Pentachlorophenol exposure induced neurotoxicity by disrupting citrulline metabolism in larvae and adult zebrafish.

Pentachlorophenol (PCP) is a ubiquitous environmental toxicant with various adverse effects. Although its neurotoxicity has been reported, the underlying mechanism and subsequent detoxification remain unclear. In this study, embryos and adult zebrafish were exposed to PCP to determine its potential neurotoxic mechanism and protective indicators. The survival rate, heart rate, mobility time, active status and moving distance were significantly decreased in larvae after 30 µg/L PCP exposure. Likewise, the mobile time, latency to the first movement, velocity and moving distance of adult zebrafish were significantly reduced by PCP exposure. Untargeted metabolomics analysis of larvae revealed that arginine and proline metabolism was the primary pathway affected by PCP exposure, reflected by increased proline and decreased citrulline (CIT) contents, which were confirmed by quantitative data. PCP exposure suppressed the conversion from arginine to CIT in larvae by downregulating the expression of nos1 and nos2a. Ornithine content was increased in the brains and intestines of adult zebrafish after PCP exposure, which inhibited ornithine catabolism to CIT by downregulating otc, resulting in reduced CIT. Intriguingly, CIT supplementation significantly restored the neurobehavioral defects induced by PCP in larvae and adult zebrafish. CIT supplementation upregulated the expression of ef1α and tuba1 in larvae and inhibited the downregulation of ef1α in the brains of adult zebrafish. Taken together, these results indicated that CIT supplementation could protect against PCP-induced neurotoxicity by upregulating the expression of genes involved in neuronal development and function.

Pentachlorophenol causes redox imbalance, inhibition of brush border membrane and metabolic enzymes, DNA damage and histological alterations in rat kidney.

Pentachlorophenol (PCP) is a synthetic organochlorine compound that is widely used in biocide and pesticide industries, and in preservation of wood, fence posts, cross arms and power line poles. Humans are usually exposed to PCP through air, contaminated water and food. PCP enters the body and adversely affects liver, gastrointestinal tract, kidney and lungs. PCP is a highly toxic class 2B or probable human carcinogen that produces large amount of reactive oxygen species (ROS) within cells. This work aimed to determine PCP-induced oxidative damage in rat kidney. Adult rats were given PCP (25, 50, 100, 150 mg/kg body weight), in corn oil, once a day for 5 days while control rats were given similar amount of corn oil by oral gavage. PCP increased hydrogen peroxide level and oxidation of thiols, proteins and lipids. The antioxidant status of kidney cells was compromised in PCP treated rats while enzymes of brush border membrane (BBM) and carbohydrate metabolism were inhibited. Plasma level of creatinine and urea was also increased. Administration of PCP increased DNA fragmentation, cross-linking of DNA to proteins and DNA strand scission in kidney. Histological studies supported biochemical findings and showed significant damage in the kidneys of PCP-treated rats. These changes could be due to redox imbalance or direct chemical modification by PCP or its metabolites. These results signify that PCP-induced oxidative stress causes nephrotoxicity, dysfunction of BBM enzymes and DNA damage.

Concurrent anaerobic chromate bio-reduction and pentachlorophenol bio-degradation in a synthetic aquifer.

Chromate [Cr(VI)] and pentachlorophenol (PCP) coexist widely in the environment and are highly toxic to public health. However, whether Cr(VI) bio-reduction is accompanied by PCP bio-degradation and how microbial communities can keep long-term stability to mediate these bioprocesses in aquifer remain elusive. Herein, we conducted a 365-day continuous column experiment, during which the concurrent removals of Cr(VI) and PCP were realized under anaerobic condition. This process allowed for complete Cr(VI) bio-reduction and PCP bio-degradation at an efficiency of 92.8 ± 4.2% using ethanol as a co-metabolic substrate. More specifically, Cr(VI) was reduced to insoluble chromium (III) and PCP was efficiently dechlorinated with chloride ion release. Collectively, Acinetobacter and Spirochaeta regulated Cr(VI) bio-reduction heterotrophically, while Pseudomonas mediated not only Cr(VI) bio-reduction but also PCP bio-dechlorination. The bio-dechlorinated products were further mineralized by Azospira and Longilinea. Genes encoding proteins for Cr(VI) bio-reduction (chrA and yieF) and PCP bio-degradation (pceA) were upregulated. Cytochrome c and intracellular nicotinamide adenine dinucleotide were involved in Cr(VI) and PCP detoxification by promoting electron transfer. Taken together, our findings provide a promising bioremediation strategy for concurrent removal of Cr(VI) and PCP in aquifers through bio-stimulation with supplementation of appropriate substrates.

