10Be is preferentially removed from the ocean at an ocean- margin site in the eastern equatorial Pacific at a rate 4-7 times greater than at 3 open-ocean sites. This study at other areas of the Pacific Ocean will determine whether or not other margins act as boundary sinks for 10Be. Scavenging of 10Be and 231Pa in open-ocean and in ocean-margin regions will cover a range of total particulate matter fluxes and a diversity of particle compositions and determine the relative importance of several factors which influence scavenging intensity. Sediments deposited during the Last Glacial Maximum will also be studied to determine whether or not the intensity of boundary scavenging changed significantly between the extreme range of climatic conditions represented by LGM and Holocene times. Completing the proposed work will achieve more than just a better understanding of the marine geochemical cycling of radiotracers such as Th isotopes, 10Be and 231Pa. Identifying: 1) the relative importance of different factors which regulate the scavening rates of particle-reactive elements in the ocean, 2) the degree to which different types of ocean margins act as important boundary sinks for particle- reactive elements, and 3) the extent to which boundary scavenging intensity has changed with time, will lead to a much better general understanding of the transport and fate of trace elements in the ocean.
