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
Oxygen isotopes in nitrite: Analysis, calibration, and equilibration
Isotopic analysis of N and O in nitrite and nitrate by sequential selective bacterial reduction to N2O
The oxygen-18 isotope approach for measuring aquatic metabolism in high-productivity waters
Ground water stratification and delivery of nitrate to an incised stream under varying flow conditions
Oxygen and chlorine isotopic fractionation during perchlorate biodegradation: Laboratory results and implications for forensics and natural attenuation studies
Nitrogen saturation in the Rocky Mountains: Linking emissions, deposition, and ecosystem effects using stable isotopes of nitrogen compounds
Methods for measuring denitrification: Diverse approaches to a difficult problem
Denitrification across landscapes and waterscapes: A synthesis
Assessment of nitrification potential in ground water using short term, single-well injection experiments
Denitrification in nitrate-rich streams: Application of N2:Ar and 15N-tracer methods in intact cores
Ammonium transport and reaction in contaminated groundwater: Application of isotope tracers and isotope fractionation studies
Regional patterns in the isotopic composition of natural and anthropogenic nitrate in groundwater, High Plains, U.S.A.
Science and Products
- Data
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Filter Total Items: 194
Oxygen isotopes in nitrite: Analysis, calibration, and equilibration
Nitrite is a central intermediate in the nitrogen cycle and can persist in significant concentrations in ocean waters, sediment pore waters, and terrestrial groundwaters. To fully interpret the effect of microbial processes on nitrate (NO3-), nitrite (NO2-), and nitrous oxide (N2O) cycling in these systems, the nitrite pool must be accessible to isotopic analysis. Furthermore, because nitrite inteAuthorsK.L. Casciotti, John Karl Böhlke, M.R. McIlvin, Stanley J. Mroczkowski, Janet E. HannonIsotopic analysis of N and O in nitrite and nitrate by sequential selective bacterial reduction to N2O
Nitrite is an important intermediate species in the biogeochemical cycling of nitrogen, but its role in natural aquatic systems is poorly understood. Isotopic data can be used to study the sources and transformations of NO2- in the environment, but methods for independent isotopic analyses of NO2- in the presence of other N species are still new and evolving. This study demonstrates that isotopicAuthorsJohn Karl Böhlke, Richard L. Smith, Janet E. HannonThe oxygen-18 isotope approach for measuring aquatic metabolism in high-productivity waters
We examined the utility of δ18O2 measurements in estimating gross primary production (P), community respiration (R), and net metabolism (P : R) through diel cycles in a productive agricultural stream located in the midwestern U.S.A. Large diel swings in O2(±200 µmol L−1) were accompanied by large diel variation in δ18O2 (±10‰). Simultaneous gas transfer measurements and laboratory‐derived isotopicAuthorsCraig R. Tobias, John Karl Böhlke, Judson W. HarveyGround water stratification and delivery of nitrate to an incised stream under varying flow conditions
Ground water processes affecting seasonal variations of surface water nitrate concentrations were investigated in an incised first-order stream in an agricultural watershed with a riparian forest in the coastal plain of Maryland. Aquifer characteristics including sediment stratigraphy, geochemistry, and hydraulic properties were examined in combination with chemical and isotopic analyses of groundAuthorsJohn Karl Böhlke, M. E. O'Connell, K.L. PrestegaardOxygen and chlorine isotopic fractionation during perchlorate biodegradation: Laboratory results and implications for forensics and natural attenuation studies
Perchlorate is a widespread environmental contaminant having both anthropogenic and natural sources. Stable isotope ratios of O and Cl in a given sample of perchlorate may be used to distinguish its source(s). Isotopic ratios may also be useful for identifying the extent of biodegradation of perchlorate, which is critical for assessing natural attenuation of this contaminant in groundwater. For thAuthorsNeil C. Sturchio, John Karl Böhlke, Abelardo D. Beloso, S.H. Streger, Linnea J. Heraty, Paul B. HatzingerNitrogen saturation in the Rocky Mountains: Linking emissions, deposition, and ecosystem effects using stable isotopes of nitrogen compounds
