HR: 0800h
AN: PP31B-1537    [Abstracts]
TI: 226-Radium Activity in Bivalve Shells as a Tracer of Paleo-groundwater Input to Elkhorn Slough, California
AU: * Street, J H
EM: jstreet@stanford.edu
AF: Stanford University, Department of Geological and Environmental Sciences, 450 Serra Mall, Bldg. 320, Stanford, CA 94305 United States
AU: Asbeck, L
EM: lasbeck@pangea.stanford.edu
AF: Stanford University, Department of Geological and Environmental Sciences, 450 Serra Mall, Bldg. 320, Stanford, CA 94305 United States
AU: Moore, W S
EM: moore@geol.sc.edu
AF: University of South Carolina, Department of Geological Sciences, Columbia, SC 29208 United States
AU: Paytan, A
EM: apaytan@pangea.stanford.edu
AF: Stanford University, Department of Geological and Environmental Sciences, 450 Serra Mall, Bldg. 320, Stanford, CA 94305 United States
AB: Groundwater discharge is recognized as a major source of freshwater, nutrients and pollutants to estuaries and the coastal ocean. Virtually nothing is known, however, about how the influence of coastal groundwater discharge has varied in the past in response to changes in climate or coastal geography. In an effort to address this gap we have developed a new application for the long-lived radium isotope 226-Ra (half-life = 1600 yrs), which has been widely used as a tracer of groundwater input to contemporary marine environments. Whereas most studies have focused on measuring radium in the water column, we have measured 226-Ra activities in the calcium carbonate shells of bivalve mollusks, where it substitutes for Ca2+ in trace quantities proportional to the Ca/Ra ratio in the water column. Thus, it is expected that bivalve shells of various ages will preserve the 226-Ra signatures, and hence a record of groundwater influence, in the estuaries in which they grew. We will present details of our Ra extraction and measurement method, as well as preliminary results from both modern and ancient shells from a variety of species collected at Elkhorn Slough, a central California estuary that has undergone major human-induced environmental change in the past two centuries.
DE: 1600 GLOBAL CHANGE
DE: 1800 HYDROLOGY
DE: 4800 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL (0460)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005