【作者】 刘运德；

【导师】 周爱国； 甘义群；

【作者基本信息】 中国地质大学 ， 环境科学与工程， 2013， 博士

【摘要】 近几十年来,受人类活动的影响,土壤和地下水系统中氯代烃等有机污染问题日益突出,开展氯代烃的地下环境行为及其原位修复研究,是环境科学领域的研究热点。然而,如何准确量化污染物降解效果和验证修复方法的有效性,是土壤和地下水污染原位修复研究中亟待解决的关键问题。同位素分析为解决该问题提供了一种有力工具,其应用的关键参数和前提条件是确定和表征污染物转化过程的同位素富分馏(即同位素富集系数ε)及其影响因素。为了更好地发挥同位素分析在环境科学领域中的应用,需要不断完善不同转化过程(或降解途径)的同位素分馏数据库。矿物催化Fenton-like反应降解有机污染物是土壤-地下水污染修复中极具前景的原位修复技术。土壤和含水层中广泛存在的天然含铁矿物,能够催化Fenton-like反应有效地降解土壤和地下水中难降解性有机污染物,而无需向污染场地额外添加可溶性铁,其亦可以用于原位构建Fenton-like反应渗透性反应墙(PRB)。此外,Fenton-like反应原位修复过程中,释放的氧气可以提供电子受体强化好氧微生物降解。矿物催化Fenton-like反应降解有机污染物的研究,不仅极大地丰富了环境矿物学和原位化学氧化修复技术,还有助于促进环境、化学、地质、矿产资源综合利用等学科的交叉渗透。然而,国内外目前关于Fenton-like反应降解氯代烃过程的碳、氯同位素分馏研究尚未涉及。因此,本文针对“如何准确有效地评价土壤和地下水污染原位修复效果”这一关键科学问题,率先系统开展了Fenton-like反应降解三氯乙烯(TCE)过程的碳、氯同位素分馏研究,为定量评价Fenton-like反应原位修复方法的有效性和适用性提供了新思路和关键技术参数。论文主要研究目标是：表征Fenton-like反应降解TCE过程的碳氯同位素分馏并揭示其分馏机理；揭示Fenton-like反应降解TCE过程中碳氯同位素分馏的影响因素；评价碳氯同位素分析量化Fenton-like反应原位修复效果的不确定性影响。论文主要研究内容和思路是：首先建立了TCE含量及其碳氯同位素测试方法,为后续开展Fenton-like反应降解三氯乙烯(TCE)过程的碳氯同位素分馏研究提供技术手段。之后研究了Fenton-like反应降解TCE的反应动力学特征,为后续开展Fenton-like反应降解TCE过程的碳氯同位素分馏研究提供实验基础。在此基础上,利用碳氯同位素分析技术,结合同位素分馏理论和前人关于其它降解过程的同位素分馏研究,分别开展了Fenton-like反应降解TCE过程的单体碳同位素分馏、二维碳氯同位素分馏研究。然后进一步揭示了环境因素(NO3-、SO42-、Cl-和腐殖酸)对该降解过程的碳氯同位素分馏的影响。最后,基于上述研究表征的碳氯同位素分馏,评价了碳氯同位素分析量化Fenton-like反应原位修复效果的不确定性影响。研究得出以下结论：(一)表征了Fenton-like反应降解TCE过程(Cl-<0.2M)的碳氯同位素分馏并揭示了其分馏机理：(1) Fenton-like反应降解TCE过程产生显著碳氯同位素分馏,其碳氯同位素富集系数的平均值分别为εC=-3.0±0.2‰和εCl=-1.04～0.1‰。Fenton-like反应降解TCE过程的碳氯同位素分馏,显著不同于零价铁和微生物还原脱氯降解过程。这主要是由于降解过程的反应机理截然不同,其中Fenton-like反应降解TCE过程的限速反应阶段是碳-碳双键(C=C键)断开为碳-碳单键(C-C键),而还原脱氯降解过程的限速反应阶段是碳-氯键(C-Cl键)断开。(2)尽管具有相似的反应机理,即限速反应阶段均是将TCE碳-碳双键(C=C)断开为碳-碳单键(C-C),但是磁铁矿催化Fenton-like反应降解TCE过程的碳同位素分馏,显著小于高锰酸钾和好氧微生物G4氧化降解过程的碳同位素分馏。磁铁矿催化Fenton-like反应与均相溶液中Fenton反应降解TCE过程的碳同位素分馏大小一致,这表明该降解过程的碳同位素分馏不受“催化胁迫”影响。Fenton-like反应降解TCE过程的碳同位素分馏相对较小,可能与该降解过程中限速反应阶段的过渡态结构有关,这有待于利用量子化学计算等手段进一步研究。(3)对于Fenton-like反应降解TCE过程的碳氯同位素分馏,其表观动力同位素效应的平均值分别为AKIEC=1.0030±0.0002和AKIECl=1.0010±0.0001。氯同位素分馏属于次级动力同位素效应,这符合Fenton-like反应降解TCE过程中C=C键断开成C-C键为限速反应阶段的预期反应机理。(4)同一元素的次级动力同位素效应一般比其主级动力同位素效应至少要小一个数量级。羟基自由基(HO·)降解有机污染物存在夺氢反应、电子迁移和加成反应三种可能的反应机理。对于Fenton-like反应降解TCE过程,如果限速反应阶段是C-H键断开,其产生的氯同位素分馏的相应表观动力同位素效应(AKIECl)为1.003(即AKIECl-1=0.003),是主级动力同位素效应(KIECl=1.013,即KIECl-1=0.013)的四分之一,其不符合次级动力同位素效应。因而夺氢反应对于Fenton-like反应降解TCE过程不成立。如果其反应机理是电子迁移或加成反应,其限速反应阶段C=C键断开为C-C键产生的的氯同位素分馏的相应表观动力同位素效应(AKIECl)为1.001(即AKIECl-1=0.001),是主级动力同位素效应(KIECl=1.013,即KIECl-1=0.013)的十三分之一,符合次级动力同位素效应。(5)对于Fenton-like反应降解TCE过程的碳氯同位素分馏,其二维碳氯同位素组成的相对变化(Λ)的平均值为0.348±0.049,相应的碳氯同位素富集系数比值(εCJ/εC)的平均值为0.349±0.057。对比零价铁还原脱氯TCE过程的碳氯同位素富集系数比值(εCl/εC=0.238),二者存在显著差异。这两种反应机理完全不同的降解过程,具有不同的二维碳氯同位素组成的相对变化(或碳氯同位素富集系数比值),表明碳氯同位素组成的相对变化(Λ)具备识别不同降解过程(或反应机理)的应用潜力。为了更好地发挥二维碳氯同位素组成的相对变化(Λ)的应用潜力,需要进一步研究其他降解过程(或反应机理)的二维碳氯同位素组成的相对变化(Λ)及其影响因素。(6)环境意义①Fenton-like反应降解TCE过程产生显著碳氯同位素分馏,因而通过同时分析碳氯同位素并结合瑞利分馏模型,可以分别独立地定量评价Fenton-like反应原位修复效果,并且可以相互验证以检验结果的可靠性。②Fenton-like反应降解TCE过程的碳同位素富集系数(εc)明显不同于微生物氧化降解过程,这是利用碳同位素分析判识Fenton-like反应和好氧微生物降解过程的关键和前提条件。微生物G4好氧降解TCE产生的碳同位素分馏非常大(εC=-18.2～20.7‰),远远大于Fenton-like反应降解过程产生的碳同位素分馏。因而,如果野外监测到TCE碳同位素分馏大于Fenton-like反应降解过程,则表明Fenton-like反应原位修复污染场地可能同时存在微生物好氧降解过程。然而,如果野外监测到TCE碳同位素分馏小于Fenton-like反应降解过程,则单独依靠碳同位素分析不能判定是否存在微生物好氧降解过程。因为微生物OB3b好氧降解TCE产生的碳同位素分馏虽然小于Fenton-like反应降解过程产生的碳同位素分馏,但是碳同位素分馏可以忽略的物理过程通过对浓度的影响而使野外监测到的碳同位素分馏偏小。这种情况下,需要结合其他证据进行分析,如水文地球化学条件、生物地球化学指标、单体多维同位素分析(MD-CSIA)等。③Fenton-like反应降解TCE过程的二维碳氯同位素分馏特征(εC、εCl、AKIEC、AKIECl、Λ),明显不同于其它衰减过程,因而,二维碳氯同位素分析可以为识别衰减过程(或反应机理)提供更全面的信息。(二)揭示了Fenton-like反应降解TCE过程中碳氯同位素分馏的影响因素：(1)反应条件(磁铁矿用量和H2O2浓度及二者的投加方式、TCE初始浓度、TCE/PCE混合污染)对Fenton-like反应降解TCE过程的碳同位素分馏不会产生显著影响。