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PubMed2004

Electro-oxidation and amperometric detection of chlorinated phenols at boron-doped diamond electrodes: a comparison of microcrystalline and nanocrystalline thin films.

We report on the electro-oxidation and amperometric detection of phenol and chlorinated phenols, the latter coupled with flow injection analysis (FIA) and high performance liquid chromatography (HPLC), using boron-doped microcrystalline and nanocrystalline diamond thin-film electrodes. The low background current, good response without extensive pretreatment, and low susceptibility to fouling are properties that make diamond an attractive new electrode for monitoring this class of pollutants. Cyclic voltammetric studies were performed to evaluate the redox response of phenol, 2-chlorophenol, 3-chlorophenol,4-chlorophenol, and pentachlorophenol (PCP) in phosphate buffer, pH 3.5, as a function of the potential scan rate and cycle number. The diamond electrode performance for the amperometric detection of these contaminants in FIA-EC and HPLC-EC was evaluated in terms of the linear dynamic range, limit of quantitation, sensitivity, response precision, and response stability. Both diamond types yielded low mass limits of quantitation of 100-1000 pg for all the phenolic compounds in FIA-EC, except PCP which was 3 ng, and 100-600 pg for all the compounds in HPLC-EC. In all cases, the S/N was 3 or greater. Both electrode types also exhibited good sensitivity, excellent response reproducibility (av 2.7% for FIA-EC and av 4.2% for HPLC-EC), and superb response stability for all the analytes. The electrodes could be used from days to weeks in the measurement with only a periodic soak in distilled 2-propanol required to maintain optimum performance. Both types of diamond outperformed glassy carbon, which exhibited short-lived responsiveness as a consequence of fouling by reaction products and potential-dependent changes in the electrode's physiochemical properties. The use of the HPLC-EC assay for the determination of 2-chlorophenol in a contaminated soil sample is also demonstrated.

Boron↗
PubMed1982

Improved degradation of monochlorophenols by a constructed strain.

Pseudomonas sp. strain B13, a strain able to degrade 3-chlorobenzoate and, after prolonged adaptation (40 days), 4-chlorophenol, could transfer the ability to degrade chlorocatechols to a recipient, Alcaligenes sp. strain A7, which is able to grow with benzoate and phenol. Representative transconjugants, such as Alcaligenes sp. strain A7-2, were able to utilize all three isomeric chlorophenols; this property was not possessed by the donor or the recipient. The ability to grow readily with 4-chlorophenol may be attributable to a more rapid induction of phenol hydroxylase by Alcaligenes sp. strain A7-2 than by Pseudomonas sp. strain B13, a property which correlates with the greater level of resistance to chlorophenols shown by the transconjugant.

Journal Article↗
PubMed2005

Effect of electron beam irradiation on the degradation of monochlorophenols in aqueous solution.

Electron beam was successfully used for the degradation of 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP) in aqueous solutions in this research. The effect of radiation dose on substrate degradation and dechlorination of solutions with concentration of 50 mg/L was investigated. The effect of initial concentration, pH and presence of oxygen was also investigated. The concentration of 2-CP and 4-CP remaining in solution after irradiation were measured by HPLC. The results showed that increased radiation dose led to increased degradation of the chlorophenols and increased Cl- yield. Deaeration was also found to significantly increase the rate of degradation of chlorophenols in water while degradation and dechlorination under alkaline condition was lower than at low to neutral pH.

Chromatography, High Pressure Liquid↗
PubMed1995

Acute aquatic toxicity of protolyzing substances studied as the microtox effect.

In tests of acute aquatic toxicity, the effects of protolyzing substances varies with pH. The Microtox toxicity of six chlorophenols was studied over a pH interval and the relation of effects to dissociation was examined. The pKa values of the chlorophenols under the optimal test conditions are presented. The results of the Microtox toxicity tests supported a simple model of two species, phenol and phenate, with different specific toxicity. In five of the six chlorophenols only the effects of the phenol form were observed. The toxicity of the phenol form was 20 times or more higher than that of the phenate.

