两种改性剂对多氯联苯污染土壤协同热脱附影响研究

采用热脱附技术处理多氯联苯污染土壤已经成为了一种主要的场地修复方式。为提高热脱附效率,降低能耗,以典型电力电容器污染土壤为对象,采用2种改性剂(零价纳米铁和氢氧化钠)研究协同热脱附下多氯联苯的去除效率、分布特性及毒性当量。结果表明纳米铁和NaOH存在的条件下,有效提高了多氯联苯和毒性当量的去除效率,在较低温度下尤其显著,因此添加改性剂能够有效地促进热脱附过程。纳米铁的协同热脱附机理为显著强化了热脱附过程的传质传热,同时伴有一定的脱氯降解。NaOH的添加在较低温度下实现了较强的脱氯降解作用,加氢脱氯机理可用来解释协同热脱附过程中多氯联苯的脱氯反应过程。上述研究结果为多氯联苯污染土壤的场地修复提供理论基础。     

High dechlorination of PCBs catalysed by carbon under mild conditions

This article reports high dechlorination of toxic polychlorinated biphenyls (PCBs) under mild conditions. PCBs are priority pollutants acting as endocrine disruptors, human carcinogens and environmental estrogens. Previous remediation methods involving high temperature and pressure have drawbacks such as high cost, de novo dioxins synthesis and difficult recovery of vaporized PCBs. On the other hand, dechlorination methods using mild conditions show the problem of catalyst deactivation. Here, activated carbon was used for the first time as catalyst to dechlorinate 2,4,5 trichlorobiphenyl. High dechlorination, of 87%, was achieved under mild conditions. 2,4,5 trichlorobiphenyl was treated at 40–150°C with calcium hydroxide, sodium hydroxide and sulfur in mixed water and organic solvents. Dechlorination products were biphenyl, orthohydroxy biphenyls, 2,4 dihydroxy biphenyls and biphenyl-2-thiol. Dichlorobiphenyl and orthochlorobiphenyls were found in trace quantities. We found that carbon particles catalysed dechlorination by substitution reactions and suppressed further chlorination. Dechlorination at biphenyl ortho position was preceded by substitution reaction by hydroxyl and thiol ions. Moreover, in the absence of carbon, dechlorination was lower and substituted products were not observed. These findings may be applied at industrial scale to remediate PCB-contaminated waste.     

Detection of polychlorinated biphenyls employing chemical dechlorination followed by biphenyl whole cell sensing system

Polychlorinated biphenyls (PCBs) are a mixture of 209 individual chlorinated compounds commonly known as PCB congeners. These compounds are hydrophobic and are persistent in the environment. Their use was banned in the US a few decades ago because of harmful health effects. Therefore, detection of PCBs in environmental samples is increasingly important. To that end, we have developed a two-step simple and sensitive method for the detection of total PCBs. Specifically, our method involves dechlorination of PCBs to biphenyl followed by detection of biphenyl using a whole cell sensing system as the detection system. The whole cell sensing system consists of cells of the strain Pseudomonas pseudoalcaligenes KF707 harboring plasmid pSD7000. Plasmid pSD7000 contains the gene of lacZ, a reporter protein under the control of the bph operon. The detection is achieved through the emission of light afforded by the expression of reporter protein triggered by the presence of biphenyl. Due to the fact that this operon is activated only by few PCB congeners, a chemical dechlorination method was employed to convert all PCBs to biphenyl, and thus all the PCBs present in a given sample are able to be detected. The results showed that PCB congeners were rapidly (30?min) and efficiently (>98.5%) dechlorinated to biphenyl using a Mg/K₂PdCl₆ catalyst, and the biphenyl could be subsequently quantified using the whole cell sensing system. This hybrid analytical method that combines classical dechlorination with novel biosensing methods may find applications in the on-site monitoring of PCBs contamination levels.     

多氯联苯污染土壤热脱附研究综述

综述了近年来国内外热脱附技术在修复多氯联苯(polychlorinated biphenyls,PCBs)污染土壤方面的研究进展。温度和停留时间是影响其脱附效率的最主要因素,另外脱附效果还受土壤性质以及载气、压力等其他因素的影响。氧气存在的条件下,脱附过程中会有呋喃(polychlorinated dibenzofurans,PCDFs)生成,导致整体毒性当量增加。PCBs的物理蒸发是其主要的脱附机制,同时伴随着脱氯和降解。协同热脱附通过添加改性剂,有效促进了PCBs的去除以及降解。冷凝,除尘,吸附一系列尾气处理用来降低尾气中PCBs的含量。文章最后给出了当前国内外的应用情况以及存在问题和今后的发展方向。     

