Articoli di riviste sul tema "Pentachlorophenol"

Background: This study aimed to investigate the biosorption of pentachlorophenol on Aspergillus niger biomass as a method for removal of pentachlorophenol from aqueous solutions. Methods: Modified A. niger biomass with NaOH was used to absorb the pentachlorophenol. The impacts of various experimental parameters like primary pentachlorophenol concentration, pH of the solution, contact time, and biomass dosage on the biosorption of pentachlorophenol were investigated. Results: The correlation of contact time, pH and initial concentration with the biosorption of pentachlorophenol by A. niger biomass was statistically significant (P<0.001). Pentachlorophenol removal increased with decreasing pH of the solution and the maximum efficiency was obtained at pH=3. The equilibrium adsorption capacity was increased from 4.23 to 11.65 mg/g by increasing initial pentachlorophenol concentration from 10 to 40 mg/L, while pentachlorophenol removal efficiency decreased from 87 to 55%. Both Langmuir and Freundlich isotherms efficiently described adsorption equilibrium of pentachlorophenol on A. niger biomass. Correlation coefficients for the second order kinetic model were almost equal to one. Conclusion: A. niger biomass can be used to reduce the toxicity of aqueous solutions containing pentachlorophenol in acidic pH conditions.

The 2nd year of a 2-year study of the fate of pentachlorophenol in outdoor artificial streams focused on details of microbial degradation by a combination of in situ and laboratory measurements. Replicate streams were dosed continuously at pentachlorophenol concentrations of 0, 48, and 144 μg/L, respectively, for an 88-d period during the summer of 1983. Pentachlorophenol was degraded both aerobically and anaerobically. Aerobic degradation was more rapid than anaerobic degradation. Mineralization of pentachlorophenol was concommitant with pentachlorophenol disappearance under aerobic conditions, but lagged behind loss of the parent molecule under anaerobic conditions. Biodegradation in the streams, or in specific stream compartments such as the sediment or water column, was characterized by an adaptation period (3–5 weeks for the stream as a whole, and reproducible from the previous year), which was inversely dependent on the concentration of pentachlorophenol and microbial biomass. The adaptation in the streams could be attributed to the time necessary for selective enrichment of an initially low population of pentachlorophenol degraders on surface compartments. The extent of biodegradation in the streams (percent loss of initial concentration of pentachlorophenol) increased with increasing pentachlorophenol input, which was explicable by an increase in the pentachlorophenol degrader population with increasing pentachlorophenol concentration. The sediment zone most significant to overall pentachlorophenol biodegradation was the top 0.5- to 1-cm layer as shown by pentachlorophenol migration rates and depth profiles of degrader density within the sediment. Pentachlorophenol profiles in sediment cores taken during and after the adaptation period for degradation showed that diffusion of pentachlorophenol into the sediment was rate limiting to degradation in this compartment. Degradation rates were independent of temperature within the temperature range of the streams during the dosing season (19–30 °C), but became increasingly slower below 19 °C. The impact of sudden increases in toxicant level (to 10 or 100 mg/L) on degradation was significant (negative), and was assessed by laboratory experiments with sediments. Total heterotrophic activity of sedimentary communities over a major part of the season was unaffected by pentachlorophenol at all stream concentrations tested.

This study is focused on the removal of pentachlorophenol from its aqueous phase by electrochemically induced degradation with Pt electrodes. The objective of this study was to contrast the electrochemical removal of pentachlorophenol at the oxidative and the reductive potentials, and further to understand how to apply the electrochemical treatment on PCP degradation. Lab experiments were conducted in a Pt electrolyzer, and the voltage source was supplied and precisely controlled by an electrochemical analyzer. In these experiments, the variables including electrolyte species, pH, voltage supply, and reaction time were examined to compare the efficiency of pentachlorophenol removal. Experimental results showed that pentachlorophenol was completely degraded after being electrolyzed for 1 h at−1.5 V in a 0.5 M KCl solution, while the removal of pentachlorophenol is negligible under the similar condition when 0.5 M NaNO3 or Na2CO3 was used as the electrolyte. The electrolyte concentration below 0.5 M is unfavourable for the electrochemical removal of pentachlorophenol. The removal efficiency of pentachlorophenol is slightly affected by pH, and the strong basic environment might impede the degradation of pentachlorophenol. Comparing with those under positive potentials, the experiments conducted under negative potentials have shown a better removal of pentachlorophenol with a higher current efficiency. It implies that pentachlorophenol degradation followed the reductive pathway. Based on the analysis of GC/MS, the intermediates of pentachlorophenol degradation were identified as 1,2-dichlorocyclohexane and 2-chlorocyclohexanol.

