HELIUM ISOTOPES AND THE STUDY OF OCEAN CIRCULATION
Helium isotopes have been used to study global ocean circulation since the 1960's, but new research has provided more detailed information on the distribution of helium isotopes, as well as their sources and sinks in the ocean. This information can now be applied to construct global fields of helium isotopes and to extract unique information on the circulation patterns at different depth levels in the ocean, as well as on local and regional processes such as ventilation of water masses in deep water formation regions. Additionally, the data sets are now sufficiently large to be useful for validation of Ocean General Circulation Models (OGCM's). Peter Schlosser, Associate Director, The Earth Institute at Columbia University (212-854-0306, schlosser@ldeo.columbia.edu).

Arsenic
TRYING TO PREVENT ARSENIC FROM LEACHING OUT OF LANDFILLS
Two papers from Lamont Doherty Earth Observatory scientists examine how a landfill in Maine causes release of naturally-occurring arsenic from sediment into groundwater, and efforts to prevent this groundwater from seeping out of this landfill. When several methods of removing the arsenic failed, the researchers came up with another idea: sequestration of arsenic through the formation of solid phase sulfides under sulfate-reducing conditions. This technique was tested in the laboratory, with promising results. Over ten days, roughly 70 to 80% of the dissolved arsenic and more than 99% of the dissolved iron was removed from solution. The prospects are promising for preventing high arsenic groundwater plumes at this and similarly affected landfill sites. Alison Keimowitz, Graduate Research Fellow, ark@ldeo.columbia.edu, 84
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Contact: Mary Tobin
mtobin@ldeo.columbia.edu
845-365-8607
The Earth Institute at Columbia University
13-Dec-2004