多氯联苯的环境行为*

本文从多氯联苯(PCBs) 的污染状况、分析方法、环境中的迁移转化、多介质模型及风险评价5 个方面综合论述了多氯联苯的环境行为, 并指出要降低PCBs 对生态环境的破坏, 需要更深入地研究PCB s 的环境行为和归趋, 大力加强其风险评价工作, 这已成为21 世纪的优先研究领域之一。     

植物油中7种指示性多氯联苯的GC-MS检测方法探讨

多氯联苯(polychlorobiphenyls,PCBs)是一种持久性环境污染物,有致癌、致畸、致突变作用,在斯德哥尔摩公约中被严禁使用.由于其化学性质稳定,难降解,加之全球迁移等因素,使得多氯联苯至今仍广泛存在于大气、水体、土壤中,同时在母乳、鸡蛋中也发现有多氯联苯存在[1-2].     

多氯联苯的羟基化代谢产物及其内分泌干扰机制

羟基多氯联苯是典型持久性有机污染物(POPs)--多氯联苯在生物体内的主要活性代谢产物,已在许多野生动物和人体内被检出.由于其化学结构与天然雌激素、甲状腺激素十分类似,因此羟基多氯联苯的内分泌干扰效应近年来已开始受到国际上的高度关注.本文对多氯联苯的代谢途径、羟基多氯联苯在生物体内的浓度水平、内分泌干扰及其多种毒性作用机制进行了综述.有关对多氯联苯的活性代谢产物--羟基多氯联苯的深入研究,将有助于进一步揭示多氯联苯的毒性机制,为我国早日建立有效的POPs污染危害评价与早期预警系统提供科学依据.     

基于分子对接技术及CoMSIA/HQSAR辅助的二羟基多氯联苯衍生物分子修饰

利用类二噁英类多氯联苯(PCBs)大气氧化降解产物二羟基多氯联苯与2,3-二羟基联苯双加氧酶(Bphc,PDB ID:1KW6)进行分子对接,构建以分子结构参数为自变量,对接打分函数(K_d,代表对接活性)为因变量的分子相似性指数分析(Co MSIA)与分子全息定量结构-活性相关关系(HQSAR)模型,并对二羟基多氯联苯进行分子修饰,研究结果表明,Bphc酶对二羟基多氯联苯均有不同程度的降解能力,影响Bphc酶对接活性的氨基酸残基为His145,Val147,Ile174,His194,His208,His209,His240,Asn242,Tyr249及Thr280,且二羟基多氯联苯与氨基酸残基对接形成的氢键越多对接活性越高.建立了CoMSIA和HQSAR模型耦合的二羟基多氯联苯分子取代活性精确定位方法,以打分函数较低的二羟基多氯联苯5,6-2OH-CB60为目标分子,设计出8种打分函数显著提升的新型分子,其对接活性提高65%~185%,分子毒性(IC_(50))下降10%~83%,生物富集性(BCF)下降4%~27%,迁移性(K_(OA))与半衰期(t_(1/2))增降幅基本不变.所设计新型分子反应路径的推断可以验证二羟基多氯联苯5,6-2OH-CB60在环境中与活性自由基或与活性分子反应生成所设计的新型5,6-2OH-CB60分子,即类二噁英类PCBs可通过大气氧化降解最终生成酶降解性显著提高的新型二羟基多氯联苯,达到进一步控制类二噁英类PCBs环境行为的目的.     

海洋沉积物中多氯联苯残留检测方法的研究

多氯联苯是环境中持久性有机污染物.由于该类物质的生物累积性,对人类和生物具有很大的潜在危害~([1]),因此研究检测海洋沉积物中多氯联苯的分析方法是环境分析中的重要课题之一.超声萃取能有效地将有机物从固体样品中萃取出来,而且超声萃取具有效率高、仪器价格便宜,操作简单等优点.     

气相色谱串联质谱法用于水产品中多氯联苯二代污染物鉴别

建立了气相色谱串联质谱法鉴别多氯联苯二代污染物羟基多氯联苯的方法,并用于水产品中羟基多氯联苯的分析。在60℃下,羟基多氯联苯经硅烷化衍生40 min,在气相色谱三重四级杆串联质谱仪全扫描模式(Full scan mode)下进行扫描,得到一级质谱全扫描图谱,确定3-羟基-多氯联苯101(3-OH-PCB101)、4-羟基-多氯联苯106(4-OH-PCB106)、4-羟基-多氯联苯112(4-OH-PCB112)等7种衍生化合物丰度最高的碎片离子,以此碎片离子为母离子,在二级质谱多反应监测模式( MRM)下进行扫描,得到二级质谱全扫描图谱,确定母离子产生的丰度最高的特征子离子,以此对应的离子对及其比例对化合物进行定性分析,分别得到7种羟基多氯联苯衍生物的一级、二级质谱图,通过串联质谱法对每种目标化合物进行定量分析,仪器检出限范围为0.02~0.14μg/L,定量检出限为0.09~0.48μg/L。将本方法用于水产品中羟基多氯联苯的鉴别,结果满意。     

