by Wai Lok Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 142-155). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstracts --- p.ii / Contents --- p.vii / List of figures --- p.xiii / List of tables --- p.xvi / Abbreviations --- p.xviii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Pentachlorophenol / Chapter 1.1.1 --- Applications of pentachlorophenol --- p.1 / Chapter 1.1.2 --- Characteristics --- p.3 / Chapter 1.1.3 --- Pentachlorophenol in the environment --- p.3 / Chapter 1.1.4 --- Toxicity of Pentachlorophenol --- p.6 / Chapter 1.2 --- Treatments of Pentachlorophenol --- p.10 / Chapter 1.2.1 --- Physical treatment --- p.10 / Chapter 1.2.2 --- Chemical treatment --- p.11 / Chapter 1.2.3 --- Biological treatment --- p.13 / Chapter 1.3 --- Biodegradation --- p.14 / Chapter 1.3.1 --- Biodegradation of PCP by bacteria --- p.14 / Chapter 1.3.2 --- Biodegradation of PCP by white-rot fungi --- p.15 / Chapter 1.4 --- Biosorption --- p.24 / Chapter 1.5 --- Proposed Strategy --- p.28 / Chapter 1.6 --- Spent Mushroom Compost / Chapter 1.6.1 --- Background --- p.28 / Chapter 1.6.2 --- Physico-chemical properties of SMC --- p.29 / Chapter 1.6.3 --- As a biosorbent --- p.29 / Chapter 1.6.3.1 --- Factors affecting biosorption --- p.31 / Chapter 1.6.3.2 --- Contact time --- p.31 / Chapter 1.6.3.3 --- Initial pH --- p.32 / Chapter 1.6.3.4 --- Concentration of biosorbent --- p.33 / Chapter 1.6.3.5 --- Initial PCP concentration --- p.34 / Chapter 1.6.3.6 --- Incubation temperature --- p.34 / Chapter 1.6.3.7 --- Agitation speed --- p.35 / Chapter 1.6.4 --- Modeling of adsorption --- p.36 / Chapter 1.6.4.1 --- Langmuir isotherm --- p.36 / Chapter 1.6.4.2 --- Freundlich isotherm --- p.36 / Chapter 1.6.5 --- As a source of PCP-degrading bacteria --- p.38 / Chapter 1.6.5.1 --- Identification of PCP-degrading bacterium --- p.40 / Chapter 1.6.6 --- As a source of fungus --- p.42 / Chapter 1.7 --- Objectives of this Study --- p.43 / Chapter 2. --- Materials and Methods --- p.44 / Chapter 2.1 --- Spent Mushroom compost (SMC) Production --- p.44 / Chapter 2.2 --- Characterization of SMC --- p.46 / Chapter 2.2.1 --- pH --- p.46 / Chapter 2.2.2 --- Electrical conductivity --- p.46 / Chapter 2.2.3 --- "Carbon, hydrogen, nitrogen and sulphur contents" --- p.46 / Chapter 2.2.4 --- Infrared spectroscopic study --- p.47 / Chapter 2.2.5 --- Metal analysis --- p.47 / Chapter 2.2.6 --- Anion content --- p.47 / Chapter 2.2.7. --- Chitin assay --- p.48 / Chapter 2.3 --- Extraction of PCP --- p.49 / Chapter 2.3.1 --- Selection of extraction solvent --- p.49 / Chapter 2.3.2 --- Selection of desorbing agent --- p.49 / Chapter 2.3.3 --- Extraction efficiency --- p.50 / Chapter 2.4 --- Adsorption of Pentachlorophenol on SMC --- p.50 / Chapter 2.4.1 --- Preparation of pentachlorophenol (PCP) stock solution --- p.50 / Chapter 2.4.2 --- Batch adsorption experiment --- p.51 / Chapter 2.4.3 --- Quantification of PCP by HPLC --- p.51 / Chapter 2.4.4 --- Data analysis for biosorption --- p.51 / Chapter 2.4.5 --- Optimization of PCP adsorption --- p.52 / Chapter 2.4.5.1 --- Effect of contact time --- p.52 / Chapter 2.4.5.2 --- Effect of initial pH --- p.52 / Chapter 2.4.5.3 --- Effect of incubation temperature --- p.53 / Chapter 2.4.5.4 --- Effect of shaking speed --- p.53 / Chapter 2.4.5.5 --- Effect of initial PCP concentration and amount of biosorbent --- p.53 / Chapter 2.4.6 --- Adsorption isotherm --- p.53 / Chapter 2.4.7 --- Effect of removal efficiency on reuse of biosorbent --- p.54 / Chapter 2.5 --- Biodegradation by Isolated Bacterium --- p.54 / Chapter 2.5.1 --- Isolation of PCP-tolerant bacteria from mushroom compost --- p.54 / Chapter 2.5.2 --- Screening for the best PCP-tolerant bacterium --- p.54 / Chapter 2.5.3 --- Identification of the isolated bacterium --- p.55 / Chapter 2.5.3.1 --- 16S ribosomal DNA sequencing --- p.55 / Chapter 2.5.3.1.1 --- Extraction of DNA --- p.55 / Chapter 2.5.3.1.2 --- Specific PCR for 16S rDNA --- p.56 / Chapter 2.5.3.1.3 --- Gel electrophoresis --- p.57 / Chapter 2.5.3.1.4 --- Purification of PCR products --- p.57 / Chapter 2.5.3.1.5 --- Sequencing of 16S rDNA --- p.58 / Chapter 2.5.3.2 --- Gram staining --- p.60 / Chapter 2.5.3.3 --- Biolog Microstation System --- p.60 / Chapter 2.5.3.4 --- MIDI Sherlock Microbial Identification System --- p.61 / Chapter 2.5.4 --- Optimization of PCP degradation by PCP-degrading bacterium --- p.62 / Chapter 2.5.4.1 --- Effect of incubation time --- p.63 / Chapter 2.5.4.2 --- Effect of shaking speed --- p.63 / Chapter 2.5.4.3 --- Effect of initial PCP concentration and inoculum size --- p.63 / Chapter 2.5.4.4 --- Study of PCP degradation pathway by isolated bacterium using GC-MS --- p.64 / Chapter 2.6 --- Biodegradation by Fungus Pleurotus pulmonarius --- p.64 / Chapter 2.6.1 --- Optimization of PCP degradation by P. pulmonarius --- p.65 / Chapter 2.6.1.1 --- Effect of incubation time --- p.65 / Chapter 2.6.1.2 --- Effect of shaking speed --- p.65 / Chapter 2.6.1.3 --- Effect of initial PCP concentration and inoculum size --- p.65 / Chapter 2.6.2 --- Study of PCP degradation pathway by fungus using GC-MS --- p.65 / Chapter 2.6.3 --- Specific enzyme assays --- p.66 / Chapter 2.6.3.1 --- Extraction of protein and enzymes --- p.66 / Chapter 2.6.3.2 --- Protein --- p.66 / Chapter 2.6.3.3 --- Laccase --- p.67 / Chapter 2.6.3.4 --- Manganese peroxidase (MnP) --- p.67 / Chapter 2.6.4 --- Microtox® assay --- p.67 / Chapter 2.7 --- Statistical Analysis --- p.68 / Chapter 3. --- Results --- p.69 / Chapter 3.1 --- Physico-chemical Properties of SMC --- p.69 / Chapter 3.2 --- Extraction Efficiency and Desorption Efficiency of PCP --- p.69 / Chapter 3.3 --- Batch Adsorption Experiments --- p.76 / Chapter 3.3.1 --- Optimization of adsorption conditions --- p.76 / Chapter 3.3.1.1 --- Effect of contact time --- p.76 / Chapter 3.3.1.2 --- Effect of initial pH --- p.76 / Chapter 3.3.1.3 --- Effect of shaking speed --- p.79 / Chapter 3.3.1.4 --- Effect of incubation temperature --- p.79 / Chapter 3.3.1.5 --- Effect of initial PCP concentration and amount of biosorbent --- p.79 / Chapter 3.3.2 --- Reuse of SMC --- p.83 / Chapter 3.3.3 --- Isotherm plot --- p.83 / Chapter 3.4 --- Biodegradation by PCP-degrading Bacterium --- p.86 / Chapter 3.4.1 --- Isolation and purification of PCP-tolerant bacteria --- p.86 / Chapter 3.4.2 --- Identification of the isolated bacterium --- p.90 / Chapter 3.4.2.1 --- 16S rDNA sequencing --- p.90 / Chapter 3.4.2.2 --- Gram staining --- p.90 / Chapter 3.4.2.3 --- Biolog MicroPlates Identification System --- p.90 / Chapter 3.4.2.4 --- MIDI Sherlock Microbial Identification System --- p.90 / Chapter 3.4.3 --- Growth curve of PCP-degrading bacterium --- p.90 / Chapter 3.4.4 --- Optimization of PCP degradation by PCP-degrading bacterium --- p.97 / Chapter 3.4.4.1 --- Effect of incubation time --- p.97 / Chapter 3.4.4.2 --- Effect of shaking speed --- p.97 / Chapter 3.4.4.3 --- Effect of initial PCP concentration and inoculum size of bacterium --- p.101 / Chapter 3.4.5 --- Determination of breakdown products of PCP by PCP-degrading bacterium --- p.101 / Chapter 3.5 --- Biodegradation by Fungus Pleurotus pulmonarius --- p.103 / Chapter 3.5.1 --- Growth curve of P. pulmonarius --- p.103 / Chapter 3.5.2 --- Optimization of PCP degradation by P. pulmonarius --- p.103 / Chapter 3.5.2.1 --- Effect of incubation time --- p.103 / Chapter 3.5.2.2 --- Effect of shaking speed --- p.103 / Chapter 3.5.2.3 --- Effect of initial PCP concentration and inoculum size of fungus --- p.108 / Chapter 3.5.3 --- Determination of breakdown products of PCP by P. pulmonarius --- p.108 / Chapter 3.5.4 --- Enzyme assays --- p.108 / Chapter 3.6 --- Integration of Biosorption by SMC and Biodegradation by P. pulmonarius --- p.112 / Chapter 3.6.1 --- Evaluation of PCP removal by an integration system --- p.112 / Chapter 3.6.2 --- Evaluation of toxicity by Micortox® assays --- p.112 / Chapter 4. --- Discussion --- p.115 / Chapter 4.1 --- Physico-chemical Properties of SMC --- p.115 / Chapter 4.2 --- Extraction Efficiency and Desorption Efficiency of PCP --- p.116 / Chapter 4.3 --- Batch Biosorption Experiment --- p.117 / Chapter 4.3.1 --- Effect of contact time --- p.117 / Chapter 4.3.2 --- Effect of initial pH --- p.118 / Chapter 4.3.3 --- Effect of shaking speed --- p.120 / Chapter 4.3.4 --- Effect of incubation temperature --- p.120 / Chapter 4.3.5 --- Effect of initial PCP concentration and amount of biosorbent --- p.121 / Chapter 4.3.6 --- Reuse of SMC --- p.122 / Chapter 4.3.7 --- Modeling of biosorption --- p.122 / Chapter 4.4 --- Biodegradation of PCP by PCP-degrading Bacterium --- p.124 / Chapter 4.4.1 --- Isolation and purification of PCP-tolerant bacterium --- p.124 / Chapter 4.4.2 --- Identification of the isolated bacterium --- p.125 / Chapter 4.4.3 --- Optimization of PCP degradation by PCP-degrading bacterium --- p.126 / Chapter 4.4.3.1 --- Effect of incubation time --- p.126 / Chapter 4.4.3.2 --- Effect of shaking speed --- p.128 / Chapter 4.4.3.3 --- Effect of initial PCP concentration and inoculum size of bacterium --- p.128 / Chapter 4.4.4 --- PCP degradation pathway by S. marcescens --- p.129 / Chapter 4.5 --- Biodegradation of PCP by Pleurotus pulmonarius --- p.130 / Chapter 4.5.1 --- Optimization of PCP degradation by P. pulmonarius --- p.130 / Chapter 4.5.1.1 --- Effect of incubation time --- p.131 / Chapter 4.5.1.2 --- Effect of shaking speed --- p.131 / Chapter 4.5.1.3 --- Effect of initial PCP concentration and inoculum size of fungus --- p.131 / Chapter 4.5.2 --- Enzyme activities --- p.132 / Chapter 4.5.3 --- PCP degradation pathway by P. pulmonarius --- p.133 / Chapter 4.6 --- Comparison of PCP Degradation between S.marcescens and P. pulmonarius --- p.133 / Chapter 4.7 --- Integration of Biosorption by SMC and Biodegradation by P. pulmonarius --- p.135 / Chapter 4.8 --- Evaluation of toxicity by Microtox® assay --- p.135 / Chapter 4.9 --- Comparison of PCP Removal by Integration System of Sorption and Fungal Biodegradation and Conventional Treatments --- p.136 / Chapter 4.10 --- Further Investigations --- p.137 / Chapter 5. --- Conclusion --- p.139 / Chapter 6. --- References --- p.142

