Chlorination of dibenzofuran and dibenzo-p-dioxin vapor by copper (II) chloride

Dibenzofuran (DF) is formed from phenol and benzene in combustion gas exhaust streams prior to particle collection equipment. Subsequent chlorination at lower temperatures on particle surfaces is a potential source of chlorinated dibenzofuran (CDF). Gas streams containing 8% O₂ and approximately 0.1% DF vapor were passed through particle beds containing copper (II) chloride (0.5% Cu, mass) at temperatures ranging from 200 to 400 °C to investigate the potential for CDF formation during particle collection. Experiment duration was sufficient to provide an excess amount of DF (DF/Cu=3). The efficiency of DF chlorination by CuCl₂ and the distribution of CDF products were measured, with effects of temperature, gas velocity, and experiment duration assessed. Results of a more limited investigation of dibenzo-p-dioxin (DD) chlorination by CuCl₂ to form chlorinated DD (CDD) products are also presented.The efficiency of DF/DD chlorination by CuCl₂ was high, both in terms of CuCl₂ utilization and DF/DD conversion. Total yields of Cl on CDF/CDD products of up to 0.5 mole Cl per mole CuCl₂ were observed between 200 and 300 °C; this suggests that nearly 100% CuCl₂ was utilized, assuming a conversion of two moles of CuCl₂ to CuCl per mole Cl added to DD/DF. In a short duration experiment (DF/Cu=0.3), nearly 100% DF adsorption and conversion to CDF was achieved. The degree of CDF chlorination was strongly dependent on gas velocity. At high gas velocity, corresponding to a gas–particle contact time of 0.3 s, mono-CDF (MCDF) yield was largest, with yields decreasing with increasing CDF chlorination. At low gas velocity, corresponding to a gas–particle contact time of 5 s, octa-CDF yield was largest. DF/DD chlorination was strongly favored at lateral sites, with the predominant CDF/CDD isomers within each homologue group those containing Cl substituents at only the 2,3,7,8 positions. At the higher temperatures and lower gas velocities studied, however, broader isomer distributions, particularly of the less CDD/CDF products, were observed, likely due to preferential destruction of the 2,3,7,8 congeners.     

Micro-scale bromination procedure for synthesis of “2,3,7,8-substituted” brominated dibenzo-p-dioxins and dibenzofurans from [C]-labeled precursors

Brominated dibenzo-p-dioxin and dibenzofuran (BDD/BDF) isomers, specifically having from one to three halogens located in the 2,3,7,8-substituent positions, that are [¹³C]-labeled for use as analytical internal standards in mass spectrometric methods are not yet commercially available. Based upon the current availability of [¹³C]-labeled dibenzo-p-dioxin and dibenzofuran (DD/DF) precursors, we have developed a simple and efficient synthetic procedure which produces brominated congeners that are predominantly substituted in the 2,3,7, and 8-positions. The gas/solid reaction of vaporized precursor and surface-supported iron (III) bromide occurs rapidly (seconds) at temperatures ≥ 240°C and can provide total product yields in the range of 30 to 50 mole % for initial precursor amounts between 1 μg and 10 mg. In this paper we shall describe the utility of this approach to produce 5 μg quantities of [¹³C₁₂]-2,7-dibromodibenzo-p-dioxin (27-DBDD) and [¹³C₁₂]-2,8-dibromodibenzo-p-dioxin (28-DBDD).     

Metal-mediated chlorinated dibenzo-p-dioxin (CDD) and dibenzofuran (CDF) formation from phenols

Heterogeneous formation of chlorinated dibenzo-p-dioxins (CDDs) and dibenzofurans (CDFs) on CuCl2 from three phenols without ortho chlorine and one phenol with two ortho chlorines was studied in a flow reactor over a temperature range of 325-450 degrees C. Heated nitrogen gas streams containing 8% oxygen, 1.5% benzene vapor, and equal amounts of phenol, 3-chlorophenol, 3,4-dichlorophenol and 2,4,6-trichlorophenol vapor (700 ppmv, each) were passed through a 1 g particle bed of silica and 0.5% (Cu mass) CuCl2. Maximum product yields of greater than 1.4% phenol conversion to CDD and 5.7% phenol conversion to CDF were observed between 400 and 450 degrees C. CDDs formed with loss of one chlorine atom were favored. While total CDD/F yield varied with temperature, CDD/F homologue and isomer distributions did not vary significantly with temperature. Based on the results of experiments with single phenol precursors, phenol precursors could be assigned to all PCDD/F products. Of the chlorinated phenols without ortho chlorine that were studied, 3,4-dichlorophenol was found to have the greatest propensity to form CDFs.     