The effect of a chromated-copper-arsenate wood preservative on the degradation of pentachlorophenol by Flavobacterium sp. strain ATCC 53874 was examined in liquid culture. Both a commercially available and a laboratory-prepared formulation were tested. Each increased the lag time required for measurable pentachlorophenol degradation and the time required for complete degradation to nondetectable levels. This response was noted at all pentachlorophenol concentrations examined (10, 25, 50, 75, and 100 μg∙mL−1). The commercial formulation of chromated-copper-arsenate had the more significant impact on pentachlorophenol degradation. Inhibitory effects were evident at chromated-copper-arsenate component metal concentrations 0.1–0.5 mg∙L−1. These levels are thousands of times below those used commercially.Key words: pentachlorophenol, biodegradation, chromated-copper-arsenate, toxicity.

Pentachlorophenol is used as an industrial wood preservative for utility poles, crossarms, fence posts, and other purposes (79%);for NaPCP (12%); and miscellaneous, including mill uses, consumer wood preserving formulations and herbicide intermediate (9%) (CMR, 1980). As a wood preservative, pentachlorophenol acts as both a fungicide and insecticide (Freiter, 1978). The miscellaneous mill uses primarily involve the application of pentachlorophenol as a slime reducer in paper and pulp milling and may constitute ∼6% of the total annual consumption of pentachlorophenol (Crosby et al., 1981). Sodium pentachlorophenate (NaPCP) is also used as an antifungal and antibacterial agent (Freiter, 1978). Pentachlorophenol also is used as a general herbicide (Martin and Worthing, 1977). Photolysis and microbial degradation are the important chemical removal mechanisms for pentachlorophenol in water. In surface waters, pentachlorophenol photolyzes rapidly (ECETOC, 1984; Wong and Crosby. 1981; Zepp et al., 1984); however, the photolytic rate decreases as the depth in water increases (Pignatello et al., 1983). Pentachlorophenol is readily biodegradable in the presence of accli-mated microorganisms; however, biodegradation in natural waters requires the presence of microbes that can become acclimated. A natural river water that had been receiving domestic and industrial effluents significantly biodegraded pentachlorophenol after a 15-day lag period, while an unpolluted natural river water was unable to biodegrade the compound (Banerjee et al., 1984). Even though pentachlorophenol is in ionized form in natural waters, sorption to organic particulate matter and sediments can occur (Schellenberg et al., 1984), with desorption contributing as a continuing source of pollution in a contaminated environment (Pierce and Victor, 1978). Experimentally determined BCFs have shown that pentachlorophenol can significantly accumulate in aquatic organisms (Gluth et al., 1985; Butte et al., 1985; Statham et al., 1976; Veith et al., 1979a,b; Ernst and Weber, 1978), which is consistent with its widespread detection in fish and other organisms. Direct photolysis may be an important environmental sink for pen tachlorophenol present in the atmosphere. The detection of pen tachlorophenol in snow and rain water (Paasivirta et al., 1985; Bevenue et al., 1972) suggests that removal from air by dissolution is possible. Soil degradation studies indicate that pentachlorophenol is biodegrad able; microbial decomposition is an important and potentially domin ant removal mechanism in soil (Baker et al., 1980; Baker and Mayfield, 1980; Edgehill and Finn, 1983; Kirsch and Etzel, 1973; Ahlborg and Thunberg, 1980). The degree to which pentachlorophenol leaches in soil is dependent on the type of soil. In soils of neutral pH, leaching may be significant, but in acidic soils, adsorption to soil generally increases (Callahan et al. , 1979; Sanborn et al. , 1977). The ionized form of pentachlorophenol may be susceptible to adsorption in some soils (Schellenberg et al., 1984). In laboratory soils, pen tachlorophenol decomposes faster in soils of high organic content as compared with low organic content, and faster when moisture content is high and the temperature is conducive to microbial activity. Half- lives are usually ∼2-4 weeks (Crosby et al., 1981). Monitoring studies have confirmed the widespread occurrence of pentachlorophenol in surface waters, groundwater, drinking water and industrial effluents (see Table 2). The U.S. EPA's National Urban Runoff Program and National Organic Monitoring Survey reported frequent detections in storm water runoff and public water supplies (Cole et al., 1984; Mello, 1978). Primary sources by which pen tachlorophenol may be emitted to environmental waters may be through its use in wood preservation and the associated effluents and its pesticidal applications. Pentachlorophenol can be emitted to the atmosphere by evaporation from treated wood or water surfaces, by releases from cooling towers using pentachlorophenol biocides or by incineration of treated wood (Skow et al., 1980; Crosby et al., 1981). Pentachlorophenol has been detected in ambient atmospheres (Caut reels et al., 1977), in snow and rain water (Paasivirta et al,. 