Simultaneous adsorption-photocatalytic treatment with TiO2-Sep nanocomposites for in situ remediation of sodium pentachlorophenol contaminated aqueous and soil.

Sodium pentachlorophenol (NaPCP) is a highly toxic and persistent organic pollutant. With sepiolite as the support, a series of TiO2-Sep nanocomposites (NCs) with different Ti/Sep ratios were developed. The objective was to understand the effect of Ti/Sep ratio on the structure and activity of the NCs in aqueous and soil systems and to evaluate the feasibility of the NCs for in situ soil remediation. The prepared NCs were characterized with XRD, SEM, TEM, and N2 adsorption-desorption, respectively. The results showed that high surface area and good dispersion of TiO2 on sepiolite surface were obtained. The photocatalytic activities in aqueous and soil of the as-developed NCs were examined using NaPCP as a model pollutant. Compared with bare sepiolite and TiO2, the heterogeneous NCs showed significantly higher photocatalytic performance in decomposing NaPCP, and the photocatalytic activities varied with the content of TiO2 in the NCs. In aqueous media, treatment with TiO2-S-30 showed excellent degradation efficiency with about 90% NaPCP decomposed in 140 min. Nevertheless, the sample TiO2-S-20 promotes maximum rate reduction of NaPCP with above 90% within 20-h irradiation in soil. The results indicate that an appropriate Ti/Sep ratio could significantly enhance the activities of NCs on NaPCP remediation and the role of carrier sepiolite is more important in soil media than that in aqueous phase. The excellent performance of the TiO2-Sep in wastewater degradation and soil remediation can be attributed to the synergistic effects between the high photocatalytic activity of TiO2 nanoparticles and the strong adsorption capacity of sepiolite nanofibers. This work revealed that sepiolite adsorption coupled with TiO2 photocatalysis can be one promising technique for in situ remediation of NaPCP-contaminated soil.

Plant extract-based green fabrication of nickel ferrite (NiFe2O4) nanoparticles: An operative platform for non-enzymatic determination of pentachlorophenol.

Environmental pollution has become a major human concern with the extensive exploitation of pesticides. Pentachlorophenol (PCP) is the most hazardous of all chlorophenols which are being used as pesticide, fungicide, and wood preservative. Thus, the fabrication of ultrasensitive electrochemical methods for the determination of pesticides is of great significance. In the present experiment, a simple, green, and sensitive electrochemical sensor was constructed for the determination of PCP by using a chemically modified nickel ferrite glassy carbon electrode (NiFe2O4/GCE). The fabricated nanoparticles were primarily characterized by several analytical tools to confirm the functionalities, surface texture, crystallinity, and elemental composition. For the investigation of conductive nature, the proposed NiFe2O4/GCE was exploited to the primary electrochemical characterization tools e.g. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The ultra-sensitive determination of PCP was carried out under the linear dynamic range from 0.01 to 90 µM at the pulse amplitude of 80 mV/s in BRB buffer pH of 4. The limit of detection of the developed methods for PCP was calculated to be 0.0016 µM. The analytical applicability of the fabricated sensor was tested in different water samples depicting the acceptable recovery values.

Role of tetrachloro-1,4-benzoquinone reductase in phenylalanine hydroxylation system and pentachlorophenol degradation in Bacillus cereus AOA-CPS1.

This study reports a ≅12.5 kDa protein tetrachloro-1,4-benzoquinone reductase (CpsD) from Bacillus cereus strain AOA-CPS1 (BcAOA). CpsD is purified to homogeneity with a total yield of 35% and specific activity of 160 U·mg-1 of protein. CpsD showed optimal activity at pH 7.5 and 40 °C. The enzyme was found to be functionally stable between pH 7.0-7.5 and temperature between 30 °C and 35 °C. CpsD activity was enhanced by Fe2+ and inhibited by sodium azide and SDS. CpsD followed Michaelis-Menten kinetic exhibiting an apparent vmax, Km, kcat and kcat/Km values of 0.071 µmol·s-1, 94 µmol, 0.029 s-1 and 3.13 × 10-4 s-1·µmol-1, respectively, for substrate tetrachloro-1,4-benzoquinone. The bioinformatics analysis indicated that CpsD belongs to the PCD/DCoH superfamily, with specific conserved protein domains of pterin-4α-carbinolamine  dehydratase (PCD). This study proposed that CpsD catalysed the reduction of tetrachloro-1,4-benzoquinone to tetrachloro-p-hydroquinone and released the products found in phenylalanine hydroxylation system (PheOHS) via a Ping-Pong or atypical ternary mechanism; and regulate expression of phenylalanine 4-monooxygenase by blocking reverse flux in BcAOA PheOHS using a probable Yin-Yang mechanism. The study also concluded that CpsD may play a catalytic and regulatory role in BcAOA PheOHS and pentachlorophenol degradation pathway.

