井)及周边区域为中试区域,采用“抽出处理+原位氧化循环”两阶段联合修复技术对污染场地开展中试研究。本文介绍了场地污染概况、地下水修复中试方案设计和实施,以及对修复效果进行评价。结果表明,中试处理后地下水中COD和二氯甲烷最高去除率分别为97.88%和99.74%。中试试验表明, “抽出处理+原位氧化循环”两阶段修复技术,对处理矿区内巷道及采空区等复杂地层结构下深层地下水中有机污染物具有较好的去除效果,可以结合现场实际情形对整个污染场区进行规模应用。     

菱铁矿催化过氧化氢过硫酸钠修复地下水中TCE时对微生物的影响

地下水中存在着一定量的土著微生物,为了了解类芬顿氧化去除地下水中三氯乙烯(trichloroethylene, TCE)时对微生物的影响,实验利用某污水处理厂好氧段活性污泥和水的混合物作为供试微生物,选择菱铁矿催化过氧化氢过硫酸钠的氧化体系,通过监测微生物的FDA(Fluorescein Diacetate,简称FDA)活性、TCE的浓度等指标,揭示该氧化体系对微生物的影响及存在TCE时微生物与TCE的相互影响。研究结果表明,该氧化体系会导致微生物的酶活性丧失,氧化剂体积与含微生物污水体积的比值(V氧∶V污)越大,对微生物的致死率越高。当V氧∶V污=1.2∶1时,即过氧化氢和过硫酸钠的浓度分别为0.1 mol/L和0.004 2 mol/L时,致死率为50%。当存在TCE时,也会导致微生物酶活性的丧失,随着TCE浓度的增加,对微生物的致死率越高。反之,微生物存在时,对该体系修复TCE几乎没有影响。     

地下水修复技术

与地下水的标准“泵抽和处理”方法，或土壤挖掘和治理技术相比，GWRTAC技术致力于原位地下水和土壤修复技术的创新。GWRTAC技术中提到的许多原位修复技术不需要抽出地下水，然而也可提出增强的泵抽和处理方法。GWRTAC修复技术包括这些通过设计和／或应用的修复技术，改善地下水水质，这是净化地下水不可缺少的方法。     

包气带土壤组成对三氯乙烯的吸附影响研究

有机质和矿物质是包气带土壤中的主要吸附介质,其吸附特性直接影响有机污染物在环境中的迁移、转化等过程。分别采用分析纯石英砂和典型粘土矿物高岭石模拟土壤的原生矿物和粘土矿物,利用批实验的方法研究土壤中各组成部分对三氯乙烯(TCE)的吸附行为。土壤有机质的吸附行为通过全土样和矿物质的对比得出。结果表明,粘土矿物是吸附氯代烃的主要矿物质,原生矿物对氯代烃的吸附量很小;土壤有机质含量和土壤吸附量之间有很好的正相关性;土壤有机碳含量与土壤粘土矿物含量的比值是影响吸附行为的另一重要因素,比值越小,Koc值越大,土壤对TCE的亲和力就越强。由于自然界中的土壤有机质大都与矿物质形成有机质-粘土矿物结合体,据此推测有机质-矿物质结合体会影响有机质的组成和形态,从而对其吸附行为有重要作用。     

Field investigation into the biodegradation of TCE and BTEX at a former metal plating works

The paper is based on a recent programme of groundwater monitoring at an industrial site in west London. Redevelopment of the site in 1997 revealed high levels of soil and groundwater pollution by hydrocarbon fuels, trichloroethylene (TCE) and soluble metal salts (e.g. free cyanide, chromium VI and nickel). The pollution originated from a previous metal plating and galvanising works at the site. As part of the redevelopment works, the owners undertook limited excavation works and groundwater extraction to remove the pollutant. However, groundwater sampling has continued to show high levels of pollution. Following discussion with the environment regulator in late 1998, a groundwater monitoring programme was agreed to investigate the potential for co-degradation of the petroleum fuel and TCE. Groundwater samples have been taken from six existing boreholes (1C to 6C). The location of the monitoring boreholes relates to past pollution spillages and the layout of the new factory building. Chemical analyses of groundwater samples show elevated aqueous concentrations of chloroethenes with a classical reduction pathway for trichloroethylene (TCE) leading to an accumulation of vinyl chloride.     