1985; Bevenue et al., 1972) and in emissions from hazardous waste incinera tion (Oberg et al., 1985). The U.S. Food and Drug Administration's Total Diet Study (conducted between 1964 and 1977) found pen tachlorophenol residues in 91/4428 ready-to-eat food composites (See Tables 4 and 5). The average American dietary intake of pen tachlorophenol during 1965-1969 was estimated to range from <0.001-0.006 mg/day (Duggan and Corneliussen, 1972). The most likely source of pentachlorophenol contamination in many food prod ucts may be the exposure of the food to pentachlorophenol-treated wood materials such as storage containers (Dougherty, 1978). Acute toxicity data indicated that salmonids are more sensitive to the toxic effects of pentachlorophenol than other fish species, with LC50 values of 34-128 μ g/l for salmonids and 60-600 μ g/l for other species. More recent data showed that carp larvae, bluegills, channel catfish and knifefish also had LC50 values < 100 μ gl (see Table 10). The most sensitive marine fishes were pinfish larvae, the goby, Gobius minutus, and eggs and larvae of the flounder, Pleuronectes platessa, all with LC50 values <100 μ g/l (Adema and Vink, 1981). The most sensitive freshwater invertebrate species were the chironomid, Chironomus gr. thummi (Slooff, 1983) and the snail, Lymnaea luteola (Gupta et al., 1984). The most sensitive marine invertebrates were the Eastern oyster (Borthwick and Schimmel, 1978), larvae of the crusta ceans, Crangon crangon and Palaemon elegans (VanDijk et al. , 1977), and the copepod, Pseudodiaptomus coronatus (Hauch et al., 1980), all with LC50 values <200 μ g/l. In chronic toxicity tests, the lowest concentration reported to cause adverse effects was 1.8 μ g/l (NaPCP), which inhibited growth of sockeye salmon (Webb and Brett, 1973). The marine species tested displayed similar thresholds for chronic toxicity. Both acute and chronic toxicity increased at lower pH, probably because a lower pH favors the un-ionized form of pentachlorophenol, which is taken up more readily and is therefore more toxic than ionized pentachlorophenol (Kobayashi and Kishino, 1980; Spehar et al., 1985). Data concerning the effects of pentachlorophenol on aquatic plants were highly variable. Therefore, it was difficult to draw conclusions from these data. Pentachlorophenol did not appear to bioaccumulate in aquatic or ganisms to very high concentrations. BCFs for pentachlorophenol were <1000 for most species tested. The highest BCF was 3830 for the polychaete, Lanice conchilega (Ernst, 1979). Some species appear to have an inducible pentachlorophenol-detoxification mechanism, as evidenced in several experiments in which pentachlorophenol tissue levels peaked in 4-8 days and declined thereafter despite continued exposure (Pruitt et al., 1977; Trujillo et al., 1982). A study by Niimi and Cho (1983) indicated that uptake of waterborne pentachlorophenol from gills was much greater than uptake from food, indicating that bioconcentration of pentachlorophenol through the food chain is unlikely. Biomonitoring data of Lake Ontario fishes showed that similar pentachlorophenol levels were found in predators andforage species. Studies with experimental ecosystems have indicated that ecological effects may occur at pentachlorophenol levels as low as those causing chronic toxicity in sensitive species in single-species tests. The lowest concentration that caused adverse effects in these studies was 15.8 μ g/l, which caused a reduction in numbers of individuals and species in a marine benthic community (Tagatz et al., 1978). Pentachlorophenol is readily absorbed from the gastrointestinal tract of rats, mice, monkeys and humans (Braun et al. , 1977, 1978; Ahlborg et al., 1974; Braun and Sauerhoff, 1976). Peak plasma concentrations are reached within 12-24 hours after oral administration to monkeys (Braun and Sauerhoff, 1976), but 4-6 hours after oral administration to rats (Braun et al., 1977). After oral administration, the highest concentration of radioactivity was found in the liver and gastrointesti nal tract of monkeys (Braun et al., 1977). In rats and mice, tet rachlorohydroquinone was identified in the urine (Jakobson and Yllner, 1971; Braun et al., 1977; Ahlborg et al., 1974) as well as unmetabolized pentachlorophenol and glucuronide-conjugated pen tachlorophenol. Although Ahlborg et al. (1974) reported that oxidative dechlorination of pentachlorophenol occurs in humans, as evidenced by the presence of tetrachlorohydroquinone in the urine of workers occupationally exposed (probably by inhalation), analysis of human urine after ingestion of pentachlorophenol revealed the presence of conjugated pentachlorophenol and unmetabolized pentachlorophenol (Braun et al., 1978). The