Hepatoprotective effects of the n-butanol extract from Perralderia coronopifolia Coss. against PCP-induced toxicity in Wistar albino rats.

In the present study, in vivo antioxidant properties of the n-butanol extract obtained from aerial parts of Perralderia coronopifolia were investigated in term of its hepatoprotective effect of female Wistar albino rats (n, 36; average age, 48 ± 5 days; weighing 150 ± 18 g) against PCP (pentachlorphenol)-induced toxicity. PCP (20 mg/kg b.w.) and plant extract (50 mg/kg b.w.) were administered daily by gavages for 2 weeks. Vitamin E (100 mg/kg b.w.) was given intraperitoneally as a positive control. Lipid peroxidation (LPO) levels, reduced glutathione (GSH) levels, and glutathione peroxidase (GPx) activities were evaluated in liver homogenates. While, aspartate aminotransferase (AST), alanine aminotransferase (ALT), cholesterol, and triglyceride parameters were analyzed in serums. The liver fragments were observed using light microscopy. Experimental results exhibited that PCP-treated group has a significant increase in the liver lipid peroxidation (LPO) levels of animals while decreased in plant extract-treated group. In addition, PCP caused significant decreases in glutathione peroxidase (GPx) activities and reduced glutathione (GSH) levels. Moreover, PCP induced hepatotoxicity by increasing serum transaminase enzymes, cholesterol, and triglyceride levels. While, these levels were restored to control value in animals treated with plant extract. The regularized levels of LPO, GSH, cholesterol, triglyceride, transaminase enzymes, and GPx activities revealed the antioxidant properties of the extract plant as well as of the vitamin E. The histological study showed the hepatoprotective effect of our extracts against PCP-induced acute intoxication, protecting the hepatic architecture and decreasing the functional and structural alterations of the liver. The plant extract had high antioxidant potential and completely prevented the toxic effect of PCP on the above of liver and serum parameters.

Bioremediation of chlorophenol-contaminated sawmill soil using pilot-scale bioreactors under consecutive anaerobic-aerobic conditions.

Chlorophenols (CPs), including pentachlorophenol (PCP), are chemicals of concern due to their toxicity and persistence. Here we describe a successful reactor-based remediation of CP-contaminated soil and assess changes in the toxicity patterns and bacterial communities during the remediation. The remediation consisted of separating half of the contaminated soil to be ground (samples M) in order to test whether the grinding expedited the remediation, the other half was left unground (samples P). Both soils were mixed with wastewater treatment sludge to increase their bacterial diversity and facilitate the degradation of CPs, and the resultant mixtures were placed in 2 bioreactors, M and P, operated for 16 months under anaerobic conditions to favor dehalogenation and for an additional 16 months under aerobic conditions to achieve complete mineralization. Samples were taken every 4 months for toxicity and microbial analyses. The results showed a 64% removal of total CPs (ΣCPs) in reactor P after just 18 months of remediation, whereas similar depletion in reactor M occurred after ∼25 months, indicating that the grinding decelerated the remediation. By the end of the experiment, both reactors achieved 93.5-95% removal. The toxicity tests showed a decrease in toxicity as the remediation progressed. The succession of bacterial communities over time was significantly associated with pH, anaerobic/aerobic phase and the concentration of the majority of CP congeners. Our data indicate that the supplementation of contaminated soil with sludge and further incubation in pilot-scale bioreactors under consecutive anaerobic-aerobic conditions proved to be effective at the remediation of CP-contaminated soil.

Nitrate supply and sulfate-reducing suppression facilitate the removal of pentachlorophenol in a flooded mangrove soil.

