At Site-300, Lawrence Livermore National Laboratory (LLNL), CA,
trichloroethene (TCE) is present along with tetraalkoxysilanes such as tetrabutoxysilane
(TBOS) and tetrakis(2-ethylbutoxy) silane (TKEBS), as subsurface contaminants.
Intrinsic transformation of TCE to cis-dichloroethene (c-DCE) was observed in the
groundwater at locations co-contaminated with TBOS or TKEBS. Attenuation of TBOS
and TKEBS...
The inhibitory effects of Corexit 9500A, Alaska North Slope Crude oil (ANSC), and mixtures of the two on the ammonia-oxidizing bacteria, Nitrosomonas europaea, and the ammonia-oxidizing archaea, Nitrosopumilus maritimus, were investigated. Corexit 9500A was found to be minimally toxic to both microorganisms with concentrations of 2000 and 3000 ppm yielding...
Chlorinated solvents are common groundwater pollutants that often exist as mixtures resulting from the use of multiple solvents and their transformation into chlorinated daughter products. These sites are often co-contaminated with the solvent stabilizer 1,4-dioxane (1,4-D), which is not treated by traditional chlorinated solvent remediation techniques. Both 1,4-D and chlorinated...
The cometabolic ability of Burkholderia vietnamiensis G4 grown on aromatic substrates was first assessed by resting suspended cells, and subsequently for cells encapsulated with and without slow release compounds (SRCs). In Chapter 3, benzyl alcohol was assessed as a food-grade growth substrate for promoting cometabolism of trichloroethene (TCE), via the...
The rising demand on freshwater resources emphasizes the benefit of biogeochemical processes that maintain clean water by removing pollutants such as excess nitrogen. The most sensitive step in the removal of nitrogen from waterways is the oxidation of ammonia, a part of nitrification, which is carried out by ammonia oxidizing...
This study investigated the use of radon-222 as an in situ partitioning tracer for quantifying nonaqueous phase liquid (NAPL) saturations in the subsurface. Laboratory physical aquifer models (PAMs), field experiments, and numerical simulations were used to investigate radon partitioning in static (no-flow) experiments and in single-well, 'push-pull' tests conducted in...
Aromatic hydrocarbons represent a large class of environmental contaminants that have a broad range of structures, physicochemical properties, and toxicities. Arising from the burning of organic matter, particularly fossil fuels, they are both widespread and abundant in all environmental compartments. Both monoaromatic hydrocarbons (BTEX) and polycyclic aromatic hydrocarbons (PAHs) are...
1,4-dioxane, a probable human carcinogen at low (< 1ppb) concentrations, has emerged as a groundwater contaminant due to its historical use as a stabilizer for the chlorinated solvent 1,1,1-trichloroethane. Aerobic cometabolism, the use of a primary substrate to induce the production of microbial enzymes that fortuitously degrade other compounds, is...
This study investigated complete reductive dechlorination of chlorinated aliphatic hydrocarbons (CAHs) over a broad range of concentrations. Tetrabutoxysilane (TBOS), as a slow-release anaerobic substrate, was studied for enhanced reductive dechlorination of tetrachioroethylene (PCE) present as a dense non-aqueous liquid (DNAPL). Four different site-mixed cultures were used in the study: Site-300...
Laboratory and modeling studies were performed with a mixed-anaerobic-culture obtained from the Evanite site in Corvallis, Oregon. The culture completely transforms trichloroethene (TCE) to cis-dichloroethene (c-DCE), vinyl chloride (VC), and finally to ethene. Acetylene inhibition studies were used to examine the culture's microbial activities. Kinetic studies determined the half-saturated constant...