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PubMed2002

Characterization of high molecular weight disinfection byproducts resulting from chlorination of aquatic humic substances.

Aquatic humic substances react with chlorine to produce numerous disinfection byproducts (DBPs) during chlorination of drinking water. Although low molecular weight (MW) chlorinated DBPs have been intensively studied over the past several decades, relatively little is known about high MW chlorinated DBPs (above 500 Da) that may be associated with adverse health implications. In this work, carrier-free radioactive 36Cl was introduced into a Suwannee River fulvic acid sample to label the chlorine-containing DBPs. By combining the fractionation techniques of ultrafiltration (UF) and size exclusion chromatography (SEC) with the detection of 36Cl, UV, and dissolved organic carbon (DOC), the high MW region in the SEC-36Cl profiles of the chlorinated sample with and without UF was defined. SEC-UV and SEC-DOC profiles were found to be approximately indicative of SEC-36Cl profiles for the high MW region. The MW distribution shows that the high MW chlorinated DBPs were highly dispersed with an average MW around 2000 Da based on calibration with polystyrene sulfonate standards. The Cl/C atomic ratios of the high MW DBPs were roughly constant (0.025), which is much lower than those of the common known chlorinated DBPs.

Chlorine Compounds↗
PubMed2004

Modified polytopic vector analysis to identify and quantify a dioxin dechlorination signature in sediments. 1. Theory.

Risk-based sediment management decisions require the characterization of contamination sources and fate processes in the field. Polytopic vector analysis (PVA) is a multivariate technique based on a linear mixing model, used to resolve chemical fingerprints and suited for forensic investigations of environmental contamination. The traditional algorithm is constrained to positive fingerprint (end-member) components and cannot resolve fingerprints with both positive and negative values required for a reactive end-member. We developed a modified algorithm (M-PVA) to resolve a dioxin dechlorination fingerprint, indicative of biotic/abiotic transformations in field samples of sediments. The new procedure isolates from the dioxin pattern net compositional changes due to dechlorination in a separate end-member. Using two artificial data sets for which the composition and sample contribution of all end-members are known, the dechlorination fingerprint was reproduced with a root mean square error of 28-41%. The dechlorination end-member contribution to the total variability (set at 4.0 and 10.0%, respectively) was overestimated 1-5-fold. The ability of M-PVA to reproduce the dechlorination pattern and its variability contribution depends on the actual contribution of dechlorination to variability. At an actual contribution of 4.0%, the model outcome deviates more strongly from the original than is the case for a contribution of 10.0%. As such, application of M-PVA to environmental data should include an uncertainty analysis to distinguish variability due to dechlorination from variability due to error. The development of the modified PVA procedure is an important step toward the field characterization of fate processes in dioxin-impacted sediments.

Algorithms↗
PubMed2004

Modified polytopic vector analysis to identify and quantify a dioxin dechlorination signature in sediments. 2. Application to the Passaic River.

Persistent contaminants such as dioxins have been documented to undergo dechlorination reactions in the laboratory; however, little is known about the importance of these reactions in the field. Polytopic vector analysis (PVA) is a statistical pattern recognition technique for multivariate data traditionally used to identify fingerprints of contaminant sources. A modified PVA algorithm with uncertainty analysis was used to model dechlorination fingerprints and sources. The technique was applied to 351 sediment core-derived dioxin samples from the lower reach of the Passaic River, New Jersey. A dechlorination fingerprint was identified with a highly positive 2,3,7,8-tetraCDD component and a highly negative heptaCDD component. The most important industrial source of 2,3,7,8-tetraCDD is a fingerprint related to 2,4,5-trichlorophenoxyacetic acid production. The dechlorination contribution to the data variance is 3.00 +/- 1.00%, corresponding to an average of 1.2 microg/kg of 2,3,7,8-tetraCDD per sample at the expense of heptaCDD. The possible occurrence of dechlorination was validated by comparing the local dechlorination contribution in the results to the value of the ratio 2,3,7,8-tetraCDD/total 2,3,7,8-PCDD, which indicates dechlorination in the laboratory. Bootstrap uncertainty analysis yielded the same dechlorination EM in 40% of the realizations. The results indicated that bootstrapping is an important statistical tool to quantify uncertainties with respect to the dechlorination EM and some of the source EMs.

