Beryllium-7 Elucidate Sediment Dynamics of the Branford River Estuary, Connecticut, USA

Authors

Gaboury Benoit, Yale Environment SchoolFollow
Matthew Hirschbeck, National Park Service - Intermountain Region
Beth Bisson, University of Maine

ORCID IDs

http://orcid.org/0000-0002-4701-5096

Date of this Version

2-18-2020

Citation

Estuaries and Coasts (2020) 43:831–842 https://doi.org/10.1007/s12237-020-00712-5

Comments

U.S. Government Works are not subject to copyright.

Abstract

Berrylium-7 elucidates sediment dynamics (i.e., sources, sinks, deposition, and resuspension) in a Connecticut estuary. Average 7 −2−1 annual atmospheric deposition of Be is 290 mBq cm year. Sediment samples from 43 locations within the estuary show that 7Be deposition is spatially complex, but were statistically indistinguishable a year apart. Weekly time series of sediments indicate 7 that levels are nearly constant on this shorter time scale on ceradio active decay is taken into account. Be levels in sediments area balance between steady losses through radioactive decay and periodic pulse inputs following rainstorms. The water column was measured intensively during three rain events, showing that 7Be is removed rapidly from the water column, with a rate constant −1 7 averaging 1.00 ± 0.12 day. A mass balance shows that Be is supplied about equally by direct precipitation onto the estuary’s surface and inflow from the watershed. Losses from the water column are split between net sedimentation (43%) and tidal flushing (57%). Variations in sedimentary 7Be levels at very short (meters) and longer (km) distances, and changes at time scales from hours to years, indicate that a large number of samples are required to capture all the variability in these highly dynamic systems. The current study differs from previous research in that a large number of measurements were conducted on a smaller system, and a full mass balance was developed.