碳同位素富集系数(εC)与该降解反应的表观速率常数(kobs)不存在显著相关性,这表明降解反应速率的变化不会直接影响碳同位素分馏。(2)不同浓度硝酸根离子(NO3-)、硫酸根离子(SO42-)或腐殖酸的实验条件下,Fenton-like反应降解TCE过程的碳氯同位素富集系数十分一致,这表明NO3-、SO42-和腐殖酸(HA)的存在与否对Fenton-like反应降解TCE过程的碳氯同位素分馏不会产生影响。(3)氯离子(Cl-)浓度的变化(0～2M)导致Fenton-like反应降解TCE过程的碳同位素富集系数(εC)变化范围为-3.0‰～-7.7‰,氯同位素富集系数(εCl)变化范围为-0.6‰～-1.1‰,并且碳同位素富集系数(εC)与氯离子(Cl-)浓度具有显著的线性正相关关系(R2=0.992)。根据这一现象,首次提出氯离子(Cl-)对Fenton-like反应降解TCE过程的碳同位素分馏产生显著影响。其原因可能是由于氯离子(Cl-)捕获Fenton-like反应中的羟基自由基(HO·)而形成Cl2·-等无机自由基,并且Cl2·-等无机自由基降解TCE过程产生的碳同位素分馏明显大于羟基自由基(HO·)降解TCE过程的碳同位素分馏。这有待于进一步利用合适的方法产生Cl2·-等无机自由基以研究其降解TCE过程的同位素分馏特征。(4)环境意义氯离子(Cl-)明显影响Fenton-like反应降解TCE过程的同位素分馏,因而根据污染修复场地Cl-含量高低选择适合的同位素富集系数至关重要。Fenton-like反应降解TCE过程的同位素分馏未受其它因素(磁铁矿用量和H202浓度及二者的投加方式、TCE初始浓度、TCE/PCE混合效应、N03-、SO42-和腐殖酸)影响,这减小了碳氯同位素分析量化Fenton-like反应原位修复效果的不确定性。(三)评价了碳氯同位素分析量化Fenton-like反应原位修复效果的不确定性影响：(1)同位素组成的分析误差对降解程度(B)的不确定性影响,随着降解程度(B)增大而逐渐降低；同位素富集系数的不确定度(△ε)对降解程度(B)的不确定性影响,随着降解程度(B)的增加而呈现先增加后降低的趋势。(2)对于Fenton-like反应原位修复TCE过程,如果同时存在OB3b或G4好氧微生物降解过程,利用Fenton-like反应降解过程的碳同位素富集系数(εc)量化修复效果,将会低估或高估实际降解程度。因而,确定和表征有机污染物降解过程的同位素富集系数(ε)至关重要。本研究的创新之处在于：为定量评价Fenton-like反应原位修复有机污染的有效性和适用性提供新思路和技术参数,率先开展了Fenton-like反应降解过程的碳氯同位素分馏研究：(1)首次确定和表征了Fenton-like反应降解三氯乙烯过程的碳氯同位素分馏；(2)系统研究了反应条件和环境因素对Fenton-like反应降解三氯乙烯过程中碳氯同位素分馏的影响,揭示了该降解过程的碳同位素富集系数(εc)在氯离子作用下的变化规律。更多还原

【Abstract】 In recent decades, contamination of soil and groundwater systems caused by organic contaminants such as chlorinated hydrocarbons become increasingly prominent due to human activities. To research environmental behaviors and in situ remediation technologies of chlorinated hydrocarbons in subsurface, has being the research focus in the environment field.A key issue for in situ soil and groundwater remediation is how to accurately quantify the extent of contaminants degradation and to verify effectiveness and applicability of remediation methods. Isotope analysis is among the most promising tools for resolving the issue. A prerequisite and critical parameter for applying this tool in the field is to determine and characterize the magnitude and variability isotope fractionation (i.e. isotope enrichment factor ε) associated with specific degradation processes and to understand the factors that influence this parameter. In order to better play the role and value of isotope analysis in the field of environmental science, it is essential to constantly enrich the database for isotope fractionation associated with various transformation processes.Mineral-catalyzed Fenton-like reaction is a promising alternative for in situ soil and groundwater remediation. Naturally-occurring iron-bearing minerals, which are widespread in soils or aquifers, can catalyze Fenton-like reaction to degradation of recalcitrant organic contaminants without the addition of external soluble iron, and can also be used to build in situ permeable reactive barrier based on Fenton-like reaction. Meanwhile, the oxygen released from Fenton-like reaction during in situ remediation process, may also provide sufficient electron acceptor to enhance in situ aerobic biodegradation. The research about mineral-catalyzed Fenton-like reaction to degrade organic contaminants, not only greatly enriches the environmental mineralogy and advanced oxidation in situ remediation technology, but also promotes the crossing and infiltrating of disciplines in environment, chemistry, geology, and comprehensive utilization for mineral resources. To date, carbon and chlorine isotope fractionation associated with degradation of chlorinated