Douglas Kent
Dr. Douglas Kent is a scientist emeritus with the Earth System Processes Division of the Water Mission Area, U. S. Geological Survey.
Doug Kent received an AA from Pasadena City College, a BA in chemistry from the University of California, San Diego and a PhD from Scripps Institution of Oceanography. He has conducted hydrologic research at the USGS since 1985.
Doug Kent's research at the USGS has focused on processes influencing the mobility of constituents that can affect the availability of water for beneficial use by humans and for sustaining aquatic ecosystems.
Science and Products
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Quantifying differences in the impact of variable chemistry on equilibrium uranium(VI) adsorption properties of aquifer sediments Quantifying differences in the impact of variable chemistry on equilibrium uranium(VI) adsorption properties of aquifer sediments
Uranium adsorption-desorption on sediment samples collected from the Hanford 300-Area, Richland, WA varied extensively over a range of field-relevant chemical conditions, complicating assessment of possible differences in equilibrium adsorption properties. Adsorption equilibrium was achieved in 500-1000 h although dissolved uranium concentrations increased over thousands of hours owing...
Authors
Deborah L. Stoliker, Douglas B. Kent, John M. Zachara
Transient groundwater chemistry near a river: Effects on U(VI) transport in laboratory column experiments Transient groundwater chemistry near a river: Effects on U(VI) transport in laboratory column experiments
In the 300 Area of a U(VI)-contaminated aquifer at Hanford, Washington, USA, inorganic carbon and major cations, which have large impacts on U(VI) transport, change on an hourly and seasonal basis near the Columbia River. Batch and column experiments were conducted to investigate the factors controlling U(VI) adsorption/desorption by changing chemical conditions over time. Low alkalinity...
Authors
Jun Yin, Roy Haggerty, Deborah L. Stoliker, Douglas B. Kent, Jonathan D. Istok, Janek Greskowiak, John M. Zachara
Redox transformations and transport of cesium and iodine (-1, 0, +5) in oxidizing and reducing zones of a sand and gravel aquifer Redox transformations and transport of cesium and iodine (-1, 0, +5) in oxidizing and reducing zones of a sand and gravel aquifer
Tracer tests were performed in distinct biogeochemical zones of a sand and gravel aquifer in Cape Cod, MA, to study the redox chemistry (I) and transport (Cs, I) of cesium and iodine in a field setting. Injection of iodide (I -) into an oxic zone of the aquifer resulted in oxidation of I - to molecular iodine (I2) and iodate (IO3-) over transport distances of several meters. Oxidation is
Authors
Patricia M. Fox, Douglas B. Kent, James A. Davis
Influence of variable chemical conditions on EDTA-enhanced transport of metal ions in mildly acidic groundwater Influence of variable chemical conditions on EDTA-enhanced transport of metal ions in mildly acidic groundwater
Adsorption of Ni and Pb on aquifer sediments from Cape Cod, Massachusetts, USA increased with increasing pH and metal-ion concentration. Adsorption could be described quantitatively using a semi-mechanistic surface complexation model (SCM), in which adsorption is described using chemical reactions between metal ions and adsorption sites. Equilibrium reactive transport simulations...
Authors
D.B. Kent, J.A. Davis, J.L. Joye, G.P. Curtis
Modeling the movement of a pH perturbation and its impact on adsorbed zinc and phosphate in a wastewater‐contaminated aquifer Modeling the movement of a pH perturbation and its impact on adsorbed zinc and phosphate in a wastewater‐contaminated aquifer
[1] Chemical conditions were perturbed in an aquifer with an ambient pH of 5.9 and wastewater-derived adsorbed zinc (Zn) and phosphate (P) contamination by injecting a pulse of amended groundwater. The injected groundwater had low concentrations of dissolved Zn and P, a pH value of 4.5 resulting from equilibration with carbon dioxide gas, and added potassium bromide (KBr). Downgradient...
Authors
Douglas B. Kent, J.A. Wilkie, J.A. Davis
Ground-water-quality data for a treated-wastewater plume undergoing natural restoration, Ashumet Valley, Cape Cod, Massachusetts Ground-water-quality data for a treated-wastewater plume undergoing natural restoration, Ashumet Valley, Cape Cod, Massachusetts
A plume of contaminated ground water extends from former disposal beds at the Massachusetts Military Reservation wastewater-treatment plant toward Ashumet Pond, and farther southward toward coastal ponds and Vineyard Sound, Cape Cod, Massachusetts. Treated sewage-derived wastewater was discharged to the rapid-infiltration beds for nearly 60 years before the disposal site was moved to a...