Mono- to tri-chlorinated dibenzodioxin (CDD) and dibenzofuran (CDF) congeners/homologues as indicators of CDD and CDF emissions from municipal waste and waste/coal combustion

Total homologue concentrations and select congener concentrations from amongst the mono- to tri-chlorinated dibenzodioxins (CDDs) and dibenzofurans (CDFs) are used to model both Total (mono- to octa-) CDD + CDF emissions and the toxicity equivalent (TEQ) of the 2,3,7,8-chlorine-substituted emissions. Analysis of emission data from two facilities indicates that use of total homologue concentrations shows limited, facility-specific correlations with Total CDDs/CDFs and TEQ. Concentrations of select mono- to tri-CDD/CDF congeners show promising correlation with CDD/CDF TEQ across facilities, suggesting that these compounds can act as TEQ indicators.     

Polychlorinated dibenzo-p-dioxins and dibenzofurans in plywood combustion gas

Polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/DF) levels in plywood combustion gas were investigated for the effects of ammonium chloride (NH4Cl) and paint. For combustion systems in which neither NH4Cl nor paint were present in the plywood samples, total amounts of PCDD/DFs in the combustion gas were in the order of 35-529 ng/Nm3, and were higher in the systems with softwood trees than broadleaf ones, depending on the Cl concentrations. For the systems with added NH4Cl and no paint, and those without NH4Cl but were painted, higher PCDD/ DF rates were observed at combustion temperatures of 270 degrees C and 500 degrees C, respectively. However, for the systems with both NH4Cl and paint, their amounts in the range of 0.6-13 ng/Nm3 were the lowest in all systems. The PCDD/DF abundance profiles were similar to their patterns in pentachlorophenol (PCP). Furthermore, it was found that the 2,3,7,8-chlorine substituted penta- and hexa-CDDs contributed more than other 2,3,7,8-chlorine substitutes to toxicity equivalency (TEQ).     

“Shorthand” numbering of chlorinated dibenzodioxins (CDD) and dibenzofurans (CDF)

Numbers in base 16 (Hex) are used for an abbreviated designation of chlorine substitution in CDD and CDF. This “shorthand” requires two hexadecimal digits. A letter (“d” or “f”) may be used to distinguish between CDD and CDF. The digits describe the substitution patterns in positions 6,7,8,9, and 4,3,2,1, assigned values of 8,4,2, and 1, respectively. For example, 66d = 2,3,7,8-tetrachlorodibenzo-p-dioxin.     

Inclusion of 13C12-labelled mono-, di-, and tri-chlorinated dibenzo-p-dioxin and dibenzofuran standards in US EPA methods 0023A/8290

13C12-Labelled mono-, di-, and tri-chlorinated dibenzo-p-dioxin (CDD) and chlorinated dibenzofuran (CDF) standards have been tested for their applicability to standard EPA sampling and analytical Methods 0023A/8290. These methods target for analysis only the tetra- through octa-CDD/CDF homologues. Extension of the isotope dilution method to include those lower chlorinated homologues is important toward obtaining reliable species concentration data on the complete, mono- to octa-chlorinated homologue profile. These data will improve our ability to model poly-CDD/CDF concentrations through understanding mechanisms of poly-CDD/CDF formation, chlorination, and dechlorination.     

Clearance of PCDD/Fs via the gastrointestinal tract in occupationally exposed persons.

A digestive tract mass balance was performed on six men with high body burdens of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Intake via food was measured by analyzing duplicate portions of the food consumed by the volunteers and excretion via feces was determined by quantitative collection and analysis of the feces. Blood samples were taken to determine the current body burden. The results showed that the quantity of non-metabolized chemical excreted in the feces clearly exceeded the uptake via food for all of the 2,3,7,8-substituted PCDDs and some of the PCDFs, indicating a significant clearance across the gastrointestinal tract. The concentrations of these PCDD/F congeners in blood and feces were highly correlated (r > 0.8), demonstrating that the fecal PCDD/F content was determined by the body burden. The half lives in the test persons due to fecal clearance of non-metabolized chemical were estimated from the excretion rate and the current body burden and ranged between 10 years (Cl8DD) and 33 years (2,3,4,7,8-Cl5DF). These were compared with the overall contaminant half-lives due to all clearance processes which were calculated from the body burden and the decrease in blood concentrations measured over several years. The fecal clearance of non-metabolized PCDD/F contributed on average between 37% (2,3,7,8-Cl4DD) and 90% (Cl8DD) to the total elimination. This indicates that the gastrointestinal pathway plays a decisive role in the clearance of most 2,3,7,8-subsituted PCDD/F congeners.     