hydrocarbons by Fenton-like reaction has not yet been studied.Thus, for the critical scientific question about how to accurately and effectively evaluate the in situ soil and groundwater remediation, this study is the first to investigate carbon and chlorine isotope fractionation during trichlorothene (TCE) degradation in Fenton-like reaction. It can provide the theory basis and technical parameters for applying isotope analysis to quantify and verify the effectiveness and applicability of in situ remediation implemented by Fenton-like reaction.The main objectives of this study were to characterize carbon and chlorine isotope fractionation associated with TCE degradation by Fenton-like reaction, and to reveal the mechanism and potential effect of factors for carbon and chlorine isotope fractionation during TCE degradation in Fenton-like reaction, and to evaluate the uncertainty for quantifying in situ degradation implemented by Fenton-like reaction using carbon and chlorine isotope analysis approach.The main research contents, ideas and methods are as follows:Firstly, analytical methods for TCE concentration and its carbon and chlorine isotope composition were established, which could provide technical means for the follow-up studies on carbon and chlorine isotope fractionation during TCE degradation in Fenton-like reaction. Secondly, the kinetics of TCE degradation by magnetite-catalyzed Fenton-like reaction were investigated, which were preliminary experiments for the follow-up studies on carbon and chlorine isotope fractionation during TCE degradation in Fenton-like reaction. Thirdly, applying carbon and chlorine isotope analysis techniques and based on isotope fractionation theory and combined with previous studies of carbon and chlorine isotope fractionation in other transformation processes, compound-specific carbon isotope fractionation and two-dimensional carbon and chlorine isotope fractionation associated with TCE degradation by Fenton-like reaction were characterized. After that, the potential effects of environmental factors (NO3-, SO42-, Cl", and humic acid) for carbon and chlorine isotope fractionation during TCE degradation in Fenton-like reaction were revealed. Finally, the uncertainty for quantifying in situ degradation implemented by Fenton-like reaction using the Rayleigh equation approach due to the influence of isotope composition and isotope enrichment factor was evaluated.The following conclusions can be drawn from the present study:(A) Carbon and chlorine isotope fractionation during TCE degradation in Fenton-like reaction were characterized, and the mechanism for carbon and chlorine isotope fractionation was revealed.(1) Significant carbon and chlorine isotope fractionation during TCE degradation in Fenton-like reaction were noticeable, with average carbon and chlorine enrichment factors of ec=-3.0±0.2%o and εCl=-1.0±0.1%o. Carbon and chlorine isotope fractionation for TCE degradation via Fenton-like reaction were substantially different from those observed for zerovalent iron and microbial reductive dechlorination of TCE. One major difference between Fenton-like reaction degradation and reductive dechlorination of TCE is the reaction mechanism for TCE degradation, which the cleavage of a carbon-carbon double bond (C=C) to a single carbon bond (C-C) as the rate-determining step associated with Fenton-like oxidation is different from the cleavage of C-Cl bond as the first step during microbial and abiotic reductive dechlorination(2) Carbon isotope