Quantitative Assessment of LNAPL Retention in Soil Porous Media

The presence of hydrocarbon contaminants in the vadose zone is a serious hazard for environment quality. Moreover, there is an urgent need for accurate and reliable knowledge of the hydraulics of hydrocarbon contaminants in porous media to enhance efficiency of NAPLs remediation methods. The objective of this study was to quantitatively assess the hydraulic properties of different porous media with petroleum, kerosene, diesel fuel, and gasoline. The related retention curves were then experimentally obtained. Parameters of the soils retention curves were obtained based on van Genuchten (1980), Brooks-Corey (1964), and Campbell (1974) retention models. The accuracy of models was then assessed by some statistics. The results indicated that, in most cases, air entry value was significantly increased in a petroleum retention curve despite the fact that it was decreased for other NAPLs. The pore size distribution parameters (i.e., n, m, λ, and 1/b) of diesel fuel, kerosene, and gasoline did not change considerably compared to water retention curve. The Leverett (1941) scaling function was adopted to scale soil-fluid retention curves data in two-phase systems. The results indicated that, except for a silty clay medium and petroleum, the Leverett (1941) J-function could scale the LNAPL retention curves based on the water retention curve data.     

Influence of UV irradiation on microbiological degradation of petroleum products

Changes in the rates of microbiological degradation of kerosene, diesel fuel, and fuel oil under the effect of UV irradiation were estimated by testing the respiratory activity of microbial communities. The strongest inhibitory effect was observed upon simultaneous UV irradiation of both natural water and petroleum products. Concentrations of CO₂ in the microbial communities (microcosms) decreased from 6.7 to 3.6 vol. % upon oxidation of kerosene, from 5.9 to 0.8 vol. % upon oxidation of diesel fuel, and from 5.7 to 0.05 vol. % upon oxidation of fuel oil.     

Construction of combustion models for rapeseed methyl ester bio-diesel fuel for internal combustion engine applications

Bio-diesel fuels are non-petroleum-based diesel fuels consisting of long chain alkyl esters produced by the transesterification of vegetable oils, that are intended for use (neat or blended with conventional fuels) in unmodified diesel engines. There have been few reports of studies proposing theoretical models for bio-diesel combustion simulations. In this study, we developed combustion models based on ones developed previously. We compiled the liquid fuel properties, and the existing detailed mechanism of methyl butanoate ester (MB, C₅H₁₀O₂) oxidation was supplemented by sub-mechanisms for two proposed fuel constituent components, C₇H₁₆ and C₇H₈O (and then, by mp2d, C₄H₆O₂ and propyne, C₃H₄) to represent the combustion model for rapeseed methyl ester described by the chemical formula, C₁₉H₃₄O₂ (or C₁₉H₃₆O₂). The main fuel vapor thermal properties were taken as those of methyl palmitate C₁₉H₃₆O₂ in the NASA polynomial form of the Burcat database. The special global reaction was introduced to “crack” the main fuel into its constituent components. This general reaction included 309 species and 1472 reactions, including soot and NO_x formation processes. The detailed combustion mechanism was validated using shock-tube ignition-delay data under diesel engine conditions. For constant volume and diesel engine (Volvo D12C) combustion modeling, this mechanism could be reduced to 88 species participating in 363 reactions.     

A rapid and sensitive immunoassay for the detection of gasoline and diesel fuel in contaminated soil

An enzyme immunoassay (EIA) was developed using a monoclonal antibody (MAb) reagent that detects gasoline and diesel fuel. Xylene and toluene derivatives, which are common components of gasoline, were synthesized with various types of spacers and conjugated to either bovine serum albumen or bovine thyroglobulin. A total of 16 different hapten conjugates were used for immunizing both Balb/c and Swiss Webster mice. A panel of MAbs were produced that recognized xylene and toluene in a competitive EIA. An enzyme‐hapten conjugate was prepared for the MAb (F12–3C8) that demonstrated the most suitable characteristics for sensitivity, cross‐reactivity, and compatibility with extraction buffers. The resulting EIA gave ED₅₀ values for m‐xylene of less than 1 ppm and values of less than 500 ppb for gasoline. Diesel fuel was also detected, with ED₃₀ values in the range of 300 ppb. When samples of gasoline were tested, the EIA gave consistent ED₃₀ values that were independent of manufacturer or octane rating. The EIA was compatible with simplified methods for the extraction of petroleum products from soil. The EIA detected gasoline in spiked soil samples, but was not affected by extracts of negative soil samples. Commercialization of this assay will offer speed, cost effectiveness, and other significant advantages over current testing methods of gasoline and diesel fuel contamination levels in soil.     