primary route of excretion after oral administrtation of all species studied is in the urine (Braun et al. , 1977, 1978; Ahlborg et al., 1974; Larsen et al., 1972; Braun and Sauerhoff, 1976). Although urinary excretion followed second-order kinetics in rats (Larsen et al., 1972; Braun et al., 1977) except in females receiving a single high dose (100 mg/kg) of pentachlorophenol, urinary excretion of pentachlorophenol in humans and monkeys followed first-order kinetics (Braun and Sauerhoff, 1976; Braun et al., 1978). Enterohepatic circulation played an importation role in the pharmacokinetics of pen tachlorophenol. The half-life of pentachlorophenol in the plasma is longer in female rats and monkeys than it is in male rats and monkeys (Braun et al. , 1978; Braun and Sauerhoff, 1976). Because many preparations of pentachlorophenol are contaminated with small but measurable amounts of highly toxic substances, such as dibenzodioxins, special attention must be paid to the composition of the pentachlorophenol solution tested. In studies where technical and purified pentachlorophenol have been evaluated (Schwetz et al., 1974; Goldstein et al., 1977; Kimbrough and Linder, 1978; Knudsen et al., 1974; Johnson et al., 1973; Kerkvliet et al., 1982), only the results of the experiments using purified pentachlorophenol were reported in detail. Oral exposure to pentachlorophenol was not carcinogenic in mice (BRL, 1968; Innes et al., 1969) or rats (Schwetz et al., 1977), regardless of the composition of the pentachlorophenol solution tested. Although there are a few studies that suggest pentachlorophenol may be mutagenic in B. subtilis (Waters et al., 1982; Shirasu, 1976), in yeast, Saccharomyces cerevisiae (Fahrig et al., 1977) and in mice, as evidenced by the coat-color spot test (Fahrig et al., 1977), no evidence of mutagenicity was reported in S. typhimurium (Anderson et al. , 1972; Simmon et al., 1977; Lemma and Ames, 1975; Moriya et al. , 1983; Waters et al., 1982; Buselmaier et al., 1973) or in E. coli (Simmon et al., 1977; Fahrig, 1974; Moriya et al., 1983; Waters et al., 1982) with or without metabolic activation. Three teratogenicitylreproductive toxicity studies (Schwetz et al., 1974, 1977; Courtney et al., 1976) indicate that pentachlorophenol is fetotoxic in rats at oral dose levels ≥5 mg/kg/day. At the highest dose tested (500 ppm) in a fourth teratogenicity/reproductive toxicity study (Exon and Koller, 1982), there was a statistically nonsignificant decrease in litter size. The lowest dose tested (5 mg/kg/day) by Schwetz et al. (1977) was the lowest dose at which any evidence offetotoxicity, as indicated by delayed ossification, was observed. No adverse fetal or reproductive effects were reported at ≤3 mg/kg/day (Schwetz et al., 1977; Exon and Koller, 1982). In subchronic and chronic toxicity studies, adverse effects occurred primarily in the liver (Kerkvliet et al., 1982; Johnson et al., 1973; Knudsen et al. , 1974; Goldstein et al. , 1977; Kimbrough and Linder, 1978; Schwetz et al., 1977), the kidney (Johnson et al., 1973; Kimbrough and Linder, 1978; Schwetz et al., 1977) and the immune system (Kerkvliet et al., 1982). Knudsen et al. (1974) reported increased liver weights in female rats and centrilobu lar vacuolization in male rats exposed to diets containing ≧50 ppm commercial pentachlorophenol, which contained 282 ppm dioxins. In the remaining studies, increased liver weight (Johnson et al., 1973) and increased pigmentation of hepatocytes (Schwetz et al., 1977) were observed at oral doses of≥10 mg/kg/day (∼90%), and SGPT levels significantly increased in rats ingesting 30 mg/kg/day pentachloro phenol (∼90%) for 2 years (Schwetz et al., 1977). Increased kidney weight unaccompanied by renal histopathology was reported in rats exposed to dietary concentration ≧20 ppm of pentachlorophenol (>99%) for 8 months (Kimbrough and Linder, 1978) and in rats ingesting 30 mg/kg/day (∼90%) for 90 days (Johnson et al., 1973). Increased pigmentation of the renal tubular epithelial cells was re ported in rats ingesting 10 or 30 mg/kg/day pentachlorophenol for 2 years (Schwetz et al., 1977). Although decreased immunocompetence was reported in mice exposed to dietary levels of 50 or 500 ppm of pentachlorophenol (>99%) for 34 weeks (Kerkvliet et al., 1982), the decrease was statistically significant only at the higher dose. An ADI of 0.03 mg/kg/day or 2.1 mg/day for a 70 kg human was derivedfrom the NOAEL of 3 mg/kg/day in rats in the chronic dietary study by Schwetz et al. (1977). An uncertainty factor of 100 was used. An RQ of 100 was derived based on the fetotoxic effects of pen tachlorophenol in rats in the study by Schwetz et al. (1974). Based on guidelines for carcinogen risk assessment (U.S. EPA, 1984b) and inadequate evidence for animal carcinogenicity or absence of human cancer data, pentachlorophenol is classified as Group D, meaning that it is not classified as a human carcinogen.

