| VOL. 23, NO. 15||FEBRUARY 20, 1998 |
Lamont-Doherty Scientists Launch a New Spectrometer for the Study of Noble Gases
BY HANNAH FAIRFIELD
cientists at Columbias Lamont-Doherty Earth Observatory (LDEO) recently fired up their newest mass spectrometer.
Peter Schlosser, professor of earth and environmental sciences and head of the LDEO Noble Gas Laboratory, and the other 15 geochemists who work in his lab have built one of the best noble gas laboratories in the world. In just eight years, these scientists obtained four mass spectrometers, which separate and measure the quantity of atoms of different masses in order to analyze the noble gas content in water and rock samples.
Noble gases do not react with other elements, so they can be tracked through time and space better than other elements.
The lab has broad applications in many areas of earth science research, such as oceanography, paleoclimate studies, hydrology and pollution studies.
We can work on scientific problems we never could before, says Schlosser. We have added a new dimension to the type of geochemistry we do here.
Right now, the noble gas scientists have wide-ranging projects, such as studying water movement on continents and in oceans, reconstructing ancient continental temperature records using groundwater as an archive, and analyzing gas exchange between the atmosphere and hydrosphere. In 1997 alone, Schlosser submitted 10 articles to various journals, including Applied Geochemistry, Journal of Geophysical Research and Water Resources Research. The publication potential for new scientific results is amazing, says Schlosser. This is just the beginning.
In the late 1970s and early 1980s, Wally Broecker, Newberry Professor of Earth and Environmental Sciences, dreamed about adding a noble gas laboratory to the geochemistry department.
I was keeping an eye out for someone of quality, Broecker says. I knew of Peters work in Heidelberg, and when we met at a conference in Toronto in 1987, I thought it was a big opportunity.
Broecker and Barry Raleigh, the director of LDEO at that time, sought funding from the W. M. Keck Foundation, a private foundation in California that funds $30$40 million annually for many natural science projects, professorships, and postdoctoral positions. By the early summer of 1988, Keck had granted $550,000 for the purchase of a fully automated (no machine operator necessary) high precision helium isotope mass spectrometer to be housed in the geochemistry building. The Lamont Noble Gas Laboratory had its first mass spec at the close of 1989. Schlosser thanks the Keck Foundation when he thinks about how quickly everything fell into place. Without funding mechanisms such as Keck, we may never have created this lab, he says.
Mass spectrometers are awe-inspiring specimens of technology. Housed behind several nondescript doors within the unassuming geochemistry building, the four machines live in a small palace designed especially for them. The Noble Gas Lab runs day and night, even when the rest of Lamont is quietly sleeping behind locked doors.
We can have 10 projects running at once, says Schlosser. The interplay of all the components is the really fun work.
The research projects in geochemistry are expanding broadly. While Martin Stute, LDEO associate research scientist, is looking at trace noble gases from wells in Maryland to find out the continental temperature of the last ice age, Sidney Hemming, also an associate research scientist, is waiting for ratios between argon isotopes to tell her the dates of mineral crystals. Because isotopes of an element have different masses, Hemming can calculate the ratios between the two, then can date the material using the known half-life of the element.
Schlosser and other members of the lab designed and constructed parts of the mass spectrometers, particularly the inlet system, which is where the noble gas is extracted from samples before analysis. Most noble gases are found in concentrations of parts per million, so the inlet system they designed had to be sensitive enough to extract minute amounts of noble gases from water and rocks. They also designed the layout of the rooms, including a glass-enclosed computer workstation so members of the lab can see the mass spectrometers while reducing the distraction of the machines continual hum. Geochemists who work in the lab know the hum is reassuring because it means the machines are working well. When the mass spectrometers malfunction, its typically the scientists themselves who fix the problem.
In 1991, Schlosser, with Martin Stute, added a semi-automated multi-purpose noble gas machine to the lab. It measures the amount of noble gases in groundwater and rocks and significantly expanded the labs research capabilities. Schlosser wrote several more grant proposals and continued to be funded by the Keck Foundation. He also received funds for machines and projects from the National Science Foundation (NSF), and the National Oceanic and Atmospheric Administration (NOAA). In 1994, continuing grants enabled the lab to purchase another helium isotope machine, and in 1997, Schlosser and Hemming added a fourth machine: an argon/argon mass spectrometer funded by NSF and Keck. Such a machine compares the ratio of argon isotopes in order to identify the age of rocks or sedimentages that are very important to geoscientists as they compare pieces of earths history. Now with four operational mass spectrometers, the lab can analyze many thousands of samples per year for a wide range of Lamont projects.