土壤与沉积物样品中多氯联苯总量的气相色谱-质谱法快速分析

建立了土壤和沉积物样品中多氯联苯总量的快速分析方法.样品经加速溶剂萃取,Bond ElutPCB SPE小柱净化后,采用气相色谱-质谱测定多氯联苯的总量,方法的平均回收率为84% ～106%,相对标准偏差为4.2% ～8.4%,多氯联苯总量的方法检出限为2.25 ng/g.该方法快速、灵敏、准确,适用于大部分土壤及沉积物样品中多氯联苯总量的快速筛查分析.     

同位素稀释-HRGC-LRMS法测定环境样品中二噁英类多氯联苯

多氯联苯(PCBS)是一类具有209种同类物的高毒性、难降解、强脂溶性和生物累积性的持久性有机污染物,自从1966年Jensen首次在鹰和鲱鱼中发现PCBs后,现在已在世界各地不同的环境介质中都发现有PCBs的存在。早在20世纪70～80年代国际上就开发了一些环境样品中PCBs的分析方法。但这些方法基本上基于某一种或几种商业PCBs混合物来对环境中多氯联苯类物质进行评价的,由于该商业PCBs是数十种或上百种PCBs的混合物,所评价的对象中PCBs的结果并不能准确反映其环境危害性。另一     

气相色谱-三重四极杆质谱同位素内标法测定鱼样中20种多氯联苯

建立了一种气相色谱-三重四极杆质谱结合双稳定性同位素内标检测鱼样中多氯联苯的方法。采用自动索氏提取器提取样品中的多氯联苯,经一根复合净化柱净化后,采用质谱多反应监测模式检测,选取两个独立的离子对。分析了20种多氯联苯,包含7种指示性多氯联苯,从三氯联苯到八氯联苯每族3个化合物,九氯联苯和十氯联苯各一个,每族使用一个相同氯代程度的¹³C₁₂标记多氯联苯作为定量内标、2种回收内标。20种多氯联苯在33 min内流出,分离良好,线性范围为0.05~10 μg/L,相关系数r均在0.99以上,低、中、高3种水平的加标回收率均在80.3%~117.6%之间,相对标准偏差（RSD,n=6）在5.09%~18.5%之间,方法检出限为0.01~0.02 μg/kg。20种多氯联苯总量在1.2~8.8 μg/kg（湿重）范围内,7个指示性多氯联苯总量在0.68~6.4 μg/kg（湿重）范围内。该方法缩短了分析时间,减少了有机溶剂的使用量,适合鱼样中多氯联苯的测定。     

双柱双检测器气相色谱法测定水样中多氯联苯Aroclor系列

采用液液萃取技术提取水样中多氯联苯系列有机物,经浓硫酸和硅胶柱净化浓缩后,利用气相色谱法分离,双电子捕获检测器(ECD)检测,根据双柱的保留值进行多氯联苯Aroclor系列的定性和定量分析。多氯联苯的基体加标回收率为73.5%～108.1%,方法检出限为0.051～0.083μg/L。     

电化学传感器检测环境中多氯联苯的研究进展

多氯联苯(PCBs)为环境中持久性有毒有机污染物之一,对生态环境产生了严重的危害。随着科研人员对PCBs危害性认识的深入,PCBs监测方法的研究日益增多。该文概述了近年来国内外PCBs的主要分析方法,重点介绍了电化学传感器检测PCBs的研究成果,指出了目前电化学传感器检测PCBs存在的问题,并对电化学传感器在PCBs检测中的发展前景进行了展望。     

An impact crushing dynamic model of waste printed circuit board particles

In order to obtain optimal particle size and distribution of crushed waste printed circuit boards (PCBs) for high-quantify separation of Cu and nonmetal, different distribution models are used to describe waste PCBs particles impact crushing distribution characteristics. The results showed that: Rosin–Rammler distribution can more accurately describe waste PCBs impact crushing distribution regularity, and can be used to predict waste PCBs particles impact crushing distribution characteristics. Based on this, a new dynamic model for impact crushing waste PCBs particle size and distribution was established. It was used to analyze the impact crushing distribution characteristics of the waste PCBs particles with the same mass and different size grades, and with the same size grades and different mass. The results have a good agreement with the actual crushing results. This model has some significance for the processing of waste PCBs impact crushing, and this research possibly offers a basis for the design of waste PCBs recycling production lines.     

