Toxicity Of Pentachlorophenol Research Articles

Efficacy of Pentachlorophenol in Biodiesel versus Diesel

Abstract Pentachlorophenol (PCP) is widely used as a wood preservative for utility poles and other wood products. It has been proposed that a modified PCP carrier system based on a diesel/biodiesel mixture should be used in place of the conventional diesel/KB3 carrier, but questions exist as to whether this modified carrier system can provide the same service life as wood products treated with PCP/diesel/KB3. The main objective of this research was to evaluate the comparative decay resistance of wood treated with carrier formulations containing either diesel/KB3 or diesel/biodiesel. A 2-year efficacy study using an accelerated soil contact decay test was initiated to compare the performance of southern yellow pine wood treated with the conventional diesel/KB3 carrier and a modified diesel/biodiesel carrier, both with and without PCP. The residual hydrocarbon levels, PCP reduction, toxicity, and leaching of PCP of the samples remained approximately at the same level for treatments with similar PCP retention values for both carriers. For wood treated with PCP in these two different carriers, there was no evidence of differences in the average modulus of elasticity. Overall, this study recommends long-term field stake tests to determine the practical significance of these results.

Comparative Toxicity of Pentachlorophenol with its Metabolites tetrachloro-1,2-hydroquinone and Tetrachloro-1,4-benzoquinone in HepG2 Cells

The organochlorine compound, pentachlorophenol (PCP), is classified as a hazardous substance. Its metabolite, tetrachloro-1,2-hydroquinone (TCHQ), has been detected in occupationally-exposed subjects and can readily be converted to tetrachloro-1,4-benzoquinone (TCBQ) under physiological conditions. Hazard characterization has previously identified the liver as the target organ of PCP toxicity in rats and dogs and as the liver is the major site of metabolism of the parent compound, this raises concern for the effects that the metabolites of PCP may have on the liver. Although the hepatotoxic effects of PCP have been described, less is known about the effects of its metabolites on hepatocyte function. Studying the effects of these metabolites on hepatocytes may provide valuable information regarding the effects that these compounds could exert on the liver itself and allude to the clinical manifestations of toxicity that can be expected. The aim of this study was therefore to assess the effect of PCP, TCHQ and TCBQ on the following cellular parameters: cell viability, mitochondrial membrane potential and intracellular ROS formation, as indicators of hepatocyte homeostasis. Both PCP and its metabolites, TCHQ and TCBQ decreased cell viability with IC 50 of 68.05, 129.40 and 144.00 ∝M, respectively. All three compounds caused mitochondrial depolarization, with the effect being more profound following exposure to TCHQ and TCBQ. PCP did not induce any ROS generation, whereas TCHQ and TCBQ produced extensive ROS. Findings from this study suggest that in hepatocytes the mechanism of toxicity of PCP differs from that of its metabolites, TCHQ and TCBQ.

Inhibition of methanogenesis by chlorophenols: a kinetic approach

Chlorophenols exert a crucial effect on the methanogenesis, considerably reducing both maximum methane potential and methanogenic rates. However, there is not enough information about the kinetic mechanism of chlorophenols toxicity on the methanogenesis, which is a key aspect for the control of the anaerobic digesters because of the sensitivity and the potential for energy recovery derived from methane release. The International Water Association-Anaerobic Digestion Model No. 1 (IWA-ADM1) can be adapted to a wide range of situations by updating or changing the equations in the model. The present study proposes a general kinetic model for methanogenesis. This model has been applied to predict the inhibition of methanogenesis by chlorophenols, and it can be used for updating the IWA-ADM1 when treating inhibitory compounds. The model was calibrated and validated using a wide broad of experimental sets of data of methane production by granular sludge in the presence of 2,4-dichlorophenol (24 DCP), 2,4,6-trichlorophenol (246TCP) and pentachlorophenol (PCP) in batch assays. A lag-phase of the effect of chlorophenols on the methanogenesis by non-adapted sludge was detected and modeled by the kinetic model proposed. In addition, the inhibitory effect of PCP was more pronounced on the acetoclastic methanogenesis than on the hydrogenotrophic one. Non-competitive and uncompetitive inhibition types were detected using 24 DCP and 246 TCP, whereas a suicide or irreversible inhibition type was observed in the case of PCP. Values of inhibition constants considerably varied depending on the chlorophenol used, between 45 mg24DCPL(-1), 41-51 mg246TCPL(-1) and 0.9-7.8 mgPCPL(-1). The higher toxicity of PCP is related with its hydrophobicity, which was determined by adsorption tests and using partition coefficients n-octanol/water. Modeling was accompanied by high statistical support in all cases, which confirmed the validation of the model proposed.

