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Microbial Degradation (microbial + degradation)
Selected AbstractsMicrobial degradation of isoproturon and related phenylurea herbicides in and below agricultural fieldsFEMS MICROBIOLOGY ECOLOGY, Issue 1 2003Sebastian R Sørensen Abstract The phenylurea herbicides are an important group of pesticides used extensively for pre- or post-emergence weed control in cotton, fruit and cereal crops worldwide. The detection of phenylurea herbicides and their metabolites in surface and ground waters has raised the awareness of the important role played by agricultural soils in determining water quality. The degradation of phenylurea herbicides following application to agricultural fields is predominantly microbial. However, evidence suggests a slow degradation of the phenyl ring, and substantial spatial heterogeneity in the distribution of active degradative populations, which is a key factor determining patterns of leaching losses from agricultural fields. This review summarises current knowledge on the microbial metabolism of isoproturon and related phenylurea herbicides in and below agricultural soils. It addresses topics such as microbial degradation of phenylurea herbicides in soil and subsurface environments, characteristics of known phenylurea-degrading soil micro-organisms, and similarities between metabolic pathways for different phenylurea herbicides. Finally, recent studies in which molecular and microbiological techniques have been used to provide insight into the in situ microbial metabolism of isoproturon within an agricultural field will be discussed. [source] Microbial biodegradation of polyaromatic hydrocarbonsFEMS MICROBIOLOGY REVIEWS, Issue 6 2008Ri-He Peng Abstract Polycyclic aromatic hydrocarbons (PAHs) are widespread in various ecosystems and are pollutants of great concern due to their potential toxicity, mutagenicity and carcinogenicity. Because of their hydrophobic nature, most PAHs bind to particulates in soil and sediments, rendering them less available for biological uptake. Microbial degradation represents the major mechanism responsible for the ecological recovery of PAH-contaminated sites. The goal of this review is to provide an outline of the current knowledge of microbial PAH catabolism. In the past decade, the genetic regulation of the pathway involved in naphthalene degradation by different gram-negative and gram-positive bacteria was studied in great detail. Based on both genomic and proteomic data, a deeper understanding of some high-molecular-weight PAH degradation pathways in bacteria was provided. The ability of nonligninolytic and ligninolytic fungi to transform or metabolize PAH pollutants has received considerable attention, and the biochemical principles underlying the degradation of PAHs were examined. In addition, this review summarizes the information known about the biochemical processes that determine the fate of the individual components of PAH mixtures in polluted ecosystems. A deeper understanding of the microorganism-mediated mechanisms of catalysis of PAHs will facilitate the development of new methods to enhance the bioremediation of PAH-contaminated sites. [source] Microbial degradation of the biocide polyhexamethylene biguanide: isolation and characterization of enrichment consortia and determination of degradation by measurement of stable isotope incorporation into DNAJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2007L.P. O'Malley Abstract Aims:, To isolate micro-organisms capable of utilizing polyhexamethylene biguanide (PHMB) as a sole source of nitrogen, and to demonstrate biodegradation of the biocide. Methods and Results:, Two consortia of bacteria were successfully enriched at the expense of PHMB, using sand from PHMB-treated swimming pools as inoculum. Both consortia were shown to contain bacteria belonging to the genera Sphingomonas, Azospirillum and Mesorhizobium. It was shown that the presence of both Sphingomonas and Azospirillum spp. was required for extensive growth of the consortia. In addition, the Sphingomonads were the only isolates capable of growth in axenic cultures dosed with PHMB. Using a stable isotope (15N),labelled PHMB, metabolism of the biocide by both consortia was demonstrated. By comparing the level of 15N atom incorporation into bacterial DNA after growth on either 15N-PHMB or 15N-labelled NH4Cl, it was possible to estimate the percentage of PHMB biodegradation. Conclusions:, The microbial metabolism of nitrogen from the biguanide moiety of PHMB has been demonstrated. It was revealed that Sphingomonas and Azospirillum spp. are the principal organisms responsible for growth at the expense of PHMB. Significance and Impact of