Publications
Dive into our publications and explore the science from the Environmental Health Program (Toxic Substances Hydrology and Contaminant Biology).
Filter Total Items: 4094
A geochemical transport model for redox-controlled movement of mineral fronts in groundwater flow systems: A case of nitrate removal by oxidation of pyrite
A one-dimensional prototype geochemical transport model was developed in order to handle simultaneous precipitation-dissolution and oxidation-reduction reactions governed by chemical equilibria. Total aqueous component concentrations are the primary dependent variables, and a sequential iterative approach is used for the calculation. The model was verified by analytical and numerical comparisons a
Authors
Peter Engesgaard, Kenneth L. Kipp
Modeling biotic uptake by periphyton and transient hyporrheic storage of nitrate in a natural stream
To a convection-dispersion hydrologic transport model we coupled a transient storage submodel (Bencala, 1984) and a biotic uptake submodel based on Michaelis-Menten kinetics (Kim et al., 1990). Our purpose was threefold: (1) to simulate nitrate retention in response to change in load in a third-order stream, (2) to differentiate biotic versus hydrologie factors in nitrate retention, and (3) to pro
Authors
Brian K.A. Kim, Alan P. Jackman, Frank J. Triska
Inductively coupled plasma-mass spectrometry as an element-specific detector for field-flow fractionation particle separation
An inductively coupled plasma-mass spectrometer was used for the quantitative measurement of trace elements In specific,submicrometer size-fraction particulates, separated by sedimentation field-flow fractionation. Fractions were collected from the eluent of the field-flow fractionation centrifuge and nebulized, with a Babington-type pneumatic nebulizer, into an argon inductively coupled plasma-ma
Authors
Howard E. Taylor, John R. Garbarino, Deirdre M. Murphy, Ronald Beckett
Use of chlorofluorocarbons (CCl3F and CCl2F2) as hydrologic tracers and age‐dating tools: The alluvium and terrace system of central Oklahoma
The use of Chlorofluorocarbons (CFCs) as an age‐dating tool and tracer in shallow groundwaters has been investigated. New methodology for field sampling and preserving groundwaters containing parts per trillion concentrations of the CFCs, F‐1l and F‐12, is presented. Samples are analyzed by purge‐and‐trap gas chromatography with an electron capture detector. Physical and chemical processes that ca
Authors
Eurybiades Busenberg, Niel Plummer
Relation of nickel concentrations in tree rings to groundwater contamination
Increment cores were collected from trees growing at two sites where groundwater is contaminated by nickel. Proton-induced X ray emission spectroscopy was used to determine the nickel concentrations in selected individual rings and in parts of individual rings. Ring nickel concentrations were interpreted on the basis of recent concentrations of nickel in aquifers, historical information about site
Authors
Thomas M. Yanosky, Don A. Vroblesky
Large-scale natural gradient tracer test in sand and gravel, Cape Cod, Massachusetts: 3. Hydraulic conductivity variability and calculated macrodispersivities
Hydraulic conductivity (K) variability in a sand and gravel aquifer on Cape Cod, Massachusetts, was measured and subsequently used in stochastic transport theories to estimate macrodispersivities. Nearly 1500 K measurements were obtained by borehole flowmeter tests and permeameter analyses of cores. The geometric mean for the flowmeter tests (0.11 cm/s) is similar to that estimated from other fiel
Authors
Kathryn M. Hess, Steven H. Wolf, Michael A. Celia
Discussion of "The modeling process and model validation" by Chin-Fu Tsang
No abstract available.
Authors
Leonard F. Konikow
Solute transport with multiple equilibrium-controlled or kinetically controlled chemical reactions
A new approach is applied to the problem of modeling solute transport accompanied by many chemical reactions. The approach, based on concepts of the concentration space and its stoichiometric subspaces, uses elements of the subspaces as primary dependent variables. It is shown that the resulting model equations are compact in form, isolate the chemical reaction expressions from flow expressions, a
Authors
John C. Friedly, Jacob Rubin
Associations between benthic flora and diel changes in dissolved arsenic, phosphorus, and related physico-chemical parameters
Diel relationships between physical and chemical parameters and biomass were examined along a 57-km reach of Whitewood Creek, South Dakota, between 29 August and 2 September 1988. A time lag of ∼3-6 h for fluctuations in soluble reactive phosphorus (SRP) concentrations (ranging from 0.1 to 0.5 μM at the downstream sites) relative to dissolved arsenic (ranging from 0.3 to 1.2 μM as arsenate (pentav
Authors
James S. Kuwabara
Reply to Dr. Stoesselfs comment on “Reaction paths and equilibrium end-points in solid-solution aqueous-solution systems”
In reply to the Critical Comment of R. K. Stoessell (this issue), limiting activity coefficients of bromide in halite (γNaBr) have been calculated by least-squares fitting of Simons et al.'s (1952) bromide distribution coefficient data for the Na(Cl,Br)-NaOH-H2O system at 35°C. Regular and subregular solidsolution model fits give γNaBr = 7.4 and γNaBr = 8.8, respectively. The Br contents of halite
Authors
Pierre D. Glynn, Eric J. Reardon, Niel Plummer, Eurybiades Busenberg
Fate of alkylbenzenesulfonates and dialkyltetralinsulfonates in sewage contaminated ground water
No abstract available.
Authors
Jennifer A. Field, Larry B. Barber, E. Michael Thurman, Billy L. Moore, David L. Lawrence, David A. Peake
Solute transport with multisegment, equilibrium-controlled, classical reactions: Problem solvability and feed forward method's applicability for complex segments of at most binary participants
The feed forward (FF) method derives efficient operational equations for simulating transport of reacting solutes. It has been shown to be applicable in the presence of networks with any number of homogeneous and/or heterogeneous, classical reaction segments that consist of three, at most binary participants. Using a sequential (network type after network type) exploration approach and, independen
Authors
Jacob Rubin