Crude oil production and classification of organic compounds on super-critical liquefaction with rice hull

The liquefaction of rice hull (a typical agricultural waste) has been conducted with n-butanol solvent at various reaction temperatures ranging from 260 to 320°C. As a result, it was found that biomass conversion rates were increased with increasing temperature up to 320dgC. However, it was observed that its rate of conversion to liquid was about 83% at 320°C for 30 min. The crude oil yield with rice hull increased up to 1,273 mg/g/L at 300°C, but the yield of Fraction 1 at 280°C was raised suddenly, and peaked at 2 times that of the initial input amount of feedstock. Furthermore, the calorific values of crude oil and Fraction 1 from rice hull were about 5,843 and 8,061 kcal/kg and were enhanced 163 and 225%, respectively, relative to its feedstock as rice hull, respectively. Fraction 1 may be suitable as an alternative liquid fuel of gasoline, based on an engine performance test. Sixty species of organic compounds in crude oil were categorized into 8 classes of compounds, including acids, alcohols, aliphatic hydrocarbons, ethers, esters, ketones, phenol, and aromatics, and others. In the crude oil from rice hull, the most common chemical types were esters and ethers accounting for 32.0 and 19.2% of the total extract, respectively. Analysis of Fraction 1 revealed that the main chemical components were C₅H₁₂O, C₇H₁₄O₂, C₈H₁₆O₂, and C₁₂H₂₆O₂. Therefore, for producing clean and green fuel energy with plant biomass liquefaction it is necessary to further investigate crude oil and to further refine Fraction 1 through catalytic cracking or hydro-de-oxygenation (HDO).     

Biochemical constituents of a wild strain of Schizophyllum commune isolated from Achanakmar-Amarkantak Biosphere Reserve (ABR), India

A wild strain of Schizophyllum commune (MTCC 9670) isolated from Achanakmar-Amarkantak Biosphere Reserve of Central India was evaluated for the production of bioactive compounds. The chemical constituents of wild and in vitro grown cultures were compared. Under optimized conditions, different organic and aqueous extracts from mycelia and fruiting bodies were used to extract chemical components from the cultures grown in vitro. The gas chromatography combined wih mass spectrometry analysis of extracts identified two phenolic compounds, namely Phenyl benzoate (C₁₃H₁₀O₂) and 4-(phenyl methoxy) phenol (C₁₃H₁₂O₂) in the ethanolic extract of in vitro grown fruiting bodies and one antibacterial compound Pyrrolo (1, 2-a) piperazine-3, 6-dione (C₇H₁₀O₂N₂) in the methanolic extract of mycelia. High-performance liquid chromatography analysis revealed that the gallic acid and l-ascorbic acid were identifiable antioxidant components in the extracts possessing high free radical scavenging activity. The findings suggest that the wild strain of S. commune may serve as the source of novel bioactive compounds with effective antimicrobial and antioxidant activities.     

