Polychlorinated dibenzo-p-dioxins（PCDDs） are a group of important persistent organic pollutants.They are highly toxic and persistent in environment.In the present study,geometrical optimization and electrostatic pot...Polychlorinated dibenzo-p-dioxins（PCDDs） are a group of important persistent organic pollutants.They are highly toxic and persistent in environment.In the present study,geometrical optimization and electrostatic potential calculations have been performed for 75 PCDD congeners and dibenzo-p-dioxin（DD） at the HF/6-31G＊ level of theory.A number of statistically based parameters have been extracted.Linear relationships between vapor pressures（logpL）,aqueous solubilities（logSw）,n-octanol/water partition coefficients（logKow） of PCDDs and structural descriptors have been established by stepwise linear regression analysis.The result shows that the quantities derived from the surface electrostatic potentials Vmin,Π,and Vs,av＋,together with Vmc（the molecular volume） and ELUMO（the energy of the lowest unoccupied molecular orbital） can be well used to express the quantitative structure-property relationships of PCDDs.Predictive capabilities of the models have also been demonstrated by leave-one-out cross-validation with the cross-validated correlation coefficient（Rcv） above 0.97.Based on these QSPR models,the predicted values have been presented for those PCDD congeners whose experimentally determined physicochemical properties are unavailable.展开更多
Polychlorinated dibenzo-p-dioxins and furans （PCDD/Fs） emissions in flue gas from two types of municipal solid waste incinerators （MSWIs） most commonly used in China were investigated in this study. The selected i...Polychlorinated dibenzo-p-dioxins and furans （PCDD/Fs） emissions in flue gas from two types of municipal solid waste incinerators （MSWIs） most commonly used in China were investigated in this study. The selected incinerators include two grate-type MSWIs： MSWI-A （350 t/d） and MSWI-B 050 t/d）, and two fluidized bed MSWIs： MSWI-C （400 t/d） and MSWI-D （400 t/d）, which are all equipped with semi-dry lime scrubber and bag filter except MSWI-D equipped with cyclone and wet scrubber （WS） as air pollutant control device （APCD）. Results indicated that the emission concentration and the international toxic equivalents （I-TEQs） of the PCDD/Fs from the stacks were in the range of 1.210-10.273 ng/Nm^3 and 0.019-0.201 ng I-TEQ/Nm^3, respectively. They were greatly lower than the emission regulation standard of PCDD/Fs in China （1.0 ng I-TEQ/Nm^3）. However, only the PCDD/Fs emission level from MSWI-C was below 0.1 ng I-TEQ/Nm^3. Although the homologue profiles were distinct, the contributions of the 2,3,7,8-subsituted congeners to the total I-TEQ were similar among all the investigated MSWIs. Two major 2,3,7,8-substituted congeners, 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDD, account for 47% and 9% （average values） of the total I-TEQ values, respectively. The correlation between PCDD/Fs levels and composition of flue gas was also discussed.展开更多
Surface sediments and bivalves were collected from the Changjiang Estuary in December 2003 and November 2004, respectively. Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in these samples were mea...Surface sediments and bivalves were collected from the Changjiang Estuary in December 2003 and November 2004, respectively. Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in these samples were measured with high-resolution chromatography (HRGC)/High Resolution Mass Spectrometer (HRMS). The concentrations of total PCDD/Fs and toxic equivalent (TEQ) were 169.83±119.63 and 0.81±0.36 pg/g dry weight (dw) in sediments, and 580.33±240.17 and 7.24±3.65 pg/g dw in bivalves. The homolog compositions of PCDD/Fs were similar among samples, the most abundant congener was octa-chlorinated dibenzo-p-dioxin (OCDD) and then octa-chlorinated dibenzofuran (OCDF) and 1,2,3,4,6,7,8-hepta-chlorinated dibenzo-p-dioxin (HpCDD). The herbicide pentachlorophenol (PCP) and sodium pentachlorophenol (Na-PCP) were proved the main source of PCDD/Fs in this area.展开更多
Electrochemical polymerization of 3-fluoroalkoxy and 3-fluoroether thiophenes gives polymers with relatively high molecular weights and good processibility. Investigation of these polymers by means of GPC indicates th...Electrochemical polymerization of 3-fluoroalkoxy and 3-fluoroether thiophenes gives polymers with relatively high molecular weights and good processibility. Investigation of these polymers by means of GPC indicates that an increase in the number of fluorine atoms in the fluorinated group results in a decrease in degree of polymerization of the polymers in the same polythiophene series. As shown by NMR and FTIR, the polyfluorinated group substituted polythiophenes have regular 2, 5-coupling in their main chains. The SEM micrographs of the polymer films exhibit that polymer (1)-poly [3-2, 2, 3, 3-tetrafluoro-propoxy) thiophene] possesses more regular structure than the other polymers do. Substitution of polythiophenes by fluorinated groups leads to the polymers with high electric, electrochemical and thermal stability.展开更多