Chlorophenols↗
PubMed1996

Metabolites of chlorinated syringaldehydes in fish bile as biomarkers of exposure to bleached eucalypt pulp effluents.

Metabolites of chlorinated phenolic compounds in fish bile have been found to be sensitive biomarkers of bleached pulp mill effluent exposure. Chlorinated syringaldehydes are largely unstudied chlorophenolics found in bleached hardwood effluent. Sand flathead (Platycephalus bassensis), Australian marine fish, were exposed to 100% chlorine dioxide-bleached eucalypt pulp effluent at concentrations of 0.5, 2, and 8% (v/v) for 4 days. Metabolites of 2-chlorosyringaldehyde (2-CSA), the predominant chlorophenolic in this effluent, were measured in the bile. The major metabolite was the conjugate of 2-chloro-4-hydroxy-3,5-dimethoxy-benzylalcohol (2-CB-OH), the reduced product of 2-CSA. 2-CB-OH was found in all fish exposed to diluted effluent and was concentrated in the bile over 1000 times above 2-CSA levels in the effluent. A separate experiment examined the metabolic fate of 2,6-dichlorosyringaldehyde (2,6-DCSA), which is one of the major chlorophenolics in chlorine-bleached eucalypt pulp effluent. Sand flathead were exposed to 2,6-DCSA by intraperitoneal injection at 15 mg/kg or through the water to 0.5, 2, or 8 micrograms/liter for 4 days. Analysis of the bile revealed the major metabolite of 2,6-DCSA to be the conjugate of 2,6-dichloro-4-hydroxy-3,5-dimethoxybenzylalcohol, which was found in all exposed fish and was concentrated in the bile over 20,000 times above 2,6-DCSA exposure levels. Results reveal that the analysis of metabolites of chlorinated syringaldehydes in fish bile can provide a biomarker of bleached hardwood effluent exposure that is sensitive to low levels of exposure, specific to certain bleaching sequences, and correlates well with exposure concentrations.

Animals↗
PubMed1991

Accumulation and depuration of chlorinated phenolics in the freshwater mussel (Anodonta anatina L.).

Uptake from ambient water and the depuration of five chlorinated phenolics, two chloroguaiacols (3,4,5-tri- and tetrachloroguaiacol), and three chlorophenols (2,4,6-tri-, 2,3,4,6-tetra-, and pentachlorophenol) were studied in the duck mussel (Anodonta anatina). Groups of animals were exposed at four acclimiation temperatures (3, 8, 13, 18 degrees C) to four chlorophenolic concentrations (total 6-56 micrograms/liter). The depuration was monitored for 72 hr. For the analysis of individual chlorophenolics by the GC/ECD technique, the soft tissue of mussels was homogenized, spiked with internal standard, acetylated, and extracted with n-hexane. The bioconcentration factors (BCF) (concn. in animal wet wt./concn. in water) were determined for mussel soft tissue. The highest BCF was found for pentachlorophenol (81-461) and the lowest for trichlorophenol (14-125). Neither water temperature nor exposure concentration affected the BCFs. The compounds studied were depurated rapidly and their depuration half-lives (T1/2) in soft tissue were generally less than 24 hr.

Animals↗
PubMed1983

Effects of chlorinated phenols on immunity in rats.

Female Sprague - Dawley rats were exposed to 0, 5, 50 or 500 ppm 2-chlorophenol (2-CP) or pentachlorophenol (PCP) from weaning to 3 weeks postparturition after breeding at 90 days of age. Progeny were weaned at 3 weeks of age and continued on chlorophenol treatment for 10 weeks at which time major immune functions were tested. Humoral immunity was measured by an indirect ELISA, cell-mediated immunity was monitored by delayed-type hypersensitivity (DTH) to oxazolone, and macrophage function was tested by phagocytosis of sheep red blood cells. Rats treated with cyclophosphamide were included as a positive immunosuppressed control. PCP-treated rats had significantly decreased antibody titers and DTH response and increased induced peritoneal macrophage numbers which displayed hyperphagocytic activity. Immune responses in rats treated with 2-CP were not significantly different from controls. The data indicate that (1) the immune system may be a sensitive target for PCP toxicity but not for 2-CP, (2) closely related chlorophenolic chemical isomers may exert different toxic effects on the immune system, and (3) PCP can exert depressive effects on some major immune parameters while enhancing others.