Effects of biosurfactants produced by Candida antarctica on the biodegradation of petroleum compounds

The effects of biosurfactants on the biodegradation of petroleum compounds were investigated. Candida antarctica T-34 could produce extracellular biosurfactant mannosylerythritol lipids (MELs) when it was cultured in vegetable oil. In addition, in our previous study, it was found that this strain could also produce a new type of biosurfactant while it grew on n-undecane (C₁₁H₂₄), and the biosurfactant was named as BS-UC. In flask culture of Candida antarctica, the addition of BS-UC could improve the biodegradation rate of some n-alkanes (e.g. 90.2% for n-decane, 90.2% for n-undecane, 89.0% for dodecane), a mixture of n-alkanes (82.3%) and kerosene (72.5%). By comparing the effects of the biosurfactants BS-UC and MEL and chemical surfactants on the biodegradation of crude oil, it was found that biosurfactants could be used to enhance the degradation of petroleum compounds instead of chemical surfactants. In a laboratory scale immobilized bioreactor, the addition of biosurfactant improved not only the emulsification of kerosene in simulated wastewater but also its biodegradation rate. The highest degradation rate of kerosene by addition of MEL and BS-UC reached 87 and 90% at 15 h, respectively. The results showed that the biosurfactant BS-UC was highly promising for work on biodegradation of hydrophobic contaminants.     

Iso-alkane oxidation by aPseudomonas Part I.—Metabolism of 2-methylhexane

Summary Pseudomonas cells adapted to 2-methylhexane oxidize 5-methylhexanoic andiso-valeric acids rapidly. The oxidation rates of 2-methylhexanoic and propionic acids are appreciably lower. It can be concluded that primary attack on the C₆ atom is distinctly favoured over that on C₁. By use of gas-liquid chromatography, 2-methylhexanoic, 5-methylhexanoic andiso-valeric acids were shown to be formed when heptane-grown cells were incubated with 2-methylhexane. When 2-methylhexane-grown cells were used the amount of 5-methylhexanoic acid decreased compared with the amount of the 2-methyl isomer. Moreover,iso-valeric acid could not be detected. The results make it probable that degradation of 2-methylhexanevia C₆, comprising 5-methylhexanoic andiso-valeric acid, is accompanied by a second pathway via 2-methylhexanoic acid. The latter pathway is of minor importance, in particular in 2-methylhexane-adaptedPseudomonas cells.     

Enhancement of lipase production from hydrocarbons by mutation of Trichosporon fermentans

Lipase high-producing mutants with petroleum products as carbon sources were successfully induced from Trichosporon fermentans WU-C12 by ultraviolet (UV) light irradiation. In the first mutation step, one mutant strain, PU-30, derived from strain WU-C12 was selected. The productivity of extracellular lipase of PU-30 reached 58 units (U)/ml in the medium containing kerosene, being approximately twice the productivity of the parental strain WU-C12. In the second mutation step, the mutant strain 2PU-18 was induced from strain PU-30. In medium containing kerosene, gas oil and liquid paraffin, the 2PU-18 produced 70 U/ml, 62 U/ml and 60 U/ml of extracellular lipase, respectively. When various n-alkanes (C₈-C₁₈) were used as carbon sources, the parental strain WU-C12 produced more than 20 U/ml of lipase only from C₉-C₁₂ alkanes, but 2PU-18 could produce more than 50 U/ml of lipase from C₈-C₁₈ alkanes. When cultivated for 3 days in medium containing liquid paraffin, the activity ratios of extracellular lipase to total lipase and the values of extracellular lipase activity per dry-cell weight were 0.44 and 0.65 U/mg for WU-C12, and 0.62 and 1.82 U/mg for 2PU-18, respectively. These results indicate that the mutant strain 2PU-18 is superior in both total lipase productivity and permeability of lipase to the parental strain WU-C12 when petroleum products are used as carbon sources. Correspondence to: S. Usami     

Protozoa in Subsurface Sediments from Sites Contaminated with Aviation Gasoline or Jet Fuel

Numbers of protozoa in the subsurface of aviation gasoline and jet fuel spill areas at a Coast Guard base at Traverse City, Mich., were determined. Boreholes were drilled in an uncontaminated location, in contaminated but untreated parts of the fuel plumes, and in the aviation gasoline source area undergoing H₂O₂ biotreatment. Samples were taken from the unsaturated zone to depths slightly below the floating free product in the saturated zone. Protozoa were found to occur in elevated numbers in the unsaturated zone, where fuel vapors mixed with atmospheric oxygen, and below the layer of floating fuel, where uncontaminated groundwater came into contact with fuel. The same trends were noted in the biotreatment area, except that numbers of protozoa were higher. Numbers of protozoa in some contaminated areas equalled or exceeded those found in surface soil. The abundance of protozoa in the biotreatment area was high enough that it would be expected to significantly reduce the bacterial community that was degrading the fuel. Little reduction in hydraulic conductivity was observed, and no bacterial fouling of the aquifer was observed during biotreatment.     

