Sauvage_23_October_2017 |
Ahearn_Olivia_23October_2017
Graduate School of Oceanography - OCG 695
23 October, 3:30 PM, Coastal Institute Auditorium
23 October, 3:30 PM, Coastal Institute Auditorium
Justine Sauvage
The contribution of water radiolysis to subseafloor sedimentary life
In marine sediment, radiolysis of water by radiation from naturally occurring radionuclides leads to production of reduced (H2) and oxidized (H2O2, O2) species. Although this radiochemical process has been known for over a century radiolytic yields in earth abundant materials are still unexplored. We experimentally quantified radiolytic H2 yields (H2 produced per unit of absorbed energy in solution) due to γ radiation (Cs-137) and α radiation (Po-210) in marine sediment by exposing seawater slurries of sediment to radiation and measuring the production of H2. These experiments demonstrate that water radiolysis is catalyzed by marine sediment. The magnitude of catalysis depends on sediment composition and radiation type. Deep-sea clay is especially effective at enhancing H2 yields, increasing yield by more than an order of magnitude relative to pure water. This previously unrecognized catalytic effect of marine sediment on radiolytic H2 production is important for fueling microbial life in the subseafloor, especially in sediment with high catalytic power. Our analysis of 9 sites in the North Atlantic, North and South Pacific suggests that H2 is the primary microbial fuel in organic-poor sediment older than a few million years; at these sites, calculated radiolytic H2 consumption rates are more than an order of magnitude higher than organic-matter oxidation rates. Similarly, in subseafloor ecosystems of continental margins, which are depleted in strong oxidants, catalyzed production of radiolytic O2 and H2O2 is a previously unrecognized cryptic source of electron acceptors.
Justine Sauvage received a BS in Physical Geography (2008), MS in Earth System Sciences (2010) and MS in Oceanography (2013) from the Free University Brussels, Leuven University and the University of Rhode Island, respectively. She entered GSO as PhD in the Spring of 2013. Her major professor are Steven’ D’Hondt, Arthur Spivack and David Fastovsky.
In marine sediment, radiolysis of water by radiation from naturally occurring radionuclides leads to production of reduced (H2) and oxidized (H2O2, O2) species. Although this radiochemical process has been known for over a century radiolytic yields in earth abundant materials are still unexplored. We experimentally quantified radiolytic H2 yields (H2 produced per unit of absorbed energy in solution) due to γ radiation (Cs-137) and α radiation (Po-210) in marine sediment by exposing seawater slurries of sediment to radiation and measuring the production of H2. These experiments demonstrate that water radiolysis is catalyzed by marine sediment. The magnitude of catalysis depends on sediment composition and radiation type. Deep-sea clay is especially effective at enhancing H2 yields, increasing yield by more than an order of magnitude relative to pure water. This previously unrecognized catalytic effect of marine sediment on radiolytic H2 production is important for fueling microbial life in the subseafloor, especially in sediment with high catalytic power. Our analysis of 9 sites in the North Atlantic, North and South Pacific suggests that H2 is the primary microbial fuel in organic-poor sediment older than a few million years; at these sites, calculated radiolytic H2 consumption rates are more than an order of magnitude higher than organic-matter oxidation rates. Similarly, in subseafloor ecosystems of continental margins, which are depleted in strong oxidants, catalyzed production of radiolytic O2 and H2O2 is a previously unrecognized cryptic source of electron acceptors.
Justine Sauvage received a BS in Physical Geography (2008), MS in Earth System Sciences (2010) and MS in Oceanography (2013) from the Free University Brussels, Leuven University and the University of Rhode Island, respectively. She entered GSO as PhD in the Spring of 2013. Her major professor are Steven’ D’Hondt, Arthur Spivack and David Fastovsky.