the Study:, This is the first study to demonstrate the microbial metabolism of PHMB. [source] Microbial degradation of the detoxification products of mustard from the Russian chemical weapons stockpileJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2005Inna T Ermakova Abstract This work was undertaken to examine the possibility of biodegradation of the organic components of the ,reaction masses' (detoxification products) generated by destruction of the chemical warfare agent mustard. The composition of these components was analysed by gas chromatography and mass spectrometry. The major components formed during chemical detoxification were identified as 1,4-perhydrothiazine derivatives. N -(2-Hydroxyethyl)-2-methyl-1,4-perhydrothiazine hydrochloride and N -(2-hydroxyethyl)-3-methyl-1,4-perhydrothiazine hydrochloride were predominant (about 70% of total 1,4-perhydrothiazine derivatives). Pseudomonas putida strains that used some organic components of the mustard reaction masses as carbon sources for growth were isolated and selected. Growth cessation in this medium (with organic carbon still available) was due to the depletion of bioutilisable substrates, primarily monoethanolamine and ethylene glycol (the residual components of the detoxifying mixture). 1,4-Perhydrothiazine derivatives were not used as carbon sources for growth of P putida strain SH1, but their concentration decreased during bacterial growth with monoethanolamine and ethylene glycol as the carbon substrates. It is suggested that 1,4-perhydrothiazines undergo transformation by the microbial cells under these conditions. Copyright © 2005 Society of Chemical Industry [source] Microbial degradation of rice and barley straws in the sheep rumen and the donkey caecumJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2003Ahoefa Agbagla-Dohnani Abstract The chemical composition, intake, digestibility, ultrastructure and microbial degradation of rice straw from Camargue were compared with barley straw. These variables were observed in two different herbivore digestive ecosystems: the sheep rumen and the donkey caecum. The two straws differed essentially in their ash content, which was three times higher in rice, owing to its silica content. Other chemical components were comparable, except a higher phenolic acids-to-lignin ratio in rice. Rice straw was better ingested than barley straw. Organic matter and neutral detergent fibre digestibilities were the same in both straws. Dry matter and cell wall disappearances could be adjusted to the exponential modelling equation with lag time, and differed between animals but not between straws. The sheep rumen had a higher extent of degradation, but the donkey caecum had a higher degradation rate. Statistical analysis revealed that cell-wall components degradation was similar in the two straws except for ferulic acid, which was more degraded in rice straw. Scanning electron microscopy showed important differences in parenchyma degradation, which was much more effective in rice. Copyright © 2003 Society of Chemical Industry [source] Laboratory persistence and fate of fluoxetine in aquatic environmentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2006Jeong-Wook Kwon Abstract The persistence and fate of fluoxetine, a selective serotonin reuptake inhibitor, has been investigated in laboratory-scale experiments, including studies with various aqueous solutions, water/sediment systems, and activated sludge-amended medium. The samples were placed in the dark and/or in a growth chamber fitted with fluorescent lamps simulating the ultraviolet output of sunlight. Over a period of 30 d, fluoxetine was hydrolytically and photolytically stable in all aqueous solutions except synthetic humic water (pH 7), in which the degradation rate was increased by approximately 13-fold in comparison with buffered solutions at the same pH. Fluoxetine rapidly dissipated from the aqueous phase in water/sediment systems, primarily because of distribution to sediments. The dissipation rate from the aqueous phase was similar between light and dark systems, indicating a low contribution of photodegradation to the dissipation of fluoxetine in this system. The potential impact of fluoxetine in aquatic environments would be decreased because of adsorption to sediments. Based on results of ready-biodegradability investigations, fluoxetine would not be expected to rapidly biodegrade in wastewater treatment plants. A photoproduct was detected only in a sample of synthetic humic water and was identified as norfluoxetine formed by demethylation. Results indicate that fluoxetine is relatively recalcitrant to hydrolysis, photolysis, and microbial degradation and that it is rapidly removed from