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
Long term atmospheric deposition as the source of nitrate and other salts in the Atacama Desert, Chile: New evidence from mass-independent oxygen isotopic compositions
Vertical gradients in water chemistry and age in the southern High Plains Aquifer, Texas, 2002
Using dual-bacterial denitrification to improve δ15N determinations of nitrates containing mass-independent 17O
Reach-scale isotope tracer experiment to quantify denitrification and related processes in a nitrate-rich stream, midcontinent United States
Contamination of groundwater under cultivated fields in an arid environment, central Arava Valley, Israel
Assessing denitrification in groundwater using natural gradient tracer tests with 15N: In situ measurement of a sequential multistep reaction
Geochemistry, radiocarbon ages, and paleorecharge conditions along a transect in the central High Plains aquifer, southwestern Kansas, USA
Residence times and nitrate transport in ground water discharging to streams in the Chesapeake Bay Watershed
Atomic weights of the elements. Review 2000 (IUPAC Technical Report)
Two new organic reference materials for δ13C and δ15N measurements and a new value for the δ13C of NBS 22 oil
Oxygen isotopes in nitrate: New reference materials for 18O:17O:16O measurements and observations on nitrate-water equilibration
The fate of wastewater-derived nitrate in the subsurface of the Florida Keys: Key Colony Beach, Florida
Science and Products
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Filter Total Items: 195
Long term atmospheric deposition as the source of nitrate and other salts in the Atacama Desert, Chile: New evidence from mass-independent oxygen isotopic compositions
Isotopic analysis of nitrate and sulfate minerals from the nitrate ore fields of the Atacama Desert in northern Chile has shown anomalous 17O enrichments in both minerals. Δ17O values of 14–21 ‰ in nitrate and 0.4 to 4 ‰ in sulfate are the most positive found in terrestrial minerals to date. Modeling of atmospheric processes indicates that the Δ17O signatures are the result of photochemical reactiAuthorsGreg Michalski, J. K. Böhlke, Mark ThiemensVertical gradients in water chemistry and age in the southern High Plains Aquifer, Texas, 2002
The southern High Plains aquifer is the primary source of water used for domestic, industrial, and irrigation purposes in parts of New Mexico and Texas. Despite the aquifer's importance to the overall economy of the southern High Plains, fundamental ground-water characteristics, such as vertical gradients in water chemistry and age, remain poorly defined. As part of the U.S. Geological Survey's NaAuthorsP. B. McMahon, J.K. Böhlke, T.M. LehmanUsing dual-bacterial denitrification to improve δ15N determinations of nitrates containing mass-independent 17O
The bacterial denitrification method for isotopic analysis of nitrate using N2O generated from Pseudomonas aureofaciens may overestimate δ15N values by as much as 1–2‰ for samples containing atmospheric nitrate because of mass-independent 17O variations in such samples. By analyzing such samples for δ15N and δ18O using the denitrifier Pseudomonas chlororaphis, one obtains nearly correct δ15N valueAuthorsTyler B. Coplen, John K. Böhlke, Karen L. CasciottiReach-scale isotope tracer experiment to quantify denitrification and related processes in a nitrate-rich stream, midcontinent United States
We conducted an in-stream tracer experiment with Br and 15N-enriched NO3- to determine the rates of denitrification and related processes in a gaining NO3- -rich stream in an agricultural watershed in the upper Mississippi basin in September 2001. We determined reach-averaged rates of N fluxes and reactions from isotopic analyses of NO3-, NO2-, N2, and suspended particulate N in conjunction with oAuthorsJ.K. Böhlke, J. W. Harvey, M.A. VoytekContamination of groundwater under cultivated fields in an arid environment, central Arava Valley, Israel
The purpose of this study is to obtain a better understanding of groundwater contamination processes in an arid environment (precipitation of 50 mm/year) due to cultivation. Additional aims were to study the fate of N, K, and other ions along the whole hydrological system including the soil and vadose zone, and to compare groundwater in its natural state with contaminated groundwater (through theAuthorsO. Oren, Y. Yechieli, J.K. Böhlke, A. DodyAssessing denitrification in groundwater using natural gradient tracer tests with 15N: In situ measurement of a sequential multistep reaction