fractionation associated with TCE degradation by magnetite-catalyzed Fenton-like reaction was significantly smaller than those reported for permanganate oxidation of TCE and aerobic mineralization of TCE by B. cepacia G4, although those reactions for abiotic and microbial oxidation of TCE have similar mechanisms involving breakage of a carbon-carbon double bond (C=C) as the rate-determining step. The similar carbon isotope fractionation observed for TCE degradation by Fenton reaction in homogeneous solution and magnetite-catalyzed Fenton-like reaction, suggests that the explanation of commitment to catalysis contribute to the small isotope fractionation observed during Fenton-like oxidation of TCE can be precluded. An alternate explanation for the large differences of ε values is likely the result of transition state structure differences between Fenton-like oxidation and other oxidation reactions (permanganate and G4oxidation). Further simulation of the transition state structure using computational methods is necessary to illuminate these relationships.(3) For carbon and chlorine isotope fractionation associated with TCE degradation by Fenton-like reaction, the average apparent kinetic isotope effects for carbon and chlorine were AKIEC=1.0030±0.0002and AKIECl=1.0010±0.0001, respectively. An observed small secondary chlorine isotope effect was consistent with the expected reaction mechanism involving breakage of a C=C bond to single carbon bond as the rate-determining step.(4) For the same element, secondary isotope effects are generally at least one order of magnitude smaller than primary isotope effects. It has been proposed that hydroxyl radicals react with organic compounds via three mechanisms:hydrogen atom abstraction, electron transfer, and addition to multiple bonds. For the hydrogen abstraction reaction, one C-H bond is broken in the rate-limiting step for TCE degradation by Fenton-like reaction. The AKIECl is1.003(or AKIECl-1=0.003), which is about a quarter of the primary chlorine isotope effect (KIECl=1.013, or KIECl-1=0.013). Thus, it is inconsistent with secondary isotope effects for chlorine, and proposed mechanism that hydroxyl radicals react with organic compounds via hydrogen atom abstraction can be precluded. For the other two mechanisms:electron-transfer and addition to the double C=C bond, the AKIECl is1.001(or AKIECl-1=0.001), and is about one thirteenth of the primary chlorine isotope effect (KIECl=1.013, or KIECl-1=0.013), which is consistent with secondary isotope effects for chlorine.(5) For carbon and chlorine isotope fractionation associated with TCE degradation by Fenton-like reaction, the relative change in carbon and chlorine isotope ratios (Λ=△δ37Cl/△δ13C) was calculated to be0.348±0.049, and approximatively equal to the ratio of chlorine and carbon isotope enrichment factors (εCl/εC=0.349±0.057). The A value for TCE degradation via Fenton-like reaction was substantially different from the εCl/εC value for reductive dechlorination of TCE by zerovalent iron. The differences in the relative changes in isotope ratios of carbon and chlorine (or the ratio of chlorine and carbon isotope enrichment factors) for different reaction mechanisms, implies that it can be applied for evaluating transformation processes. In order to better play the role and worth of the relative changes in isotope ratios of carbon and chlorine, it is essential to further investigate the relative changes in isotope ratios of carbon and chlorine and its potential effect factors for various transformation processes.