Three series of polythiophenes containing fluoroalkoxy and fluoroether substituents were prepared by electrochemical polymerization. The effect of substituents with fluoroalkoxy or ether functional groups on the elect...Three series of polythiophenes containing fluoroalkoxy and fluoroether substituents were prepared by electrochemical polymerization. The effect of substituents with fluoroalkoxy or ether functional groups on the electrochemical polymerization of thiophene monomers and properties of the obtained polymers were analyzed. The introduction of a fluoroether functional group at the 3-position of the thiophene ring leads to an increase of the oxidation potential of the monomer and to a decrease of the conductivity of the resulting polymers, even with the use of a CH2 group as spacer. Conversely, the presence of an oxygen atom directly at the 3-position of the thiophene ring, which offsets the negative withdrawing effect of fluoroalkyl groups, facilitates the synthesis of highly conducting polythiophenes.展开更多
The thermodynamic properties and molecular volumes （Vm） of 76 polychlorophenazines （PCPZs） have been calculated at the B3LYP/6-31G^＊ level by using density functional theory. The isodesmic reactions were designed...The thermodynamic properties and molecular volumes （Vm） of 76 polychlorophenazines （PCPZs） have been calculated at the B3LYP/6-31G^＊ level by using density functional theory. The isodesmic reactions were designed to calculate standard enthalpy of formation （△fH^θ） and standard free energy of formation （△fG^θ） of PCPZ congeners. According to the relative magnitude of their △fG^θ, the order of relative stability of PCPZ congeners was theoretically proposed. Comparing the results with those of polychlorinated dibenzo-p-dioxin （PCDD） isomers, it was found that S^θ, △fH^θ, △fG^θ, Vm and the order of relative stability of PCPZ congeners were quite similar to those of PCDDs.展开更多
We analyzed polychlorinated dibenzofurans (PCDF) and dibenzo-p-dioxins (PCDD) in 27 tree bark samples from the industrialized area near Sauget, Illinois, USA. The trees were located within 4 km of the W. G. Krummrich ...We analyzed polychlorinated dibenzofurans (PCDF) and dibenzo-p-dioxins (PCDD) in 27 tree bark samples from the industrialized area near Sauget, Illinois, USA. The trees were located within 4 km of the W. G. Krummrich (WGK) plant, the oldest and largest chemical plant in Sauget, with 24 of 27 samples collected from residential areas. The percent of total PCDF or PCDD profiles of ten 2,3,7,8- Cl substituted PCDF and seven PCDD congeners is homogeneous: 90% of the variance among the samples is explained by 3 eigenvalues in a principal components analysis. The homogeneity of the data suggests that samples were affected by similar types of sources which may have been influenced by electric power generation, chemical waste incineration, and large-scale thermal production of chlorinated chemicals. Quantitatively, the 2,3,7,8-Cl substituted congener analysis does not account for 90% of the concentration of tetra- and penta-Cl homologues and 80% of hexa-Cl and 50% of hepta-Cl homologues. The World Health Organization stated during establishment of toxic equivalence factors (TEF, 2005 version) that calculation of toxic equivalents (TEQs) is not suitable for abiotic matrices, such as tree bark, which are not involved in human exposures. Our results show that the non-2,3,7,8-Cl substituted congeners have high concentrations and should be included in analysis.展开更多
A rapid pretreatment method of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in soil and analysis by high resolution gas chromatograph-high resolution mass spectrometry was present.The extraction and a...A rapid pretreatment method of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in soil and analysis by high resolution gas chromatograph-high resolution mass spectrometry was present.The extraction and alumina clean up of PCDD/Fs in soil was achieved by accelerated solvent extractor.Then the multi-layer silica-gel column was used for further clean up.The whole method has been evaluated on certified reference soil and farm soil.Accuracy and precision of this method was tested with satisfactory results.展开更多