CuCl2-catalyzed PCDD/F formation and congener patterns from phenols

Homologue and isomer patterns of polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) in CuCl2-catalyzed formation were studied in an isothermal flow reactor using a distribution of 20 phenols as measured in municipal waste incinerator (MWI) exhaust gases. A mixture of 20 phenols was synthesized and used as reactants for this study because phenols are known to be key precursors in the formation of PCDD/F. Experiments were conducted at 400 degrees C. The 92% of nitrogen (N2) and 8% of oxygen (O2) were used as a carrier gas. PCDD/F homologue and isomer patterns with dibenzo-p-dioxin (DD) and dibenzofuran (DF) were obtained from a mixture of 20 phenols. DF+PCDF formation was favored over DD+PCDD formation. The major homologue groups formed were non-chlorinated DD and DF, and PCDD/F homologue fraction decreased with the degree of chlorination. PCDD/F homologue and isomer distributions were almost constant. Phenol and lower chlorinated phenols present in high amount played an important role in PCDD/F congener distributions. The results presented here can be used as characteristics or fingerprints for homologue and isomer patterns of PCDD/F formation attribution in CuCl2-catalyzed reaction from phenols.     

Ambient air monitoring of PCDD/Fs and co-PCBs in Gyeonggi-do, Korea

We started the monitoring for PCDD/Fs in ambient air and soil in August 2001, and co-PCBs in January 2002. Decreasing of PCDD/Fs and co-PCBs levels in ambient air were observed. The higher PCDD/Fs levels were found in winter and lower in autumn. We found that the industrial incinerators influenced the PCDD/Fs levels in ambient air. In the 2,3,7,8-substituted PCDD/Fs concentration profiles, the three major congeners occupied 67% of the total mass. In case of co-PCBs, PCB#118, #105 and #77 were observed as the main congeners. Five cluster groups discriminated by ratio of four components, O(8)CDD, 1,2,3,4,6,7,8-H(7)CDD, 1,2,3,4,6,7,8-H(7)CDF and O(8)CDF, were obtained from HCA (hierarchical cluster analysis).     

Formation of PCDDs and PCDFs by the chlorination of water

Two samples of tab water and double distilled water were chlorinated using chlorine gas. A series of PCDFs could be identified from these experiments, however no PCDDs could be found. The two water samples gave very similar isomeric patterns ( . . tetra-CDFs), however the congener profile (Cl₄ --- Cl₈) was different. These experiments indicate that all products formed by chlorination reactions are potentially contaminated by PCDFs by a specific “chlorine pattern”.     

Degradation of aquatic humic material by ultraviolet light

Natural humic water was treated with ultraviolet (UV) light and UV + hydrogen peroxide (UV/H₂O₂. The effects on the dissolved organic carbon content (DOC), the UV-absorbance at 254 nm (UV-abs.), the molecular size distribution, pH, and mutagenic activity were monitored, and the identity and concentrations of the most abundant gas chromatographable organic degradation products were determined.

The DOC content and the UV-abs. of the water decreased substantially during treatment with UV/H₂O₂. The decreases were dependent on the time of irradiation (UV dose) as well as on the H₂O₂ dose applied. The humus macromolecules were degraded to smaller fragments during irradiation. At higher UV doses, however, part of the dissolved organic matter (DOM) was found to precipitate, probably as a result of polymerization. Oxalic acid, acetic acid, malonic acid, and n-butanoic acid were the most abundant degradation products detected. These acids were found to account for up to 20% and 80% of the DOM in UV- and UV/H₂O₂-treated waters, respectively. No mutagenic activity was generated by the UV irradiation or the UV/H₂O₂ treatment. It is further concluded that the substantial mutagenic activity formed during chlorination of humic waters cannot be decreased by using UV irradiation as a pretreatment step.     