(6) Environmental significance.①Significant carbon isotope fractionation effects were noticeable during TCE degradation in magnetite-catalyzed Fenton-like reaction. Thus, stable carbon and chlorine isotope analysis in combination with the Rayleigh equation approach, can be used to independently quantify the efficacy of in situ remediation implemented by Fenton-like reaction and authenticate each other.②The results demonstrate significant differences in isotope fractionation for Fenton-like oxidation and aerobic biological processes, which is a first step toward potentially distinguishing between Fenton-like oxidation versus aerobic biological processes. The previously reported ε value (ε=-18.2to-20.7%o) for microbial TCE transformation by B. cepacia G4was more negative than those for Fenton-like oxidation. Thus, field-derived ε values that are more negative than those for Fenton-like oxidation, may indicate the occurrence of aerobic biological processes at contaminated sites undergoing in situ remediation with Fenton-like reaction. The more negative field-derived ε values, the more aerobic biological processes contribute to the transformation of TCE. However, field-derived ε values that are less negative than those for Fenton-like oxidation are unable to determine whether there is the occurrence of aerobic biological processes such as B. cepacia OB3b with only carbon isotope analysis, because non-fractionating processes such as physical processes may also result in "dilution" or underestimation of field-derived εvalues at contaminated sites undergoing in situ remediation with Fenton-like reaction. In these cases, other lines of evidence should be considered, including hydrogeochemical conditions, biogeochemical indicators, multidimensional compound-specific isotope analysis, etc.③The two-dimensional carbon and chlorine isotope fractionation (εC,εCl, AKIEc, AKIECl, A) associated with TCE degradation by Fenton-like reaction was significant different from those observed for other attenuation processes. Thus, two-dimensional carbon and chlorine analysis can provide more exhaustive information for distinguishing between Fenton-like reaction versus other attenuation processes (or degradation mechanisms).(B) The potential effect of factors for carbon and chlorine isotope fractionation during TCE degradation in Fenton-like reaction was revealed.(1) The carbon enrichment factors (εC) were robust and reproducible, and relatively insensitive to different initial reactive conditions (magnetite/H2O2dosage and delivery method, TCE concentration, TCE/PCE co-contamination). There was no discernible relationship between carbon enrichment factors (εC) and apparent first-order rate constants (kobs), which indicates that variations of reaction rate do not directly affect carbon isotope fractionation for TCE degradation in Fenton-like reaction.(2) Enrichment factors for TCE degradation by Fenton-like reaction under various initial concentrations of nitrate ion (NO3-), sulfate ion (SO42-), and humic acid agreed closely, which indicates that NO3-, SO42-, and humic acid do not significantly affect carbon and chlorine isotope fractionation for TCE degradation in Fenton-like reaction.