Labeled polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)were extracted by three different methods,i.e.,soxhlet extraction,hot extraction and accelerated solvent extraction(ASE).The PCDD/Fs were detected by...Labeled polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)were extracted by three different methods,i.e.,soxhlet extraction,hot extraction and accelerated solvent extraction(ASE).The PCDD/Fs were detected by high resolution gas chromatography-high resolution mass spectrometry.Comparisons of the three methods were carried out by recovery of PCDD/Fs,solvent consumption and extraction time.The results showed that all of the method could extract labeled PCDD/Fs efficiently.ASE was a time saving procedure with lowest consumption of solvents compared with the other two methods.展开更多
基金supported by the Analysis and Measurement Planning Project of Zhejiang Province (2007F70053)
文摘Polychlorinated dibenzo-p-dioxins（PCDDs） are a group of important persistent organic pollutants.They are highly toxic and persistent in environment.In the present study,geometrical optimization and electrostatic potential calculations have been performed for 75 PCDD congeners and dibenzo-p-dioxin（DD） at the HF/6-31G＊ level of theory.A number of statistically based parameters have been extracted.Linear relationships between vapor pressures（logpL）,aqueous solubilities（logSw）,n-octanol/water partition coefficients（logKow） of PCDDs and structural descriptors have been established by stepwise linear regression analysis.The result shows that the quantities derived from the surface electrostatic potentials Vmin,Π,and Vs,av＋,together with Vmc（the molecular volume） and ELUMO（the energy of the lowest unoccupied molecular orbital） can be well used to express the quantitative structure-property relationships of PCDDs.Predictive capabilities of the models have also been demonstrated by leave-one-out cross-validation with the cross-validated correlation coefficient（Rcv） above 0.97.Based on these QSPR models,the predicted values have been presented for those PCDD congeners whose experimentally determined physicochemical properties are unavailable.
基金the Natural Science Foundation of Zhejiang Province (No. X206955)Zhejiang Medical and Health Research Fund (No. 2007A047)the Education Bureau of Zhejiang Prov-ince (No. N20080181), China
文摘Polychlorinated dibenzo-p-dioxins and furans （PCDD/Fs） emissions in flue gas from two types of municipal solid waste incinerators （MSWIs） most commonly used in China were investigated in this study. The selected incinerators include two grate-type MSWIs： MSWI-A （350 t/d） and MSWI-B 050 t/d）, and two fluidized bed MSWIs： MSWI-C （400 t/d） and MSWI-D （400 t/d）, which are all equipped with semi-dry lime scrubber and bag filter except MSWI-D equipped with cyclone and wet scrubber （WS） as air pollutant control device （APCD）. Results indicated that the emission concentration and the international toxic equivalents （I-TEQs） of the PCDD/Fs from the stacks were in the range of 1.210-10.273 ng/Nm^3 and 0.019-0.201 ng I-TEQ/Nm^3, respectively. They were greatly lower than the emission regulation standard of PCDD/Fs in China （1.0 ng I-TEQ/Nm^3）. However, only the PCDD/Fs emission level from MSWI-C was below 0.1 ng I-TEQ/Nm^3. Although the homologue profiles were distinct, the contributions of the 2,3,7,8-subsituted congeners to the total I-TEQ were similar among all the investigated MSWIs. Two major 2,3,7,8-substituted congeners, 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDD, account for 47% and 9% （average values） of the total I-TEQ values, respectively. The correlation between PCDD/Fs levels and composition of flue gas was also discussed.
基金supported by National Research Program (No. 2003CB415005)"Youth Chen-Guang Project" of Wuhan Bureau of Science and Technology (No. 200750731259).
文摘Surface sediments and bivalves were collected from the Changjiang Estuary in December 2003 and November 2004, respectively. Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in these samples were measured with high-resolution chromatography (HRGC)/High Resolution Mass Spectrometer (HRMS). The concentrations of total PCDD/Fs and toxic equivalent (TEQ) were 169.83±119.63 and 0.81±0.36 pg/g dry weight (dw) in sediments, and 580.33±240.17 and 7.24±3.65 pg/g dw in bivalves. The homolog compositions of PCDD/Fs were similar among samples, the most abundant congener was octa-chlorinated dibenzo-p-dioxin (OCDD) and then octa-chlorinated dibenzofuran (OCDF) and 1,2,3,4,6,7,8-hepta-chlorinated dibenzo-p-dioxin (HpCDD). The herbicide pentachlorophenol (PCP) and sodium pentachlorophenol (Na-PCP) were proved the main source of PCDD/Fs in this area.
基金This work was supported by the National Natural Science Foundation of China.