An anaerobic incubation was launched with varying nitrate (1, 5, 10 and 20 mM exogenous NaNO3) and molybdate (20 mM Na2MoO4, a sulfate-reducing inhibitor) additions to investigate the characteristics of PCP dechlorination, as well as the reduction of natural co-occurring electron acceptors, including NO3-, Fe(III) and SO42-, and the responses of microbial community structures under a unique reductive mangrove soil. Regardless of exogenous addition, nitrate was rapidly eliminated in the first 12 days. The reduction process of Fe(III) was inhibited, while that of SO42- reduction depended on addition concentration as compared to the control. PCP was mainly degraded from orth-position, forming the only intermediate 2,3,4,5-TeCP by anaerobic microbes, with the highest PCP removal rate of average 21.9% achieved in 1 and 5 mM NaNO3 as well as 20 mM Na2MoO4 treatments and the lowest of 7.5% in 20 mM NaNO3 treatment. The effects of nitrate on PCP dechlorination depended on addition concentration, while molybdate promoted PCP attenuation significantly. Analyses of the Illumina sequencing data and the relative abundance of dominant microorganisms indicated that the core functional groups regulated PCP removal at genera level likely included Bacillus, Pesudomonas, Dethiobacter, Desulfoporosinus and Desulfovbrio in the nitrate treatments; while that was likely Sedimentibacter and Geosporobacter_Thermotalea in the molybdate treatment. Nitrate supplement but not over supplement, or addition of molybdate are suggested as alternative strategies for better remediation in the nitrate-deficient and sulfur-accumulated soil ecosystem contaminated by PCP, through regulating the growth of core functional groups and thereby coordinating the interaction between dechlorination and its coupled soil redox processes due to shifts of more available electrons to dechlorination. Our results broadened the knowledge regarding microbial PCP degradation and their interactions with natural soil redox processes under anaerobic soil ecosystems.

Aerobic Biodegradation of OCDD by P. Mendocina NSYSU: Effectiveness and Gene Inducement Studies.

The goals of this study were to assess the effectiveness of (1) enhancing octachlorinated dibenzo-p-dioxin (OCDD) biodegradation under aerobic conditions by Pseudomonas mendocina NSYSU (P. Mendocina NSYSU) with the addition of lecithin, and (2) inducing OCDD ring-cleavage genes by pentachlorophenol (PCP) and OCDD addition. P. Mendocina NSYSU could biodegrade OCDD via aerobic cometabolism and lecithin was used as a primary substrate. Approximately 74 and 67% of OCDD biodegradation was observed after 60 days of incubation with lecithin and glucose supplement, respectively. Lecithin was also used as the solubilization additive resulting in OCDD solubilization and enhanced bioavailability of OCDD to P. Mendocina NSYSU. Two intradiol and extradiol ring-cleavage dioxygenase genes (Pmen_0474 and Pmen_2526) were identified from gene analyses. Gene concentration was significantly enhanced after the inducement by PCP and OCDD. Higher gene inducement efficiency was obtained using PCP as the inducer, and Pmen_2526 played a more important role in OCDD biodegradation.

Treatment of a mixed wood preservative leachate by a hybrid constructed wetland and a willow planted filter.

The performance and removal mechanisms of a hybrid constructed wetland (HCW) followed by a willow planted filter (WPF) were evaluated for the treatment of a leachate contaminated by wood pole preservatives (pentachlorophenol (PCP) and chromated copper arsenate) to reach the storm sewer discharge limits. The HCW aimed to dechlorinate the PCP and polychlorodibenzo-p-dioxins/polychlorodibenzofuran (PCDD/F) and to remove metals by adsorption and precipitation. The HCW was efficient in removing PCP (>98.6%), oil, arsenic (99.4%), chromium (>99.2%), copper (>99.6%%) and iron (29%) to under their discharge limits, but it was unable to reach those of Mn and PCDD/F, with residual concentrations of 0.11 mg Mn/L and 0.32 pg TEQ/L. Iron and manganese could be removed but were subsequently released by the HCW due to low redox conditions. No dechlorination of PCDD/F was observed since its chlorination profile remained the same in the different sections of the HCW. Adsorption was the most probable removal mechanism of PCDD/F. The WPF was able to remove some residual contamination, but it released Mn at a gradually decreasing rate. Total evapotranspiration of the leachate by a larger fertilized WPF and the construction of an underground retention basin are proposed to prevent any discharge of PCDD/F traces in the environment.

