Search

Methyl tert-butyl ether(MTBE) is a gasoline additive used for octane enhancement in the United States, which results in lower emissions of ozone and carbon monoxide precursor compounds, and it thought to have potentially dangerous health risks associated with it. Research of the amount of MTBE transported by groundwater flow shows that MTBE can quickly mineralize to carbon dioxide under artificial and natural oxic conditions.

The microorganisms collected from 11 stream and lake bed sediments in the United States. showed significant mineralization of methyl-tert-butyl ether (MTBE), indicating that aerobic bed sediment microbial processes may provide an environmental sink for MTBE in surface water systems and may help in the transience of MTBE in some surface waters.

This study examines the relationship of methanogens to the degradation of vinyl chloride.

Intrinsic bioremediation appears to be an effective method in decontaminating highly-polluted aquifer systems. Results revealed that bed-sediment microorganisms indigenous to a creek have rapidly mineralized vinyl chloride (VC) and dichloroethene (DCE) under aerobic conditions. The rates of DCE and VC mineralization, however, depends on contaminant concentration.

Quantitative analysis of oxidation-reduction potentials (Eh) and levels of dissolved H2 was conducted in jet fuel-contaminated aquifers of Wurtsmith Air Force Base, MI. The Eh potentials of the contaminated aquifers were indicated by the presence of high H2 levels which is located in the center of the plume. The groundwater samples also exhibited high levels of oxygen, sulfate, methane and Fe(II) which act as potential electron acceptors for redox reactions.

Abundant electron donor availability enabled methanogenc bacteria (MB) to sequester a portion of the electron flow in a petroleum hydrocarbon-dominated aquifer, even in the presence of sufficient concentrations of sulfate to enable sulfate reduction. Limited electron donor availability, on the other hand, allowed sulfate-reducing bacteria (SRB) to outcompete MB for available substrate at a lower concentration of sulfate than when electron donor was abundant. Thus, fluctuations in electron donor availability influenced the competition between SRB and MB for control of electron flow.

Stable carbon isotopes in dissolved inorganic carbon (DIC) provide evidence of the zonation of 13C-depleted hydrocarbon biodegradation processes under the influence of hydrologically controlled electron-acceptor availability. A four-year study of biodegradation zonation in a sandy, noncarbonate shallow aquifer contaminated with jet-fuel petroleum hydrocarbons showed a range from -28 to +11.9% in (delta)13C values in DIC.

A study was conducted to determine whether the rates of microbial hydrocarbon degradation in low-temperature groundwater systems are more depressed than degradation in more temperate aquifers. Microbial metabolism in sediments from two different aquifers in Adak, AK, showed low rates for aquifers in temerate systems, suggesting that the assumption is incorrect.

The effect of the environment on microbial mineralization of trinitrotoluene (TNT) in contaminated soil is investigated. The results showed that the addition of cellobiose and syringate had an inhibiting effect on the mineralization process. Microorganisms were capable of metabolizing TNT but they preferred other substances when possible. There were indications that aerobic and anaerobic conditions can enhance TNT degradation.

Reduction-oxidation reactions in anoxic groundwaters was investigated using concentrations of dissolved H2. The latter was used to determine if Fe(III) reduction, sulfate reduction or methanogenesis was the terminal electron accepting process in both pristine and contaminated aquifers. Although the study could not obtain the predominating terminal electron accepting processes in contaminated aquifers, it revealed a similarity between the H2 concentrations of the two aquifers and those measured in aquatic sediments.

Atrazine mineralization potential under aerobic conditions in alluvial-aquifer sediments is dependent on the structure of the atrazine compound, according to a recent study conducted in an Ohio flood plain. Less than .1% of an atrazine compound with a ring structure was mineralized in 23 days. In contrast, ethyl-2-carbon atrazine mineralization, under aerobic conditions, was observed in shallow sediments and was sometimes detectable in deep sediments. Thus, atrazine compounds, which are often used in herbicides, may pass through to the water table if the structures are ringed.

Researchers from the U.S. Geological Survey demonstrated that oxidative acetogenesis, followed by oxidative acetogenesis may be effective in the microbial anaerobic degradation of vinyl chloride to CH4.

Vinyl chloride is a highly toxic and carcinogenic compound most often found in aquifer systems. Biodegradation of vinyl chloride by indigenous microorganisms has been proposed for contaminated, anaerobic aquifer systems. The approach requires iron(III)-reducing conditions to promote anaerobic oxidation of the compound. This process of rapid microbial degradation is also known as anaerobic mineralization.

Provides evidence that methane can be a significant product of chloroethene biodegradation under methanogenic conditions. Radiometric detection headspace analyses of microcosms containing bed sediments; Implications for the use of natural attenuation as a component of contaminant remediation.

Presents a study on the kinetics of DCE and VC mineralization under methanogenic and Fe (lll)-reducing conditions as a function of dissolved contaminants. Examination of microorganisms indigenous to creek bed sediments; Information on the recovery rate of radioactivity; Discussion on the results of the study.

Examines the use of 1,2-dichloroethene (1,2-DCE) as sole carbon substrate for aerobic metabolism of microorganisms. Toxic effects of DCE isomers under anaerobic conditions; Process of DCE mineralization under aerobic conditions; Maintenance of aerobic microbial mineralization of 1,2-DCE in three sequential transfer.

Responds to Jan Dolfing's comment on the authors' article `Methane as a product of chloroethene biodegration under methanogenic conditions.' Benefits derived from the microbial reduction of chloroethenes to the responsible microorganisms; CH4 as a significant product of chloroethene biodegration under methanogenic conditions.