The influence of particle concentration and composition on the fractionation of 210 Po and 210 Pb along the North Atlantic GEOTRACES transect GA03

• Published in: Deep Sea Research Part I: Oceanographic Research Papers
• Main Authors: Tang, Yi, Stewart, Gillian, Lam, Phoebe J., Rigaud, Sylvain, Church, Thomas
• Other Authors: School of Earth and Environmental Sciences Queens New York, Queens College New York, City University of New York New York (CUNY)-City University of New York New York (CUNY), University of California Santa Cruz (UC Santa Cruz), University of California (UC), Détection, évaluation, gestion des risques CHROniques et éMErgents (CHROME) / Université de Nîmes (CHROME), Université de Nîmes (UNIMES), School of Marine Science and Policy, College of Earth, Ocean, and Environment Newark (CEOE), University of Delaware Newark -University of Delaware Newark, Funding for ship time, sampling operations, and hydrographic data was supported by the U.S. National Science Foundation to the US GEOTRACES North Atlantic Transect Management team of W. Jenkins (OCE-0926423), E. Boyle (OCE-0926204), and G. Cutter (OCE-0926092). This work was funded by grants from the NSF to T. Church (OCE-0961653), M. Baskaran (OCE-0961351) and G. Stewart (OCE-0960924).
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: North Atlantic Ocean; particle concentration; particle; 210 Po; 210 Pb; GEOTRACES; [SDE]Environmental Sciences; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; North Atlantic
• Online Access: https://hal.science/hal-01662380; https://hal.science/hal-01662380/document; https://hal.science/hal-01662380/file/YiTang%20et%20al_Manuscript_NAZT_Final.pdf; https://doi.org/10.1016/j.dsr.2017.09.001

International audience The disequilibrium between 210Po and 210Pb has been used as a proxy for the particle flux from the upper ocean. The particle concentration and composition effect on the partitioning behavior of 210Po and 210Pb is, however, still unclear. Here, we investigate this association by comparing dissolved (< 0.45 μm) and particulate (small: 1-51 μm; large: > 51 μm) 210Po and 210Pb activity with size-fractionated major particle concentration and composition data from the US GEOTRACES GA03 zonal transect cruises. We observed inverse relationships between partition coefficients (Kd) for the radionuclides and the concentration of suspended particulate matter (SPM) in the water column, known as the “particle concentration effect.” We examined the relationships between 210Po, 210Pb, and particle composition in the top 500m by using Pearson pairwise correlations for individual phases and principal components analysis (PCA) for variations among multiple phases. In addition to these analyses, an end- member mixing model was developed to estimate Kd for 210Po and 210Pb in the small particulate size fraction from the compositional phases. The model predicted the range of observed Kd(Pb) well, but was unable to predict the observed Kd(Po) as consistently, possibly because of the bio-reactive nature of 210Po. Despite this, we found a strong relationship between 210Po and both CaCO3 and POM, as well as between 210Pb and both opal and lithogenic phases. All of our analyses demonstrated that the fractionation of 210Po and 210Pb differed between the coast and open ocean along the GA03 transect.