The use of ultrasound-assisted anaerobic compost tea washing to remove poly-chlorinated dibenzo-p-dioxins (PCDDs), dibenzo-furans (PCDFs) from highly contaminated field soils.

The remediation of dioxin-contaminated soil of a specific coastal area previously employed for the manufacture of pentachlorophenol (PCP) in southern Taiwan's Tainan City has attracted much attention of researchers there. This work addresses the possibility of providing an effective and environmentally friendly option for removing PCDD/Fs from soil in that field. Soil screening/sieving was first conducted to assess particle distribution. Fine sand was observed to be the major component of the soil, accounting for more than 60% of the total mass. A combination of ultrasonification and mechanical double-blade agitation was used to facilitate the washing of the soil using the biosurfactant anaerobic compost tea. More than 85 and 95% of total removal efficiencies were achieved for moderately and highly contaminated soils after 6 and 10 washing cycles, respectively, under ambient temperature, a soil/liquid ratio 1:2.5, 700 rpm, and over a relatively short duration. These results were achieved through the collision and penetration effects of this combined treatment as well as PCDD/F partitioning between the particles and anaerobic compost tea. This study represents the first to report the use of anaerobic compost tea solvent to wash soil highly contaminated by dioxin. It was concluded that anaerobic compost tea, rich in non-toxic bio-surfactants (e.g., alcohols, humic acids), can be used to improve bioavailability and bioactivity of the soil making bio-attenuation and full remediation more efficient.

Effect of phosphorus addition on the reductive transformation of pentachlorophenol (PCP) and iron reduction with microorganism involvement.

The transformation of phosphorus added to the soil environment has been proven to be influenced by the Fe biochemical process, which thereby may affect the transformation of organic chlorinated contaminants. However, the amount of related literatures regarding this topic is limited. This study aimed to determine the effects of phosphorus addition on pentachlorophenol (PCP) anaerobic transformation, iron reduction, and paddy soil microbial community structure. Results showed that the transformation of phosphorus, iron, and PCP were closely related to the microorganisms. Moreover, phosphorus addition significantly influenced PCP transformation and iron reduction, which promoted and inhibited these processes at low and high concentrations, respectively. Both the maximum reaction rate of PCP transformation and the maximum Fe(II) amount produced were obtained at 1 mmol/L phosphorus concentration. Among the various phosphorus species, dissolved P and NaOH-P considerably changed, whereas only slight changes were observed for the remaining phosphorus species. Microbial community structure analysis demonstrated that adding low concentration of phosphorus promoted the growth of Clostridium bowmanii, Clostridium hungatei, and Clostridium intestinale and Pseudomonas veronii. By contrast, high-concentration phosphorus inhibited growth of these microorganisms, similar to the curves of PCP transformation and iron reduction. These observations indicated that Clostridium and P. veronii, especially Clostridium, played a vital role in the transformation of related substances in the system. All these findings may serve as a reference for the complicated reactions among the multiple components of soils.

Response of selenium-dependent glutathione peroxidase in the freshwater bivalve Anodonta woodiana exposed to 2,4-dichlorophenol,2,4,6-trichlorophenol and pentachlorophenol.

2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) pose a health risk to aquatic organism and humans, and are recognized as persistent priority pollutants. Selenium dependent glutathione peroxidase (Se-GPx) belongs to the family of selenoprotein, which acts mainly as an antioxidant role in the cellular defense system. In the current study, a Se-GPx full length cDNA was cloned from Anodonta woodiana and named as AwSeGPx. It had a characteristic codon at 165TGA167 that corresponds to selenocysteine(Sec) amino acid as U44. The full length cDNA consists of 870 bp, an open reading frame (ORF) of 585 bp encoded a polypeptide of 195 amino in which conserved domain (68LGFPCNQF75) and a glutathione peroxide-1 GPx active site (32GKVILVENVASLUGTT47) were observed. Additionally, the eukaryotic selenocysteine insertion sequence (SECIS) was conserved in the 3'UTR. The AwSeGPx amino acid sequence exhibited a high similarity with that of other Se-GPx. Real-time PCR analysis revealed that AwSeGPx mRNA had a widely distribution, but the highest level was observed in hepatopancreas. AwSeGPx mRNA expression was significantly up-regulated in hepatopancreas, gill and hemocytes after 2,4-DCP, 2,4,6-TCP and PCP exposure. Under similar environment, clams A. woodiana showed a more sensitive to PCP than that of 2,4-DCP and 2,4,6-TCP. These results indicate that AwSeGPx plays a protective role in eliminating oxidative stress derived from 2,4-DCP, 2,4,6-TCP and PCP treatment.