Toxicity of pentachlorophenol to native aquatic species in the Yangtze River

While the literature is replete with studies of the toxic potency of pentachlorophenol (PCP), site-specific criteria for native aquatic species that can be used in ecological risk assessments has been lacking and application of toxicity information for non-native species is controversial. In the present study, acute and chronic toxicities of PCP to six aquatic species native to the Yangtze River were determined. The HC₅ and HC₅₀ (hazardous concentration for 5% and 50% of species) were derived from dose-response curves for these native aquatic species and were then compared with those derived for non-native species. The acute toxicity values for the native species ranged from 8.8 × 10⁻² mg l⁻¹ (Plagiognathops microlepis) to 1.1 mg l⁻¹ (Soirodela polyrhiza), while chronic toxicity values based on no observed effect concentrations (NOECs) ranged from 0.01 mg l⁻¹ (Macrobrachium superbum) to 0.25 mg l⁻¹ (Soirodela polyrhiza). Native aquatic benthos was more sensitive to acute PCP exposure than non-native species. There was no significant difference in NOECs derived from native fish species and those based on non-native fish species. The median acute HC₅ and HC₅₀ derived from the toxicity data of native taxa were both less than those derived from non-native taxa. There was no significant difference between chronic HC₅s derived from the two sets of taxa. However, the median chronic HC₅₀ derived from native taxa was less than that derived from non-native taxa. The study upon which we report here provides site-specific toxicity information developed for native species which can be used for the protection of local aquatic life from a common contaminant, PCP.

Impact of chlorophenols on microbiota of an unpolluted acidic soil: microbial resistance and biodegradation

The impact of 2-monochlorophenol (MCP), 2,4,6-trichlorophenol (TCP) and pentachlorophenol (PCP) on the microbial community of an acidic forest soil was studied under controlled laboratory conditions by spiking microcosms with the pollutants at concentrations ranging from 0.1 to 5000 mg kg(-1). A decrease in the cumulative respirometric values and changes in the bacterial and fungal community composition were detected at 1000 mg MCP kg(-1), 100 mg TCP kg(-1) and 100 and 1000 mg PCP kg(-1). However, drastic effects on the microbial community were revealed only at higher concentrations of MCP and TCP, although the toxicity of PCP was expected to be stronger. The acidic condition of the soil presumably reduces bioavailability of PCP, leading to less pronounced effects than the other pollutants. This finding highlights the consideration of pollutant bioavailability in each environment to adequately assess contamination effects. Twenty-two different chlorophenol-resistant and potentially degrading microorganisms were isolated from highly polluted microcosms. The most resistant isolates were related to Burkholderia arboris, Bacillus circulans, Paenibacillus taichungensis, Luteibacter rhizovicina and Janibacter melonis. These isolates also showed the capacity to reduce the concentration of TCP or PCP between 15% and 35% after 5 days of incubation (initial concentration of 50 mg L(-1)). The isolate related to B. circulans is an atypical case of a member of the Firmicutes group for which chlorophenol-degrading capacities have been described.