Tritium�Chelium groundwater age used to constrain a groundwater flow model of a valley-fill aquifer contaminated with trichloroethylene (Quebec, Canada)

Tritium?Chelium groundwater dating was carried out in a trichloroethylene (TCE)-contaminated valley-fill aquifer system in Quebec, Canada, where a numerical groundwater flow model was developed. Forty seven discrete groundwater and dissolved gas samples were obtained along two flow paths originating from known TCE source zones whose related plumes converge down gradient to form a single plume. Sampling points in monitoring wells were projected onto vertical sections showing particle tracks along the two flow paths. At these points, simulated advective ages obtained from particle tracking were matched to tritium?Chelium ages using different porosity values; the best match was 0.35. Ages were also obtained above and below a prodeltaic silty aquitard in a portion of the aquifer where some source zones are located, which provide groundwater and TCE transit times through the aquitard as well as a mean vertical hydraulic conductivity that agrees with previous estimates used in the model. In certain locations, anomalously old ages associated with high terrigenic ⁴He indicate areas where groundwater from the underlying proglacial unit flows upward into the deltaic sand aquifer through aquitard windows. Upflow locations correspond with increased TCE concentrations, suggesting significant TCE provenance through the proglacial unit originating from a previously unrecognized TCE source zone.     

地下水三氯乙烯(TCE)生物修复的研究进展

目前三氯乙烯(TCE)引起的环境污染已成为一个非常值得关注的问题。本文通过对国内外TCE生物降解于究进行总结，从降解机理、降解动力学和微生物种类三方面进行了概迷，特别是总结了好氧条件下生物降解TCE取得的显著成果。     

Fate and transport of volatile organic compounds in glacial till and groundwater at an industrial site in Northern Ireland

Volatile organic compound (VOC) contamination of subsurface geological material and groundwater was discovered on the Nortel Monkstown industrial site, Belfast, Northern Ireland. The objectives of this study were to (1) investigate the characteristics of the geological material and its influences on contaminated groundwater flow across the site using borehole logs and hydrological evaluations, and (2) identify the contaminants and examine their distribution in the subsurface geological material and groundwater using chemical analysis. This report focuses on the eastern car park (ECP) which was a former storage area associated with trichloroethene (TCE) degreasing operations. This is where the greatest amount of volatile organic compounds (VOCs), particularly TCE, were detected. The study site is on a complex deposit of clayey glacial till with discontinuous coarser grained lenses, mainly silts, sands and gravel, which occur at 0.45–7.82 m below ground level (bgl). The lenses overall form an elongated formation that acts as a small unconfined shallow aquifer. There is a continuous low permeable stiff clayey till layer beneath the lenses that performs as an aquitard to the groundwater. Highest concentrations of VOCs, mainly TCE, in the geological material and groundwater are in these coarser lenses at ∼4.5–7 m bgl. Highest TCE measurements at 390,000 μg L⁻¹ for groundwater and at 39,000 μg kg⁻¹ at 5.7 m for geological material were in borehole GA19 in the coarse lens zone. It is assumed that TCE gained entrance to the subsurface near this borehole where the clayey till was thin to absent above coarse lenses which provided little retardation to the vertical migration of this dense non-aqueous phase liquid (DNAPL) into the groundwater. However, TCE is present in low concentrations in the geological material overlying the coarse lens zone. Additionally, VOCs appear to be associated with poorly drained layers and in peat <3.0 m bgl in the ECP. Some indication of natural attenuation as VOCs degradation products vinyl chloride (VC) and dichloromethane (DCM) also occur on the site.     

