Showing papers in "Journal of Contaminant Hydrology in 2006"

TL;DR: The general applicability of random walk particle tracking in comparison to the standard transport models is discussed and it is concluded that in advection-dominated problems using a high spatial discretization or requiring the performance of many model runs, RWPT represents a good alternative for modelling contaminant transport.

TL;DR: Simulations that included straining, liberation, attachment, and detachment significantly improved the description of the experimental data and could not account for the observed concentration dependent mass recovery.

TL;DR: Results show that mobility and elimination of diclofenac, ibuprofen, and propyphenazone is about in the same range as for experiments under saturated conditions whereas carbamazepine had a significantly lower sorption and elimination under unsaturated conditions.

TL;DR: The relationship between dense non-aqueous phase liquid (DNAPL) mass reduction and contaminant mass flux was investigated experimentally in four model source zones to investigate the relationship between flux and the up-gradient NAPL architecture.

TL;DR: The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process and permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone.

TL;DR: Results of simulations conducted with the model show that the largest porosity reductions occur between the entrance and mid-plane of the PRB as a result of precipitation of carbonate minerals and that smaller porosity reduction occurs between the mid-planes and exit face due to precipitation of ferrous hydroxide.

TL;DR: The hydraulic, physical, and chemical nonequilibrium processes governing herbicide transport under variably saturated flow conditions were studied andverse parameter estimation suggested that two-site kinetic sorption in inter-aggregate flow paths was reduced as compared to within aggregates.

TL;DR: A semi-analytical inverse method and the corresponding program FADEMain for parameter estimation of the fractional advection-dispersion equation (FADE) were developed and found to be adequate for predicting scale-dependent transport in the homogeneous column, while the prediction for the heterogeneous column was less satisfactory.

TL;DR: Groundwater and contaminant fluxes were measured, using the passive flux meter (PFM) technique, in wells along a longitudinal transect passing approximately through the centerline of a trichloroethylene (TCE) plume at a former manufacturing plant located in the Midwestern US.

TL;DR: The results illustrate the importance of fringe degradation processes in contaminant plumes and highlight the relevance of using high-resolution sampling techniques as well as controlled microcosm experiments in the assessment of the natural attenuation capacity of contaminants plumes in groundwater.

TL;DR: A mathematic model is proposed, which captures all aspects of the release process quantitatively, and can be used to describe the coupling between transport of major cations and the release of colloidal particles.

TL;DR: The results imply that, in the presence of dissolved organic matter (DOM), viruses can be transported for long distances thanks to two effects: attachment is poor because DOM has occupied favourable sites for attachment and inactivation of virus may have decreased.

TL;DR: It was determined that the best estimate of the average groundwater velocity could only be obtained using the largest apertures in the aperture distribution, at the scale of the measurement area used for the cubic law calculations.

TL;DR: It is demonstrated that modified Fenton's reagent can rapidly and effectively destroy DNAPLs of contaminants characterized by minimal reactivity with hydroxyl radical, and should receive more consideration as aDNAPL cleanup technology.

TL;DR: Because extensive accumulations of secondary oxyhydroxides of ferric iron are already present, remediation strategies for the ETMA should focus on mitigating the release of sulfide oxidation products rather than on preventing further oxidation.

TL;DR: The combination of CRLS with the global optimization solver achieved better performance than the combination of a non-robust estimator, i.e., the nonnegative least squares (NNLS) method, with the same solver.

TL;DR: The feasibility of surfactant-enhanced remediation to reduce the mass in the source zone and significantly reduce the PCE aqueous concentration and therefore the risk associated with the contaminant plume is demonstrated.

TL;DR: This study presents the set-up of a LCA framework in order to compare the secondary impacts caused by two conceptually different technologies at the site of a former manufactured gas plant in the city of Karlsruhe, Germany.

TL;DR: A 250 ha agricultural catchment has been characterized with respect to its hydrogeology and groundwater contamination by pesticides from October 1999 to August 2004, which indicates a long time transfer in the unsaturated or saturated zone with a progressive leaching of the stock of At and DEA probably accumulated in the soil and the vadose zone.

TL;DR: Reactive transport modeling of a permeable reactive barrier for the treatment of mine drainage was used to integrate a comprehensive data set including pore water chemistry and solid phase data from several sampling events over a >3-year time period, and generally confirm, and further strengthen, the existing conceptual model for the site.

TL;DR: This paper evaluates the accuracy of the operator-splitting approach for multicomponent systems for typical soil environmental problems involving transient atmospheric boundary conditions (precipitation, evapotranspiration, and layered soil profiles) and the recently developed HP1 code was used to solve the coupled transport and chemical equations.

TL;DR: For many readily biodegradable compounds transverse-dispersive mixing rather than reaction kinetics is the limiting factor for natural attenuation, and if alphat, aquifer and source geometry and concentrations of electron acceptors and donors are known, the length of the steady state contaminant plume can be predicted.

TL;DR: It is shown that estimation errors can be reduced only if spatial sampling intervals are in due proportion to spatial correlation length scales, and the role of the interplay between the spatial resolution of the sampling grid and aquifer heterogeneity with respect to the accuracy of the mass discharge estimation is investigated.

TL;DR: The findings suggest that the uncertainty associated with the prediction of the location of the outer boundary of well catchment at the "Lauswiesen" site is significantly affected by the conceptual model adopted to incorporate the heterogeneous nature of the aquifer domain in a predictive framework.

TL;DR: There remains a need to redefine bioavailability indices in order that bioavailability concepts can be better incorporated into site characterization, remediation design, and regulatory oversight.

TL;DR: Among the degradation products, TBA was found to be a useful intermediate to identify MTBE degradation, at least under microaerobic conditions, and significantly accumulated as an intermediate by-product.

TL;DR: All field models suggested a significantly higher degradation rate for benzene than the rates measured in the lab, suggesting that the field microbial community was superior in developing benzene degrading activity.

TL;DR: Modelling the field tracer experiments performed in the variably saturated chalk shows the adequacy and usefulness of the new conceptual, mathematical and numerical model.

TL;DR: A generic image analysis package is developed that automatically segments regions in photographic images that require unique concentration calibration curves due to varying porous media properties or lighting nonuniformities and verifies the closeness of the experimental, image-processed longitudinal dispersivity to that obtained from the field statistics.

TL;DR: Despite the discrepancies between the field observations and simulated results, integrating field observations with numerical modelling of the P-area tailings impoundment allowed for a more complete understanding of what affects the complex geochemical reactions.