Degradation of carbazole and its derivatives by a Pseudomonas sp.

Carbazole, carbazoles with monomethyl or dimethyls substituted on different positions (C₁-carbazoles or C₂-carbazoles), and benzocarbazoles, as toxic and mutagenic components of petroleum and creosote contamination, were biodegradable by an isolated bacterial strain Pseudomonas sp. XLDN4-9. C₁-carbazoles were degraded in preference to carbazole and C₂-carbazoles. The biodegradation of C₁-carbazoles or C₂-carbazoles was influenced by the positions of methyl substitutions. Among C₁-carbazole isomers, 1-methyl carbazole was the most susceptible. C₂-carbazole isomers with substitutions on the same benzo-nucleus were more susceptible at a concentration of less than 3.4 μg g⁻¹ petroleum, especially when harboring one substitution on position 1. In particular, 1,5-dimethyl carbazole was the most recalcitrant dimethyl isomer.     

Biodegradation of diesel fuel by a microbial consortium in the presence of 1-alkoxymethyl-2-methyl-5-hydroxypyridinium chloride homologues

Fast development of ionic liquids as gaining more and more attention valuable chemicals will undoubtedly lead to environmental pollution. New formulations and application of ionic liquids may result in contamination in the presence of hydrophobic compounds, such as petroleum mixtures. We hypothesize that in the presence of diesel fuel low-water-soluble ionic liquids may become more toxic to hydrocarbon-degrading microorganisms. In this study the influence of 1-alkoxymethyl-2-methyl-5-hydroxypyridinium chloride homologues (side-chain length from C₃ to C₁₈) on biodegradation of diesel fuel by a bacterial consortium was investigated. Whereas test performed for the consortium cultivated on disodium succinate showed that toxicity of the investigated ionic liquids decreased with increase in side-chain length, only higher homologues (C₈–C₁₈) caused a decrease in diesel fuel biodegradation. As a result of exposure to toxic compounds also modification in cell surface hydrophobicity was observed (MATH). Disulphine blue active substances method was employed to determine partitioning index of ionic liquids between water and diesel fuel phase, which varied from 1.1 to 51% for C₃ and C₁₈ homologues, respectively. We conclude that in the presence of hydrocarbons acting as a solvent, the increased bioavailability of hydrophobic homologues is responsible for the decrease in biodegradation efficiency of diesel fuel.     

Microbial degradation of petroleum hydrocarbons in a polluted tropical stream

Summary Crude oil degradation was observed in water samples from three sites along the course of a polluted stream in Lagos, Nigeria. Consistent increase and decrease in the total viable counts (TVCs) of indigenous organisms occurred in the test and control experiments, respectively. Enrichments of the water samples with crude oil resulted in the isolation of nine bacteria belonging to seven genera. A mixed culture was developed from the assemblage of the nine species. The defined microbial consortium utilized a wide range of pure HCs including cycloalkane and aromatic HCs. Utilization of crude oil and petroleum cuts, i.e., kerosene and diesel resulted in an increase in TVC (till day 10) concomitant with decreases in pH and residual oil concentration. Crude oil, diesel and kerosene were degraded by 88, 85 and 78%, respectively, in 14 days. Substrate uptake studies with axenic cultures showed that growth was not sustainable on either cyclohexane or aromatics while degradation of the petroleum fractions fell below 67% in spite of extended incubation period (20 day). From the GC analysis of recovered oil, while reductions in peaks of n-alkane fractions and in biomarkers namely n-C₁₇/pristane and n-C₁₈/phytane ratios were observed in culture fluids of pure strains, complete removal of all the HC components of kerosene, diesel and crude oil including the isoprenoids was obtained with the consortium within 14 days.     

