Quantifying 'Blue Carbon' Exports from Salt Marshes Using Radium Isotopes
Description/Abstract/Artist Statement
In this study, we seek to determine if there is significant groundwater flushing within a salt marsh environment and to what degree this groundwater contributes to carbon exports from the salt marsh to the ocean. We also seek to categorize whether inorganic carbon in the water is exported as alkalinity or dissolved carbon dioxide and, as a result, how long we can expect it to remain sequestered in the ocean. Data collection occurred at The Nature Conservancy’s Brownsville Preserve on the Eastern Shore of Virginia. We collected samples of surface water from the onsite stream and of groundwater from four sites near the stream for radium and carbon analysis. We also gathered segments of a sediment core from six depths at one of the sites for radium and thorium analysis. Using the Radium Delayed Coincedence Counter (RaDeCC) method, we measured the concentration of radioactive radium-223 and radium-224 isotopes in the samples in order to quantify the water flux through the groundwater system and estimate the rate of flushing of radium compared to the background rate of radium generation from its parent material, thorium. In the scope of this study, radium and thorium were in secular equilibrium in every sample collected, indicating no significant groundwater flushing. However, this does not preclude the occurrence of flushing at other depths or locations not sampled. Also discussed are the abundance of inorganic carbon in the system and its speciation, whether it contributes alkalinity to the waters or exists primarily as dissolved carbon dioxide, and any spatial variations in this pattern.
Faculty Advisor/Mentor
Joseph Tamborski, David Burdige
Faculty Advisor/Mentor Department
Ocean and Earth Sciences Department
College Affiliation
College of Sciences
Presentation Type
Poster
Disciplines
Geochemistry | Geology | Hydrology
Session Title
Poster Session
Location
Learning Commons Lobby @ Perry Library
Start Date
3-25-2023 8:30 AM
End Date
3-25-2023 10:00 AM
Quantifying 'Blue Carbon' Exports from Salt Marshes Using Radium Isotopes
Learning Commons Lobby @ Perry Library
In this study, we seek to determine if there is significant groundwater flushing within a salt marsh environment and to what degree this groundwater contributes to carbon exports from the salt marsh to the ocean. We also seek to categorize whether inorganic carbon in the water is exported as alkalinity or dissolved carbon dioxide and, as a result, how long we can expect it to remain sequestered in the ocean. Data collection occurred at The Nature Conservancy’s Brownsville Preserve on the Eastern Shore of Virginia. We collected samples of surface water from the onsite stream and of groundwater from four sites near the stream for radium and carbon analysis. We also gathered segments of a sediment core from six depths at one of the sites for radium and thorium analysis. Using the Radium Delayed Coincedence Counter (RaDeCC) method, we measured the concentration of radioactive radium-223 and radium-224 isotopes in the samples in order to quantify the water flux through the groundwater system and estimate the rate of flushing of radium compared to the background rate of radium generation from its parent material, thorium. In the scope of this study, radium and thorium were in secular equilibrium in every sample collected, indicating no significant groundwater flushing. However, this does not preclude the occurrence of flushing at other depths or locations not sampled. Also discussed are the abundance of inorganic carbon in the system and its speciation, whether it contributes alkalinity to the waters or exists primarily as dissolved carbon dioxide, and any spatial variations in this pattern.