SGER: A Pilot Study of Plutonochronology: Rapid Dating of Recent Sediments and Soils using Pu Activities and 240Pu/239Pu Determined by ICPMS.

Northern Arizona University, Flagstaff AZ

Investigators

Abstract

ABSTRACT A Pilot Study of Plutonochronology: Rapid Dating of Recent Sediments and Soils using Pu Activities and 240 Pu/ 239 Pu Determined by ICPMS. Studies of the chronology and inventory of anthropogenic pollutants in the environment require a well-calibrated timeline in soils and sediments. These sediment and soil profiles are most frequently and reliably dated using time-consuming radiocounting measurements of excess 210Pb, 137Cs, and 239+240Pu. Dating of recent soils and sediments using plutonium isotopes has not been more extensively pursued because of analytical difficulties. The fact that the application of quadrupole ICPMS to Pu chronology has been overlooked represents one of the more striking missed opportunities of the 1990s in isotope geochemistry, as ICPMS technology has been suited to this task for at least the last decade. The goal of this project is to demonstrate and further develop the use of inductively coupled plasma mass spectrometry (ICPMS) in Pu dating of soils and sediments. This approach will provide a much faster complement or alternative to established radiodecay counting of 137Cs and/or excess 210Pb. It will examine Pu activity and isotope ratio profiles in Lake Coeur DAlene, Idaho, and Pine Valley Reservoir (Washington Co., UT).