Animals↗
PubMed1985

Acute toxicity of monochlorophenols, dichlorophenols and pentachlorophenol in the mouse.

Acute oral LD50 values were determined for 2-, 3-, and 4-chlorophenol, 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, and 3,5 dichlorophenol and pentachlorophenol in male and female mice. LD50 values (mg/kg) ranged from 117 (females) and 177 (males) for pentachlorophenol to 2389 (females) and 2643 (males) for 3,5-dichlorophenol. It was found that 2-chlorophenol and 3-chlorophenol were considerably more toxic than the dichlorophenol series. Values for males and females were generally similar, the major differences being with pentachlorophenol and 2,5-dichlorophenol, where in both cases the female LD50 was lower.

Animals↗
PubMed2006

Sequential treatment via Trametes versicolor and UV/TiO2/Ru(x)Se(y) to reduce contaminants in waste water resulting from the bleaching process during paper production.

An efficient sequential, biological and photocatalytic treatment to reduce the pollutant levels in wastewater due to the bleaching process during paper production is reported. For a biological pre-treatment, 800 ml of non-sterilized effluent was inoculated with Trametes versicolor immobilized in polyurethane foam, with 25 g l(-1) glucose, 6.75 mM CuSO(4), and 0.22 mM MnSO(4) added, and cultured at 25 degrees C with an air flow of 800 ml min(-1) for 8d. The fungus did not inhibit growth of the heterotropic populations of the effluent. After 4d of culture, the chemical oxygen demand (COD) reduction and colour removal (CR) were 82% and 80%, respectively, with laccase (LAC) and manganese peroxidase (MnP) activities of 345 U l(-1) and 78 U l(-1), respectively. The COD reduction and CR correlated positively (p<0.0001) with LAC and MnP activities. Chlorophenol removal was 99% of pentachlorophenol, 99% of 2,3,4,6-tetrachlorophenol (2,3,4,6-TCP), 98% of 3,4-dichlorophenol (3,4-DCP) and 77% of 4-chlorophenol (4-CP), while 2,4,5-trichlorophenol (2,4,5-TCP) increased to 0.2 mg l(-1). The pre-treated effluent was then exposed to a photocatalytic treatment. The treatment with photolysis resulted in 9% CR and 46% COD reduction, 42% CR and 60% COD reduction by photocatalysis, and 62% CR and 85% COD reduction by heterogeneous photocatalysis with the system TiO(2)/Ru(x)Se(y) (Fig. 4). With this treatment the bacterial and fungal populations also decreased by 5 logarithmic units with respect to the biological treatment alone (Fig. 5). The total sequential treatment resulted in a 92% CR (from 5800 UC), 97% COD reduction (from 59 g l(-1)) and 99% chlorophenol removal at 96 h and 20 min.

Biodegradation, Environmental↗
PubMed2004

Anaerobic treatment of 2,4,6-trichlorophenol in an expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactor at 15 degrees C.

Expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors were operated at 15 degrees C for the treatment of 2,4,6-trichlorophenol (TCP)-containing volatile fatty acid (VFA)-based wastewaters. The seed sludge used as inoculum for the control (no TCP) and test reactor was unexposed to chlorophenols (CPs) prior to the 425-day trial. TCP supplementation to the feed at 50 mg TCPl(-1) partially inhibited the anaerobic degradation of the VFA feed measured as COD removal efficiency. However, the withdrawal and subsequent application of stepwise increments to the TCP loading resulted in steady COD removal. Terminal restriction fragment length polymorphism analysis showed Methanosaeta-like Archaea in the control reactor over the experimental period. Different methanogenic populations were detected in the test reactor and responded to the changes in feed composition. Bacterial community analyses indicated changes in the community structure over time and suggested the presence of Campylobacter-like, Acidimicrobium-like and Heliophilum-like organisms in the samples. TCP mineralisation was by a reductive dechlorination pathway through 2,4-dichlorophenol (DCP) and 4-chlorophenol (4-CP) or 2-chlorophenol (2-CP). CP degradation rates in sludge granules from the lower chamber of the hybrid EGSB-AF reactor was in the order TCP > DCP > 4-CP > 2-CP. However, a biodegradability order of lower CPs > TCP was observed in fixed-film biomass taken from the upper reactor chamber, thus reflecting the role of this reactor section in the metabolism of residual lower CPs from the lower sludge-bed stage of operation.

Bacteria, Anaerobic↗
PubMed2004

Expression of glutathione S-transferase and peptide methionine sulphoxide reductase in Ochrobactrum anthropi is correlated to the production of reactive oxygen species caused by aromatic substrates.

Peptide methionine sulphoxide reductase (MsrA) and glutathione S-transferases (GSTs) are considered as detoxification enzymes. In the xenobiotics-degrading bacterium Ochrobactrum anthropi the two enzymes are co-induced by toxic concentrations of aromatic substrates such as phenol and 4-chlorophenol. In aerobic organisms, degradation of aromatic substrates by mono- and dioxygenases leads to a generation of oxidative stress that causes the occurrence of reactive oxygen species (ROS). A capillary electrophoretic method, using the intracellular conversion of dihydrorhodamine-123 into rhodamine-123, was developed to measure the content of ROS in the bacteria. The presence of toxic concentrations of the aromatic substrate 4-chlorophenol, an inducer of GST and MsrA, leads to a significant increase in the production of ROS. These results strongly suggest that GST and MsrA enzymes are part of the bacterial defence mechanism against particular oxidative stress conditions. As oxidative stress is known to be present predominantly close to the cytoplasmic membrane, we investigated the subcellular distribution of both MsrA and GST enzymes in this bacterium grown in the presence of 4-chlorophenol. By Western blotting, MsrA and GST was assayed in the cytoplasm as well as in the periplasm. Moreover, immunolocalisation by colloidal gold immunoelectron microscopy identified the two proteins associated with the cell envelope.

Chlorophenols↗
PubMed2005

Freeze-dried recombinant bacteria for on-site detection of phenolic compounds by color change.

We herein report the development of a recombinant bacterial biosensor for the rapid and easy detection of phenolic compounds in the field. A plasmid was designed to encode a beta-galactosidase reporter gene under the control of capR, an activator involved in phenolic compound degradation. The construct was transformed into Escherichia coli, and transformed cells were stored after being freeze-dried in the presence of sucrose. For detection of phenolic compounds, the cells were rehydrated, and used instantly, without any growth step. In the presence of 0.1 microM-10mM phenol, we observed a red color from hydrolysis of chlorophenol red beta-D-galactopyranoside (CPRG) or an indigo color from hydrolysis of X-galactopyranoside (X-gal). Other phenolic compounds could be detected by this system, including catechol, 2-methylphenol, 2-chlorophenol, 3-methylphenol, 2-nitrophenol, and 4-chlorophenol. These results suggest that this novel bacteria biosensor may be useful for easy, on-site detection of phenolic compounds without the need for unwieldy equipment or sample pretreatment. Indeed, biosensor systems involving beta-galactosidase-expressing freeze-dried recombinant bacteria could prove useful for the in situ detection of many more compounds in the future.

Biosensing Techniques↗
PubMed2006

Removal of 2,4-dichlorophenol and pentachlorophenol from waters by sorption using coal fly ash from a Portuguese thermal power plant.

