A model for simulating microbial growth‐degradation processes in porous media is developed. It assumed that the bulk of microorganisms an aquifer grow microcolonies attached to matrix surfaces. As developed, applies growth and decay aerobic, heterotrophic whose limited by lack a carbon energy source (substrate), oxygen or both simultaneously as described modified Monod kinetics. Transport substrate medium be governed advection‐dispersion equations with surface adsorption. total five coupled...

A model to simulate organic carbon biodegradation by facultative bacteria in saturated porous media using oxygen‐ and/or nitrate‐based respiration is developed. Basic assumptions incorporated into the concept include a simulated particle‐bound microbial population comprised of heterotrophic, which metabolism controlled lack either an carbon‐electron donor source (substrate), electron acceptor (O 2 NO 3 − ), or mineral nutrient (NH 4 + all three simultaneously. system nine coupled nonlinear...

[1] The hyporheic zone is often defined as where mixing of surface water and groundwater occurs in shallow sediments beneath adjacent to rivers. This credited with creating unique biogeochemical conditions that can attenuate contaminants from either upstream or under gaining conditions. However, reactions upwelling may be more dependent on such than water. We numerically modeled between flow paths induced by riverbed dunes deeper groundwater. Results show only 12.7% less tracer mass...

In situ stimulation of denitrification has been proposed as a mechanism to remediate groundwater nitrate contamination. this study, sodium formate was added sand and gravel aquifer on Cape Cod, MA, test whether could serve potential electron donor for subsurface denitrification. During 16- 10-day trials, from an anoxic nitrate-containing zone (0.5−1.5 mM) continuously withdrawn, amended with bromide, pumped back into the aquifer. Concentrations constituents were monitored in multilevel...

Current understanding of transport processes in aquifers is limited by lack precise point chemical concentration measurements. Recently, however, some careful measurements vertical profiles have been made at several locations around the world that appear to support a consistent picture concerning persistence large gradients and, implication, existence very small transverse dispersivities. These data were obtained supporting microbial activity. Data analysis using mathematical model which...

Abstract The hyporheic zone is known to attenuate contaminants originating from surface water, yet the ability of in upwelling groundwater plumes as they exit water less understood. We used MODFLOW and SEAM3D simulate flow cells induced by riverbed dunes together with mixing‐dependent denitrification an nitrate ( ) plume. Our base case modeled labile dissolved organic carbon (DOC) oxygen (DO) advecting DO groundwater, typical certain agricultural areas. conducted sensitivity analyses that...

A seven-year study was conducted to assess the effectiveness of hybrid poplar trees remediate polycyclic aromatic hydrocarbon (PAH) compounds in soil and groundwater at a creosote-contaminated site. reduction areal extent PAH plume observed upper half 2-m-thick saturated zone, concentration levels declined throughout plume. concentrations began decline during period between third fourth growing seasons, which coincided with propagation tree roots water table region. Remediation limited...

This paper describes and demonstrates a numerical model for subsurface solute transport with aerobic sequential anaerobic biodegradation. The can depict multiple constituents in three-dimensional (3D), anisotropic, heterogeneous domain. Hydrocarbon contaminants are simulated as electron donors microbial growth, available acceptors (EAs) may be utilized simultaneously or the following sequence: O2, NO3-, Mn(IV), Fe(III), SO42-, CO2. account Mn(II), Fe(II), H2S, CH4, user-defined nitrogenous...

A field study was initiated in 1997 to assess the ability of tall fescue grass remediate an aged creosote-contaminated surface soil. Field monitoring combined with aerobic microcosm experiments, microbial enumerations, and plant tissue analysis determine impact on degradation six polycyclic aromatic hydrocarbons (PAHs), acenaphthene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, elucidate mechanisms remediation. Fescue had a beneficial all PAHs except phenanthrene. Mean...

Abstract Multilevel slug tests were conducted in a confined, granular aquifer near Mobile, Alabama. Tracer injection and travel time experiments, more direct measurements of transport the aquifer, also at same location. The objective was to compare results two field investigations ascertain accuracy utility testing measure properties aquifer. Nondimensional hydraulic conductivity profiles inferred from tracer experiments similar. similarity supported multilevel characterize profile test data...

Abstract The multilevel slug test is a technique that provides data for determining the local value of hydraulic conductivity at specific elevation. However, existing analysis techniques developed fully screened and/or partially tests (Cooper et al., 1967; and Bouwer Rice, 1976) packer (Dagan, 1978) are not adequate application to general case. Through numerical flow model problem, new means analyze developed. Simulations performed both confined unconfined cases using finite‐element yield...

A two-dimensional numerical solute transport model was developed for simulating an enhanced in situ denitrification experiment performed a nitrate-contaminated aquifer on Cape Cod, Massachusetts. In this experiment, formate (HCOO-) injected period of 26 days into the carbon-limited to stimulate denitrification. Calibration vertical-profile site demonstrated through error analysis and comparison with formate, nitrate, nitrite concentration data monitored along transect three multilevel...

Phytoremediation systems are known to reduce groundwater contamination by at least three major mechanisms: plant uptake, phytovolatilization, and enhanced rhizosphere bioremediation. The potential for such enhance a fourth remediation pathway--direct surface volatilization of contaminants through the subsurface into atmosphere-has not yet been investigated in field. A vertical flux chamber was used measure direct naphthalene over nine months creosote-contaminated site Oneida, Tennessee,...

Mass transfer rate coefficients were quantified by employing an inverse modeling technique to high-resolution aqueous phase concentration data observed following experimental release of a multicomponent nonaqueous liquid (NAPL) at field site. A solute transport model (SEAM3D) was employed simulate advective-dispersive over time coupled NAPL dissolution. Model calibration demonstrated accurately reproducing the breakthrough times and peak concentrations multiple observation points, mass...

Abstract A three‐dimensional solute transport model with biological reactions is presented for simulating the natural attenuation study (NATS) at Columbus Air Force Base in eastern Mississippi. NATS consisted of release a petroleum‐based nonaqueous phase liquid (NAPL) and subsequent monitoring BTEX (benzene, toluene, ethylbenzene, p‐xylene), naphthalene, decane, bromide shallow, unconfined aquifer. Conceptual mathematical models were developed NAPL source release, sequential...

Abstract Because remediation timeframes using monitored natural attenuation may span decades or even centuries at chlorinated solvent sites, new approaches are needed to assess the long‐term sustainability of reductive dechlorination in ground water systems. In this study, extraction procedures were used investigate mass indigenous organic carbon aquifer sediment, and experiments conducted determine if extracted could support chloroethenes. Aquifer sediment cores collected from a site...

The combined remediation mechanisms of volatilization and biodegradation in the vadose zone were investigated for naphthalene at a creosote-contaminated site where poplar tree-based phytoremediation system has been installed. Concurrent field laboratory experiments conducted to study transport zone. Soil gas sampling showed that more than 90% vapors biodegraded aerobically within 5–10 cm above water table during summer months. Peak soil concentrations observed late summer, corresponding with...