Algorithms↗
PubMed2003

Importance of chlorine speciation on de novo formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans.

The role of chlorine speciation on de novo formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) has been studied thoroughly in an entrained flow reactor during simulated waste combustion. The effects of gas-phase chlorine species such as chlorine (Cl2), hydrogen chloride (HCl), and chlorine radicals (Cl*), as well as ash-bound chlorine, on PCDD/F de novo formation were isolated for investigation. The ash-bound chlorine alone was observed to be a sufficient chlorine source for PCDD/F formation. The addition of HCl to the system did not influence the yields of the PCDDs/Fs nor the degree of chlorination due to its poor chlorinating ability. Addition of 200 ppm of Cl2 to the ash-feed system resulted in increased PCDD/F yields, especially for the octa- and hepta-chlorinated congeners. Altering the reaction temperature to enable the presence of only Cl2 to the system did not change the yields of PCDD/F compared to those when both Cl2/Cl* were present. However, comparison between ash-bound and gas-phase chlorine, the latter at a concentration typical of a realistic combustion process, revealed ash-bound chlorine to be the more important chlorine source for de novo formation of PCDD/F in a full-scale incinerator.

Air Pollutants↗
PubMed2003

Complete dechlorination of 1-chloronaphthalene by electrochemical reduction with naphthalene radical anion as mediator.

The possibility of electrochemical reduction for the complete dechlorination of toxic chlorinated aromatic compounds was investigated using 1-chloronaphthalene as a substrate. Sufficient current was obtained at the reduction potential of naphthalene rather than that of the substrate, and complete (>99.99%) dechlorination was achieved in tetra-n-butylammonium perchlorate/dimethylformamide solution in less than 1 h. The reaction was considered to proceed autocatalytically with the naphthalene radical anion, which was derived from the reduction of the initial dechlorination product (naphthalene) of the substrate, as mediator. The reaction rate was increased by the use of an excess of naphthalene at the start of the reaction, and complete dechlorination was possible without significant loss of current efficiency even if the water concentration was 0.3% v/v. The order of reaction of the mediated reduction was determined kinetically to be 0.5 for the substrate and 1 for naphthalene. Although the reaction of the naphthalene radical anion with 1-chloronaphthalene was very fast, it was considered to be the rate-determining step.

Catalysis↗
PubMed2003

Polychlorinated naphthalenes in foods: estimated dietary intake by the population of Catalonia, Spain.

Concentrations of polychlorinated naphthalenes (PCNs) were measured in foodstuffs randomly acquired in seven cities of Catalonia, Spain. A total of 108 samples, belonging to 11 food groups (vegetables, tubers, fruits, cereals, pulses, fish and shellfish, meat and meat products, eggs, milk, dairy products, and oils and fats), were analyzed by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). The levels of tetra-, penta-, hexa-, and hepta-CNs, those of octachloronaphthalene, and the mean sum concentration of tetra-octa-CN were determined. The highest concentration of total PCNs was found in oils and fats (447 pg/g), followed by cereals (71 pg/g), fish and shellfish (39 pg/g), and dairy products (36 pg/g). In general, tetra-CN was the predominant homologue in all food groups except for fruits and pulses, which had greater proportions of hexa-CNs. The dietary intake of total PCNs was subsequently determined. For calculations, recent data on consumption of the selected food items were used. Intake of PCNs was estimated for five population groups of Catalonia: children, adolescents, male and female adults, and seniors. When the dietary intake of total PCNs was expressed in nanogram per kilogram of body weight per day, it was age-dependent, with the highest and lowest values corresponding to children (1.65) and seniors (0.54), respectively. The largest contribution to the daily PCNs intake came from oils and fats and from cereals. The result of the current study is the first published report concerning human exposure to PCNs through the diet.

Adolescent↗
PubMed2004

Polychlorinated naphthalenes in Swedish background air.