(3) An increase in the initial chloride ion (Cl-) concentration from0to2M caused the carbon isotope enrichment factors (εC) ranged from-3.0‰to-7.7‰, and the chlorine isotope enrichment factors (εCl) ranged from-0.6‰to-1.1‰for TCE degradation in Fenton-like reaction, respectively. There was a significant positive linear correlation between the Cl-concentrations and the εC values (R2=0.992). This indicates that Cl-significantly affected carbon isotope fractionation for TCE degradation in Fenton-like reaction. The effect of Cl-on isotope fractionation may be explained by the change in reaction mechanism due to the scavenging of Cl-for hydroxyl radicals (HO·) to generate inorganic radicals such as Cl2-, and carbon isotope fractionation for TCE degradation by Cl2-may be substantially larger than those observed for TCE degradation by HO-. Follow up studies are required to characterize the isotope fractionation associated with Cl2·-radicals degradation of TCE using a more appropriate method for generating inorganic radicals.(4) Environmental significance.Chloride ion (Cl-) significantly affected isotope fractionation for TCE degradation in Fenton-like reaction. Thus, for a quantitative assessment of in situ remediation using the Rayleigh equation approach, it is crucial and necessary to select an appropriate and representative isotope enrichment factors (ε) according to the Cl-concentration in fields. The isotope fractionation associated with TCE degradation by Fenton-like reaction was relatively insensitive to other factors (magnetite/H2O2dosage and delivery method, TCE concentration, TCE/PCE co-contamination, NO3-, SO42-, and humic acid), which can reduce the uncertainty associated with application of carbon isotope analysis for quantification of in situ remediation by Fenton-like reaction.(C) The uncertainty for quantifying in situ degradation implemented by Fenton-like reaction using carbon and chlorine isotope analysis was evaluated.(1) The uncertainty of degradation extent (B) introduced by analytical errors of isotope composition steadily decreases towards higher amounts of degradation. The uncertainty of degradation extent (B) introduced by the uncertainty in isotope enrichment factors firstly increases and then decreases with the increase of degradation extent (B).(2) If aerobic degradation of TCE by OB3b or G4occur simultaneously at contaminated sites undergoing in situ remediation implemented by Fenton-like reaction, the extent of degradation may be underestimated or overestimated using the Rayleigh equation approach with the carbon enrichment factor for TCE degradation in Fenton-like reaction. Therefore, for a quantitative assessment of in situ remediation using the Rayleigh equation approach, it is crucial and necessary to select an appropriate and representative isotope enrichment factors (ε) for specific degradation processes and to understand the factors that influence this parameter.The main innovations are as follows:To provide the theory basis and technical parameters for applying isotope analysis to quantify and verify the effectiveness and applicability of in situ remediation implemented by Fenton-like reaction, this study is the first to investigate carbon and chlorine isotope fractionation during trichlorothene (TCE) degradation in Fenton-like reaction:(1) The carbon and chlorine isotope fractionation for TCE degradation in Fenton-like reaction has been first determined and characterized.(2) The potential effects of reactive conditions and environmental factors for carbon and chlorine isotope fractionation during TCE degradation in Fenton-like reaction has been studied systematically, and the variation for the carbon isotope enrichment factor (εc) of TCE degradation by Fenton-like reaction due to Cl-effect was revealed.更多还原