Chlorophenols are one of the most important groups of priority pollutants, due to their high toxicity, mutagenicity and carcinogenicity. Although activated carbon has been the preferred choice for the removal of such pollutants from wastewaters, the search for cheaper alternative sorbents became common in the last years. Fly ash, a by-product from coal burning power plants, has a surface composition that may enable the sorption of specific organic compounds. Therefore, this feasibility study presents the optimization of the operating parameters of a fixed-bed column containing fly ash particles, percolated by aqueous solutions of 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP) with concentrations of 1 and 100 microg/ml. Both chlorophenols were analysed by gas chromatography with electron capture detection (GC-ECD), after solid-phase microextraction (SPME), with limits of detection (LODs) of 7.28 microg/l for 2,4-DCP and 1.76 microg/l for PCP. Removal efficiencies above 99% were obtained for an initial concentration of 10 microg/ml of chlorophenols. Column saturation was achieved after 7h of continuous operation for 2,4-DCP and 10h for the PCP for feed levels of 10 microg/ml. Fly ash exhibited more affinity towards the sorption of PCP, in comparison to 2,4-DCP.

Adsorption↗
PubMed2006

Assessment of genotoxicity of 14 chemical agents used in dental practice: ability to induce chromosome aberrations in Syrian hamster embryo cells.

To assess the genotoxicity of 14 chemical agents used as locally applied agents in dental practice, the ability of these agents to elicit chromosome aberrations was examined using Syrian hamster embryo (SHE) cells. Chromosome aberrations in SHE cells were induced by treatment with three of eight chemical agents used as endodontic medicaments, i.e. ethylenediaminetetraacetic acid (EDTA), formocresol (a mixture of formalin and tricresol), and sodium arsenite. The other five chemical agents, i.e. chloramphenicol, p-chlorophenol, p-phenolsulfonic acid, sodium hypochlorite, and tetracycline hydrochloride exhibited a negative response for chromosome aberrations. Assessment of three dyes used for disclosing dental plaque showed chromosome aberrations induced by basic fuchsin but not by acid fuchsin and erythrosine B. Three local anesthetics, lidocaine hydrochloride, prilocaine hydrochloride, and procaine hydrochloride, were negative for chromosome aberrations. Among the ten chemical agents that exhibited a negative response in the assay, p-chlorophenol, sodium hypochlorite, and erythrosine B induced chromosome aberrations in SHE cells when treated in the presence of exogenous metabolic activation. The percentages of cells with polyploidy or endoreduplication were enhanced by formocresol, sodium arsenite, p-chlorophenol, p-phenolsulfonic acid, sodium hypochlorite, erythrosine B, prilocaine hydrochloride, and procaine hydrochloride in the absence or presence of exogenous metabolic activation. Our results indicate that the chemical agents that had a positive response in the present study are potentially genotoxic to mammalian cells.

Anesthetics↗
PubMed2005

Effect of hydrogen peroxide on the decomposition of monochlorophenols by sonolysis in aqueous solution.

The decomposition rates of several monochlorophenol by sonolysis were enhanced by the presence of hydrogen peroxide. An optimum concentration of hydrogen peroxide was observed for achieving maximum sonolysis rate of monochlorophenol. The decomposition rates of 3-chlorophenol by sonolysis were higher than those for 2- and 4-chlorophenol for most experiments conducted, suggesting that the ring structure of 3-chlorophenol provides more sites available for free radical attack. The temporal decomposition behavior of monochlorophenol in aqueous solutions is markedly influenced by the species distribution and the volatility of specific monochlorophenol.

Chlorophenols↗
PubMed2005

Effect of long-term exposure, biogenic substrate presence, and electron acceptor conditions on the biodegradation of multiple substituted benzoates and phenolates.