Polychlorinated naphthalenes (PCNs) with four to eight chlorines were studied in air collected at two background stations in Sweden, one southerly and one northerly. Air was sampled with a high-volume sampler, and gas-phase adsorbents and filters were analyzed separately. The sum of TeCNs to HxCNs in the gaseous phase ranged between 1 and 10 pg/m3 with significantly higher concentrations at the southern location Hoburgen. HpCNs and OCN were below the detection limit. The highest concentrations were found in two samples from Hoburgen with the air masses coming from SW and W and during warm weather (+11 degrees C). The lowest concentration was found in a sample from the northern location Ammarnäs at cold weather (-22 degrees C) when the air came from the east. A correlation was found between logP and 1/T indicating that temperature has a larger effect than location on the concentration in the gas phase. The TeCNs constituted 50-75% in the gaseous phase. In most filter samples TeCNs and PeCNs were below the limit of quantitation. PUF samples with air trajectories from W to NE had relatively higher concentrations of late eluting TeCNs and PeCNs, while in samples with winds from SE to S the early eluting congeners dominated. Samples with early eluting congeners were mainly collected at lower temperature. TriCNs constituted the dominant homologue group both in the gaseous and particulate phase of air samples as well as in bulk deposition from a rural monitoring station south of Stockholm. The octanol-air partition coefficient described the gas/particle interaction well for samples collected at temperatures down to -8 degrees C.

Air Pollutants↗
PubMed2003

Chlorinated aromatics from combustion: influence of chlorine, combustion conditions, and catalytic activity.

Research on the formation of chlorinated aromatics in combustion processes has mainly taken place in the laboratory. Previous attempts to correlate observation data from commercial plants have been inconclusive. This study reports on the outcome of an industrial experiment in a full-scale afterburner. The influence of chlorine input, combustion temperature, and catalytic activity was investigated in a factorial design with two blocks. Polychlorinated benzenes, dibenzo-p-dioxins, and dibenzofurans were formed both at combustion temperatures and below 400 degrees C. The results show that all three experimental factors have statistically significant impact on the formation and release of these toxic byproducts. The quantitative dependence between chlorine input and the occurrence of chlorinated aromatics is of particular interest due to previous controversy. The purpose with this study was to ensure that the installation of a boiler for energy recovery would not cause elevated emissions of chlorinated aromatics. The experiment demonstrated that this risk is probably low, since the presence of catalytic material or an increase in chlorine input is required for this to happen. A general conclusion was that industrial experimentation employing the principles of statistical design could improve the validity in recommendations regarding commercial plant operation.

Air Pollutants↗
PubMed2004

Cl K-edge X-ray spectroscopic investigation of enzymatic formation of organochlorines in weathering plant material.

The contribution of halocarbons from plant weathering to the total organohalogen budget of terrestrial systems is gaining recognition. To evaluate the formation of such halocarbons, speciation of chlorine in Sequoia sempervirens (redwood) needles was examined in the presence of an external chloroperoxidase (CPO) enzyme using Cl K-edge X-ray absorption spectroscopy. The Cl forms in fresh and naturally weathered needles and in model laboratory reactions were compared. To provide a straightforward analogue to the enzymatic chlorination in plants, chlorination reactions were conducted for phenol, a common moiety of plant macromolecules. Plant material chlorination was also examined in the presence of hypochlorite in an ancillary mechanistic investigation. The dominant form of Cl in fresh, unreacted plant material was found to be inorganic Cl-, which was partially converted to organochlorine in the presence of CPO. Chlorination is affected by the nature of reactant (CPO, H2O2) addition, reaction time, and temperature. The organochlorines produced in these laboratory investigations closely resemble those produced during the natural weathering of redwood needles. A striking consistency in chlorine speciation observed among the various sample types suggests that (i) CPO produced by terrestrial organisms could play a vital role in the generation of organochlorines associated with the degradation of plant material and (ii) initial targets of enzymatic chlorination might include lignin-like macromolecules rich in aromatic character and hydroxyl groups. These findings lend further credibility to a significant biogenic contribution to the global organohalogen burden by elucidating a probable route of enzymatic chlorination of natural organic matter in terrestrial systems.

Chloride Peroxidase↗
PubMed2004

Production of macromolecular chloramines by chlorine-transfer reactions.