surface waters by adsorption to sediment, where it appears to be persistent. [source] Variations in ,-Hexachlorocyclohexane enantiomer ratios in relation to microbial activity in a temperate estuaryENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2003Tiruponithura V. Padma Abstract Changes in the enantiomer ratios (ERs) of chiral pollutants in the environment are often considered evidence of biological alteration despite the lack of data on causal or mechanistic relationships between microbial parameters and ER values. Enantiomer ratios that deviate from 1:1 in the environment provide evidence for the preferential microbial degradation of one enantiomer, whereas ER values equal to 1 provide no evidence for microbial degradation and may mistakenly be interpreted as evidence that biodegradation is not important. In an attempt to link biological and geochemical information related to enantioselective processes, we measured the ERs of the chiral pesticide ,-hexachlorocyclohexane (,-HCH) and bacterial activity (normalized to abundance) in surface waters of the York River (VA, USA) bimonthly throughout one year. Despite lower overall ,-HCH concentrations, ,-HCH ER values were unexpectedly close to 1:1 in the freshwater region of the estuary with the highest bacterial activity. In contrast, ER values were nonracemic (ER , 1) and ,-HCH concentrations were significantly higher in the higher salinity region of the estuary, where bacterial activity was lower. Examination of these data may indicate that racemic environmental ER values are not necessarily reflective of a lack of biodegradation or recent input into the environment, and that nonenantioselective biodegradation may be important in certain areas. [source] Rapid decomposition of phytate applied to a calcareous soil demonstrated by a solution 31P NMR studyEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2010A. L. Doolette myo -Inositol hexakisphosphate (phytate) is widely regarded as an abundant form of soil organic phosphorus (P) in many soils. Its abundance is believed to be because of its resistance to microbial degradation. We examined the fate of phytate added to a calcareous soil as a solution at a concentration of 58 mg P kg,1, with and without the addition of wheat straw. The soil was incubated for 13 weeks, with phytate concentrations determined at 0, 1, 4, 7 and 13 weeks using NaOH-EDTA soil extraction followed by 31P nuclear magnetic resonance (NMR) spectroscopy. The phytate concentration declined rapidly, with 18% (phytate + wheat straw) and 12% (phytate) of the initial phytate remaining after 13 weeks. This coincided with an increase in the proportion of orthophosphate relative to total NaOH-EDTA extractable P (from 65 to 81%) and a small increase in , - and , -glycerophosphate concentration, providing evidence for the microbial degradation of phytate. The decrease in phytate concentration was consistent with a first-order decay with a half-life for phytate of 4,5 weeks. This study demonstrates that in the calcareous soil examined, phytate was not highly stable, but a potentially biologically available form of P. In order to quantify the concentration of P species, we developed an improved method of spectral deconvolution. This method accounted for a broad signal (3.5,6.5 ppm) in the monoester region of the spectra that represented up to 23% of the total extractable P. We found that when this broad signal was not included, phytate concentrations were over-estimated by up to 54%. [source] Microbial degradation of isoproturon and related phenylurea herbicides in and below agricultural fieldsFEMS MICROBIOLOGY ECOLOGY, Issue 1 2003Sebastian R Sørensen Abstract The phenylurea herbicides are an important group of pesticides used extensively for pre- or post-emergence weed control in cotton, fruit and cereal crops worldwide. The detection of phenylurea herbicides and their metabolites in surface and ground waters has raised the awareness of the important role played by agricultural soils in determining water quality. The degradation of phenylurea herbicides following application to agricultural fields is predominantly microbial. However, evidence suggests a slow degradation of the phenyl ring, and substantial spatial heterogeneity in the distribution of active degradative populations, which is a key factor determining patterns of leaching losses from agricultural fields. This review summarises current knowledge on the microbial metabolism of isoproturon and related phenylurea herbicides in and below agricultural soils. It addresses topics such as microbial degradation of phenylurea herbicides in soil and subsurface environments, characteristics of known phenylurea-degrading soil micro-organisms, and