Elevated levels of atmospheric N deposition are affecting terrestrial and aquatic ecosystems at high elevations in Rocky Mountain National Park and adjacent areas of the Front Range of Colorado. Federal and state agencies are now working together to develop cost-effective means for reducing atmospheric N deposition. A discussion on N saturation covers the need for better understanding of N emissioAuthorsK. Campbell, L. Nanus, J.K. Böhlke, K. Harlin, J. CollettMethods for measuring denitrification: Diverse approaches to a difficult problem
Denitrification, the reduction of the nitrogen (N) oxides, nitrate (NO3−) and nitrite (NO2−), to the gases nitric oxide (NO), nitrous oxide (N2O), and dinitrogen (N2), is important to primary production, water quality, and the chemistry and physics of the atmosphere at ecosystem, landscape, regional, and global scales. Unfortunately, this process is very difficult to measure, and existing methodsAuthorsPeter M Groffman, Mary A. Altabet, J.K. Böhlke, Klaus Butterbach-Bahl, Mary B. David, Mary K. Firestone, Anne E. Giblin, Todd M. Kana, Lars Peter Nielsen, Mary A. VoytekDenitrification across landscapes and waterscapes: A synthesis
Denitrification is a critical process regulating the removal of bioavailable nitrogen (N) from natural and human-altered systems. While it has been extensively studied in terrestrial, freshwater, and marine systems, there has been limited communication among denitrification scientists working in these individual systems. Here, we compare rates of denitrification and controlling factors across a raAuthorsS. Seitzinger, J. A. Harrison, J.K. Böhlke, A.F. Bouwman, R. Lowrance, B. Peterson, C. Tobias, G. Van DrechtAssessment of nitrification potential in ground water using short term, single-well injection experiments
Nitrification was measured within a sand and gravel aquifer on Cape Cod, MA, using a series of single-well injection tests. The aquifer contained a wastewater-derived contaminant plume, the core of which was anoxic and contained ammonium. The study was conducted near the downgradient end of the ammonium zone, which was characterized by inversely trending vertical gradients of oxygen (270 to 0 μM)AuthorsR. L. Smith, L.K. Baumgartner, D.N. Miller, D.A. Repert, J.K. BöhlkeDenitrification in nitrate-rich streams: Application of N2:Ar and 15N-tracer methods in intact cores
Rates of benthic denitrification were measured using two techniques, membrane inlet mass spectrometry (MIMS) and isotope ratio mass spectrometry (IRMS), applied to sediment cores from two NO3−‐rich streams draining agricultural land in the upper Mississippi River Basin. Denitrification was estimated simultaneously from measurements of N2:Ar (MIMS) and 15N[N2] (IRMS) after the addition of low‐levelAuthorsLesley K. Smith, M.A. Voytek, J.K. Böhlke, J. W. HarveyAmmonium transport and reaction in contaminated groundwater: Application of isotope tracers and isotope fractionation studies
Ammonium (NH4+) is a major constituent of many contaminated groundwaters, but its movement through aquifers is complex and poorly documented. In this study, processes affecting NH4+ movement in a treated wastewater plume were studied by a combination of techniques including large‐scale monitoring of NH4+ distribution; isotopic analyses of coexisting aqueous NH4+, NO3−, N2, and sorbed NH4+; and inAuthorsJ.K. Böhlke, Richard L. Smith, Daniel N. MillerRegional patterns in the isotopic composition of natural and anthropogenic nitrate in groundwater, High Plains, U.S.A.
Mobilization of natural nitrate (NO3-) deposits in the subsoil by irrigation water in arid and semiarid regions has the potential to produce large groundwater NO3- concentrations. The use of isotopes to distinguish between natural and anthropogenic NO3- sources in these settings could be complicated by the wide range in δ15N values of natural NO3-. An ∼10 000 year record of paleorecharge from theAuthorsP. B. McMahon, J.K. Böhlke