Abstract This research was to evaluate the treatment efficiency for in-situ treatment of pentachlorophenol (PCP) contaminated soil by electrokinetics-Fenton process combined with biodegradation. An electric gradient of 1V/cm, and graphite electrodes were employed in all experiments. Soil types, catalyst types and dosage, hydrogen peroxide concentration, cathode reservoir liquid species and reaction time were employed as the experimental factors in this study. In this study, no matter electrokinetics-Fenton process or the electrokinetics-biodegradation in the latter, prolong the reaction time can promote the removal and destruction efficiency (DRE) of target pollutant from soil. By using 0.0196 M FeSO4 with 3.5% H2O2, the DRE was only lower 2% than 0.098 M FeSO4 with 3.5% H2O2.It showed that using 0.0196 M FeSO4 can provide enough Fe2+ to react with H2O2. By increasing H2O2 concentration from 0.35% to 3.5%, a DRE rised from 68.34% to 79.77%. When iron powder was used as catalyst, the residual pentachloroplenol concentration near to anode reservoir lower than 0.0196 M FeSO4 was used. But the DRE was 56.58% lower than the 68.34% of using 0.0196 M FeSO4.As the influences of soil types to electrokinetics-Fenton process, the residual concentration of pollutant for Soil No. 2 was higher than Soil No. 1. A DRE of only 59.22% was obtained. It is postulated that a much higher content of organic matter with Soil No. 2 whereas lower the treatment efficiency because of consumption of hydroxyl radicals by the organic matter of soil. For the influence of different reservoir liquid species, in this study 0.1M acetic buffer solution was used as cathode reservoir liquid, expected to promote the removal efficiency. From the result of experiment that could not reach the expected treatment efficiency of increasing the removal efficiency from soil. From the experiment of electrokinetics process combined with cometabolism, a treatment efficiency of only 25.67% was obtained. The content of pollutant within every section of soil column were still higher than predict. But by using electrokinetics-Fenton process to pretreat the pollutant within soil first, the increasing efficiency of biodegradation was found. Even when reaction time was prolonged, the pollutant could be completely eliminated from soil. If only used iron minerals to proceed electrokinetics-Fenton process naturally exited in the soil, a DRE of only 20

Organochlorine (OC) compounds that include several pesticides as well as an array of industrial chemicals were very efficacious for their intended use but were also characterized by deleterious environmental impacts when released either intentionally or inadvertently. Their lipophilic nature, long persistence in the environment and threat to human health caused all the developed countries to ban the production of these chemicals as well as restricted the use of formulations containing these material for food production. / A number of scientists have become involved in the development of intentional degradation methods/techniques for these compounds using zero-valent metals or bimetallic mixtures. To date, there is no single, simple and continuous procedure available to completely dechlorinate lindane or pentachlorophenol (PCP). This work describes the complete dechlorination of lindane and pentachlorophenol by zero-valent Zn, Fe and Fe/Ag bimetallic mixture as well as a supercritical fluid extraction technique for a more efficient mass transfer of the substrates to the surfaces of the metal catalyst. The dechlorination reaction occurs on the surface of metal particles with the removal of all the chlorine atoms from lindane and PCP in a matter of minute, and yields completely dechlorinated hydrocarbon molecules and chloride as products. (Abstract shortened by UMI.)