similarities between metabolic pathways for different phenylurea herbicides. Finally, recent studies in which molecular and microbiological techniques have been used to provide insight into the in situ microbial metabolism of isoproturon within an agricultural field will be discussed. [source] Processes governing river water quality identified by principal component analysisHYDROLOGICAL PROCESSES, Issue 16 2002I. Haag Abstract The present study demonstrates the usefulness of principal component analysis in condensing and interpreting multivariate time-series of water quality data. In a case study the water quality system of the lock-regulated part of the River Neckar (Germany) was analysed, with special emphasis on the oxygen budget. Pooled data of ten water quality parameters and discharge, which had been determined at six stations along a 200 km reach of the river between the years 1993 and 1998, were subjected to principal component analysis. The analysis yielded four stable principal components, explaining 72% of the total variance of the 11 parameters. The four components could be interpreted confidently in terms of underlying processes: biological activity, dilution by high discharge, seasonal effects and the influence of wastewater. From analysing the data of single stations separately, these processes were found to be active throughout the complete reach. Considering the oxygen budget of the river, the variance of biological activity, representing the counteracting processes of primary production and microbial degradation, was found to be most important. This principal component explained 79% of the observed variance of oxygen saturation. In contrast, the analysis of a reduced data set from the 1970s showed that oxygen saturation was then dominated by discharge and temperature variations. The findings indicate that the oxygen budget used to be governed directly by the emission of degradable matter, whereas nowadays eutrophication is most important for extreme oxygen concentrations. Therefore, controlling eutrophication has to be the primary goal, in order to mitigate the rare episodes of pronounced oxygen over- and undersaturation in the future. Copyright © 2002 John Wiley & Sons, Ltd. [source] Penicillium strains as dominant degraders in soil for coffee residue, a biological waste unsuitable for fertilizationJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007Katsuhiko Fujii Abstract Aims:, Coffee residue is an agricultural waste which inhibits the growth of several crops. Therefore coffee residue-degrading microbes in soil were screened, isolated and characterized. Methods and Results:, Forty isolates were obtained after enrichment culture of soil samples. Seven strains (fast degraders) showed strong degrading activity, while 18 strains (slow degraders) showed weak degrading activity. DNA analysis suggested that the fast degraders are Penicillium, and the slow degraders are Penicillium, Trichoderma/Hypocrea, Fusarium/Gibberella, Phaeoacremonium/Togninia or Acidocella. The all fast degraders are cellulolytic, mannolytic and pectinolytic. Conclusions:, Although it is generally thought that fungi such as Trichoderma contribute largely to aerobic degradation of cellulosic biomass, our data suggested that Penicillium overwhelms them in coffee residue degradation. It was implied that polysaccharides in coffee residue are not degraded independently by different microbes, but degraded simultaneously by strains with cellulolytic, mannolytic and pectinolytic activity. Since there is no report of an ascomycete possessing all the three enzyme activities, the fast degraders are ecologically important and have the potential to be used as producers of the costly enzymes from agricultural wastes. Significance and Impact of Study:, The present results advance our understanding of microbial degradation of a phytotoxic agricultural waste, and offer a new tool for recycling it. [source] Degradation of naphthenic acids by sediment micro-organismsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2006L.F. Del Rio Abstract Aims:, Naphthenic acids (NAs) are naturally occurring, linear and cyclic carboxylic surfactants associated with the acidic fraction of petroleum. NAs account for most of the acute aquatic toxicity of oil sands process-affected water (OSPW). The toxicity of OSPW can be reduced by microbial degradation. The aim of this research was to determine the extent of NA degradation by sediment microbial communities exposed to varying amounts of OSPW. Methods and Results:, Eleven wetlands, both natural and process-affected, and one tailings settling pond in Northern Alberta were studied. The natural wetlands and process-affected sites fell into two distinct