Quantification of polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) in the picogram/liter range in water of the river Elbe

Sampling and determination of dissolved and particlebound PCBs and HCB in the river Elbe are described. A new filtration/adsorption unit for sampling of dissolved lipophilic contaminants was developed. The detection limit for dissolved PCBs and HCB was 5 pg/l. The data show that more than 98% of the PCBs and of HCB in the water of the river Elbe are particle-bound.     

Accumulation and efflux of polychlorinated biphenyls in Escherichia coli

Polychlorinated biphenyls (PCBs) are environmental pollutants that have been associated with numerous adverse health effects in human and animals. Hydroxylated PCBs (HPCBs) are the product of the oxidative metabolism of PCBs. The presence of hydroxyl groups in HPCBs makes these compounds more hydrophilic than the parent PCBs. One of the best approaches to break down and remove these contaminants is bioremediation; an environmentally friendly process that uses microorganisms to degrade hazardous chemicals into non-toxic ones. In this study, we investigated the cellular accumulation and toxicity of selected PCBs and HPCBs in Gram-negative bacteria, using Escherichia coli as a model organism. We found that none of the five PCBs tested were toxic to E. coli, presumably due to their limited bioavailability. Nevertheless, different HPCBs tested showed different levels of toxicity. Furthermore, we demonstrated that the primary multidrug efflux system in E. coli, AcrAB-TolC, facilitated the efflux of HPCBs out of the cell. Since AcrAB-TolC is constitutively expressed in E. coli and is conserved in all sequenced Gram-negative bacterial genomes, our results suggest that the efflux activities of multidrug resistant pumps may affect the accumulation and degradation of PCBs in Gram-negative bacteria.     

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry of polychlorinated biphenyls

A sample mixture of polychlorinated biphenyls (PCBs) was measured by gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOF-MS) using four types of laser sources. When a fourth harmonic emission (266 nm) of a picosecond Nd:YAG laser (1064 nm) was utilized, highly chlorinated PCBs larger than hepta-CBs were not observed. A fifth harmonic emission (213 nm) of the picosecond Nd:YAG laser allowed the measurement of PCBs from di-CBs to octa-CBs, and the limit of detection (LOD) was several pg for each component of PCBs. The LOD for the total amount of PCBs, which was calculated using the protocol provided by the Ministry of the Environment, Japan, was 1000 pg. The signal intensity of the congeners with chlorine atoms at the ortho positions (non-coplanar PCBs) was enhanced by using the fifth harmonic emission. When the fourth harmonic emission remaining after fifth harmonic generation was simultaneously used, the LOD for total PCBs was improved to 667 pg. The PCB sample was also measured using a third harmonic emission (267 nm) of a femtosecond Ti:sapphire laser (800 nm), providing an LOD of 677 pg. Thus, the two-color beam (266/213 nm) of a picosecond Nd:YAG laser had a comparable, or even slightly superior, performance to the more expensive femtosecond Ti:sapphire laser.     

Halogen Bonding Interactions of Polychlorinated Biphenyls and the Potential for Thyroid Disruption

Polychlorinated biphenyl (PCB) flame retardants are persistent pollutants and inhibit neurodevelopment, particularly in the early stages of life. Halogen bonding (XB) to the iodothyronine deiodinases (Dio) that modulate thyroid hormones (THs) is a potential mechanism for endocrine disruption. Cl⋅⋅⋅Se XB interactions of PCBs with SeMe⁻, a small model of the Dio active site selenocysteine, are compared with previous results on polybrominated diphenylethers (PBDEs) and THs using density functional theory. PCBs generally display weaker XB interactions compared to PBDEs and THs, consistent with the dependence of XB strength on the size of the halogen (I>Br>Cl). PCBs also do not meet a proposed energy threshold for substrates to undergo dehalogenation, suggesting they may behave as competitive inhibitors of Dio in addition to other mechanisms of endocrine disruption. XB interactions in PCBs are position-dependent, with ortho interactions slightly more favorable than meta and para interactions, suggesting that PCBs may have a greater effect on certain classes of Dio. Flexibility of PCBs around the biphenyl C−C bond is limited by ortho substitutions relative to the biphenyl linkage, which may contribute to the ability to inhibit Dio and other TH-related proteins.     

Real-time measurements of polychlorinated biphenyls using laser ionization time-of-flight mass spectrometry.