Orientadores: Antonio José Gomez Cobo, Antonio Guerrero Ruiz / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-17T07:20:21Z (GMT). No. of bitstreams: 1 Silva_MarcioWagnerda_D.pdf: 2089172 bytes, checksum: f1cfbcb71bbf10a37c5a4215dbf395c6 (MD5) Previous issue date: 2010 / Resumo: Alguns compostos organoclorados são motivo de grande preocupação, em razão da elevada toxicidade e persistência, tanto no meio ambiente quanto em organismos vivos. Dentre tais compostos, encontra-se o pentaclorofenol, utilizado para a conservação de madeira e na proteção de lavouras. Uma das tecnologias mais promissoras para o tratamento dessa classe de compostos tóxicos é a hidrodescloração catalítica, através da qual é possível recuperar a matéria-prima utilizada na síntese do contaminante. Embora diferentes catalisadores possam ser utilizados nesta reação, destacam-se os sólidos à base de Pd e Ru, notadamente devido à maior atividade catalítica. No entanto, os elevados preços destes metais nobres podem aumentar significativamente os custos do processo. Nesse contexto, o objetivo do presente trabalho é estudar os efeitos da presença dos metais básicos Fe e Ni em catalisadores à base de Pd e Ru, destinados à hidrodescloração do pentaclorofenol em fase líquida. Para tanto, catalisadores monometálicos e bimetálicos, suportados em alumina (Al2O3) ou titânia (TiO2), foram preparados a partir dos precursores clorados, através do método de co-impregnação a seco. Os sólidos obtidos foram caracterizados por meio das técnicas de adsorção de N2 (método BET), microscopia eletrônica de varredura com espectrometria de energia dispersiva de raios-X (MEV-EDX), espectroscopia fotoeletrônica de raios-X (XPS), redução à temperatura programada (TPR) e microscopia eletrônica de transmissão (MET). A hidrodescloração do pentaclorofenol foi conduzida num reator Parr® do tipo "slurry", à temperatura de 383 K e sob pressão de H2 de 0,5 MPa. Na reação de interesse, a adição de Ni ao catalisador de Ru/TiO2 diminui a atividade catalítica, porém mantém a elevada seletividade de cicloexanol, possibilitando, portanto, uma diminuição do custo do catalisador, sem perda de seletividade. Já para o catalisador de Pd/TiO2, a presença de Ni também diminui a atividade catalítica, assim como observado no caso do catalisador de Ru/TiO2, mas verifica-se uma diminuição da seletividade de fenol. Por sua vez, a adição de Fe ao catalisador de Pd/TiO2 tem pouca influência sobre a atividade e a seletividade, possibilitando, assim, uma significativa diminuição do custo do catalisador, sem prejuízo do desempenho catalítico. Os comportamentos catalíticos observados são analisados e interpretados à luz dos resultados obtidos através das caracterizações dos sólidos, assim como das informações disponíveis na literatura / Abstract: Some organic chlorine compounds are of great concern, because of high toxicity and persistence, both the environment and in living organisms. Among these compounds, is the pentachlorophenol, which is used to Wood conservation and for the protection of crops. A very promising technology to treating this class of toxic compounds is the catalytic hydrodechlorination, through which it is possible the recovery of raw material used in the synthesis of the contaminant. Although various catalysts may be used in this reaction, we highlight the solids Pd and Ru, mainly due to higher catalytic activity. However, the high prices of these noble etals can increase significantly the process costs. In this context, the objective of this work is to study the effects of base metals addition, Fe and Ni, in the catalysts based on Pd and Ru, for the pentachlorophenol hydrodechlorination in liquid phase. For this, monometallic and bimetallic catalysts, supported in alumina (Al2O3) or titanium oxide (TiO2), were prepared from chlorinated precursors by the incipient impregnation method. The obtained solids were characterized by techniques of N2 adsorption (BET method), scanning electronic microscopy with X-ray spectrometry