Pentachlorophenol degradation by Janibacter sp., a new actinobacterium isolated from saline sediment of arid land.

Many pentachlorophenol- (PCP-) contaminated environments are characterized by low or elevated temperatures, acidic or alkaline pH, and high salt concentrations. PCP-degrading microorganisms, adapted to grow and prosper in these environments, play an important role in the biological treatment of polluted extreme habitats. A PCP-degrading bacterium was isolated and characterized from arid and saline soil in southern Tunisia and was enriched in mineral salts medium supplemented with PCP as source of carbon and energy. Based on 16S rRNA coding gene sequence analysis, the strain FAS23 was identified as Janibacter sp. As revealed by high performance liquid chromatography (HPLC) analysis, FAS23 strain was found to be efficient for PCP removal in the presence of 1% of glucose. The conditions of growth and PCP removal by FAS23 strain were found to be optimal in neutral pH and at a temperature of 30 °C. Moreover, this strain was found to be halotolerant at a range of 1-10% of NaCl and able to degrade PCP at a concentration up to 300 mg/L, while the addition of nonionic surfactant (Tween 80) enhanced the PCP removal capacity.

Evaluating the phytoremediation potential of Phragmites australis grown in pentachlorophenol and cadmium co-contaminated soils.

Pot-culture experiments were conducted to evaluate the phytoremediation potential of a wetland plant species, Phragmites australis in cadmium (Cd) and pentachlorophenol (PCP) co-contaminated soil under glasshouse conditions for 70 days. The treatments included Cd (0, 5 and 50 mg kg(-1)) without or with PCP (50 and 250 mg kg(-1)). The results showed that growth of P. australis was significantly influenced by interaction of Cd and PCP, decreasing with either Cd or PCP additions. Plant biomass was inhibited and reduced by the rate of 89 and 92% in the low and high Cd treatments and by 20 and 40% in the low and high PCP treatments compared to the control. The mixture of low Cd and low PCP lessened Cd toxicity to plants, resulting in improved plant growth (by 144%). Under the joint stress of the two contaminants, the ability of Cd uptake and translocation by P. australis was weak, and the BF and TF values were inferior to 1.0. A low proportion of the metal is found aboveground in comparison to roots, indicating a restriction on transport upwards and an excluding effect on Cd uptake. Thus, P. australis cannot be useful for phytoextraction. The removal rate of PCP increased significantly (70%) in planted soil. Significant positive correlations were found between the DHA and the removal of PCP in planted soils which implied that plant root exudates promote the rhizosphere microorganisms and enzyme activity, thereby improving biodegradation of PCP. Based on results, P. australis cannot be effective for phytoremediation of soil co-contaminated with Cd and PCP. Further, high levels of pollutant hamper and eventually inhibit plant growth. Therefore, developing supplementary methods (e.g. exploring the partnership of plant-microbe) for either enhancing (phytoextraction) or reducing the bioavailability of contaminants in the rhizosphere (phytostabilization) as well as plant growth promoting could significantly improve the process of phytoremediation in co-contaminated soil.

Effects of petroleum mixture types on soil bacterial population dynamics associated with the biodegradation of hydrocarbons in soil environments.

Soil bacterial population dynamics were examined to assess patterns in microbial response to contamination by different petroleum mixtures with variation in n-alkane profiles or toxic constituents such as pentachlorophenol (PCP). Three soil types from distinct areas of the United States (Montana, Oregon, and Arizona) were used in controlled perturbation experiments containing crude oil, kerosene, diesel, or diesel plus PCP spiked with (14)C-hexadecane or (14)C-tridecane. After a 50-day incubation, 30-70% of added (14)C-alkanes were mineralized to (14)CO2 in Montana and Oregon soils. In contrast, significantly lower mineralization was observed with diesel or kerosene (< 5%) compared to crude-oil treatment (~45%) in the Arizona soil. Different hydrocarbon mixtures selected both unique and common microbial populations across all three soils. Conversely, the contamination of different soils with the same mixture selected for distinct microbial populations. The most consistent genotype observed, a Rhodococcus-like population, was present in the Montana soil with all mixture types. The addition of PCP selected for PCP-tolerant alkane-degrading specialist populations. The results indicated that petroleum mixture type influenced hydrocarbon degradation rates and microbial population selection and that soil characteristics, especially organic content, could also be an important determinant of community responses to hydrocarbon perturbation.