Chlorination of treated wastewaters is undertaken to prevent dispersal of human pathogens into the environment. Except in well-nitrified effluents, the primary agents in chlorination, Cl2(g) or NaOCl(aq), are short-lived and quickly transfer oxidative chlorine to secondary agents (N-chloramines), which then participate in the disinfection process. Maturation of residual chlorine resulting from chlorine-transfer reactions is still poorly characterized. Using gel permeation and reversed-phase liquid chromatography combined with a novel, oxidant-specific detector, unanticipated trends during the maturation of residual chlorine in wastewater are identified. Within 2 min after addition of NaOCl, and continuing for several hours at least, significant amounts of oxidative chlorine are transferred to secondary agents that are moderately to strongly hydrophobic and to agents that have high relative molecular masses (Mr 1300-25000). It is hypothesized that hydrophobic stabilization of organic chloramines (RNHCl(o)) thermodynamically drives these transfers, making macromolecular chloramines the ultimate oxidative chlorine carriers. Macromolecular chloramines are expected to be sluggish oxidants, as observed in their reduction by sulfite, and are expected to be poor disinfectants. If transfer of oxidative chlorine to high Mr components occurs widely at treatment plants, then this phenomenon offers a new, physicochemical explanation for the well-known impotency of organic chloramines in wastewater disinfection.

Chloramines↗
PubMed2004

Bioaccumulation, biotransformation, and biochemical effects of brominated diphenyl ethers in juvenile lake trout (Salvelinus namaycush).

Juvenile lake trout (Salvelinus namaycush) were exposed to three dietary concentrations (0, approximately 2.5, and approximately 25 ng/g per BDE congener) of 13 BDE congeners (3-10 Br atoms) in the laboratory for 56 days, followed by 112 days of clean food, to examine bioaccumulation parameters and potential biochemical effects. The bioaccumulation of BDEs by the trout was highly influenced by biotransformation, via debromination, which resulted in bioaccumulation parameters that were much different than would be expected based on studies of chlorinated organic compounds (e.g., PCBs). Half-lives (t1/2's) for some BDE congeners (e.g., BDE-85 and -190) were much lower than expected based on their Kow, which was likely due to biotransformation, whereas t1/2's of other BDE congeners (e.g., BDE-66, -77, -153, and -154) were much longer than anticipated based on Kow. This was likely because the metabolites of BDE formed via debromination had the same chemical structure of these BDE congeners, which supplemented measured concentrations. The detection of three BDE congeners (an unknown penta, BDE-140, and an unknown hexa) in the fish that were not present in the food or in the control fish provide further evidence forthe debromination of BDEs. Half-lives of BDEs ranged from 38 +/- 9 to 346 +/- 173 days and biomagnification factors ranged from 1.6 (BDE-190) to 45.9 (BDE-100), but these bioaccumulation parameters need to be viewed with caution because they were highly influenced by debromination and relative abundance of individual BDEs that the fish were exposed to. CYP1A enzyme activity, measured as EROD, and free tri-iodothyronine (T3) concentrations in the plasma of lake trout varied significantly throughout the experiment but were not related to BDE exposure. In contrast, plasma levels of thyroxine levels (T4) were lower in both groups of PBDE-exposed fish compared with control fish after 56 days of exposure, and after 168 days in the high dose, suggesting that PBDEs may influence thyroid homeostasis at levels that are higher than what is normally found in the environment.

Administration, Oral↗
PubMed2004

Oxidation of the cyanobacterial hepatotoxin microcystin-LR by chlorine dioxide: reaction kinetics, characterization, and toxicity of reaction products.

Cyanobacteria are known producers of cytotoxins, hepatotoxins, and neurotoxins. The main toxins are microcystins, cyclic heptapeptide hepatotoxins, produced by strains of several cyanobacterial genera frequently found in eutrophied freshwaters. Due to the acute and chronic toxicity of microcystins, successful removal of these toxins in drinking water treatment processes is of increasing concern. In the present work the kinetics of microcystin-LR (MC-LR) oxidation by chlorine dioxide (ClO2) was studied with UV-spectrometry and high performance liquid chromatography (HPLC). Characterization of reaction products was performed with mass spectrometric (MS) analysis, while the toxicity of reaction products was tested with a protein phosphatase inhibition assay (PPIA). The main reaction products formed, dihydroxy isomers of MC-LR as identified by MS, were nontoxic according to the PPIA. The overall rate constant k for the reaction between MC-LR and ClO2 at 293 K and pH 5.65 was modest, k = 1.24 M(-1) s(-1), suggesting that ClO2 is not a suitable oxidant for the degradation of microcystins in drinking water treatment processes.

