John Karl Bohlke
Dr. John Karl Bohlke is a Scientist Emeritus with the USGS Water Resources Mission Area and the Reston Stable Isotope Laboratory.
Professional Experience
Hydrologist, National Research Program and Earth System Processes Division, Water Mission Area, US Geological Survey, Reston, Virginia (since 1991)
[Adjunct Assist/Assoc Professor (Geology), University of Maryland (1992-2016)]
Geologist, Eastern Mineral Resources, US Geological Survey, Reston, Virginia
Postdoc (Geoscience), Argonne National Laboratory, Chicago, Illinois
Geologist, Western Mineral Resources, US Geological Survey, Menlo Park, California
Cartographer, US Soil Conservation Service, Hyattsville, Maryland
Education and Certifications
PhD (Geology and Geophysics), University of California, Berkeley, California
MS (Marine Geology), Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Florida
BS (Geology), University of Michigan, Ann Arbor, Michigan
Science and Products
Mixing effects on apparent reaction rates and isotope fractionation during denitrification in a heterogeneous aquifer
Comprehensive inter-laboratory calibration of reference materials for δ18O versus VSMOW using various on-line high-temperature conversion techniques
Errata: Atomic weights of the elements: Review 2000
Atacama perchlorate as an agricultural contaminant in groundwater: Isotopic and chronologic evidence from Long Island, New York
A simple technique for continuous measurement of time-variable gas transfer in surface waters
Contrasting residence times and fluxes of water and sulfate in two small forested watersheds in Virginia, USA
Flow and geochemistry of groundwater beneath a back-barrier lagoon: The subterranean estuary at Chincoteague Bay, Maryland, USA
Biogeochemistry at a wetland sediment-alluvial aquifer interface in a landfill leachate plume
Nitrification and denitrification in a midwestern stream containing high nitrate: In situ assessment using tracers in dome-shaped incubation chambers
Dynamic modeling of nitrogen losses in river networks unravels the coupled effects of hydrological and biogeochemical processes
Fractionation of stable isotopes in perchlorate and nitrate during in situ biodegradation in a sandy aquifer
Multi-scale measurements and modeling of denitrification in streams with varying flow and nitrate concentration in the upper Mississippi River basin, USA
Science and Products
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Filter Total Items: 194
Mixing effects on apparent reaction rates and isotope fractionation during denitrification in a heterogeneous aquifer
Gradients in contaminant concentrations and isotopic compositions commonly are used to derive reaction parameters for natural attenuation in aquifers. Differences between field‐scale (apparent) estimated reaction rates and isotopic fractionations and local‐scale (intrinsic) effects are poorly understood for complex natural systems. For a heterogeneous alluvial fan aquifer, numerical models and fieAuthorsChristopher T. Green, John K. Böhlke, Barbara A. Bekins, Steven P. PhillipsComprehensive inter-laboratory calibration of reference materials for δ18O versus VSMOW using various on-line high-temperature conversion techniques
Internationally distributed organic and inorganic oxygen isotopic reference materials have been calibrated by six laboratories carrying out more than 5300 measurements using a variety of high-temperature conversion techniques (HTC) in an evaluation sponsored by the International Union of Pure and Applied Chemistry (IUPAC). To aid in the calibration of these reference materials, which span more thaAuthorsWilli A. Brand, Tyler B. Coplen, Anita T. Aerts-Bijma, John Karl Bohlke, Matthias Gehre, Heike Geilmann, Manfred Groning, Henk G. Jansen, Harro A. J. Meijer, Stanley J. Mroczkowski, Haiping Qi, Karin Soergel, Hilary Stuart-Williams, Stephan M. Weise, Roland A. WernerErrata: Atomic weights of the elements: Review 2000
No abstract available.AuthorsJohn R. de Laeter, John Karl Bohlke, P. De Bievre, H. Hidaka, H.S. Peiser, K.J.R. Rosman, P.D.P. TaylorAtacama perchlorate as an agricultural contaminant in groundwater: Isotopic and chronologic evidence from Long Island, New York
Perchlorate (ClO4−) is a common groundwater constituent with both synthetic and natural sources. A potentially important source of ClO4− is past agricultural application of ClO4−-bearing natural NO3− fertilizer imported from the Atacama Desert, Chile, but evidence for this has been largely circumstantial. Here we report ClO4− stable isotope data (δ37Cl, δ18O, and Δ17O), along with other supportingAuthorsJohn K. Bohlke, Paul B. Hatzinger, Neil C. Sturchio, Baohua Gu, Irene Abbene, Stanley J. MroczkowskiA simple technique for continuous measurement of time-variable gas transfer in surface waters