Abstract A new, simple, and sensitive spectrophotometric method is described for determination of pentachlorophenol, a widely used insecticide and herbicide, in various environmental samples. The method is based on the reaction of pentachlorophenol with concentrated nitric acid to form chloranil, which liberates iodine from potassium iodide. The liberated iodine then selectively oxidizes leucocrystal violet to form crystal violet, which has an absorption maximum at 592 nm. Beer's law is obeyed over the concentration range of 0.1-1.6 μg pentachlorophenol/ 25 ml_ (0.004-0.064 ppm). The method was applied satisfactorily to determination of pentachlorophenol in air, water, plant material, textile effluent, and biological samples.

The long-term use of plant protection products in agriculture, including pentachlorophenol (PCP), has contributed to their widespread distribution in the natural environment. So far, no cheap and effective techniques for removing chlorophenols by physicochemical or biological methods have been developed. Therefore, alternative methods of neutralizing them are currently being sought. The aim of the study was to investigate the possibility of pentachlorophenol decomposition by high temperature thermohydrolysis. The decomposition process was carried out at a constant pressure of 25 MPa, in the temperature range of 20°C to 500°C and at various volumetric flows of PCP through the reactor. Detailed analysis of the results showed that the process and degree of pentachlorophenol reduction depended on residence time in the reactor and the process temperature. The obtained results indicate that thermohydrolysis in supercritical water is not an effective method to neutralize pentachlorophenol. The high costs of conducting this process together with an average degree of PCP conversion (the conversion of pentachlorophenol at the lowest volumetric flow rate through the reactor reached about 45%) cause that thermohydrolysis at high temperature is not a costeffective method of neutralizing pentachlorophenol.

Pentachlorophenol (PCF) in room temperature is a crystalline solid with phenol-like odor. It is soluble in most organic solvents (diethyl ether, acetone, carbon tetrachloride, methanol). It is slightly soluble in water. Pentachlorophenol is used as a fungicide, insecticide and as non-selective herbicide (defoliant) in cotton crops. It is also used as antimicrobial agent in leather, paper and textile industry. It has been widely used as wood preservative in wood and construction industry. Occupational exposure to pentachlorophenol may cause irritation of mucous membranes of the eyes and the upper respiratory tract and skin lesions. It may also lead to changes in the central nervous system like headache, insomnia, vertigo and depression. Acute poisoning may cause pulmonary edema, cardio-respiratory disorder and even death. Pentachlorophenol is also suspected to be carcinogenic to humans. The aim of this study was to develop and validate a sensitive method for determining pentachlorophenol concentrations in workplace air in the range from 1/10 to 2 MAC values, in accordance with the requirements of Standard No. PN-EN 482. The study was performed using a liquid chromatograph with spectrophotometric detection. All chromatographic analysis were performed with Zorbax SB-CN 250 × 4.6 mm analytical column, which was eluted with mixture of 0.1% phosphoric acid in acetonitrile and 0.1% phosphoric acid in water (6: 4 v/v). The method is based on the collection of pentachlorophenol on XAD 7 resin preceded by a glass fiber filter, extraction with methanol and chromatographic determination of resulted solution with HPLC technique. The method is linear (r = 0.9997) within the investigated working range 0.625–12.5 μg/ml (0.05–1.0 mg/m3 for a 25-L air sample). The calculated limit of detection (LOD) and limit of quantification (LOQ) were 0.014 μg/ml and 0.048 μg/ml, respectively. The average extraction efficiency of pentachlorophenol from filter and XAD 7 amounted to 95% and samples stored in refrigerator are stable for 14 days. The analytical method described in this paper enables determination of pentachlorophenol in workplace air. The method is precise, accurate and it meets the criteria for procedures for measuring chemical agents listed in Standard No. PN-EN 482. The method can be used for assessing occupational exposure to pentachlorophenol and associated risk to workers’ health. The developed method of determining pentachlorophenol has been recorded as an analytical procedure (see Appendix). This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.

