Environmental & Climate Sciences Department Seminar

"Marine dissolved organic matter reactivity and a possible aerosol sink? Insights from radiocarbon (14C) analyses"

Presented by Steven R. Beaupré, School of Marine and Atmospheric Sciences, Stony Brook University

Thursday, November 9, 2017, 11:00 am — Conference Room Bldg 815E

Marine dissolved organic matter (DOM) is a complex mixture of molecules comprising the largest reservoir of organic matter in seawater, yet its sources and sinks remain largely unconstrained. While radiocarbon (14C) is a powerful tracer of time and mass, the lack of specificity in bulk 14C measurements and the analytical costs of compound specific 14C analyses have limited our observations. As an alternative, monitoring the 14C content of CO2 evolved during quantitative oxidation in concert with chemical kinetics analyses provides rapid insights into the compositions, reactivities, and coarse 14C "age" spectra of complex natural mixtures. In this talk, I will first demonstrate how monitoring photochemical and thermal oxidation reinforces a long-standing, but confusing, two-component age model of marine DOM. That is, the 14C age of DOM throughout the water column can be described as a mixture of molecules that fall into just two distinct age groups: recently produced vs. refractory DOM (RDOM). Second, I will discuss a test of one recently hypothesized sink of RDOC: namely, that RDOC could be removed from the oceans through adsorption onto the surfaces of rising bubble plumes produced by breaking waves, ejection into the atmosphere via bubble bursting as a component of primary marine aerosol (PMA), and subsequent oxidation in the atmosphere. In this test, measured the 14C signatures of PMA produced in a high capacity generator at two biologically-productive and two oligotrophic hydrographic stations in the Northwest Atlantic Ocean during a research cruise aboard the R/V Endeavor (Sep – Oct 2016). The 14C signatures of PMA generated were compared with corresponding 14C signatures in seawater of near-surface dissolved inorganic carbon (DIC, a proxy for recently produced organic matter), bulk deep DOC (a proxy for RDOC), and near-surface bulk DOC. Preliminary results and their constraints on the selectivity of PMA formation from RDOC will be discusse

Hosted by: Ernie Lewis

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