Mass balance models of dissolved gases in streams, lakes, and rivers serve as the basis for estimating wholeecosystem rates for various biogeochemical processes. Rates of gas exchange between water and the atmosphere are important and error-prone components of these models. Here we present a simple and efficient modification of the SF6 gas tracer approach that can be used concurrently while collecAuthorsCraig R. Tobias, John Karl Bohlke, Judson W. Harvey, Eurybiades BusenbergContrasting residence times and fluxes of water and sulfate in two small forested watersheds in Virginia, USA
Watershed mass balances for solutes of atmospheric origin may be complicated by the residence times of water and solutes at various time scales. In two small forested headwater catchments in the Appalachian Mountains of Virginia, USA, mean annual export rates of SO4= differ by a factor of 2, and seasonal variations in SO4= concentrations in atmospheric deposition and stream water are out of phase.AuthorsJ.K. Böhlke, R. L. MichelFlow and geochemistry of groundwater beneath a back-barrier lagoon: The subterranean estuary at Chincoteague Bay, Maryland, USA
To better understand large-scale interactions between fresh and saline groundwater beneath an Atlantic coastal estuary, an offshore drilling and sampling study was performed in a large barrier-bounded lagoon, Chincoteague Bay, Maryland, USA. Groundwater that was significantly fresher than overlying bay water was found in shallow plumes up to 8 m thick extending more than 1700 m offshore. GroundwatAuthorsJ.F. Bratton, J.K. Böhlke, D.E. Krantz, C.R. TobiasBiogeochemistry at a wetland sediment-alluvial aquifer interface in a landfill leachate plume
The biogeochemistry at the interface between sediments in a seasonally ponded wetland (slough) and an alluvial aquifer contaminated with landfill leachate was investigated to evaluate factors that can effect natural attenuation of landfill leachate contaminants in areas of groundwater/surface-water interaction. The biogeochemistry at the wetland-alluvial aquifer interface differed greatly betweenAuthorsM.M. Lorah, I.M. Cozzarelli, J.K. BöhlkeNitrification and denitrification in a midwestern stream containing high nitrate: In situ assessment using tracers in dome-shaped incubation chambers
The extent to which in-stream processes alter or remove nutrient loads in agriculturally impacted streams is critically important to watershed function and the delivery of those loads to coastal waters. In this study, patch-scale rates of in-stream benthic processes were determined using large volume, open-bottom benthic incubation chambers in a nitrate-rich, first to third order stream draining aAuthorsR. L. Smith, J.K. Böhlke, D.A. Repert, C.P. HartDynamic modeling of nitrogen losses in river networks unravels the coupled effects of hydrological and biogeochemical processes
The importance of lotic systems as sinks for nitrogen inputs is well recognized. A fraction of nitrogen in streamflow is removed to the atmosphere via denitrification with the remainder exported in streamflow as nitrogen loads. At the watershed scale, there is a keen interest in understanding the factors that control the fate of nitrogen throughout the stream channel network, with particular attenAuthorsRichard B. Alexander, John K. Böhlke, Elizabeth W. Boyer, Mark B. David, Judson W. Harvey, Patrick J. Mulholland, Sybil P. Seitzinger, Craig R. Tobias, Christina Tonitto, Wilfred M. WollheimFractionation of stable isotopes in perchlorate and nitrate during in situ biodegradation in a sandy aquifer
An in situ experiment was performed in a shallow alluvial aquifer in Maryland to quantify the fractionation of stable isotopes in perchlorate (Cl and O) and nitrate (N and O) during biodegradation. An emulsified soybean oil substrate that was previously injected into this aquifer provided the electron donor necessary for biological perchlorate reduction and denitrification. During the field experiAuthorsP.B. Hatzinger, John Karl Bohlke, N.C. Sturchio, B. Gu, L.J. Heraty, R.C. BordenMulti-scale measurements and modeling of denitrification in streams with varying flow and nitrate concentration in the upper Mississippi River basin, USA
Denitrification is an important net sink for NO3− in streams, but direct measurements are limited and in situ controlling factors are not well known. We measured denitrification at multiple scales over a range of flow conditions and NO3− concentrations in streams draining agricultural land in the upper Mississippi River basin. Comparisons of reach-scale measurements (in-stream mass transport and tAuthorsJohn K. Böhlke, Ronald C. Antweiler, Judson W. Harvey, Andrew E. Laursen, Lesley K. Smith, Richard L. Smith, Mary A. Voytek