Pentachlorophenol (PCP) was, and still is, one of the most frequently used fungicides and pesticides, Its toxicity is due to interference with oxidative phosphorylation. Acute and chronic poisoning may occur by dermal absorption, inhalation or ingestion. Chronic poisoning occurs mainly in sawmill workers or people living in log homes treated with PCPcontaining wood protecting formulations. Quantitative determination of PCP in urine and serum is useful to detect occupational or subclinical exposure. The clinical features of acute and chronic PCP poisoning can be classified systematically into effects on the skin, metabolism (fever), the haematopoietic tissue, the respiratory system, the central and peripheral nervous system, the kidney and the gastrointestinal tract. Although PCP is not classified as a human carcinogen, some epidemiological observations suggest that exposure to chlorophenols in general and PCP solutions in particular may result in an increased risk for certain malignant disorders such as nasal carcinoma and soft tissue sarcoma. There is concern that contamination of PCP-solutions with products such as chlorodibenzo-p-dioxins is the real cause of this suspected carcinogenicity. No specific antidote exists for the treatment of (acute) PCP poisoning. The basis of the treatment of acute poisoning is intensive supportive care with prevention of dangerous rise in temperature. Use of PCP-based products as indoor wood preservatives poses an unacceptable risk to human health.

Responses of postlarval brown shrimp (Penaeus aztecus) to pentachlorophenol (0–450 μg∙L−1) were measured in synthetic seawater and estuarine water using a laminar-flow choice chamber. This chamber provides individual postlarvae with equal exposure to two parallel olfactant streams separated by a steep concentration gradient. Shrimp detected and avoided pentachlorophenol concentrations above 91 μg∙L−1 in synthetic seawater. This detection threshold reflects limitations in statistical power, and with increased replication the physiological threshold could probably be resolved at a much lower concentration. Pentachlorophenol appeared to be more repellent when dissolved in estuarine water from Galveston Bay, Texas. The 96-h LC50 for pentachlorophenol was 317 μg∙L−1 which suggests that postlarvae are capable of avoiding acutely toxic concentrations of this pollutant. For postlarvae of this species, behavioral avoidance appears to provide a more sensitive indicator of pollutant responses than the conventional toxicity bioassay.

Reducing chemical risk in raw water from the River Cauca (caused by the presence of pentachlorophenol and organic matter (real color, UV254 absorbance)) was evaluated at bench scale by using three treatment sequences: adsorption with powdered activated coal (PAC); adsorption – coagulation; and, adsorption – disinfection – coagulation. The results showed that although PAC is appropriate for pentachlorophenol removal, and its use together with the coagulant (aluminium sulphate) significantly improved phenolic compound and organic matter removal (promoting enhanced coagulation), the most efficient treatment sequence was adsorption – disinfection - coagulation, achieving minor pentachlorophenol levels than detection (1.56 μg/l) and WHO limits (9μg/l) due to the effect of chloride on PAC.

The destructive oxidation of pentachlorophenol in alkaline aqueous solution has been attempted with tetraoxoruthenium species as catalysts and hypochlorite as the terminal oxidant. The product solution contained no pentachlorophenol. Only traces of chlorinated compounds which could be extracted with dichloromethane were present. Measurements of the quantity of base and of hypochlorite added to the reaction mixture indicated that the oxidation did not proceed to completely to carbonate, but rather to unidentified compounds with an average carbon oxidation state of about three. Oxidation with peroxodisulfate indicated that only two-thirds of the chlorine was present as ionic chloride in the product solution. In contrast, oxidation with permanganate, in the absence of ruthenium, led to the complete oxidation of pentachlorophenol and to release of all of the chlorine as ionic chloride. Qualitative rate measurements were made with the pH-stat technique. Some experiments were also conducted with 2,4,6-trichlorophenol, p- chlorophenol and phenol. Attempts to oxidize both phenol and pentachlorophenol at various ruthenium-containing electrodes in either basic or acidic solutions were unsuccessful.