groups based on their water chemistry. The extent of degradation of a 14C-labelled monocyclic NA surrogate [14C-cyclohexane carboxylic acid (CCA)] was relatively uniform in all sediments (approximately 30%) after 14 days. In contrast, degradation of a bicyclic NA surrogate [14C-decahydronaphthoic acid (DHNA)]was significantly lower in non process-affected sediments. Enrichment cultures, obtained from an active tailings settling pond, using commercially available NAs as the sole carbon source, resulted in the isolation of a co-culture containing Pseudomonas putida and Pseudomonas fluorescens. Quantitative GC,MS analysis showed that the co-culture removed >95% of the commercial NAs, and partially degraded the process NAs from OSPW with a resulting NA profile similar to that from ,aged wetlands'. Conclusions:, Exposure to NAs induced and/or selected micro-organisms capable of more effectively degrading bicyclic NAs. Native Pseudomonas spp. extensively degraded fresh, commercial NA. The recalcitrant NAs resembled those found in process-affected wetlands. Significance and Impact of the Study:, These results suggest that it may be possible to manipulate the existing environmental conditions to select for a microbial community exhibiting higher rates of NA degradation. This will have significant impact on the design of artificial wetlands for water treatment. [source] Is thermal oxidation at different temperatures suitable to isolate soil organic carbon fractions with different turnover?JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 1 2010Mirjam Helfrich Abstract Findings of previous studies suggest that there are relations between thermal stability of soil organic matter (SOM), organo-mineral associations, and stability of SOM against microbial decay. We aimed to test whether thermal oxidation at various temperatures (200°C, 225°C, 275°C, 300°C, 400°C, or 500°C) is capable of isolating SOM fractions with increasing stability against microbial degradation. The investigation was carried out on soils (Phaeozem and Luvisol) under different land-use regimes (field, grassland, forest). The stability of the obtained soil organic carbon (SOC) fractions was determined using the natural- 13C approach for continuously maize-cropped soils and radiocarbon dating. In the Luvisol, thermal oxidation with increasing temperatures did not yield residual SOC fractions of increasing microbial stability. Even the SOC fraction resistant to thermal oxidation at 300°C contained considerable amounts of young, maize-derived C. In the Phaeozem, the mean 14C age increased considerably (from 3473 y BP in the mineral-associated SOC fraction to 9116 y BP in the residual SOC fraction after thermal oxidation at 300°C). An increasing proportion of fossil C (calculated based on 14C data) in residual SOC fractions after thermal oxidation with increasing temperatures indicated that this was mainly due to the relative accumulation of thermally stable fossil C. We conclude that thermal oxidation with increasing temperature was not generally suitable to isolate mineral-associated SOC fractions of increasing microbial stability. [source] Microbial degradation of rice and barley straws in the sheep rumen and the donkey caecumJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2003Ahoefa Agbagla-Dohnani Abstract The chemical composition, intake, digestibility, ultrastructure and microbial degradation of rice straw from Camargue were compared with barley straw. These variables were observed in two different herbivore digestive ecosystems: the sheep rumen and the donkey caecum. The two straws differed essentially in their ash content, which was three times higher in rice, owing to its silica content. Other chemical components were comparable, except a higher phenolic acids-to-lignin ratio in rice. Rice straw was better ingested than barley straw. Organic matter and neutral detergent fibre digestibilities were the same in both straws. Dry matter and cell wall disappearances could be adjusted to the exponential modelling equation with lag time, and differed between animals but not between straws. The sheep rumen had a higher extent of degradation, but the donkey caecum had a higher degradation rate. Statistical analysis revealed that cell-wall components degradation was similar in the two straws except for ferulic acid, which was more degraded in rice straw. Scanning electron microscopy showed important differences in parenchyma degradation, which was much more effective in rice. Copyright © 2003 Society of Chemical Industry [source] High-density polyethylene (HDPE)-degrading potential bacteria from marine ecosystem of Gulf of Mannar, IndiaLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2010V. Balasubramanian