Authors
Jennifer G. Savoie, Richard L. Smith, Douglas B. Kent, Kathryn M. Hess, Denis R. LeBlanc, Larry B. Barber
Long-term natural attenuation of carbon and nitrogen within a groundwater plume after removal of the treated wastewater source Long-term natural attenuation of carbon and nitrogen within a groundwater plume after removal of the treated wastewater source
Disposal of treated wastewater for more than 60 years onto infiltration beds on Cape Cod, Massachusetts produced a groundwater contaminant plume greater than 6 km long in a surficial sand and gravel aquifer. In December 1995 the wastewater disposal ceased. A long-term, continuous study was conducted to characterize the post-cessation attenuation of the plume from the source to 0.6 km...
Authors
D.A. Repert, L. B. Barber, K.M. Hess, S.H. Keefe, D.B. Kent, D.R. LeBlanc, R. L. Smith
Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations
To study transport and reactions of arsenic under field conditions, a small-scale tracer test was performed in an anoxic, iron-reducing zone of a sandy aquifer at the USGS research site on Cape Cod, Massachusetts, USA. For four weeks, a stream of groundwater with added As(V) (6.7 μM) and bromide (1.6 mM), was injected in order to observe the reduction of As(V) to As(III). Breakthrough of...
Authors
R. Hohn, M. Isenbeck-Schroter, D.B. Kent, J.A. Davis, R. Jakobsen, S. Jann, V. Niedan, C. Scholz, S. Stadler, A. Tretner
Kinetics of sorption and abiotic oxidation of arsenic(III) by aquifer materials Kinetics of sorption and abiotic oxidation of arsenic(III) by aquifer materials
The fate of arsenic in groundwater depends largely on its interaction with mineral surfaces. We investigated the kinetics of As(III) oxidation by aquifer materials collected from the USGS research site at Cape Cod, MA, USA, by conducting laboratory experiments. Five different solid samples with similar specific surface areas (0.6–0.9 m2 g−1) and reductively extractable iron contents (18...
Authors
A. Amirbahman, D.B. Kent, G.P. Curtis, J.A. Davis
Changes in ground-water quality near two granular-iron permeable reactive barriers in a sand and gravel aquifer, Cape Cod, Massachusetts, 1997-2000 Changes in ground-water quality near two granular-iron permeable reactive barriers in a sand and gravel aquifer, Cape Cod, Massachusetts, 1997-2000
Two experimental permeable reactive barriers (PRBs) of granular zero-valent iron were emplaced in the path of a tetrachloroethene plume (the Chemical Spill-10 plume) at the Massachusetts Military Reservation, Cape Cod, Massachusetts, in June 1998. The goal of the field experiment was to achieve emplacement of a granular-iron PRB deeper than attempted before. The PRBs were expected to...
Authors
Jennifer G. Savoie, Douglas B. Kent, Richard L. Smith, Denis R. LeBlanc, David W. Hubble
The influence of groundwater chemistry on arsenic concentrations and speciation in a quartz sand and gravel aquifer The influence of groundwater chemistry on arsenic concentrations and speciation in a quartz sand and gravel aquifer
We examined the chemical reactions influencing dissolved concentrations, speciation, and transport of naturally occurring arsenic (As) in a shallow, sand and gravel aquifer with distinct geochemical zones resulting from land disposal of dilute sewage effluent. The principal geochemical zones were: (1) the uncontaminated zone above the sewage plume [350 μM dissolved oxygen (DO), pH 5.9];...
Authors
D.B. Kent, P.M. Fox
Phosphorus in a ground-water contaminant plume discharging to Ashumet Pond, Cape Cod, Massachusetts, 1999 Phosphorus in a ground-water contaminant plume discharging to Ashumet Pond, Cape Cod, Massachusetts, 1999
The discharge of a plume of sewagecontaminated ground water emanating from the Massachusetts Military Reservation to Ashumet Pond on Cape Cod, Massachusetts, has caused concern about excessive loading of nutrients, particularly phosphorus, to the pond. The U.S. Air Force is considering remedial actions to mitigate potentially adverse effects on the ecological characteristics of the pond...
Authors
Timothy D. McCobb, Denis R. LeBlanc, Donald A. Walter, Kathryn M. Hess, Douglas B. Kent, Richard L. Smith
Non-USGS Publications**
Kent, D. B., and Kastner, M., 1985, Mg2+ removal in the system Mg2+‑amorphous SiO2‑H2O by adsorption and Mg‑hydroxysilicate precipitation: Geochimica et Cosmochimica Acta, v. 49, p. 1123‑1136.