Catalytic decomposition of polychlorinated biphenyls (PCBs)

In this study, polychlorinated biphenyls (PCBs) were decomposed by low‐temperature heat treatment with metallic catalyst, and with metallic catalyst and a hydrogen source. Of the catalysts used, iron (Fe) was the most active catalyst for the decomposition of PCBs, and the decomposition was due to dechlorination. The addition of hydrogen sources accelerated the decomposition of PCBs in the presence of catalyst. Surface analysis of the catalyst using X‐ray photoelectron spectroscopy (XPS) suggested that the emitted chlorine was presumed to form metal chloride. The reactions of each homolog can be expressed by a successive first‐order reaction model. This means that a substituted chlorine is successively detached during this reaction. The overall decomposition rate in this reaction system was controlled by that of the lower chlorinated homologs. The decomposition rates with Fe and NaBH₄ for the lower chlorinated homologs were about 10 times as fast as the rates with only Fe.     

Development and characterization of an anaerobic microcosm for reductive dechlorination of PCBs

The toxic and recalcitrant polychlorinated biphenyls (PCBs) adversely affect human and biota by bioaccumulation and biomagnification through food chain. In this study, an anaerobic microcosm was developed to extensively dechlorinate hexa- and hepta-CBs in Aroclor 1260. After 4 months of incubation in defined mineral salts medium amended PCBs (70 mmol·L^–1) and lactate (10 mmol·L^–1), the culture dechlorinated hexa-CBs from 40.2% to 8.7% and hepta-CBs 33.6% to 11.6%, with dechlorination efficiencies of 78.3% and 65.5%, respectively (all in moL ratio). This dechlorination process led to tetra-CBs (46.4%) as the predominant dechlorination products, followed by penta-(22.1%) and tri-CBs (5.4%). The number of meta chlorines per biphenyl decreased from 2.50 to 1.41. Results of quantitative real-time PCR show that Dehalococcoides cells increased from 2.39 ×10⁵±0.5 × 10⁵ to 4.99 × 10⁷±0.32 × 10⁷ copies mL^–1 after 120 days of incubation, suggesting that Dehalococcoides play a major role in reductive dechlorination of PCBs. This study could prove the feasibility of anaerobic reductive culture enrichment for the dehalogenation of highly chlorinated PCBs, which is prior to be applied for in situ bioremediation of notorious halogenated compounds.

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Reductive dechlorination of chlorobenzene in supercritical water catalyzed by Fe/ZrO<Subscript>2</Subscript>

Reductive dechlorination of chlorobenzene by Fe/ZrO₂ in supercritical water was investigated. The effects of the operation conditions were studied. The dechlorination of chlorobenzene obeyed pseudo-first-order kinetics models. In supercritical water, the rate constant increases more rapidly with temperature than those in subcritical water. The results showed that the rate-determining step of dechlorination in subcritical water is diffusion; whereas the rate-determining of dechlorination in supercritical water is chemical reaction. The reaction mechanism in subcritical water might involve with an ionic mechanism; whereas the reaction mechanism in supercritical water might involve with a homolytic reaction.     

持久性有机污染物(POPs)的生物降解与外生菌根真菌对POPs的降解作用

综述了持久性有机污染物(POPs)的生物降解途径,以及国内外在外生菌根真菌降解POPs方面的研究进展,阐述了其机制与优势.根据作用的微生物和环境条件的不同,POPs如PCBs、DDT等可以通过脱氯或开环等途径生物降解.外生菌根真菌能降解多种POPs,具有较大的潜力.图2表2参30     

红壤胶体铁氧化物界面有机氯的非生物转化研究进展

综述了红壤胶体铁氧化物的结构、形态及其转化;铁氧化物界面有机氯的非生物转化过程及其影响因素;异化铁还原作用下的有机氯转化过程。有机氯的非生物转化主要包括氧化转化与脱氯转化过程。氧化转化包括暗态下的化学氧化与光化学氧化过程;脱氯转化包括脱氢卤化、加氢脱氯、脱双卤、二聚脱氯与亲核置换脱氯等反应过程。有机氯的非生物转化主要受胶体界面pH、Eh、水溶性有机物、金属离子、铁氧化物形态与铁还原细菌等的显著影响。有机氯非生物转化的化学-微生物耦合机制、复合污染条件下重金属对界面有机氯非生物转化过程的影响机制、红壤胶体界面有机氯污染的综合调控技术方法等三个方面值得关注,有助于推动土壤胶体界面环境化学的发展。     

Fast 62–92 % yield preparation of amino acid dithiocarbamates in green solvent at room temperature