Biodegradation rates of benzoate and related aromatic compounds, 3-nitrobenzoate, 4-chlorobenzoate, 4-chlorophenol, and 2,4-dichlorophenol by unexposed (unacclimated) and long-term exposed (acclimated) biomass were quantified using a modified fed-batch technique. The acclimated biomass was taken after approximately 1-year of operation from three lab-scale sequencing batch reactors (SBR). These reactors were operated under various cycling electron acceptor conditions with a continuous feed of a synthetic wastewater containing biogenic and nonbiogenic chemicals including benzoate, 3-nitrobenzoate, and 4-chlorophenol, but not 4-chlorobenzoate or 2,4-dichlorophenol. The unexposed biomass was taken from a full-scale wastewater treatment plant, which constituted one of the original sources of inoculum for the lab-scale SBRs. The acclimated biomass manifested high removal rates of benzoate and related aromatic compounds with additional removal of structurally similar chemicals (4-chlorobenzoate and 2,4-dichlorophenol). The unacclimated biomass showed no removal of 3-nitrobenzoate, 4-chlorobenzoate or 2,4-dichlorophenol. Addition of biogenic substrates reduced the degradation of most aromatic compounds tested, but it enhanced 2,4-dichlorophenol removal. Biodegradation rates of each aromatic compound with the biomass from the anoxic/aerobic SBR were further determined under anaerobic (absence of aeration and NO3-), anoxic (no aeration, but with surplus NO3-), standard oxygen (DO > 0.2 mg/L), and elevated oxygen (DO > 25 mg/L) conditions. The removal rate of both benzoate and 3-nitrobenzoate decreased under anaerobic condition but not under the anoxic condition; 4-chlorophenol biodegradation, on the other hand, was reduced significantly under both anoxic and anaerobic conditions. The removal rates of aromatic compounds, particularly those of 3-nitrobenzoate and 2,4-dichlorophenol, increased significantly under elevated dissolved oxygen conditions. Our results demonstrated that when the biochemical conditions shifted from oxygen-respiration to nitrate respiration, to anaerobiosis, the biodegradation rates of test aromatic compounds decreased or ceased.

Adsorption↗
PubMed2001

In situ polychlorophenol bioremediation potential of the indigenous bacterial community of boreal groundwater.

The composition and chlorophenol-degrading potential of groundwater bacterial community in a permanently cold, oxygen-deficient chlorophenol contaminated aquifer at Kärkölä, Finland was studied with the aim of evaluating in situ bioremediation potential. The groundwater contained from 10(4) to 10(7) microscopically counted cells/ml and up to 10(5) CFU/ml heterotrophic bacteria cultivable at 8 and 20 degrees C. Of the 102 pure cultures, of which 86% Gram-negative, from the plume area (10,000 microg of chlorophenols/l), 57% degraded 2, 3, 4, 6-tetrachlorophenol (TeCP), the main component of the wood preservative which was the source of contamination: 17% also degraded pentachlorophenol (PCP). The degraders were scattered among 16 different clusters of Gram-negatives mainly proteobacteria and members of Cytophaga/Flexibacter/Bacteroides phylum judged by the composition of whole-cell fatty acids. Only one Gram-positive degrading cluster was found containing seven actinobacteria closest to Nocardioides. Of the 88 pure cultures isolated from outside the plume (< 10 microg of chlorophenols/l) 67% were Gram-negative. Seven percent of the isolates degraded 2, 3. 4, 6-TeCP and/or PCP. Five of the Gram-positive isolates from outside the plume were Mycobacterium/Rhodococcus-related actinobacteria and O-methylated 2, 3, 4, 6-TeCP and PCP. The results show that chlorophenol degrading bacterial flora had been enriched as a result of contamination of the aquifer. This suggests significant in situ bioremediation potential of the site.

Bacteria↗
PubMed2001

PCDD/F reduction in incinerator flue gas by adding urea to RDF feedstock.

The effect of urea on PCDD/F formation in a pilot incinerator was studied by incinerating urea with refuse-derived fuel (RDF) at three concentrations (0.1%, 0.5% and 1.0%, of the fuel feed). A distinct reduction in both PCDD/F and chlorophenol concentrations could be noticed when urea was introduced into the system. Partial-least-square (PLS) analysis of the data showed the importance of certain chlorophenol isomers as PCDD/F precursors, pointing to the possibility that the impact point of the urea inhibitor could be before the precursor molecules, i.e. chlorophenols, have been formed.

Air Pollutants↗