Kent, D. B., 1983, On the surface chemical properties of synthetic and biogenic amorphous silica: Ph.D. dissertation, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, 420 pp.
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
Filter Total Items: 15
No Result Found
Filter Total Items: 53
Quantifying differences in the impact of variable chemistry on equilibrium uranium(VI) adsorption properties of aquifer sediments Quantifying differences in the impact of variable chemistry on equilibrium uranium(VI) adsorption properties of aquifer sediments
Uranium adsorption-desorption on sediment samples collected from the Hanford 300-Area, Richland, WA varied extensively over a range of field-relevant chemical conditions, complicating assessment of possible differences in equilibrium adsorption properties. Adsorption equilibrium was achieved in 500-1000 h although dissolved uranium concentrations increased over thousands of hours owing...
Authors
Deborah L. Stoliker, Douglas B. Kent, John M. Zachara
Transient groundwater chemistry near a river: Effects on U(VI) transport in laboratory column experiments Transient groundwater chemistry near a river: Effects on U(VI) transport in laboratory column experiments
In the 300 Area of a U(VI)-contaminated aquifer at Hanford, Washington, USA, inorganic carbon and major cations, which have large impacts on U(VI) transport, change on an hourly and seasonal basis near the Columbia River. Batch and column experiments were conducted to investigate the factors controlling U(VI) adsorption/desorption by changing chemical conditions over time. Low alkalinity...
Authors
Jun Yin, Roy Haggerty, Deborah L. Stoliker, Douglas B. Kent, Jonathan D. Istok, Janek Greskowiak, John M. Zachara
Redox transformations and transport of cesium and iodine (-1, 0, +5) in oxidizing and reducing zones of a sand and gravel aquifer Redox transformations and transport of cesium and iodine (-1, 0, +5) in oxidizing and reducing zones of a sand and gravel aquifer
Tracer tests were performed in distinct biogeochemical zones of a sand and gravel aquifer in Cape Cod, MA, to study the redox chemistry (I) and transport (Cs, I) of cesium and iodine in a field setting. Injection of iodide (I -) into an oxic zone of the aquifer resulted in oxidation of I - to molecular iodine (I2) and iodate (IO3-) over transport distances of several meters. Oxidation is
Authors
Patricia M. Fox, Douglas B. Kent, James A. Davis
Influence of variable chemical conditions on EDTA-enhanced transport of metal ions in mildly acidic groundwater Influence of variable chemical conditions on EDTA-enhanced transport of metal ions in mildly acidic groundwater
Adsorption of Ni and Pb on aquifer sediments from Cape Cod, Massachusetts, USA increased with increasing pH and metal-ion concentration. Adsorption could be described quantitatively using a semi-mechanistic surface complexation model (SCM), in which adsorption is described using chemical reactions between metal ions and adsorption sites. Equilibrium reactive transport simulations...
Authors
D.B. Kent, J.A. Davis, J.L. Joye, G.P. Curtis
Modeling the movement of a pH perturbation and its impact on adsorbed zinc and phosphate in a wastewater‐contaminated aquifer Modeling the movement of a pH perturbation and its impact on adsorbed zinc and phosphate in a wastewater‐contaminated aquifer
[1] Chemical conditions were perturbed in an aquifer with an ambient pH of 5.9 and wastewater-derived adsorbed zinc (Zn) and phosphate (P) contamination by injecting a pulse of amended groundwater. The injected groundwater had low concentrations of dissolved Zn and P, a pH value of 4.5 resulting from equilibration with carbon dioxide gas, and added potassium bromide (KBr). Downgradient...
Authors
Douglas B. Kent, J.A. Wilkie, J.A. Davis
Ground-water-quality data for a treated-wastewater plume undergoing natural restoration, Ashumet Valley, Cape Cod, Massachusetts Ground-water-quality data for a treated-wastewater plume undergoing natural restoration, Ashumet Valley, Cape Cod, Massachusetts
A plume of contaminated ground water extends from former disposal beds at the Massachusetts Military Reservation wastewater-treatment plant toward Ashumet Pond, and farther southward toward coastal ponds and Vineyard Sound, Cape Cod, Massachusetts. Treated sewage-derived wastewater was discharged to the rapid-infiltration beds for nearly 60 years before the disposal site was moved to a...