Dithiocarbamate and their derivatives are of importance in medicinal chemistry due to their biological activities, in agriculture as fungicides and in organic synthesis as versatile synthetic intermediates. Green solvents such as deep eutectic solvents and polyethylene glycol are new emerging alternatives to conventional harmful organic solvents. Here, we report the synthesis of amino acid–based dithiocarbamates by one-pot three-component reaction of the electrophilic reagent, carbon disulfide and α-amino acids in deep eutectic solvent and polyethylene glycol as a catalyst and reaction media. In situ preparation of dithiocarbamates by the reaction of different amino acids and carbon disulfide, followed by addition reaction with epoxides, alkyl halides and α, β-unsaturated enones at room temperature, gave the corresponding products in 62–92 % yield with a short reaction time without any tedious workup procedures. The deep eutectic solvents and polyethylene glycol were recycled without activity or yield decrease. Therefore, the synthesis of amino acid–based dithiocarbamates in green solvents is a promising alternative to previously used procedures.     

Modeling primary and secondary fractionation effects and atmospheric transport of polychlorinated biphenyls through single-source emissions

The Chinese Gridded Industrial Pollutants Emission and Residue Model (ChnGIPERM) was used to investigate potential fractionation effects and atmospheric transport of polychlorinated biphenyls (PCBs) derived from single-source emissions in China. Modeling the indicative PCBs (CB28, CB101, CB153, and CB180) revealed spatiotemporal trends in atmospheric transport, gas/particle partitioning, and primary and secondary fractionation effects. These included the inference that the Westerlies and East Asian monsoons affect atmospheric transport patterns of PCBs by influencing the atmospheric transport time (ATT). In this study, dispersion pathways with long ATTs in winter tended to have short ones in summer and vice versa. The modeled partitioning of PCB congeners between gas and particles was mainly controlled by temperature, which can further influence the ATT. The potential for primary and secondary fractionation was explored by means of numerical simulations with single-source emissions. Within ChnGIPERM, these phenomena were mainly controlled by the temperature and soil organic carbon content. The secondary fractionation of PCBs is a slow process, with model results suggesting a timescale of several decades.

     

Detailed analysis of PCBs and PCDD/Fs impurities in a dielectric oil sample （ASKAREL Nr 1740） from an imported transformer in China

Homolog and congener profiles of polychlori- nated biphenyls （PCBs）, polychlorinated dibenzo-p- dioxins （PCDDs） and polychlorinated dibenzofurans （PCDFs） in commercial PCBs formulations are useful information for the source appointment of PCBs contam- ination as well as the risk assessment caused by potential exposure. Dielectric oil （ASKAREL Nr 1740） in an imported transformer found in China was sampled and analyzed by isotope dilution technology using high resolution gas chromatography-high resolution mass spectrometry （HRGC/HRMS）. The detailed homolog and congener profiles of PCBs obtained were compared with those of known Aroclor formulations. High similarity in the homolog profile between the oil sample and Aroclor 1260was found, with the hexachlorinated and hepta- chlorinated biphenyls accounting for more than 80.2% of the total PCBs concentration. Severn indicator PCBs contribute about 30%, while 12 PCB congeners （i.e., # 153, #143, #168, #180, #149, #165, #138, #170, #190, #187, #174, #181） account for more than 50% of the total PCB concentrations. Total concentration ofPCDDs, PCDFs and dioxin-like PCBs （DL-PCBs） was found to be 740 ng TEQ/g, of which 620 ng TEQ/g came from DL-PCBs. The contribution of PCDDs to the total TEQ was neglectable. The concentration of PCDFs homologs follows the order of OCDF 〉 HxCDFs 〉 HpCDFs 〉 PeCDFs 〉 TeCDFs, which is in consistence with the previous study on Aroclor 1260. Three DL-PCBs congeners （i.e., #118, #156, #157） accounted for 77% of the total concentration of DL-PCBs, also they contribute 72% in the TEQ caused by DL-PCBs.     