Ethylene Production and Leaflet Abscission in Mèlia azédarach L

Ethylene production or content was compared to leaflet abscission in detached, compound leaves of Mèlia azédarach L. In late autumn, when abscission was progressing from basal leaves upward, the oldest leaves both produced ethylene at the highest rates and abscised their leaflets first. When C₂H₄ levels were measured in intercellular air removed immediately after leaves were harvested, C₂H₄ levels were also highest in basal leaves and declined progressively in more apical leaves. Levels as high as 1.8 microliters C₂H₄ liter⁻¹ air were observed. Earlier in the season groups of leaves demonstrated a pattern of sequential initiation of abscission from base to apex, but the peak rates of C₂H₄ production followed an opposite trend, being highest in the youngest leaves. Peak rates of C₂H₄ production occurred after the initiation of leaflet abscission and presumably are related to either the auxin content or a climacteric-like, autocatalytic phase of C₂H₄ production not directly involved in the initiation of abscission. In these experiments, the early abscission of the older leaflets reflects their greater sensitivity to C₂H₄, presumably due to lower auxin content. C₂H₄ production rates in all experiments, with rare exceptions, exceeded 3 microliters per kilogram fresh weight per hour at least 24 hours before leaflet abscission reached 10%. This achieving of a threshold internal C₂H₄ level is viewed as an initiating event in leaflet abscission. Hypobaric conditions, to facilitate the escape of endogenous C₂H₄, delayed abscission compared to controls, and termination of hypobaric exposure allowed a normal progression of abscission as well as normal C₂H₄ synthesis rates. All of the data indicate that C₂H₄ initiates leaflet abscission in intact but detached leaves of Mèlia azédarach L. The seasonal patterns observed suggest that C₂H₄, in concert with those hormones which govern sensitivity to C₂H₄, regulate autumn leaf fall in this species.     

The Effect of Source—Sink Manipulations on Nitrogen Fixation in Peas

The effect on nitrogen fixation of excising leaves or pods in pea (Pisum sativum L. cv. Alaska) was determined over a 60-day period. Flower buds or their subtending leaves were removed, and C₂H₂ reduction, H₂ evolution and N accumulation were measured at weekly intervals. Highest percentage nitrogen content in all treatments coincided with time of maximal C₂H₂-reduction rates. Nitrogen fixation, calculated from C₂H₂ reduction and H₂- evolution data, was significantly lower in the partially defoliated and generally higher in the depodded plants than in the controls. Total N accumulation was greatest in the depodded plants and least in the defoliated ones. Percentage nitrogen content and N₂-fixation rates in the depodded plants were maximized approximately 10 days later than in the defoliated or control plants. The absolute rates of C₂H₂ reduction and H₂ evolution were significantly altered by plant organ removal, but the relative rates were proportional. As a result the ratios of H₂/C₂H₄ production and the related relative efficiency of N₂ fixation in the treatments were not significantly different from the controls.     

Bioengineering of microorganisms for C₃ to C₅ alcohols production

Production of renewable fuels and chemicals is an absolute requirement for the sustainability of societies. This fact has been neglected during the past century as cheap and abundant, yet not renewable, sources of hydrocarbons were available. Since fossil fuel availability is decreasing, biological production of fuels and chemicals has been proposed to be a potential alternative to fossil sources. Higher alcohols (from C₃ to C₅) are useful substitutes for gasoline because of their high energy density and low hygroscopicity and are important feedstocks for other chemicals. Some Clostridia species are known to naturally ferment sugars to isopropanol and 1-butanol. However, other C₃ to C₅ alcohols are not produced in large quantities by natural microorganisms. A non-fermentative strategy to produce a broad range of higher alcohols has been devised using the ubiquitous keto acid biosynthetic pathways. This review provides a current overview of these different strategies.     