Polyphasic characterization of two microbial consortia with wide dechlorination spectra for chlorophenols.

Two soil-free anaerobic dechlorinating cultures (3-CP and 35-DCP) were enriched from a pentachlorophenol (PCP)-to-phenol dechlorinating soil-dependent culture, using 3-chlorophenol (3-CP) and 3,5-dichlorophenol (3,5-DCP) as specific respective substrates, and characterized polyphasically. Physiological characterization indicated that the 3-CP and 35-DCP cultures had similar features, but with some variations. Both cultures utilized formate or acetate preferably as optimum electron donors for reductive dechlorination, and they shared similar patterns of dechlorination spectra for chlorophenols ranging from mono-CPs to a tetra-CP, with preferred dechlorination pathways in the ortho and meta positions. Alternative electron acceptors such as NO(3)(-) but not SO(4)(2-) inhibited the dechlorination activity in both cultures, while amorphous iron oxides (FeOOH) suppressed dechlorination activity only in the 35-DCP culture. Complete inhibition of dechlorination was observed in both cultures supplemented with chloramphenicol and vancomycin. The addition of 2-bromoethanesulfonate resulted in delayed dechlorination activity in the 35-DCP culture but not in the 3-CP culture; molybdate did not exert any inhibitory effect in either culture. Phylogenetic analysis based on 16S rRNA genes confirmed that the two cultures exhibited similar bacterial species but with varied responsible dechlorinators. Dehalobacter spp. were the likely dechlorinators in the 3-CP culture versus Sulfurospirillum spp. in the 35-DCP culture, with Clostridium and Clostridium-like spp. as candidate dechlorinators in both cultures.

Effect of low temperature thermal treatment on soils contaminated with pentachlorophenol and environmentally persistent free radicals.

The effect of low temperature thermal treatment on soils from a former Superfund wood-treating site contaminated with pentachlorophenol (PCP) and the environmentally persistent free radical (EPFR), pentachlorophenoxyl, was determined. The pentachlorophenoxyl EPFRs' and the PCP molecules' chemical behavior were simultaneously monitored at temperatures ranging from 25 to 300 °C via electron paramagnetic resonance (EPR) spectroscopy and GC-MS analysis, respectively. Two types of thermal treatment were employed: a closed heating (oxygen-starved condition) where the soil was heated under vacuum and an open heating system (oxygen-rich conditions), where the soil was heated in ambient air. EPR analyses for closed heating indicated the EPFR concentration was 2-12 × 10(18) spins/g of soil, with a g-factor and line width (ΔHp-p) of 2.00311-2.00323 and 4.190-5.472 G, respectively. EPR analyses for the open heating soils revealed a slightly broader and weaker radical signal, with a concentration of 1-10 × 10(18) spins/g of soil, g-factor of 2.00327-2.00341, and ΔHp-p of 5.209-6.721 G. This suggested the open heating resulted in the formation of a more oxygen-centered structure of the pentachlorophenoxyl radical or additional, similar radicals. The EPFR concentration peaked at 10 × 10(18) spins/g of soil at 100 °C for open heating and 12 × 10(18) spins/g at 75 °C for closed heating. The half-lives of the EPFRs were 2-24 days at room temperature in ambient air. These results suggest low temperature treatment of soils contaminated with PCP can convert the PCP to potentially more toxic pentachlorophenoxyl EPFRs, which may persist in the environment long enough for human exposure.

Degradation of pentachlorophenol by potato polyphenol oxidase.

In this study, polyphenol oxidase (PPO) was extracted from commercial potatoes. Degradation of pentachlorophenol by potato PPO was investigated. The experimental results show that potato PPO is more active in weak acid than in basic condition and that the optimum pH for the reaction is 5.0. The degradation of pentachlorophenol by potato PPO reaches a maximum at 298 K. After reaction for 1 h, the removal of both pentachlorophenol and total organic carbon is >70% with 6.0 units/mL potato PPO at pH 5.0 and 298 K. Pentachlorophenol can be degraded through dechlorination and ring-opening by potato PPO. The work demonstrates that pentachlorophenol can be effectively eliminated by crude potato PPO.