Chlorine Compounds↗
PubMed2005

Reactions of chlorine atoms with a series of aromatic hydrocarbons.

Aromatic hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs), are present in urban and rural atmospheres. Reactions of PAHs with Cl atoms may occur in the marine boundary layer and in coastal regions. To assess the importance of these reactions and to investigate whether any unique chlorine-containing products are formed from these reactions, we have measured the rate constants for the gas-phase reactions of Cl atoms with toluene-d8, 1,3,5-trimethylbenzene (1,3,5-TMB), naphthalene, 1-methylnaphthalene-d10 (1-MN-d10), 1- and 2-methylnaphthalene (1- and 2-MN), 1- and 2-ethylnaphthalene (1- and 2-EN), and the dimethylnaphthalenes (DMNs) at 296 +/- 2 K. A relative rate technique was used, and, using our measured rate constant forthe reaction of Cl atoms with 1,3,5-TMB of 2.42 x 10(-10) cm3 molecule(-1) s(-1), the rate constants (in units of 10(-10) cm3 molecule(-1) s(-1)) are as follows: naphthalene, < or = 0.0091 +/- 0.0003; 1-MN, 1.21 +/- 0.16; 2-MN, 1.05 +/- 0.13; 1-EN, 2.12 +/- 0.35; 2-EN, 1.38 +/- 0.27; 1,2-DMN, 3.61 +/- 0.68; 1,3-DMN, 2.90 +/- 0.22; 1,4-DMN, 2.93 +/- 0.30; 1,5-DMN, 2.31 +/- 0.19; 1,6-DMN, 2.15 +/- 0.20; 1,7-DMN, 3.05 +/- 0.34; 1,8-DMN, 3.07 +/- 0.44; 2,3-DMN, 2.93 +/- 0.49; 2,6-DMN, 2.34 +/- 0.18; and 2,7-DMN, 2.00 +/- 0.22, where the indicated errors are two standard deviations and do not include the uncertainty in the rate constant for 1,3,5-TMB. The measured deuterium isotope effects for the toluene-d8 and 1-MN-d10 reactions indicate that the reactions proceed by initial H- (or D-) atom abstraction. The products identified and quantified from the toluene and 1-MN reactions using gas chromatography and in situ direct air sampling atmospheric pressure ionization tandem mass spectrometry were benzaldehyde (84% +/- 7% yield) and benzyl alcohol (11% +/- 2% yield) from toluene and 1-naphthaldehyde (approximately 36%, lower limit to yield) and 1-naphthyl alcohol (approximately 12%, lower limit to yield) from 1-MN. These products confirm that H-atom abstraction is the dominant, if not sole, reaction pathway for the alkylbenzenes and alkylnaphthalenes, consistent with the 100-fold lower rate constant measured for naphthalene compared to the alkylnaphthalenes and with the measured deuterium isotope effects.

Atmosphere↗
PubMed2005

Phenol chlorination and photochlorination in the presence of chloride ions in homogeneous aqueous solution.

Phenol chlorination was studied in the presence of dissolved Fe(III) and chloride under irradiation and of hydrogen peroxide and chloride in dark acidic solutions. In the former case phenol photochlorination is most likely due to the formation of Cl2*- as a consequence of Fe(III) irradiation in the presence of chloride. The most efficient pathway is the photolysis of FeOH2+ producing hydroxyl, which oxidizes chloride to Cl*. The latter finally yields Cl2*- upon further reaction with chloride. The importance of the pathway involving FeOH2+ is higher at higher pH and moderately low chloride concentration. At pH 2.0 and [Cl-] > 0.03 M chlorophenol generation rate decreases with increasing [Cl-], due to the formation of the much less photoactive species FeCl2+/FeCl2+. The photolysis of FeCl2+/ FeCl2+ yielding Cl* is likely to play an important role at pH 0.5 and high chloride, but under such conditions chlorophenol formation rates are about an order of magnitude lower than at pH 2.0. Due to pH and kinetic constraints, under most environmental conditions the photochemistry of FeCl2+/FeCl2+ can be expected to play a minor role toward chlorination when compared with the one of FeOH2+, which leads to hydroxyl-mediated chloride oxidation. Hydrogen peroxide and chloride react in dark acidic solutions to yield HClO, involved in electrophilic chlorination processes. Chlorophenol formation rates under such conditions are directly proportional to [H+]. The described chlorination and photochlorination processes can take place in acidic aerosols of marine origin, naturally rich in chloride and Fe(III). Antarctic aerosol is also rich of hydrogen peroxide and often strongly acidic due to the presence of sulfuric acid of biogenic origin.