Abstract Aims:, Assessment of high-density polyethylene (HDPE)-degrading bacteria isolated from plastic waste dumpsites of Gulf of Mannar. Methods and Results:, Rationally, 15 bacteria (GMB1-GMB15) were isolated by enrichment technique. GMB5 and GMB7 were selected for further studies based on their efficiency to degrade the HDPE and identified as Arthrobacter sp. and Pseudomonas sp., respectively. Assessed weight loss of HDPE after 30 days of incubation was nearly 12% for Arthrobacter sp. and 15% for Pseudomonas sp. The bacterial adhesion to hydrocarbon (BATH) assay showed that the cell surface hydrophobicity of Pseudomonas sp. was higher than Arthrobacter sp. Both fluorescein diacetate hydrolysis and protein content of the biofilm were used to test the viability and protein density of the biomass. Acute peak elevation was observed between 2 and 5 days of inoculation for both bacteria. Fourier transform infrared (FT-IR) spectrum showed that keto carbonyl bond index (KCBI), Ester carbonyl bond index (ECBI) and Vinyl bond index (VBI) were increased indicating changes in functional group(s) and/or side chain modification confirming the biodegradation. Conclusion:, The results pose us to suggest that both Pseudomonas sp. and Arthrobacter sp. were proven efficient to degrade HDPE, albeit the former was more efficacious, yet the ability of latter cannot be neglected. Significance and Impact of the Study:, Recent alarm on ecological threats to marine system is dumping plastic waste in the marine ecosystem and coastal arena by anthropogenic activity. In maintenance phase of the plastic-derived polyethylene waste, the microbial degradation plays a major role; the information accomplished in this work will be the initiating point for the degradation of polyethylene by indigenous bacterial population in the marine ecosystem and provides a novel eco-friendly solution in eco-management. [source] Enzymatic Hydrolysis of , - and , -Oligo(L -aspartic acid)s by Poly(aspartic acid) Hydrolases-1 and 2 from Sphingomonas sp.MACROMOLECULAR BIOSCIENCE, Issue 3 2004Abstract Summary: The enzymatic hydrolysis of , - and , -oligo(L -aspartic acid)s by PAA hydrolase-1 and PAA hydrolase-2 (purified from Sphingomonas sp. KT-1) was performed to elucidate the mechanism of the microbial degradation by Sphingomonas sp. KT-1 of the thermally synthesized ,,, -poly(D,L -aspartic acid) (tPAA). GPC analysis of the hydrolyzed products of , - and , -tetra(L -aspartic acid)s by PAA hydrolase-1 has showed that PAA hydrolase-1 is capable of hydrolyzing only the specific amide bonds between , -aspartic acid units. The RP-HPLC analysis of the enzymatic hydrolysis of , -oligo(L -aspartic acid)s (4 and 5 mers) by PAA hydrolase-1 has suggested that the enzymatic hydrolysis of , -oligo(L -aspartic acid)s occurs via an endo-mode cleavage. In contrast, PAA hydrolase-2 hydrolyzed both , - and , -oligo(L -aspartic acid)s via an exo-mode cleavage to yield L -aspartic acid as a final product. A kinetic study on the enzymatic hydrolysis of , -oligo(L -aspartic acid)s (3 to 7 mers) by PAA hydrolase-2 has indicated that Km values are almost independent of the number of monomer units in oligomers of 4 to 7 mers, while that Vmax values are markedly dependent on the chain length and show a maximum value at 5 mer. A proposed mechanism of the enzymatic hydrolysis of tPAA by PAA hydrolase-1 and PAA hydrolase-2 in the cell of Sphingomonas sp. KT-1. [source] White lupin has developed a complex strategy to limit microbial degradation of secreted citrate required for phosphate acquisitionPLANT CELL & ENVIRONMENT, Issue 5 2006LAURE WEISSKOPF ABSTRACT White lupins (Lupinus albus L.) respond to phosphate deficiency by producing special root structures called cluster roots. These cluster roots secrete large amounts of carboxylates into the rhizosphere, mostly citrate and malate, which act as phosphate solubilizers and enable the plant to grow in soils with sparingly available phosphate. The success and efficiency of such a P-acquisition strategy strongly depends on the persistence and stability of the carboxylates in the soil, a parameter that is influenced to a large extent by biodegradation through rhizosphere bacteria and fungi. In this study, we show that white lupin roots use several mechanisms to reduce microbial growth. The abundance of bacteria associated with cluster roots was decreased at the mature state of the cluster roots, where a burst of organic acid excretion and a drastic pH decrease is observed. Excretion of phenolic compounds, mainly isoflavonoids, induced fungal sporulation, indicating that vegetative growth, and thus potential citrate consumption, is reduced. In addition, the activity of two