Impact of black carbon originated from fly ash and soot on the toxicity of pentachlorophenol in sediment

The widely existing fly ash and soot produced during the process of combustion, which are often known as waste but also an important source of black carbon (BC) in the environment, were treated by HCl and HF solution for this study, and recorded as FC and SC, respectively. A series of experiments were carried out to investigate the toxicity of pentachlorophenol (PCP) in sediment, influence of various BCs in sediment with different contents (0%, 0.5%, 1%, 2%, 5% and 10%) on the extractability and toxicity of PCP (50 mg/kg), and toxicity of various BC in sediment. The results demonstrated that the PCP exposure to wheat seed exhibited a dose-dependent behavior, and the extractability and toxicity of PCP decreased with the increasing content of BC in sediment. The PCP extractable rate was significantly ( P < 0.01) influenced by the higher content of BCs. Noticeably, each BC had no toxic but stimulative effect on root elongation and early seedling growth. Furthermore, it was found that the inhibitive effect on the extractability and toxicity of PCP and the stimulative effect on root elongation and early seedling growth caused by SC were more evident than FC.

Photostability and toxicity of pentachlorophenol and phenanthrene

Fate of organic contaminants under UV irradiation as environmental variable was studied. Aqueous solutions of pentachlorophenol and phenanthrene were subjected to simulated solar radiation and monitored during ≤93 h. Immobilization tests were conducted using Daphnia magna neonates in pre-irradiated water for the assessment of photoproduct-mediated toxicity. We observed a time-dependent decrease in exposure concentrations following irradiation, which correlated positively with reduced immobilization of the animals. A complete disappearance of the lowest and highest concentrations of pentachlorophenol was noted after 25 h and 75 h, respectively. Survivorship of the animals increased until 100% and correlated positively with irradiation time. However, phenanthrene was rather persistent under irradiation, with less than 25% decline in exposure concentrations after 93 h. Neonates were not immobilized at maximum aqueous solubility of phenanthrene. Rate constants ( k) for the photodegradation of pentachlorophenol at 0.41, 0.59, 1.1, and 2.1 mg l −1 were in the range of 7.2 × 10 −2 and 4.9 × 10 −2 h −1, showing a slight decrease with increasing initial pentachlorophenol concentration. Nonetheless, pentachlorophenol degradation in the studied concentration range could still be described by the pseudo-first-order kinetics. K values for phenanthrene at 0.12 and 0.22 mg l −1 were 2.9 × 10 −3 h −1 and 4.2 × 10 −3 h −1, respectively.

Pentachlorophenol induced physiological–biochemical changes in Chlorella pyrenoidosa culture

Present study investigated physiological and biochemical changes in a green alga culture ( Chlorella pyrenoidosa) upon exposure to varied concentrations of pentachlorophenol (PCP) (0, 0.4 mg L −1, 2.5 mg L −1 and 10 mg L −1). The results revealed that with the increase of PCP concentration, a decrease of the algal biomass, levels of photosynthetic pigments (chlorophyll a, b and carotenoid), soluble protein and an increase of nitrate reductase (NR) activity were observed. This suggests that the PCP may serve as an uncoupler, causing low ATP level within the algal cells and led most of the NR molecules to be in the dephosphoration state (i.e. active from). Moreover, it shows that photosynthetic pigments especially carotenoid were more sensitive indicators to indicate PCP toxicity as compared to the other parameters.

Bacillus subtilis as a bioindicator for estimating pentachlorophenol toxicity and concentration

Pentachlorophenol (PCP) and its sodium salt (Na-PCP) are extremely toxic chemicals responsible for important soil and groundwater pollution, mainly caused by wastes from wood-treatment plants, because chlorinated phenols are widely used as wood preservatives. The methods most commonly used for routine analysis of pesticides such as PCP and Na-PCP are high-performance liquid chromatography (HPLC) and gas chromatography-mass spectroscopy (GC-MS). A variety of rapid biological screening tests using marine organisms, bioluminescent bacteria, and enzymes have also been reported. In this study, rapid biological screening analysis using Bacillus subtilis was developed, to assess the biodegradation of PCP and its by-products in liquid samples. An empirical model is proposed for spectrophotometric analysis of Na-PCP concentration after growth of Bacillus subtilis.

