The Relationship Between Particulate Composition and 210Po and 210Pb Content along Three GEOTRACES Transects
Yi Tang1, Gillian Stewart1, Pere Masque2, Thomas M Church3, Maxi Castrillejo4 and Hiu Yan Choi5, (1)CUNY Queens College, School of Earth and Environmental Sciences, Flushing, NY, United States, (2)The University of Western Australia Oceans Institute, University of Western Australia, Crawley, Australia, (3)University of Delaware, Newark, DE, United States, (4)Universitat Autònoma de Barcelona, Department of Physics and Institut de Ciència i Tecnologia Ambientals, Barcelona, Spain, (5)Delaware Department of Natural Resources and Environmental Control, DE, United States
Abstract:
The naturally occurring radionuclide 210Po is typically deficient relative to its grandparent 210Pb in the surface ocean due to its tendency to rapidly adsorb to particles (scavenging). The removal of 210Po is therefore proposed to depend on the composition and population of suspended and settling particles. Small and large particulate (0-51 μm and > 51 μm) and dissolved (< 0.45 μm) 210Po and 210Pb activity were measured for water column samples collected from seven super stations along GA03 (NAZT), six super stations along GP16 (EPZT), and ten super stations along GA01(GEOVIDE). This large dataset of particulate 210Po/210Pb activities will be compared to the available data on the trace element and major phase (POC, CaCO3, BSi, etc.) composition of particles collected on these cruises in order to elucidate relationships between particle type and composition and the radionuclide activity. Preliminary data from GA03 indicates that there is a positive correlation between particulate Cu and Zn concentrations and 210Po activity on the large particles, confirming previous findings that Po acts like a bio-reactive sulfur-seeking trace metal. In contrast, 210Pb correlates with lithogenic Al and Ti, as well as carbonates in the same particles. There has also been interest in using Po to trace particulate organic carbon flux from the surface ocean due to its unique behavior, short half-life, and bioaccumulation in organisms. Along the GA03 transect, there is a very strong and statistically significant relationship between organic carbon content of particles and the scavenging rate of 210Po, except at the near shore stations. In this presentation, data from all three cruises and a variety of oceanic regimes will be incorporated into multivariable models to examine the fractionation of 210Po and 210Pb onto small and large particles.
