AUTHOR=Cui Xinyun , Lamborg Carl H. , Hammerschmidt Chad R. , Xiang Yang , Lam Phoebe J. 

TITLE=The Effect of Particle Composition and Concentration on the Partitioning Coefficient for Mercury in Three Ocean Basins

JOURNAL=Frontiers in Environmental Chemistry

VOLUME=2

YEAR=2021

URL=https://www.frontiersin.org/journals/environmental-chemistry/articles/10.3389/fenvc.2021.660267

DOI=10.3389/fenvc.2021.660267

ISSN=2673-4486

ABSTRACT=<p>The downward flux of sinking particles is a prominent Hg removal and redistribution process in the ocean; however, it is not well-constrained. Using data from three U.S. GEOTRACES cruises including the Pacific, Atlantic, and Arctic Oceans, we examined the mercury partitioning coefficient, <italic>K</italic><sub>d</sub>, in the water column. The data suggest that the <italic>K</italic><sub>d</sub> varies widely over three ocean basins. We also investigated the effect of particle concentration and composition on <italic>K</italic><sub>d</sub> by comparing the concentration of small-sized (1–51 μm) suspended particulate mass (SPM) as well as its compositional fractions in six different phases to the partitioning coefficient. We observed an inverse relationship between <italic>K</italic><sub>d</sub> and suspended particulate mass, as has been observed for other metals and known as the “particle concentration effect,” that explains much of the variation in <italic>K</italic><sub>d</sub>. Particulate organic matter (POM) and calcium carbonate (CaCO<sub>3</sub>) dominated the Hg partitioning in all three ocean basins while Fe and Mn could make a difference in some places where their concentrations are elevated, such as in hydrothermal plumes. Finally, our estimated Hg residence time has a strong negative correlation with average log bulk <italic>K</italic><sub>d</sub>, indicating that <italic>K</italic><sub>d</sub> has significant effect on Hg residence time.</p>