Delineation of recharge patterns and contaminant transport using 3H–3He in a shallow aquifer contaminated by chlorinated solvents in South Korea

Stable isotopes of water and ³H–³He were used to delineate recharge patterns and contaminant transport for a granitic regolith aquifer in an industrial complex in Wonju, South Korea, that has historically been contaminated with chlorinated solvents including trichloroethene (TCE) and carbon tetrachloride (CT). Groundwater recharge mainly occurred in upgradient forested areas while little recharge occurred in the downgradient industrial areas covered with extensive sections of impermeable pavement and paddy fields. δ¹⁸O and δD data indicated that groundwater was mainly derived from summer precipitation. The apparent groundwater ages using ³H–³He ranged from 1 to 4 yrs in the upgradient area and from 9 to 10 yrs in the downgradient area. Comparison of groundwater flow velocities based on Darcy’s law and those calculated with simple mass balance models and groundwater age supported the presence of preferential pathways for TCE movement in the study area. Measureable TCE was observed in groundwater irrespective of groundwater age. Considering the 3-yr duration of the TCE spill, 14 yrs before sampling, this indicates that TCE plumes were continuously fed from sources in the unsaturated zone after the spill ended and moved downgradient without significant degradation in the aquifer.     

Impact of iron sulfide transformation on trichloroethylene degradation

Trichloroethylene (TCE) is one of the most common and persistent groundwater contaminants encountered at hazardous waste sites around the world. A growing body of evidence indicates that iron sulfides play an important role in degrading TCE in natural environments and in engineered systems designed for groundwater cleanup. In this study, we investigate transformation processes of iron sulfides and consequent impacts on TCE degradation using batch experimental techniques, transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). Our results show that mackinawite is highly reactive toward TCE and no detectable mineralogical changes were detected during the course of reaction. However, freeze-dried FeS transformed to a mixture of mackinawite and greigite during the freeze drying process, with further mineralogical changes during reaction with TCE to lepidocrocite, goethite and pyrite. Newly formed lepidocrocite is a transient phase, with conversion to goethite over time. TCE transformation kinetics show that freeze-dried FeS is 20-50 times less reactive in degrading TCE than non-freeze-dried FeS, and the TCE degradation rate increases with pH (from 5.4 to 8.3), possibly due to an increase of surface deprotonation or electron transfer at higher pH. Results suggest that freeze drying could cause FeS particle aggregation, decreased surface area and availability of reactive sites; it also could change FeS mineralogy and accelerate mineral transformation. These aspects could contribute to the lower reactivity of freeze-dried FeS toward TCE degradation. Modeling results show that FeS transformation in natural environments depends on specific biogeochemical conditions, and natural FeS transformation may affect mineral reactivity in a similar way as compared to the freeze drying process. Rapid transformation of FeS to FeS₂ could significantly slow down TCE degradation in both natural and engineered systems.     

硝酸根对颗粒状铁降解三氯乙烯的影响(英文)

为研究硝酸根对颗粒状铁降解三氯乙烯的影响,进行了柱实验和相应的反应铁腐蚀电位测定。在硝酸根离子存在条件下,铁的腐蚀电位相应升高,系统条件也因之发生变化,导致钝性的铁氧化物在铁表面生成。因而,三氯乙烯和硝酸根离子降解速率明显减小, 并且降解速率减小的程度与硝酸根离子的浓度成比例。当污染液流过反应柱时,硝酸根离子与铁反应, 被还原为氨根离子。该反应造成硝酸根离子的浓度梯度,使钝化区在柱中上移,从而影响了三氯乙烯的降解曲线。与三氯乙烯单独与铁反应相比,当含4 7 mg/L硝酸根的三氯乙烯溶液流经反应柱170 孔隙体积后,降解50% 三氯乙烯所需的时间(t50) 从小于4 h增加到大于10 h;而当三氯乙烯溶液中加入100 mg/L硝酸根离子,仅17 孔隙体积溶液流经反应柱后,三氯乙烯降解t50就已大于14 h。研究结果表明,由于硝酸根离子对铁的腐蚀电位和铁表面氧化膜的不利作用,在处理靶污染物为高浓度硝酸根离子和三氯乙烯共同污染的地下水时,铁渗透反应隔栅不是最佳选择。如果靶污染物中硝酸根离子浓度比较低,则在设计铁隔栅时应考虑到硝酸根离子造成的不利因素,相应增加铁墙的厚度,从而确保三氯乙烯的降解效果。