Aerosols↗
PubMed2005

Detailed study of factors controlling atmospheric concentrations of PCNs.

Atmospheric concentrations of polychlorinated naphthalenes (PCNs) (108 samples in total) were measured at two rural/ semirural sites in England and one remote site on the west coast of Ireland in the years 2001 and 2000, respectively. Detailed analysis of the factors affecting concentrations is performed. At Mace Head (MH) Ireland, concentrations of sigmaPCNs ranged between 1.7 and 55 pg m(-3) with a mean of 15 pg m(-3) and were controlled primarily by advection. sigmaPCNs concentrations at Hazelrigg (HR), northwest England, ranged between 31 and 310 pg m(-3) with a mean of 110 pg m(-3), and at Chilton (CH), southwest England, ranged between 31 and 180 pg m(-3) with a mean of 85 pg m(-3). Data from the HR site shows that PCN concentrations have not declined between the early 1990s and 2001, while PCB concentrations have declined. The ratio of the sigmaPCNs/ sigmaPCBs was close to or greater than 1 at all sites. From air mass back trajectories, it is clear that local/regional sources influenced concentrations of PCNs at all sites, particularly at MH. At the two English sites during the summer, concentrations of PCNs were strongly influenced by temperature, indicating that air-surface exchange processes play an important role. Advection became more influential during winter, particularly at CH, where a different homologue profile was observed in some samples when air masses approached from the southwest and PCN concentrations increased. The average mixture profile of PCNs in air was similar to that observed in other studies and different from that in Halowax 1014.

Air Movements↗
PubMed2005

Stable isotope evidence for biodegradation of chlorinated ethenes at a fractured bedrock site.

Stable carbon isotope analysis of chlorinated ethenes and ethene was performed at a site contaminated with trichloroethene (TCE), a dense non-aqueous phase liquid (DNAPL). The site is located in fractured bedrock and had variable groundwater hydraulic gradients during the study due to a local excavation project. Previous attempts to biostimulate a pilot treatment area at the site resulted in the production of cis-1,2-dichloroethene (cis-DCE), the first product of reductive dechlorination of TCE. Cis-DCE concentrations accumulated however, and there was no appreciable production of the breakdown products from further reductive dechlorination, vinyl chloride (VC) and ethene (ETH). Consequently, the pilot treatment area was bioaugmented with a culture of KB-1, a natural microbial consortium known to completely reduce TCE to nontoxic ETH. Due to ongoing dissolution of TCE from DNAPL in the fractured bedrock, and to variable hydraulic gradients, concentration profiles of dissolved TCE and its degradation products cis-DCE, VC, and ETH could not convincingly confirm biodegradation of the chlorinated ethenes. Isotopic analysis of cis-DCE and VC, however, demonstrated that biodegradation was occurring in the pilot treatment area. The isotope values of cis-DCE and VC became significantly more enriched in 13C over the last two sampling dates (in one well from -17.6%o to -12.8%o and from -22.5%o to -18.2%o for cis-DCE and VC, respectively). Quantification of the extent of biodegradation in the pilot treatment area using the Rayleigh model indicated that, depending on the well, between 21.3% and 40.7% of the decrease in cis-DCE and between 15.2% and 36.7% of the decrease in VC concentrations can be attributed to the effects of biodegradation during this time period. Within each well, the isotope profile of TCE remained relatively constant due to the continuous input of undegraded TCE due to DNAPL dissolution.

Biodegradation, Environmental↗