John Karl Bohlke, PhD
Dr. John Karl Bohlke is a Scientist Emeritus affiliated with the Earth Systems Processes Division and the Reston Stable Isotope Laboratory of the USGS Water Resources Mission Area.
Dr. John Karl (JK) Bohlke retired as a Senior Research Scientist and currently serves as a Scientist Emeritus affiliated with the Earth System Processes Division and the Reston Stable Isotope Laboratory of the Water Mission Area. During his career with USGS, he has studied processes related to both mineral resources and water resources. His published work includes field and laboratory-based studies of water-rock interactions, geochronology, and chemical transport in diverse hydrogeologic settings. Recent activities include development of stable isotopic methods and applications in hydrology and biogeochemistry, use of isotopes and environmental tracers to determine transport and reaction rates in groundwater and surface water, and multidisciplinary investigations of contaminant origin and migration. Selected priority topics related to water quality include excess nutrients and inorganic contaminants, effects of agriculture and wastewater disposal practices, watershed responses to land use change, groundwater/surface water interactions, and environmental forensics.
Professional Experience
Hydrologist, National Research Program and Earth System Processes Division, Water Mission Area, US Geological Survey, Reston, Virginia (since 1991)
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
Use of isotopes, age-dating, and numerical simulation to evaluate source histories and transport of NO3- to public supply wells in principal aquifers of the United States
Ground water beneath coastal bays of the Delmarva Peninsula: Ages and nutrients
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
Isotope geochemistry and chronology of offshore ground water beneath Indian River Bay, Delaware
Atomic weights of the elements. Review 2000 (IUPAC Technical Report)
Non-USGS Publications**
**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
Use of isotopes, age-dating, and numerical simulation to evaluate source histories and transport of NO3- to public supply wells in principal aquifers of the United States
Ground water beneath coastal bays of the Delmarva Peninsula: Ages and nutrients
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
Isotope geochemistry and chronology of offshore ground water beneath Indian River Bay, Delaware
Atomic weights of the elements. Review 2000 (IUPAC Technical Report)
Non-USGS Publications**
**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.