Polychlorinated biphenyls (PCBs) are hazardous compounds for which there are few methods involving real-time measurement. Recently, the development of the pulsed-laser technique has enabled us to measure aromatic hydrocarbons quite rapidly. In particular, the LI-TOFMS (laser ionization time of flight mass spectrometry) technique is expected to be a powerful method for on-line, selective and sensitive measurements. In the context of developing a highly selective and sensitive technique, the effective laser wavelength and pulse duration for laser ionization of 2-4 chlorinated PCBs are considered. Excitation at lambda = 266 nm was found to be substantially more effective than at lambda = 280, 300 or 320 nm. Also, picosecond excitation for PCBs underwent more efficient ionization (by a factor of over 10) and less fragmentation than nanosecond excitation. The achievable sensitivity for trichlorinated biphenyl in a real-time (1 min) measurement using the LI-TOFMS technique was estimated to be in the sub-ppbV range (< 0.01 mg/Nm3).     

Development of a gas chromatography/ion trap mass spectrometry based method for the quantification of polybrominated diphenyl ethers and polychlorinated biphenyls in adipose tissue

A combined gas chromatographic mass spectrometric (GC/MS/MS) method for the determination of seven polybrominated diphenyl ethers (PBDEs) and seven marker polychlorinated biphenyls (PCBs) in adipose tissue has been developed. Adipose tissue was melted and filtered through anhydrous sodium sulphate to obtain pure fat. Clean-up was performed using a glass column containing acidified silica, deactivated alumina and anhydrous sodium sulphate. Polybrominated biphenyl (PBB) 155 and Mirex were added as internal standards for PBDEs and PCBs, respectively. Injection standards, PBB 103 and PCB 143, for PBDEs and PCBs, respectively, were added before analysis with GC/MS/MS. The developed GC/MS/MS method has the advantage of being more selective than single MS methods because matrix effects are largely eliminated. Validation of this method was conducted according to Commission Decision 2002/657/EC. Decision limits for PBDEs and PCBs ranged from 0.06-0.15 ng g(-1) and from 0.35-1.22 ng g(-1), respectively. Detection capabilities were all between 0.23-0.55 ng g(-1) for PBDEs and between 0.98-2.29 ng g(-1) for PCBs. Precision, recovery, bias and selectivity were tested, with satisfactory results.     

Analysis of Affinity Energy Between Biphenyl Dioxygenase and Polychlorinated Biphenyls Using Molecular Docking

Molecular docking was used to calculate the affinity energy between biphenyl dioxygenases(BphA),including 1ULJ,1WQL,2YFJ,2YFL,2GBX,2XSH,2B4P,3GZX,and 3GZY(selected from the Protein Data Bank)and 209 polychlorinated biphenyl(PCB)congeners.The relationships between the calculated affinity energy and the persistent organic pollutant characteristics(migration,octanol-air partition coefficients,lgKOA;persistence,half-life,lgt1/2;toxicity,half-maximal inhibitory concentration,IgIC50;bioaccumulation,bioconcentration factor,lgBCF)of the PCBs were studied to mderstand the BphA mediated degradation of PCBs.The effect of substituent characteristics on the affinity energy was explored through full factorial experimental design.The affinities of nine kinds of BphA proteins on PCBs ranked as follows:2GBX>2YFJ>2YFL>3GZX>2XSH>3GZY>2E4P>1 WQL>1ULJ.The relationships between the calculated affinity energy and the molecular weight,lgKOA,lgBCF,and lgt1/2 of the PCBs were statistically signiflcant(p<0.01),whereas the relationship with the lgIC50 of PCBs was not statistically significant(p>0.05).PCBs were more difficult to degrade following an increase in the free energy of binding.Correlation analysis showed that the average affinity energy values of PCBs gradually increased as the number of chlorine atoms increased,regardless of the substituent position.The substituents at the ortho-positions interacted mainly through a second-order interaction,whereas those at the para-positions did not participate via a second-order interaction.     

Efficient isolation of polyaromatic fraction from aliphatic compounds in complex extracts using dimethylformamide-pentane partitionings

A liquid-liquid partitioning method was optimized for the rapid and quantitative separation of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) from aliphatic hydrocarbons in complex primary extracts. This technique was based on the selective extraction of PAHs and PCBs from an aliphatic solvent into dimethylformamide (DMF). Partition experiments demonstrated that the optimal performance was achieved with a DMF (5% H2O)-n-pentane binary system. The optimized application of two consecutive DMF (5% H2O)-n-pentane treatments to extracts from two different polluted sediments facilitated the elimination of alkanes and unresolved complex mixture by more than 94% while the average recoveries of spiked deuterated-PAHs and 13C labeled PCBs ranged from 84 to 94 and 75 to 96%, respectively.