antifungal cell wall-degrading enzymes, chitinase and glucanase, were highest at the stage preceding the citrate excretion. Therefore, our results suggest that white lupin has developed a complex strategy to reduce microbial degradation of the phosphate-solubilizing agents. [source] Site characterization to support permeable reactive barrier designREMEDIATION, Issue 4 2005Lynn A. Morgan Careful design studies and selection of an effective technique for the installation of permeable reactive barriers (PRBs) are important contributors to the overall success of zero-valent iron PRBs. This article provides a case study summarizing the successful design and construction of a PRB installed at the former Carswell Air Force Base located in Fort Worth, Texas. Expedited site characterization using a cone penetrometer rig equipped with a mass spectrometer was employed to provide real-time characterization and lithologic data. These data proved to be invaluable for the design of the PRB and allowed for the development of an accurate preconstruction cost estimate. Field data gained from the expedited water quality and geologic characterization along with aquifer testing and a bench-scale treatability study provided a comprehensive basis for the design. The biopolymer slurry construction technique provided additional unanticipated benefits to the designed zero- valent iron treatment by promoting the development of anaerobic conditions favorable for microbial degradation of trichloroethene. Postconstruction monitoring data are discussed to illustrate the successful performance of the PRB. © 2005 Wiley Periodicals, Inc. [source] CLIMATE FORCINGS AND THEIR INFLUENCE ON ALPINE HISTORY AS RECONSTRUCTED THROUGH THE APPLICATION OF SYNCHROTRON-BASED X-RAY MICROFLUORESCENCE ON LAYERED STALAGMITES*ARCHAEOMETRY, Issue 2 2005S. FRISIA Solar variability and volcanic activity strongly interact with climate and the environment. Synchrotron radiation X-ray microfluorescence (micro-XRF) to an annually laminated Alpine stalagmite confirmed that annual laminae result from hydrological variability and changes in the duration of soil microbial degradation. The latter is modulated by solar variability. At the centennial timescale, growth rate and solar activity appear to be correlated with temperature change, with low temperatures at solar minima. By combining micro-XRF and absorption spectroscopy techniques (XANES), we also found that speleothems are a new archive of aerosol sulphate related to volcanic activity. Peaks in S-concentration from c. 5.2 to 5.0 ka bp in an Alpine stalagmite suggest that multiple volcanic sulphate aerosol emissions enhanced Mid-Holocene summer cooling, thus favouring the preservation of the Alpine Iceman mummy in a persistent ice casket. [source] Ultrasonically enhanced delivery and degradation of PAHs in a polymer,liquid partitioning system by a microbial consortiumBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Pedro A. Isaza Abstract The current study examined the effects of ultrasonic irradiation on mass transfer and degradation of PAHs, by an enriched consortium, when delivered from polymeric matrices. Rates of release into methanol under sonicated conditions, relative to unmixed cases, for phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene were increased approximately fivefold, when delivered from Desmopan 9370 A (polyurethane). Similar effects were observed in Hytrel and Kraton® D4150 K polymers as well as recycled Bridgestone tires. Enhancements were also displayed as shifts to higher release equilibria under sonicated conditions, relative to non-sonicated cases, agreeing with current knowledge in sonochemistry and attributed to cavitation. Ultrasonic effects on microbial activity were also investigated and cell damage was found to be non- permanent with consortium re-growth being observed after sonic deactivation. Finally, the lumped effect of sonication on degradation of phenanthrene delivered from Desmopan was examined under the absence and presence of sonication. Rates of degradation were found to be increased by a factor of four demonstrating the possibility of using ultrasonic irradiation for improved mass transport in solid,liquid systems. Cellular inactivation effects were not evident, and this was attributed to the attenuation of sonic energy arising from the presence of solid polymer materials in the medium. The findings of the study demonstrate that sonication can be used to improve mass transport of poorly soluble compounds in microbial degradations, and alleviate limiting steps of soil remediation processes proposed in previous research. Biotechnol. Bioeng. 2009; 104: 91,101 © 2009 Wiley Periodicals, Inc. [source] | |||||||||||||||||||