Studies on Polyoxins,Antifungal Antibiotics

Seven additional components, polyoxins C, D, E, F, G, H and I were isolated from polyoxin complex. They have molecular formulae corresponding to C₁₁H₁₅N₃O₈, C₁₇H₂₃N₅O₁₄, C₁₇H₂₃N₅O₁₃, C₂₃H₃₀N₆O₁₅, C₁₇H₂₅N₅O₁₂, C₂₃H₃₂N₆O₁₃ and C₁₉H₂₄N₄O₁₂, respectively. These polyoxins except inactive polyoxins C and I were highly active against various kinds of phytopathogenic fungi. The close structural similarity among them including polyoxins A and B is also discussed.     

Squalenes,phytanes and other isoprenoids as major neutral lipids of methanogenic and thermoacidophilic “archaebacteria”

Summary The neutral lipids of nine species of methanogenic bacteria including five methanobacilli, two methanococci, a methanospirillum, one methanosarcina as well as two thermoacidophilic bacteria, Thermoplasma and Sulfolobus, were analyzed. The major components were C₃₀, C₂₅ and/or C₂₀ acyclic isoprenoid hydrocarbons with a continuous range of hydroisoprenoid homologues. The range of acyclic isoprenoids detected were from C₁₄ to C₃₀. Apart fromMetbanosarcina barkeri, squalene and/or hydrosqualene derivatives were the predominant components in all species studied. The components ofMetbanosarcina barkeri were a family of C₂₅ homologues. The distribution of the neutral lipid components and their specItIc variations in relative intensities emphasized the differences between the test organisms while the generic nature of the isoprenoid hydrocarbons demonstrated similarities between the diverse bacteria.The neutral lipid compositions from these bacteria, many of which exist in evironmental conditions like those described for the various evolutionary stages of the archean ecology, resemble the isoprenoid distribution isolated from ancient sediments and petroleum. Therefore, these findings may have major implications to biological and biogeochemical evolution.     

Flooding-induced soil and plant ethylene accumulation and water status response of field-grown tobacco

Summary Ethylene (C₂H₄) accumulation in flooded soil was related to oxygen (O₂), redox potential (Eh), and flooding rate. The water status response of tobacco (Nicotiana, tabacum L.) to these conditions was evaluated from stem diameter, relative water content, leaf water potential, and C₂H₄ content of leaf tissue. Treatments were: flooded with either 0,5, or 15 cm of water per day for 6 days. By the third day, O₂ in the soil decreased to less than 9% in treatments flooded with 5 or 15 cm of water. When O₂ in the soil air was less than 9% and redox potential (Eh) was less than +150 mv, most of the soil air samples contained some C₂H₄ and 16% contained more than 6 ppm. Very little C₂H₄ was present in soil air when O₂ exceeded 9%. Tobacco leaf C₂H₄ peaked 3 days after flooding and then declined to the preflooding level a day later, one day ahead of the rapid increase in soil C₂H₄. Wilting developed progressively beginning with the rise of C₂H₄ in the soil; leaf water potential, stem diameter, and relative leaf water content all were decreased. Soil-and plant-produced C₂H₄ are suggested as factors in reducing root permeability and increasing resistance to water uptake by tobacco.Contribution of the USDA-SEA/AR, in cooperation with the South Carolina Experiment Station.     

Hydrocarbon composition of newly isolated strains of the green microalga Botryococcus braunii

Four new strains of Botryococcus braunii were isolated from Japanese waters and cultured under defined conditions. Their hydrocarbon content and composition were analyzed and compared with those of the Darwin and Berkeley strains. The Yamanaka strain produced only alkadienes characteristic of the A race, whereas the others, the Yayoi, Kawaguchi-1 and -2 strains as well as the Darwin and Berkeley strains, produced botryococcenes peculiar to the B race. The hydrocarbon content of the Yamanaka strain was 16.1 % dry weight and that of the B race strains ranged from 9.7 to 37.9%. Botryococcene composition of the Japanese strains differed from each other as well as from the Darwin and Berkeley strains. More than 50% of the hydrocarbons in the Yayoi, Darwin, and Berkeley strains were composed of C₃₄H₅₈, but the main components were different from one another as isomers. The Kawaguchi-1 and -2 strains did not have a high level of C₃₄ botryococcenes, C₃₂ ones being the main components. In these strains significant amounts of squalene-related compounds were detected.