Pentachlorophenol (PCP) (2,3,4,5,6- pentachlorophenol) is an organochlorine compound used as a pesticide and a disinfectant. PCP is used as a herbicide, insecticide, fungicide and disinfectant. Some applications include agricultural seeds (for nonfood uses), leather, masonry, wood preservation, cooling tower water, rope, and paper mills. Determination of Pentachlorophenol was based on the reaction of PCP with concentrated nitric acid followed by potassium iodide for the liberation of iodine. Liberated iodine reacted with leuco malachite green for the formation of green colour dye which was measured at 610 nm against a reagent blank. Parameters affecting the reaction were studied. The interfering effect of various species was also investigated and the methods were applied on some vegetables and fruit samples.

Pentachlorophenol resistance was investigated in bacteria isolated from glycine- or water-percolated soils where the bacterial flora was modified by the addition of pentachloropenol. The strains isolated from the water-percolated soil amended with PCP had the highest resistance, and the addition of glycine to the percolated soil weakened the resistance. The strains from the glycine-percolated soil without pentachlorophenol had a medium degree of resistance, and the resistance of the strains from the water-percolated soil without PCP was the lowest. The bacterial groups were sorted taxonomically; differences in pentachloropenol resistance were correlated with taxonomic groupings. Relative growth rate in the presence of pentachlorophenol was proposed as a useful means to distinguish among the bacterial species.

ABSTRACT The gene cassette (camA + camB + camC) encoding a cytochrome P-450cam variant was integrated into the nonessential gene pcpM of the pentachlorophenol degrader Sphingobium chlorophenolicum ATCC 39723 by homologous recombination. The recombinant strain could degrade hexachlorobenzene at a rate of 0.67 nmol · mg (dry weight)−1 · h−1, and intermediate pentachlorophenol was also identified.

The white rot fungus Phanerochaete chrysosporium can degrade toxic compounds under specific nutrient conditions. This attribute was utilized in order to determine the effect of fungal pretreatment on model compounds pentachlorophenol and toluene. The fungal culture was purchased from ATCC, cultured on dextrose agar, and the mycelia harvested to degrade the model compounds. P. chrysosporium was able to degrade up to 74% of initial pentachlorophenol concentration in eight days and up to 31% initial toluene in 31 hours. Specific growth rates of activated sludge and selected microbial consortia were determined on untreated and fungal-pretreated parent model compounds. Specific growth rates for activated sludge and selected microbial consortia were enhanced by fungal pretreatment of both model compounds. Specific growth rates indicated more efficient use of toluene by activated sludge than by toluene-selected microbial consortia, while pentachlorophenol- selected microbial consortia exhibited more favorable growth rates on pentachlorophenol than did activated sludge. Pretreatment results indicated that the toxicity of model compounds was reduced by fungal pretreatment. The growth rates were compared and used as an indication of toxicity reduction which can be exploited at contaminated waste sites or at industrial pretreatment facilities.

The mechanisms of heavy-metal resistance used by adapted sulfidogenic and methanogenic enrichments degrading pentachlorophenol in the presence of cadmium (Cd) were studied. The enrichment cultures adapted to and readily tolerated bioavailable Cd concentrations up to 50 ppm while degrading an equal concentration of pentachlorophenol. Both cultures removed >95% of the Cd from solution. Transmission electron micrographs revealed (i) the presence of electron-dense particles surrounding the cells in the sulfidogenic enrichments and (ii) the unusual clumping of cells and the presence of an exopolymer in the methanogenic enrichments. Energy dispersive X-ray analysis showed that the sulfidogenic enrichments removed Cd by extracellular precipitation of cadmium sulfide, while the methanogenic enrichment culture removed Cd by extracellular sequestration of Cd into the exopolymer.Key words: cadmium, pentachlorophenol, sulfidogenic, methanogenic, resistance.