Live algae as a vector candidate for hydrophobic polychlorinated biphenyls translocation to bivalve filter feeders for laboratory toxicity test

Live algae carrying hydrophobic xenobiotics can be an effective vector candidate for the chemical translocation to filter feeders in the laboratory toxicity test, but information on their application is lacking. Time-course uptake and elimination of polychlorinated biphenyls (PCBs) (0, 50, 100, and 500 ng g(-1) by two key algal foods, Isochrysis galbana and Tetraselmis suecica, were measured. Both of the algae achieved maximum concentration in an hourafter PCBs exposure regardless the chemical concentrations in our time-course measurements (0, 1, 5, 10, 24, 48 and 72 hrs). Once achieved the maximum concentration, the algae shortly exhibited elimination or eliminating tendency depending on the chemical concentrations. Algae exposed to the chemical for 1 and 24 hrs (hereafter 1 and 24 hr vectors, respectively) were then evaluated as a chemical translocation vector by feeding test to larval and spat Crassostrea gigas. In the feeding test the 24 hr vector, which contained lower chemicals than the 1-hr vector, appeared to be more damaging the early lives of the oyster. This was particularly significant for vectors of higher PCBs (p<0.05), probably due to algal reduction in food value by the prolonged chemical stress. These findings imply that 1 hr exposure is long enough for a generation of algal vector for laboratory toxicity test, minimizing data error resulted from reduction in food value by longer chemical stress.     

Isomer‐specific determination and toxic evaluation of potentially hazardous coplanar PCBs,dibenzofurans and dioxins in the tissues of “Yusho” PCB poisoning victim and in the causal oil

In the light of new discoveries on the extremely toxic non‐ortho coplanar 3,3’,4,4'‐tetra‐ (T₄CB), 3,3’,4,4’,5‐penta‐(P₅CB) and 3,3'4,4’,5,5'‐hexachlorobiphenyl (H₆CB) and their mono‐ and di‐ortho analogs, tissue samples of a Yusho poisoning victim and Yusho causal oils were subjected to a thorough congener/isomer‐specific investigation for polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzo‐p‐dioxins (PCDDs). Among the many PCB congeners detected in Yusho oil, non‐ortho coplanar T₄CB constituted 3.1%, P₅CB‐0.17% and H₆CB‐0.0072% in total PCBs. Their concentrations in liver and adipose tissue were 130–700 (T₄CB), 54–720 (P₅CB) and 50–380 (H₆CB) pg/g on wet weight basis. The observed concentrations in adipose tissue were two to four fold higher than that detected in unexposed individuals. Among the PCDFs identified, toxic 2,3,7,8‐substituted isomers including 2,3,4,7,8‐P₅CDF were the dominant ones. Tetra‐ through hepta‐CDDs were detected in the oil, whereas octa‐CDD was the dominant isomer in the patient. A comparison with KC‐400 revealed enrichment of coplanar PCBs in Yusho oil along with toxic PCDFs. Enrichment was highest for 3,3'4,4'5,5'‐H₆CB followed by 3,3’,4,4'5‐P₅CB. A comparative toxic evaluation of these chemical groups in Yusho patient's adipose tissue based on “2,3,7,8‐T₄CDD Toxic Equivalent Analysis” revealed accountable toxic contribution from coplanar PCBs. This analysis also confirmed that 2,3,4,7,8‐P₅CDF was the principal causative agent in Yusho poisoning.     

多氯联苯在土壤中的吸附规律及其影响因素研究

为了建立定量描述土壤中多氯联苯（PCBs）迁移规律的数学模型,以采自现代黄河三角洲地区的土壤为研究对象,针对类二噁英类多氯联苯PCB81及阻转类多氯联苯PCB95在土壤中的吸附行为进行了研究,获得了其吸附等温方程并分析了土壤有机质含量、颗粒组成、pH、矿物质含量等特性参数对吸附量的影响。结果表明,PCBs在土壤中的吸附行为符合Langmuir吸附等温方程;PCBs的吸附量与土壤中有机质含量和土壤粘粒含量呈正相关关系,与土壤pH值及土壤矿物质含量无明显相关关系。     

Synthesis of nickel nanoparticles by chemical and green route and their comparison in respect to biological effect and toxicity

Recent reports demonstrated an increase in the synthesis of nanoparticles (NP) and its applications. The chemical preparation of NP may be harmful. Thus, in this study, the biological activity and toxicology of nickel nanoparticles (NiNP) synthesized through chemical and green routes were compared. Chemical synthesis of NiNP was mediated by polyethylene glycol and hydrazine hydrate as stabilizing and reducing agent, respectively. Desmodium gangeticum aqueous root extract was used to prepare NiNP without any stabilizing and reducing agent. Nickel nanoparticles synthesized by both methods were characterized (ultraviolet–visible spectroscopy, X-ray diffractrometry, Fourier transform infrared spectroscopy, zeta potential and vibrating sample magnetometer) and compared. There was no major significant difference in the nature of the NP prepared by both methods. However, green synthesized NiNP showed reduced size and better monodispersity compared to chemical synthesized one. Free radical scavenging activities and antibacterial activities of NiNP prepared by chemical and green route suggest that these NP, prepared by green route possess reliable antioxidant and antibacterial activity. Evaluation of toxicity in animal and cell line suggests that NiNP synthesized by green route are nontoxic.     