Effect of perfluorooctane sulfonate on toxicity and cell uptake of other compounds with different hydrophobicity in green alga

Perfluorooctane sulfonate (PFOS) was evaluated alone and in binary mixtures with pentachlorophenol, atrazine and diuron, respectively to investigate the effects of interactions between PFOS and other compounds on the growth rate in Scenedesmus obliquus. Single application of PFOS showed no inhibition on the growth of S. obliquus below 40 mg L −1, whereas PFOS acting with pentachlorophenol resulted in higher algal growth inhibition in comparison with pentachlorophenol alone. A maximum increase of 45% in the growth inhibition was observed at a pentachlorophenol concentration of 2.56 mg L −1 together with a PFOS concentration of 40 mg L −1. On the contrary, the algal growth inhibition of atrazine and diuron was depressed by PFOS. Furthermore, cell uptake was examined to gain some insights into the mechanisms of the effects of PFOS on the toxicity of the other compounds. Cell uptake of pentachlorophenol increased while that of atrazine and diuron was reduced in cells that have been exposed to PFOS. The effects of PFOS on the toxicity of pentachlorophenol, atrazine and diuron were possibly related to the influence of PFOS on the cell uptake of these hydrophobic compounds. Results suggested that PFOS influenced the cell uptake and toxicity of structurally different compounds in dissimilar manners and potentially increased the accessibility and toxicity of more hydrophobic compounds to algal cells.

Individual and joint toxic effects of pentachlorophenol and bisphenol A on the development of zebrafish ( Danio rerio) embryo

Investigation of the toxicological effects of pentachlorophenol (PCP) and bisphenol A (BPA) alone and in combination was carried out following the method of the early life stage (ELS) test on zebrafish embryos. Both chemicals revealed lethal and sub-lethal effects, such as no blood flow, cardiac edema, delayed hatching, and tail malformations. According to their median effective concentrations (EC 50 values) in the single exposure, the toxic level of PCP was about two orders of magnitude higher than that of BPA. Result of the joint action modes varied depending on different endpoints. Synergistic action was observed based on the endpoint of 24 h mortality and antagonistic effect displayed based on the endpoint of 72 h cardiac edema. It was also found that the toxicity of PCP would be enhanced with the addition of BPA even below its no observed effect concentration (NOEC) level at the endpoint of 32 h with no blood flow, and the level of the increase was influenced by the toxic unit (TU) ratio.

Toxicity and bioaccumulation of xenobiotic organic compounds in the presence of aqueous suspensions of aggregates of nano-C 60

The potential of C 60-nanoparticles (Buckminster fullerenes) as contaminant carriers in aqueous systems was studied in a series of toxicity tests with algae ( Pseudokirchneriella subcapitata) and crustaceans ( Daphnia magna). Four common environmental contaminants (atrazine, methyl parathion, pentachlorophenol (PCP), and phenanthrene) were used as model compounds, representing different physico-chemical properties and toxic modes of action. The aggregates of nano-C 60 formed over 2 months of stirring in water were mixed with model compounds 5 days prior to testing. Uptake and excretion of phenanthrene in 4-days-old D. magna was studied with and without addition of C 60 in aqueous suspensions. It was found that 85% of the added phenanthrene sorbed to C 60-aggregates >200 nm whereas about 10% sorption was found for atrazine, methyl parathion, and pentachlorophenol. In algal tests, the presence of C 60-aggregates increased the toxicity of phenanthrene with 60% and decreased toxicity of PCP about 1.9 times. Addition of C 60-aggregates reduced the toxicity of PCP with 25% in tests with D. magna, whereas a more than 10 times increase in toxicity was observed for phenanthrene when results were expressed as water phase concentrations. Thus, results from both toxicity tests show that phenanthrene sorbed to C 60-aggregates is available for the organisms. For atrazine and methyl parathion no statistically significant differences in toxicities could be observed in algal and daphnid tests as a result of the presence of C 60-aggregates. In bioaccumulation studies with phenanthrene in D. magna it was found that the uptake of phenanthrene was faster when C 60 was present in suspension and that a 1.7 times higher steady-state concentration was reached in the animals. However, a very fast clearance took place when animals were transferred to clean water resulting in no accumulation of phenanthrene. This study is the first to demonstrate the influence of C 60-aggregates on aquatic toxicity and bioaccumulation of other environmentally relevant contaminants. The data provided underline that not only the inherent toxicity of manufactured nanoparticles, but also interactions with other compounds and characterisation of nanoparticles in aqueous suspension are of importance for risk assessment of nanomaterials.