analysis (EDX), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR) and transmission electronic microscopy. The pentachlorophenol hydrodechlorination was carried out in a "slurry" Parr® reactor, at the temperature of 373 K under the hydrogen pressure of 0,5 MPa. In the interest reaction, the addition of Ni to the Ru/TiO2 catalysts reduces the catalytic activity, but the high cyclohexanol selectivity is maintained, enabling thus, decrease the catalyst cost, without loss of selectivity. To the Pd/TiO2 catalyst, the i presence reduce the catalytic activity, like to the observed to the Ru/TiO2 case, but is verified the decreasing of phenol selectivity. In turn, the Fe addition to the Pd/TiO2 catalyst has little influence on the activity and selectivity, leading thus to a significant decrease in the catalyst cost, without prejudice to the catalytic performance. The observed catalytic behaviors are analyzed and interpreted based in the results obtained through the characterization of solids, as well as information available in the literature / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

The effects of pentachlorophenol (PCP), a widely used pesticide, on the electrical characteristics of lipid bilayer membranes has been studied. When a small amount of PCP (even at a concentration of a few micromoles per liter) is present in the electrolytic solution surrounding the membrane, the electrical conductivity of the membrane significantly increases. The present work was concerned with detailed measurements of the changes in the conductivity caused by PCP under chemically controlled conditions. The experimental results were analyzed to determine the permanent species in the membrane, and an attempt was made to correlate the data with existing models of transport.

Pentachlorophenol (PCP) is one of the prominent environmental pollutant that has penetrated into food chain and is present in humans. Health concerns have been raised since daily intake of PCP by the US population is estimated to be 16-19 µg. PCP facilitates dissipation of electrochemical potential gradients of hydrogen ions across energy transducing membranes, which are the energy sources for the conversion of adenosine diphosphate into adenosine triphosphate. Closely linked to these dissipative effects is the development of electrical conductivity in lipid membranes, induced by the presence of PCP. Three modes of PCP - induced membrane electrical conductivity were theoretically analyzed and experimentally verifiable formulations of each models were developed. Experimental studies using the charge - pulse method involved characterization of the time dependent transmembrane voltage over a wide pH range, from 1.8 to 9.5, for 30 µM concentrations of PCP. Lipid membranes were prepared from dioleoyl phosphatidylcholine. It was shown that three PCP molecular species were determining the transmembrane transfer of hydrogen ions: electrically neutral PCP molecules (HA), negatively charged pentachlorophenolate ions (A⁻) and negatively charged heterodimers (AHA⁻). It was found that at pH>9 the membrane electrical conductivity was determined by the transmembrane movement of A⁻ ions, whenever pHAHA⁻ species. Two new membrane surface reactions were proposed as supplementary mechanisms for the generation of AHA⁻ in addition to the formation of AHA⁻ by the recombination of HA and A⁻, HA + A⁻→ AHA⁻. These new reactions are, (i) 2HA → H⁺ + AHA⁻, and (ii) H20 + 2A⁻ → OH' + AHA⁻. Reaction (i) provides formation of membrane permeable heterodimers AHA⁻ at pH < < 5.5 and reaction (ii) at pH> > 5.5. The maximum surface density of AHA" heterodimers was 0.09 pmol/cm² • The rate constant of formation of AHA' by recombination, HA + A⁻ → AHA' was estimated to be k[subscript f] = 2.6xl0⁹ cm² mol⁻¹ s⁻¹ and the dissociation rate constant for AHA⁻ Further, it was possible to determine the rate constants of transmembrane translocation for A' and AHA⁻ ions to be k[subscript a] = 6.6x10⁻⁵ s⁻¹ and k[subscript aha] = 1200 S⁻¹, respectively.