Authors
Jennifer G. Savoie, Richard L. Smith, Douglas B. Kent, Kathryn M. Hess, Denis R. LeBlanc, Larry B. Barber
Long-term natural attenuation of carbon and nitrogen within a groundwater plume after removal of the treated wastewater source Long-term natural attenuation of carbon and nitrogen within a groundwater plume after removal of the treated wastewater source
Disposal of treated wastewater for more than 60 years onto infiltration beds on Cape Cod, Massachusetts produced a groundwater contaminant plume greater than 6 km long in a surficial sand and gravel aquifer. In December 1995 the wastewater disposal ceased. A long-term, continuous study was conducted to characterize the post-cessation attenuation of the plume from the source to 0.6 km...
Authors
D.A. Repert, L. B. Barber, K.M. Hess, S.H. Keefe, D.B. Kent, D.R. LeBlanc, R. L. Smith
Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations
To study transport and reactions of arsenic under field conditions, a small-scale tracer test was performed in an anoxic, iron-reducing zone of a sandy aquifer at the USGS research site on Cape Cod, Massachusetts, USA. For four weeks, a stream of groundwater with added As(V) (6.7 μM) and bromide (1.6 mM), was injected in order to observe the reduction of As(V) to As(III). Breakthrough of...
Authors
R. Hohn, M. Isenbeck-Schroter, D.B. Kent, J.A. Davis, R. Jakobsen, S. Jann, V. Niedan, C. Scholz, S. Stadler, A. Tretner
Kinetics of sorption and abiotic oxidation of arsenic(III) by aquifer materials Kinetics of sorption and abiotic oxidation of arsenic(III) by aquifer materials
The fate of arsenic in groundwater depends largely on its interaction with mineral surfaces. We investigated the kinetics of As(III) oxidation by aquifer materials collected from the USGS research site at Cape Cod, MA, USA, by conducting laboratory experiments. Five different solid samples with similar specific surface areas (0.6–0.9 m2 g−1) and reductively extractable iron contents (18...
Authors
A. Amirbahman, D.B. Kent, G.P. Curtis, J.A. Davis
Changes in ground-water quality near two granular-iron permeable reactive barriers in a sand and gravel aquifer, Cape Cod, Massachusetts, 1997-2000 Changes in ground-water quality near two granular-iron permeable reactive barriers in a sand and gravel aquifer, Cape Cod, Massachusetts, 1997-2000
Two experimental permeable reactive barriers (PRBs) of granular zero-valent iron were emplaced in the path of a tetrachloroethene plume (the Chemical Spill-10 plume) at the Massachusetts Military Reservation, Cape Cod, Massachusetts, in June 1998. The goal of the field experiment was to achieve emplacement of a granular-iron PRB deeper than attempted before. The PRBs were expected to...
Authors
Jennifer G. Savoie, Douglas B. Kent, Richard L. Smith, Denis R. LeBlanc, David W. Hubble
The influence of groundwater chemistry on arsenic concentrations and speciation in a quartz sand and gravel aquifer The influence of groundwater chemistry on arsenic concentrations and speciation in a quartz sand and gravel aquifer
We examined the chemical reactions influencing dissolved concentrations, speciation, and transport of naturally occurring arsenic (As) in a shallow, sand and gravel aquifer with distinct geochemical zones resulting from land disposal of dilute sewage effluent. The principal geochemical zones were: (1) the uncontaminated zone above the sewage plume [350 μM dissolved oxygen (DO), pH 5.9];...
Authors
D.B. Kent, P.M. Fox
Phosphorus in a ground-water contaminant plume discharging to Ashumet Pond, Cape Cod, Massachusetts, 1999 Phosphorus in a ground-water contaminant plume discharging to Ashumet Pond, Cape Cod, Massachusetts, 1999
The discharge of a plume of sewagecontaminated ground water emanating from the Massachusetts Military Reservation to Ashumet Pond on Cape Cod, Massachusetts, has caused concern about excessive loading of nutrients, particularly phosphorus, to the pond. The U.S. Air Force is considering remedial actions to mitigate potentially adverse effects on the ecological characteristics of the pond...
Authors
Timothy D. McCobb, Denis R. LeBlanc, Donald A. Walter, Kathryn M. Hess, Douglas B. Kent, Richard L. Smith
Non-USGS Publications**
Kent, D. B., and Kastner, M., 1985, Mg2+ removal in the system Mg2+‑amorphous SiO2‑H2O by adsorption and Mg‑hydroxysilicate precipitation: Geochimica et Cosmochimica Acta, v. 49, p. 1123‑1136.
Kent, D. B., 1983, On the surface chemical properties of synthetic and biogenic amorphous silica: Ph.D. dissertation, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, 420 pp.
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.