Rhizoremediation of pentachlorophenol by Sphingobium chlorophenolicum ATCC 39723

Sphingobium chlorophenolicum is well known as a pentachlorophenol (PCP) degrader. The objective of this study was to evaluate PCP degradation in a loamy sandy soil artificially contaminated with PCP using phytoremediation and bioaugmentation. Measurements of PCP concentrations were carried out using high performance liquid chromatography analyses (HPLC). The toxic effect of PCP on plants was studied through the monitoring of weight plant and root length. The biodegradation of PCP by S. chlorophenolicum in soil was assessed with a bioluminescence assay of Escherichia coli HB101 pUCD607. Bacterial analyses were carried out by plating on Mineral Salt Medium (MSM) for S. chlorophenolicum, MSM for PCP-degrading/tolerant organisms and Trypticase Soy Broth Agar (TSBA) for heterotrophic organisms. The introduction of S. chlorophenolicum into soil with plants showed a faster degradation when compared to the non-inoculated soil. The monitoring of the plant growth showed a protective role of S. chlorophenolicum against the toxicity of PCP. The bioassay confirmed that initial toxicity was lowered while degradation progressed. There was a significant increase of organisms tested in the roots in comparison to those in the soil. This study showed that the presence of S. chlorophenolicum enhanced the PCP degradation in a loamy soil and also it had a protective role to prevent phytotoxic effects of PCP on plant growth. The combined use of bioaugmentation and plants suggests that the rhizosphere of certain plant species may be important for facilitating microbial degradation of pesticides in soil with important implications for using vegetation to stabilize and remediate surface soils.

Bioaugmentation of pentachlorophenol in soil and hydroponic systems

Abstract Sphingobium chlorophenolicum is well known as pentachlorophenol (PCP) degrader. The objective of this study was to evaluate the PCP degradation in soil and hydroponic systems using a bioaugmentation technique. Measurements of PCP concentrations were carried out using high-performance liquid chromatography (HPLC) analyses. The toxic effect of PCP on plants was studied through the monitoring of plant weight. An acute toxicity assay of PCP was performed using Escherichia coli HB101 pUCD607. The introduction of S. chlorophenolicum into soil with plants showed a faster degradation when compared to the non-inoculated soil. In the soil system, plants acted as a vector to the target compound, PCP. The monitoring of the plant growth showed a protective role of S. chlorophenolicum against the toxicity of PCP. In the hydroponic system S. chlorophenolicum showed the ability to degrade 16 mg l−1 after 7 days of experiments at both concentrations tested (20 and 30 mg l−1 PCP). The bioassay confirmed that initial toxicity was lowered while degradation progressed in both systems.

Bioremediation of soil contaminated with pentachlorophenol (PCP) using humic acids bound on zeolite

We determined the toxicity of various chlorophenols, especially pentachlorophenol (PCP), on five bacterial strains and studied PCP biodegradation in soils amended with an organomineral complex (OMC) prepared from humic acids (organic part) bound on zeolite (inorganic part). Both components of OMC have excellent sorption properties and are of natural origin and therefore suitable to be used in the environment. Toxicity of chlorophenols depends not only on the number of chlorine atoms but also on their position on aromatic ring, and is thus regiospecific. Biodegradation of PCP was studied in three real completely characterized soil samples, Chernozem, Fluvisol, and Regosol, with and without the addition of OMC. The soils were sterilized and bioaugmented with the bacterial isolate Comamonas testosteroni CCM 7530. The immobilization effect of OMC in relation to PCP depends on the concentration of humic acids (HAs), the PCP concentration, and the content of organic carbon in soil. The microbial activity and the simulated action of acid rains led to the gradual release and biodegradation of the reversibly bound PCP without no initial toxic effect on indigenous or bioaugmented microorganisms. OMC appeared to be a good trap for PCP with potential applications in remediation technology because it reduces the potential toxicity of PCP to microbial community by lowering its bioavailability and thus facilitates its biodegradation.