Effect of boiler operation and RDF feedstock on emissions of dioxins and furans from an RDF fired sp reader-stoker system in Albany, NY

The data on dioxin and furan emissions revealed, based on individual analysis for 2,3,7,8-TCDD, TCDD, 2,3,7,8-TCDF and TCDF for the six test periods and the operation of the two RDF-fired boilers, that there is no apparent consistent relationship between the dioxin and furan emissions and the individual or combined (averaged) boiler steam flow, total flue gas flow, sidewall furnace temperature, furnace temperature at 2-second residence time, or total furnace residence time at this plant. Only RDF feeder balance begins to show a correlation. However, there was a difference between RDF-natural gas firing and RDF-only firing; the RDF-only firing had lower PCDD and PCDF emissions while consistently operating at lower excess air.

The dioxin and furan emissions from this testing are comparable to the low end of the range of these emissions measured by the U.S. EPA at resource recovery plants in the past 4 years. This may be due in part to the calculated average furnace retention of 4 to 5 seconds during Tests #4–6, with average furnace temperatures at 2-second residence time from 1650°F to 1750°F. However, there was no correlation between dioxin and furan emissions in the stack and individual boiler operation, as judged by the average concentrations of O₂, CO, CO₂, 1-CO/CO₂), NO_x, HCl, SO₂, or TSP, and furnace upset conditions versus normal operation as judged by instantaneous steam flow, sidewall furnace temperature, O₂, CO, NO_x, or SO₂.     

The distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans in Jackfish Bay, Lake Superior, in relation to a kraft pulp mill effluent

Samples of whole effluent and effluent suspended solids from a kraft pulp mill and sediments and biota from Jackfish Bay, Lake Superior were analyzed for polychlorinated dibenzo-p-dioxins (CDDs) and dibenzofurans (CDFs). Tetra-CDFs (4CDF) were consistently detected in whole effluent at levels ranging between 0.3 and 1.3 ng/L. Effluent suspended solids also contained 4CDFs as well as traces of 4CDD, 5CDF, 8CDF and 8CDD. The horizontal sediment distribution suggests that the effluent was the only active source of 4CDF in the area but that 8CDD originated from a more general source such as the atmosphere. An abrupt appearance of 4CDF in the more recent sections of a core profile taken in the bay suggests that an operational change at the pulp mill resulted in the formation of 4CDFs in the mill effluent some time after 1973. Moderate values of 4CDF and low values of 4CDD were found in samples of the shrimp confirming the presence of an active source of 4CDF in Jackfish Bay.     

Chlorination of bisphenol A in aqueous media: formation of chlorinated bisphenol A congeners and degradation to chlorinated phenolic compounds

The chlorination of bisphenol A (BPA) in aqueous media was investigated in order to describe the degradation profile of this compound and the formation of chlorinated products. Aqueous solutions of BPA (approx. 1 mg/l) were chlorinated by sodium hypochlorite solution at room temperature and under weakly alkaline conditions. Chlorinated compounds were extracted with dichloromethane and determined by gas chromatography/mass spectrometry (GC/MS). BPA was consumed completely within 5 min of chlorination, when the initial chlorine concentration was 10.24 mg/l (molar ratio to BPA, 58.7). On the other hand, when the initial chlorine concentration was 1.03 mg/l (molar ratio, 6.56), 9.3% of BPA still remained after 60 min chlorination. Five chlorinated BPA congeners, 2-chlorobisphenol A (MCBPA), 2,6-dichlorobisphenol A (2,6-D2CBPA), 2,2'-dichlorobisphenol A (2,2'-D2CBPA), 2,2',6-trichlorobisphenol A (T3CBPA) and 2,2', 6,6'-tetrachlorobisphenol A (T4CBPA) were formed in the earlier stages of chlorination. Several chlorinated phenolic compounds, 2,4,6-trichlorophenol (T3CP), 2,6-dichloro-1,4-benzoquinone (D2CBQ), 2,6-dichloro-1,4-hydroquinone (D2CHQ), C9H10Cl2O2, C9H8Cl2O and C10H12Cl2O2, were also formed by further chlorination.     