Denitrification was measured within a nitrate‐contaminated aquifer on Cape Cod, Massachusetts, using natural gradient tracer tests with 15N nitrate. The aquifer contained zones of relatively high concentrations of nitrite (up to 77 μM) and nitrous oxide (up to 143 μM) and has been the site of previous studies examining ground water denitrification using the acetylene block technique. Small‐scale (AuthorsRichard L. Smith, John K. Böhlke, Stephen P. Garabedian, Kinga M. Revesz, Tadashi YoshinariGeochemistry, radiocarbon ages, and paleorecharge conditions along a transect in the central High Plains aquifer, southwestern Kansas, USA
Water samples from short-screen monitoring wells installed along a 90-km transect in southwestern Kansas were analyzed for major ions, trace elements, isotopes (H, B, C, N, O, S, Sr), and dissolved gases (He, Ne, N2, Ar, O2, CH4) to evaluate the geochemistry, radiocarbon ages, and paleorecharge conditions in the unconfined central High Plains aquifer. The primary reactions controlling water chemisAuthorsP. B. McMahon, J.K. Böhlke, S. C. ChristensonResidence times and nitrate transport in ground water discharging to streams in the Chesapeake Bay Watershed
One of the major water-quality problems in the Chesapeake Bay is an overabundance of nutrients from the streams and rivers that discharge to the Bay. Some of these nutrients are from nonpoint sources such as atmospheric deposition, agricultural manure and fertilizer, and septic systems. The effects of efforts to control nonpoint sources, however, can be difficult to quantify because of the lag timAuthorsBruce D. Lindsey, Scott Phillips, Colleen A. Donnelly, Gary K. Speiran, Niel Plummer, John Karl Bohlke, Michael J. Focazio, William C. Burton, Eurybiades BusenbergAtomic weights of the elements. Review 2000 (IUPAC Technical Report)
A consistent set of internationally accepted atomic weights has long been an essential aim of the scientific community because of the relevance of these values to science and technology, as well as to trade and commerce subject to ethical, legal, and international standards. The standard atomic weights of the elements are regularly evaluated, recommended, and published in updated tables by the ComAuthorsJohn R. de Laeter, John Karl Böhlke, P. De Bièvre, H. Hidaka, H.S. Peiser, K.J.R. Rosman, P.D.P. TaylorTwo new organic reference materials for δ13C and δ15N measurements and a new value for the δ13C of NBS 22 oil
Analytical grade L-glutamic acid is chemically stable and has a C/N mole ratio of 5, which is close to that of many of natural biological materials, such as blood and animal tissue. Two L-glutamic acid reference materials with substantially different 13C and 15N abundances have been prepared for use as organic reference materials for C and N isotopic measurements. USGS40 is analytical grade L-glutAuthorsHaiping Qi, Tyler B. Coplen, Heike Geilmann, Willi A. Brand, J.K. BöhlkeOxygen isotopes in nitrate: New reference materials for 18O:17O:16O measurements and observations on nitrate-water equilibration
Despite a rapidly growing literature on analytical methods and field applications of O isotope-ratio measurements of NO3− in environmental studies, there is evidence that the reported data may not be comparable because reference materials with widely varying δ18O values have not been readily available. To address this problem, we prepared large quantities of two nitrate salts with contrasting O isAuthorsJ.K. Böhlke, S.J. Mroczkowski, T. B. CoplenThe fate of wastewater-derived nitrate in the subsurface of the Florida Keys: Key Colony Beach, Florida
Shallow injection is the predominant mode of wastewater disposal for most tourist-oriented facilities and some residential communities in the US Florida Keys National Marine Sanctuary. Concern has been expressed that wastewater nutrients may be escaping from the saline groundwater system into canals and surrounding coastal waters and perhaps to the reef tract 10 km offshore, promoting unwanted algAuthorsE.M. Griggs, L.R. Kump, J.K. Böhlke