REMEDIAÇÃO DE PENTACLOROFENOL EM DOIS DIFERENTES TIPOS DE SOLO POR &lt;i&gt;Sphingomonas chlorophenolica&lt;/i&gt; ATCC 39723

O objetivo deste trabalho foi estudar a degradação de pentaclorophenol (PCP) por S. chlorophenolica em dois diferentes tipos de solo (arenoso e argiloso) na presença e ausência de plantas (trigo - Triticum aestivum). As concentrações de PCP foram determinadas mediante Cromatografia a Líquido de Alta Eficiência (CLAE). Os efeitos tóxicos de PCP foram estudados pelo monitoramento do crescimento das plantas (em peso, g) e medidas das raízes (cm). A biodegradação de PCP por S. chlorophenolica nos dois tipos de solo foi acompanhada por análises de bioluminescência de Escherichia coli HB101 pUCD607. Contagens bacterianas foram realizadas em três meios de cultura: meio mineral para S. chlorophenolica, meio mineral para organismos degradadores/tolerantes ao PCP e ágar triptose caldo de soja para organismos heterotróficos. No solo argiloso com vegetação, a degradação de PCP ocorreu de forma mais rápida após a introdução de S. chlorophenolica que no solo sem plantas. O monitoramento do crescimento da planta mostrou o papel protetivo exercido pela S.chlorophenolica contra a toxicidade do PCP. O bioensaio confirmou que a toxicidade inicial causada pelo PCP diminuiu conforme o prosseguimento da degradação. No solo arenoso não houve degradação significativa. As determinações cromatográficas sugerem que mais de 75% do PCP estava adsorvido ao solo (não-disponível aos organismos degradadores). Não houve efeito deletério de PCP sobre o crescimento da planta nem sobre as raízes. Em ambos os solos houve aumento significativo nas populações bacterianas de Sphingomonas chlorophenolica, organismos PCP-degradadores/tolerantes e heterotróficos quando comparadas com as populações presentes nas raízes. Este estudo mostrou que a presença do inóculo Sphingomonas chlorophenolica melhorou a degradação de PCP em solo argiloso e seu papel protetor contra o efeito fitotóxico do PCP sobre plantas. A rizosfera de certas plantas pode ser importante para facilitar a degradação microbiana de pesticidas em solos com importantes implicações ao se utilizar a vegetação para estabilizar e remediar solos superficiais.

Oxidation and detoxification of pentachlorophenol in aqueous phase by ozonation

The degradation and detoxification performance of ozonation in treating pentachlorophenol (PCP) contaminated wastewater was determined. All experiments were conducted in a bench scale glass column equipped with ceramic diffuser and a lab-scale ozone generator under ambient temperature and pH 7. The decomposition rate of PCP in this study was primarily controlled by the ozone mass transfer rate from gas to liquid phases. Principal intermediates found were 2,3,4,6- and 2,3,5,6-tetrachlorophenols (TeCP) and phenol. PCP seems to be more vulnerable to ozone than its intermediates. A bioluminescence technique was used to evaluate the toxicity of PCP with Vibrio fisheri NRRL B-11177 as the test bacterium, and the EC 50 of PCP was found to be 1.0 mg l −1. Detoxification occurred as the PCP and TeCP reacted with ozone and decomposed to less chlorinated congeners and phenol.

Bioavailability and toxicity of pentachlorophenol in contaminated soil evaluated on coelomocytes of Eisenia andrei (Annelida: Lumbricidae)