Transport,distribution and toxic effects of polychlorinated biphenyls in ecosystems: Review

Investigation of various aspects of the ecological problems of polychlorinated biphenyls (PCBs) has grown and continues to grow with remarkable intensity. However, it appears that certain areas of PCBs research are developed further than the others. For example, chemical and physical behavior and synthesis of PCBs are well studied, while the metabolism of PCBs and other routes of degradation, including toxicological significance and environmental impact, continue to challenge the scientists.In this paper, the chemical and physical properties of PCBs as well as the implications of these properties for the behavior of PCBs in ecological systems are discussed. The effect of PCBs on interrelated ecological systems are described. The distribution and fate of PCBs in the atmosphere, hydrosphere and lithosphere, and transport of PCBs through these systems are discussed. The toxic significance, biological accumulation and ecological magnification are described at various trophic levels.     

Simulation of germination of pioneer species along an experimental drought gradient

The germination of ten plant species from the Iberian Peninsula was assessed along a water deficit gradient between -0. 1652 (moist) and -0.4988 MPa (dry) of osmotic potential, created by addition of increasing concentrations of polyethylene glycol (PEG 6000) to distilled water in which plants were grown hydroponically. The level and rate of germination of Daucus carota and Thapsia villosa significantly decreased with decreasing psi. Seeds of Dactylis glomerata and Dittrichia viscosa had positive germination responses to low osmotic potentials; germination of Epilobium hirsutum was not affected by osmotic potential. Germination of Medicago arabica, Cynosurus cristatus, Cistus ladanifer and Cistus albidus, was no favored by the addition of polyethylene glycol (PEG). Germination of Foeniculum vulgare and Thapsia villosa was inhibited by PEG.     

Seasonal and spatial character of PCBs in a chemical industrial zone of Shanghai,China

As one of China’s great metropolises, Shanghai is suffering from the impact of manufacture and the use of chemical industrial products, and it faces serious pollution from polychlorinated biphenyls (PCBs). Therefore, in this study, in order to assess the seasonal and spatial character of contamination from chemical industrial zones, the concentrations of PCBs have been measured in various environmental media, including soil, leaves, and atmospheric particulate samples collected in a chemical industrial zone of Shanghai and compared with samples from presumably unpolluted sites of rural areas. In soils, the PCB concentrations ranged from 0.5 ng g⁻¹ (unpolluted site) to 586.85 ng g⁻¹ (chlor-alkali industry site). The concentrations of PCBs in evergreen leaves ranged from 0.3 ng g⁻¹ to 32.46 ng g⁻¹, and more chlorinated biphenyls congeners, such as penta-biphenyls and hexa-biphenyls, were the dominant contributors in winter and spring. Seasonal differences and the constitution patterns of congeners might be affected by the temperature and industrial activities. The PCB concentrations in the leaves of deciduous trees increase over time as the leaves grow. The PCB concentration in atmospheric particulates was in the range of 9.22–14.15 × 10³ pg m⁻³, which might be the result of influence from climate and industrial activities. The relativity of PCB contents among the environmental media was discussed. The results in this paper provide an important profile of the current contamination status of a key chemical industrial zone in China.     

Environmentally significant photochemistry of chlorinated benzenes and their derivatives in aquatic systems†

The pollution of soil and aquatic environments by chlorinated aromatic pollutants (CAPs) such as polychlorobenzenes (PCBzs), polychlorophenols (PCPs), polychloro‐diphenyl ethers (PCDPEs), phenoxyacetic acids, etc., creates growing public anxiety. Phototransformation is an important process for pollutants in aquatic systems. This article extensively reviews the environmentally significant solution phase photochemistry of PCBzs as well as other CAPs derived therefrom. The paper includes photochemical fate of these CAPs at wavelengths >285 nm on the one hand and their photolysis in solution in aquatic systems on the other. In this article, photolytic reductive dechlorination and isomerization of PCBzs are reviewed together with the photoformation of several products including polychlorobiphenyls (PCBs) from PCBzs. Recently developed phenomena of photoincorporation of PCBzs into humic model monomers is also described. This review also describes the environmental photochemistry of chlorobenzene derivatives, namely, α‐substituted p‐chlorotoluenes of the general structure p‐ClC₆H₄CH₂‐X (X = H, Cl, CN, COOH and OH), di‐through pentachlorophenols, PCDPEs (having Cl_1–5 contents) with and without o‐OH substituents, and 2,4‐di‐ and 2,4,5‐trichlorophenoxyacetic acid (2,4‐D and 2,4,5‐T, respectively) as well as their esters and some formulations.