No description available.

No description available.

The focus of this research was to acquire a better understanding of the sorption and desorption of pentachlorophenol to soil organic matter. In order to separate the reactions controlling the interactions with the soil organic matter from those associated with mineral surfaces, these experiments used only humic acids extracted from soil samples. The major focus of this study was to examine the effects of solution pH, humic acid concentration and contact time on the degree of sorption. The association reactions proceeded slowly. Even after 28 days, many solutions had not attained equilibrium. An increase in the solution pH led to a reduction in the amount of partitioning onto the humic material. At solution concentrations between 100 mg/L and 800 mg/L of total organic carbon (TOC), an increase in the humic acid concentration resulted in a lower partition coefficient. However, above a concentration of 800 mg/L TOC, further increases in the amount of humic material caused enhanced sorption. The particulate humic acids demonstrated a higher affinity for the pentachlorophenol than did the dissolved polymers. In the concentrated solutions, the majority of the humic acids were present in the particulate form. Two experiments focused on the effect of sorption on the bioavailability and solvent extraction of pentachlorophenol. The bioavailability data Suggested that the sorbed contaminant was not readily accessible to the microorganisms. The humic acids prevented the extraction of the sorbate by methyl-tert-butyl ether and methylene chloride. Recovery of the pentachlorophenol sorbed to the dissolved humic acids ranged from zero to 42.9 percent, depending on the solution pH. The removal of pentachlorophenol from the particulate matter varied from 25 percent to 90 percent. Longer contact times diminished the transfer of PCP associated with the solid humic acids to the solvent phase. The experimental results were not consistent with a simple, one mechanism model. The best explanation of the data was provided by a model which included liquid-liquid partitioning, surface sorption, absorption, and chemisorption. The dominant process depended on the contact time, solution pH, and concentration and nature of the humic acids. / Master of Science

The radiorespirometric technique, a modification of the heterotrophic activity assay, was evaluated as a monitor of toxic perturbation. The basis for the technique consists of trapping ¹⁴CO₂ evolved from the catabolism of a ¹⁴C-labeled substrate, and analyzing the resultant activity in a scintillation counter. An index of change in heterotrophic activity, the percent suppression, was calculated from the ratio of a toxified sample to a control. The effect of pentachlorophenol (PCP) on the heterotrophic activity of a laboratory-maintained aquatic culture was evaluated. The radiorespirometric technique detected changes in the heterotrophic activity for shorter exposure times and for PCP concentrations an order of magnitude lower than previously reported in the literature. Only 0.75 mg/L PCP caused approximately a 54 percent suppression of heterotrophic activity after a 30 min exposure. Radiolabeled glucose and glutamic acid were evaluated, and the radiorespirometric method was more sensitive at detecting changes in heterotrophic activity when the substrate used was glutamic acid. Whereas the error associated with the evolution and trapping of ¹⁴CO₂ apart from that introduced by microbial activity was only 13 to 20 percent, the variability induced by variations in the composition of the stock culture was quite high. The variability and lack of replicability of the heterotrophic activity experiments was the result of the heterogenous distribution of microorganisms and the alterations in the composition of the stock culture with time. The fit of the data to the first-order model of saturation kinetics was evaluated. The data derived during the study did not fit the first-order model probably because the added substrate concentrations were at trace levels. A protocol for the radiorespirometric technique is recommended. / M.S.