Pentachlorophenol (PCP) is widely distributed and highly persistent in soil, and represents a threat to the health of ecosystems. The present study aimed to assess the toxicity and bioavailability of PCP in soils as a function of different aging periods with the attempt to select a good toxicological assay for Eisenia andrei Bouché (Annelida: Lumbricidae). The experiments were performed on soil contaminated with PCP at 15 and 150 ppm. After different aging periods (20, 60 and 120 days from spiking), bioavailability and toxicity were evaluated on E. andrei kept for 7 and 14 days in treated soils. The actual bioavailability decreased in relation to the aging for both PCP concentrations. No membrane damage was observed on coelomocytes collected by ethanol extrusion. Modifications in distribution of coelomocyte subpopulations were detected by flow cytometry on samples aged for 60 and 120 days at 150 ppm PCP contamination. The reduction of lysosomal membrane stability, measured by neutral red retention time, was observed in all treatments. Worm mortality increased with aging in soils spiked with 150 ppm of PCP. In conclusion, aging did not seem to reduce PCP cytotoxicity. This is the first report on in vivo toxicity of PCP evaluated on coelomocytes of E. andrei using different assays.

Effects of pH and cyclodextrins on pentachlorophenol degradation (mineralization) by white-rot fungi

White-rot fungi (WRF) such as Trametes hirsuta completely degrade (mineralize) pentachlorophenol (PCP) and many other organopollutants. This has led to them being used to decontaminate various substrates (e.g. soil) through biorememediation. However, because PCP is a biocide, it can inhibit fungal growth and thereby its own degradation. It was hypothesized that substrate pH might affect PCP degradation, because when the pH is lower than 4.7 (the pKa for PCP) the phenol predominates, while at higher pH the phenate does. These two PCP species differ markedly in physical and biological properties. The effect of cyclodextrins was also investigated since it is known that the inclusion complexes these form with PCP differ in bioavailability and toxicity from non-complexed PCP. Tests were first made in liquid and agar media (where conditions are relatively easy to control), and then in a sawdust, because it is a common target matrix for WRF bioremediation. Results with the liquid and agar media showed that growth in the presence of inhibitory PCP concentrations decreased as the pH decreased, consistent with the phenol being more toxic. Growth in sawdust was less affected by PCP regardless of the pH, presumably because the PCP sorbed to the wood which decreased its bioavailability. Some cyclodextrins markedly decreased the PCP's toxicity in liquid, agar and sawdust media. Rates of PCP mineralization (measured from production of 14CO 2 from 14C PCP) in liquid cultures containing 0.5 mg kg −1 PCP (a sub-inhibitory concentration) were similar from pH 2.5–7.5, indicating that the phenol and the phenate were equally degradable. Degradation of a growth inhibiting concentration on sawdust (1000 mg kg −1) could be increased slightly by lowering the pH below the pKa, this increasing sorption to the wood. Degradation increased more when the pH was raised well above the pKa, presumably due to the phenate being less toxic and more soluble, making it more available to the degradative system. Although some cyclodextrins decreased growth inhibition, they also interfered with degradation. If this interference could be overcome, cyclodextrins could be used to increase the maximal PCP concentration that could be treated by WRF bioremediation.

Body residues as dose for sublethal responses in alevins of landlocked salmon (Salmo salar m. sebago): A direct calorimetry study

Questions of organism-specific factors, toxicity endpoints, and their relation to mode-of-action all are related to consistency and applicability of body residue-based approaches. To address this issue, direct calorimetry was used to evaluate metabolic responses of alevins of landlocked salmon (Salmo salar m. sebago) to pentachlorophenol (PCP) exposure ranging from 0 to 1.04 microM for 24 h or 24, 48, and 72 h (0, 0.26, and 0.55 microM, respectively). The body residues were used as a dose metric for sublethal responses. The body size, rapid ontogenetic development, and exposure to a specific pollutant all were heat output-modifying factors. The acute exposure (24-72 h) to PCP led to a heat output-enhancing effect, which directly was related to an internal concentration of PCP in the range of 0.01 to 0.15 micromol/g. Within the treatments, body size per level of metabolic rate and magnitude of physiological response were not correlated, thus the alevins with higher mass-specific metabolic rate were not more sensitive to PCP. Primarily, increasing metabolic rate during posthatch development controls PCP toxicity only by affecting bioaccumulation kinetics, not the toxic potency of the chemical. New information of a relationship between observed natural variation in measured physiological trait of fish and PCP-induced response and its body residue-based level is of ecotoxicological importance.