Bacteria isolated from a pentachlorophenol (PCP) contaminated site grew in the presence of 50 µg PCP/mL but were not able to degrade it in either liquid medium or the presence of 1% sterile potting soil as a solid support. Probes developed using the gene sequence of PCP-4-monooxygenase (pcpB) from Sphingomonas chlorophenolica sp.nov hybridized to two separate isolates. Identification based on fatty acid methyl ester profiles (Sherlock™), substrate utilization (BIOLOG™), and 16S rRNA showed that the two strains were different from each other and from Sphingomonas chlorophenolica. Sequences from these isolates, amplified by polymerase chain reaction, confirmed the homology with pcpB. The presence of pcpB sequences in these nondegraders indicated that growth and hybridization data alone were insufficient for predicting degradation capability. Key words: pentachlorophenol, Sphingomonas chlorophenolica, pcpB gene, pentachlorophenol-4-monooxygenase.

1 Urinary chlorophenols of the general population of Barcelona, Spain were determined. Pentachlorophenol (PCP: 25.0 ± 3.9 ng/ml; x ± s.e.m., n = 50) and tetrachlorophenol (TCP: 6.2 ± 1.6 ng/ml; x ± s.e.m., n = 25) were found in all samples. 2 Pentachlorophenol and hexachlorobenzene were also determined in serum. Both were present in all samples (PCP: 21.9 ± 1.9 ng/ml; HCB: 11.1 ± 1.1 ng/ml; x ± s.e.m., n = 100). Their concentrations do not show any correlation, suggesting no metabolic relation between them.

A method was estimated to detect pentachlorophenol and sodium pentachlorophenolate in fishery products by gas chromatography with μ-ECD detector. Procedures of the method included extraction, alkaline stripping and derivatization. The pH of sample matrix was modified to 3-4 by nitric acid solution(nitric acid:water 1:1). Target compounds were extracted by hexane first and 0.2mol/L potassium hydroxide solution was used as stripping reagent to isolate pentachlorophenol from hexane. Acetic anhydride was taken as derivatizing reagent to convert target compounds into nonpolar ester compounds according to acylation reaction. Derivatized compound was extracted by hexane for the analysis of GC. The limit of detection is 2µg/kg . The average recoveries ranged from 73.01 to 104.68% spiked at 2.0,4.0,10.0µg/kg. And the relative standard deviations ranged from1.5 to 8.3%. The method can be used for the determination of pentachlorophenol and sodium pentachlorophenolate in fishery products,and it provides an rapid and acute method for food safety determination.

Exposure of juvenile bluegill sunfish (Lepomis macrochirus) to 48 and 173 μg/L pentachlorophenol (20 and 72% of 96-h LC50, respectively) for 22 days produced a significant reduction in food conversion efficiency measured over the last 10 days of exposure. A 22-day recovery period in untreated water caused food conversion efficiency values to increase so that there was no longer a significant difference between previously exposed and control fish. For bluegill sunfish, exposure to sublethal levels of pentachlorophenol can decrease food-conversion efficiency, but recovery from this state of reduced growth is rapid when fish are placed in a toxicant-free environment. Although other studies have found that a number of biochemical indicators of pentachlorophenol exposure cause long-lasting changes, this study used a new method of measuring food conversion over a very short period to show that food-conversion efficiency, which integrates many biochemical and physiological effects, recovers quickly.

Fluorescent Pseudomonads strains were considered as plant growth promoting bacteria. They exhibited antagonistic activities against phytopathogens and showed bio-fertilizing properties. The strain Pseudomonas fluorescens PsWw128, isolated from wastewater, can use the pentachlorophenol (PCP) as the sole source of carbon and energy. High-performance liquid chromatography (HPLC) and spectrophotometric methods were used to follow the PCP degradation and biomass PsWw128 formation. However, the removal efficiency of PCP was highly significant. Thus, PsWw128 was able to degrade more than 99% of PCP when this isolate was grown under a high concentration of PCP (250 mg L–1) in a mineral salts medium (MSM). The simultaneous utilization of glucose and PCP indicates the diauxic growth pattern of PsWw128. PCP addition (100 mg L–1) in the growth medium can contribute to a decrease of the antibiotic susceptibility, and increase the biofilm development. In the presence of the toxic pollutant PCP (100, 200 and 250 mg L–1), the antibiotic sensitivity showed a decrease concerning the seven antibiotics tested. Furthermore, the biofilm formation appeared very low with OD600 = 0.075 in the Brain infusion broth supplemented with 25% of glucose, and developed a significant growth with an OD600 = 1.809 in the MSM supplemented with 250 mg L–1 of PCP.