Isotope Geochemistry and Isotope Hydrology

Ron Kistler, emeritus geologist at the USGS in Menlo Park, was the first person to conduct isotopic studies at the Menlo Park center. In 1960, Ron built a small argon extraction line on the second floor of Building 2 and brought his gases to the laboratory at the University of California, Berkeley for mass spectrometric analysis. In 1961, the Branch of Isotope Geology (BIG) was established and Ron became its first research scientist in Menlo Park. Shortly afterward, Marv Lanphere and Brent Dalrymple, experienced in Rb/Sr and K/Ar dating techniques, respectively, were brought into BIG and new solid-source and gas source mass spectrometers were constructed and installed.

While radiogenic isotope geochemistry flourished over the years at the USGS in Menlo Park, it was stable isotope geochemistry that had the greater appeal to water chemists and hydrologists. In 1965, Jim O’Neil was hired to establish a stable isotope laboratory in BIG, Menlo Park. Because Jim used dangerous chemicals (F2 and BrF5) in his work, he was not allowed to build this new laboratory in Building 2 where other experimental laboratories were housed. The decision was made to house the laboratory in a prefabricated structure (a Trailer) to be located directly behind Building 2. It was to take about 3 months to clear the land and erect the trailer for Jim. When Ivan Barnes, a respected geochemist with the Water Resources Division, learned of this plan, he proposed that additional laboratories be constructed on the site so that experimental work could be more effectively conducted by other scientists in both the Geologic and Water Resources Divisions. In that golden era of expansion and abundant funds, the proposal was granted. Within a year and a half 14 trailers were erected and outfitted with special wiring, fume hoods, and assorted equipment to conduct research in geochemistry. Many groundbreaking studies were conducted in those trailers, structures that are now, sadly, but a memory. These trailers and other old wooden buildings were removed in 1996 after the new Building 15 was occupied, and the land is now covered by a parking lot.

In the 1960s and 1970s cooperative stable isotope studies in the broad fields of hydrology and low-temperature aqueous processes were conducted principally by Jim O’Neil, Don White and Al Truesdell of the Geologic Division and Ivan Barnes and Yousif Kharaka of the Water Resources Division. In the 1980s, Ivan purchased a new commercial isotope ratio mass spectrometer and continued to conduct stable isotope studies under the aegis of the Water Resources Division. Ivan later added two more mass spectrometers to the lab, including a solid-source machine, which greatly expanded the range of isotopic systems that could be investigated. With no available space for the new mass spectrometers, Ivan personally built two temporary labs, acquiring concrete, lumber, and roofing bit by bit under the then-mandated single-purchase limit of $500. With Doug White at the controls, these mass spectrometers turned out thousands of isotopic analyses of volcanic gases, geothermal fluids, and selenium-laden irrigation waters over the years.

Isotope data became critical components of the geothermal studies carried out by Bob Mariner, Mike Sorey, and Bill Evans on various geothermal and volcanic related systems in the western U.S. Cooperative studies between NRP personnel and WRD District researchers and support for District studies that needed stable isotope data became common. Bill Young in Idaho; Alan Welch, Mike Lico, and Pat McKinley in Nevada; Bob Leonard in Montana; Scott Hamlin in California were early District users of light stable isotope data generated in the Menlo Park isotope facility, and availability of isotope data greatly improved products generated in these District studies. Isotope studies have progressed from being unique parts of the work we do to being a common but critical component of many research studies undertaken in the USGS (http://wwwrcamnl.wr.usgs.gov/isoig/period/index.html).

Jim O’Neil left the USGS in 1987, Ivan Barnes died in 1989, and several isotope geochemists retired in the mid-1990s. The end of an era -- but not the end of the legacy as Carol Kendall and Tom Bullen continued to use and expand the capabilities of mass spectrometry in Menlo Park. They joined the WRD group in Menlo Park in 1990, and inherited the mass spectrometers that Ivan Barnes had purchased. Two of these mass spectrometers are still in use, on the first floor of Building 15. Tom uses the solid-source mass spectrometers to trace sources and reaction mechanisms for various metal and semi-metal isotopes such as Se, Pb, Sr, Cr, Fe, Li, B, Ca, etc. Carol has subsequently purchased 3 other stable isotope “gas source” mass spectrometers that are used for analyzing waters, solutes, gases, and biological materials for C, H, N,O, and S isotopes. The main focus of her research has been tracing sources of nitrate using N and O isotopes, and tracing sources of organics (http://wwwrcamnl.wr.usgs.gov/isoig/projects/fingernails/studies/sciresearch.html) and food web relations (http://wwwrcamnl.wr.usgs.gov/isoig/projects/fingernails/foodweb/isotopes.html) using C, N, and S isotopes. Bob Michel joined the WRD isotope contingent in 1995, bringing his tritium laboratory and 4 liquid scintillation counters from the USGS office in Reston to Menlo Park. These counters are used to analyze waters for T and sulfates for S-35.

In 1998, the Stanford-USGS SHRIMP RG ion microprobe (http://shrimprg.stanford.edu/index.html) was installed in the Green building in Stanford University. This instrument was purchased as part of a partnership between the USGS and Stanford, and is maintained and managed by a team that includes USGS personnel Joe Wooden, Charlie Bacon, and Brad Ito. The SHRIMP is used mainly for U-Pb geochronology, osmium isotopes, and trace metal studies, but there are also stable isotope applications.

The USGS in Menlo Park has an open house exhibition every 3 years. During the 2002 and 2003 Open House exhibitions, team members of the Isotope Tracers Project analyzed fingernails of visitors for carbon and nitrogen stable isotope ratios in "real time", using two mass spectrometers. The purpose of this exhibit was to demonstrate the usefulness of isotope techniques for determining differences in diets between individuals. This technique is often used for isotopic studies of food webs -- which is a method for determining who is eating what. This kind of information can be very useful for understanding how toxic materials, including mercury, become bioaccumulated in animals high on the food chain (http://wwwrcamnl.wr.usgs.gov/isoig/projects/fingernails/).

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