文摘Electrochemical polymerization of 3-fluoroalkoxy and 3-fluoroether thiophenes gives polymers with relatively high molecular weights and good processibility. Investigation of these polymers by means of GPC indicates that an increase in the number of fluorine atoms in the fluorinated group results in a decrease in degree of polymerization of the polymers in the same polythiophene series. As shown by NMR and FTIR, the polyfluorinated group substituted polythiophenes have regular 2, 5-coupling in their main chains. The SEM micrographs of the polymer films exhibit that polymer (1)-poly [3-2, 2, 3, 3-tetrafluoro-propoxy) thiophene] possesses more regular structure than the other polymers do. Substitution of polythiophenes by fluorinated groups leads to the polymers with high electric, electrochemical and thermal stability.
基金This work was supported by the National Natural Science Foundation of China.
文摘Three series of polythiophenes containing fluoroalkoxy and fluoroether substituents were prepared by electrochemical polymerization. The effect of substituents with fluoroalkoxy or ether functional groups on the electrochemical polymerization of thiophene monomers and properties of the obtained polymers were analyzed. The introduction of a fluoroether functional group at the 3-position of the thiophene ring leads to an increase of the oxidation potential of the monomer and to a decrease of the conductivity of the resulting polymers, even with the use of a CH2 group as spacer. Conversely, the presence of an oxygen atom directly at the 3-position of the thiophene ring, which offsets the negative withdrawing effect of fluoroalkyl groups, facilitates the synthesis of highly conducting polythiophenes.
基金supported by the National Natural Science Foundation of China (No. 20737001 and No. 20477018)
文摘The thermodynamic properties and molecular volumes （Vm） of 76 polychlorophenazines （PCPZs） have been calculated at the B3LYP/6-31G^＊ level by using density functional theory. The isodesmic reactions were designed to calculate standard enthalpy of formation （△fH^θ） and standard free energy of formation （△fG^θ） of PCPZ congeners. According to the relative magnitude of their △fG^θ, the order of relative stability of PCPZ congeners was theoretically proposed. Comparing the results with those of polychlorinated dibenzo-p-dioxin （PCDD） isomers, it was found that S^θ, △fH^θ, △fG^θ, Vm and the order of relative stability of PCPZ congeners were quite similar to those of PCDDs.
文摘We analyzed polychlorinated dibenzofurans (PCDF) and dibenzo-p-dioxins (PCDD) in 27 tree bark samples from the industrialized area near Sauget, Illinois, USA. The trees were located within 4 km of the W. G. Krummrich (WGK) plant, the oldest and largest chemical plant in Sauget, with 24 of 27 samples collected from residential areas. The percent of total PCDF or PCDD profiles of ten 2,3,7,8- Cl substituted PCDF and seven PCDD congeners is homogeneous: 90% of the variance among the samples is explained by 3 eigenvalues in a principal components analysis. The homogeneity of the data suggests that samples were affected by similar types of sources which may have been influenced by electric power generation, chemical waste incineration, and large-scale thermal production of chlorinated chemicals. Quantitatively, the 2,3,7,8-Cl substituted congener analysis does not account for 90% of the concentration of tetra- and penta-Cl homologues and 80% of hexa-Cl and 50% of hepta-Cl homologues. The World Health Organization stated during establishment of toxic equivalence factors (TEF, 2005 version) that calculation of toxic equivalents (TEQs) is not suitable for abiotic matrices, such as tree bark, which are not involved in human exposures. Our results show that the non-2,3,7,8-Cl substituted congeners have high concentrations and should be included in analysis.
文摘A rapid pretreatment method of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in soil and analysis by high resolution gas chromatograph-high resolution mass spectrometry was present.The extraction and alumina clean up of PCDD/Fs in soil was achieved by accelerated solvent extractor.Then the multi-layer silica-gel column was used for further clean up.The whole method has been evaluated on certified reference soil and farm soil.Accuracy and precision of this method was tested with satisfactory results.
文摘Labeled polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)were extracted by three different methods,i.e.,soxhlet extraction,hot extraction and accelerated solvent extraction(ASE).The PCDD/Fs were detected by high resolution gas chromatography-high resolution mass spectrometry.Comparisons of the three methods were carried out by recovery of PCDD/Fs,solvent consumption and extraction time.The results showed that all of the method could extract labeled PCDD/Fs efficiently.ASE was a time saving procedure with lowest consumption of solvents compared with the other two methods.