Selective accumulation of chlorinated paraffins (C12 and C16) in the olfactory organ of rainbow trout

Three ¹⁴C-labelled polychloroalkanes (C₁₂ and C₁₆), representing low (23% Cl by weight), medium (51%), and highly (68%) chlorinated paraffin (CP) mixtures, were presented to rainbow trout via the water. The uptake in fat-rich tissues was positively correlated to the degree of chlorination of the preparations. Notably, all preparations gave rise to a high and selective uptake of radioactivity in the olfactory organ and gills. This selective radiolabelling may reflect a general ability of these organs to enrich xenobiotics from the surrounding water. The olfactory organ may be a hitherto unforseen target for toxic environmental pollutants in fish.     

Cold season CH4, CO2 and N2O fluxes from freshwater marshes in northeast China

Cold season (winter and thaw) CH₄, CO₂ and N₂O fluxes from freshwater marshes (47°35′N, 133°31′E, Northeast China) were measured, using the static chamber method. The mean CH₄ and CO₂ fluxes from Carex lasiocarpa (Cl) were 0.5 ± 0.19 and 6.23 ± 1.36 mg C m⁻² h⁻¹, respectively, and those from Deyeuxia angustifoli (Da) were 0.18 ± 0.15 and 5.22 ± 2.48 mg C m⁻² h⁻¹, respectively in winter. There was no significant difference between Cl and Da (p > 0.05). The contributions of winter CH₄ fluxes were about 5.5% and 3% in the Cl and Da, respectively. Marshes are an important potential N₂O sink in winter season in northeast China. During thaw, the CH₄ and CO₂ emissions rapidly increased, 4.5–6 times of winter emissions. Wetland became a source of N₂O. Cold season gases flux from northern wetlands play an important role in the seasonal gas exchange.     

Chlorination of p-cymene by chlorine in carbon tetrachloride: Model compounds for environmental analyses

p-Cymene was chlorinated by chlorine in CCl₄. The products of the chlorination were separated by distillation and purified by preparative gas chromatography. The structures of chlorocompounds were confirmed by means of their NMR and mass spectra. The distillation gave as the main compounds: (2) 2-chloro-, (4) 2,3-dichloro-, (5) 2,5-dichloro-, (6) 2,3,6-trichloro-, (7) 2,3,5,6-tetrachloro-p-cymenes and as by-products: (8) 2,5,7-trichloro-p-cymene, (9) 2,6-dichloro-1-methyl-4-(1-methylethenyl)benzene (cymenene), and (10) 2,3,6-trichloro-1-methyl-4-(1-methylethenyl)benzene (cymenene).     

Formation of chlorinated phenols, dibenzo-p-dioxins, dibenzofurans, benzenes, benzoquinnones and perchloroethylenes from phenols in oxidative and copper (II) chloride-catalyzed thermal process

Formation of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and chlorinated phenols on CuCl(2) from unsubstituted phenol and three monochlorophenols was studied in a flow reactor over a temperature range of 100-425 degrees C. Heated nitrogen gas streams containing 8.0% oxygen were used as carrier gas. The 0.00024mol of unsubstituted phenol and 0.00039mol of each monochlorophenol were passed through a 1g and 1cm SiO(2) particle containing 0.5% (Cu by mass) CuCl(2). Chlorination preferentially occurred on ortho-(2, 6) and para-(4) positions. Chlorination increased up to 200 degrees C, and thereafter decreased as temperature increased. Chlorination of phenols plays an important role in the formation of the more chlorinated PCDD/Fs. Chlorinated benzenes are formed possibly from both chlorination of benzene and chlorodehydroxylation of phenols. Chlorinated phenols with ortho chlorine formed PCDD products, and major PCDD products were produced via loss of one chlorine. For PCDF formation, at least one unchlorinated ortho carbon was required.     

Dependence of GC-RRTs on the solvent-accessible surface area of dioxins and related compounds

The correlation between gas chromatograph relative retention times (GC-RRTs) of dioxins and related compounds, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated naphthalenes (PCNs), and their solvent-accessible surface area (SAS) was analyzed for congeners and isomers. GC-RRTs were linearly dependent on SAS for congeners while there was little dependence for isomers. However, by using classification parameters, Nad-Cl, Nad-H, N1,9Cl, and NalphaCl, based on the substitution positions and patterns of chlorine and/or hydrogen atoms bound to the molecular skeleton, a linear relationship was found among isomers. Furthermore, the GC-RRTs of CDD, CDF, and CN isomers, which are planar, decreased despite increasing SAS, and this tendency was enhanced with the above classification. The retention behavior was explained in terms of the effective enhancement of molecular hydrophobicity caused by an increase in the number of adjacent chlorine pairs.