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At least 721 records · Page 40Linked to original sources
PubMed2001

Microcosm studies of microbial degradation in a coal tar distillate plume.

Investigation of a groundwater plume containing up to 24 g l(-1) phenolic compounds suggested that over a period of nearly 50 years, little degradation had occurred despite the presence of a microbial community and electron acceptors within the core of the plume. In order to study the effect of contaminant concentration on degradation behaviour, laboratory microcosm experiments were performed under aerobic and anaerobic conditions at four different concentrations obtained by diluting contaminated with uncontaminated groundwater. The microcosms contained groundwater with total phenols at ca. 200, 250, 660 and 5000 mg l(-1), and aquifer sediment that had been acclimatised within the plume for several months. The microcosms were operated for a period of 390-400 days along with sterile controls to ascertain whether degradation was microbially mediated or abiotic. Under aerobic conditions, degradation only occurred at concentrations up to 660 mg l(-1) total phenols. At phenol concentrations below 250 mg l(-1) a benzoquinone intermediate, thought to originate from the degradation of 2,5-dimethylphenol, was isolated and identified. This suggested an unusual degradative pathway for this compound; its aerobic degradation more commonly proceeding via catecholic intermediates. Under anaerobic conditions, degradation only occurred in the most dilute microcosm (total phenols 195 mg l(-1)) with a loss of p-cresol accompanied by a nonstoichiometric decrease in nitrate and sulphate. By inference, iron(III) from the sediment may also have been used as a terminal electron acceptor, in which case the amount of biologically available iron released was calculated as 1.07 mg Fe(III)/g of sediment. The study shows that natural attenuation is likely to be stimulated by dilution of the plume.

Aerobiosis↗
PubMed1990

Toxicology of selected pesticides, drugs, and chemicals. Petroleum distillates and turpentine.

Companion animal exposures to volatile hydrocarbons and turpentine accounted for 2% of all calls received by the IAPIC in 1987. Volatile hydrocarbons are also used as vehicle solvents (e.g., pesticides), and both vehicle and active ingredients pose a significant hazard to companion animals. The most significant clinical effects of the hydrocarbons are related to aspiration pneumonia. The likelihood of aspiration is generally related to the compound's viscosity, with more volatile and most widely available compounds posing the greatest risk. Treatment generally is conservative. Gastrointestinal decontamination methods (e.g., emetics and activated charcoal administration) are used only in massive ingestions or when other toxicants are present in conjunction with the hydrocarbons. Oxygen therapy and cage rest are recommended for the dyspneic animal. Close monitoring of an exposed animal and symptomatic care as needed are also recommended for at least 12 hours after exposure.

Animals↗
PubMed2000

Biodesulfurization and the upgrading of petroleum distillates.

Biotechnology offers an alternative way to process fossil fuels. There have been several important advances in the elucidation of the mechanisms of biodesulfurization and the development of a biocatalytic desulfurization process. These include a detailed analysis of the rate and extent of desulfurization of real target molecules in a diesel matrix, the directed evolution of rate- and extent-limiting enzymes for better performance and the expression of the genes in alternative hosts. Process innovations include new reactor designs, separations and recovery strategies and the production of value-added byproducts during desulfurization.

Bacteria↗
PubMed2003

Identification of odor-active 3-mercapto-3-methylbutyl acetate in volatile fraction of roasted coffee brew isolated by steam distillation under reduced pressure.

In a roasted Arabica coffee brew, the potent roasty odor quality compound was identified as 3-mercapto-3-methylbutyl acetate by comparison of its Kovats gas chromatography retention index, mass spectrum, and odor quality to those of the synthetic authentic compound. 3-Mercapto-3-methylbutyl acetate has been identified for the first time in the coffee, and according to the results of the aroma extract dilution analysis, the contribution of this compound to the flavor of the roasted coffee brew varied depending on the degree of the coffee bean roasting. The concentration of this compound in the coffee brews as with 3-mercapto-3-methylbutyl formate increased with an increase in the degree of roasting. However, the slope of the amount of both esters was different, and 3-mercapto-3-methylbutyl acetate hardly increased with a low degree of roasting at more than a 21 luminosity (L)-value, but it rapidly increased when the roasting degree of the coffee beans reached the L-value of 18. These results suggested that the contribution of 3-mercapto-3-methylbutyl acetate to the overall flavor is peculiar to the flavor of the highly roasted coffee.

Acetates↗