Publication Date:
2022-10-18
Description:
© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tamborski, J., Cai, P., Eagle, M., Henderson, P., & Charette, M. Revisiting 228Th as a tool for determining sedimentation and mass accumulation rates. Chemical Geology, 607, (2022): 121006, https://doi.org/10.1016/j.chemgeo.2022.121006.
Description:
The use of 228Th has seen limited application for determining sedimentation and mass accumulation rates in coastal and marine environments. Recent analytical advances have enabled rapid, precise measurements of particle-bound 228Th using a radium delayed coincidence counting system (RaDeCC). Herein we review the 228Th cycle in the marine environment and revisit the historical use of 228Th as a tracer for determining sediment vertical accretion and mass accumulation rates in light of new measurement techniques. Case studies comparing accumulation rates from 228Th and 210Pb are presented for a micro-tidal salt marsh and a marginal sea environment. 228Th and 210Pb have been previously measured in mangrove, deltaic, continental shelf and ocean basin environments, and a literature synthesis reveals that 228Th (measured via alpha or gamma spectrometry) derived accumulation rates are generally equal to or greater than estimates derived from 210Pb, reflecting different integration periods. Use of 228Th is well-suited for shallow (〈15 cm) cores over decadal timescales. Application is limited to relatively homogenous sediment profiles with minor variations in grain size and minimal bioturbation. When appropriate conditions are met, complimentary use of 228Th and 210Pb can demonstrate that the upper layers of a core are undisturbed and can improve spatial coverage in mapping accumulation rates due to the higher sample throughput for sediment 228Th.
Description:
This research was undertaken thanks in part to funding from the Canada First Research Excellence Fund, through the Ocean Frontier Institute. This project was supported by U.S. Geological Survey Coastal and Marine Hazards and Resources Program. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. PC acknowledges the support of the Natural Science Foundation of China (NSFC) through Grants No. 92058205.
Keywords:
Sedimentation
;
Mass accumulation
;
Thorium isotopes
;
Lead-210
;
Wetlands
;
Sea level rise
Repository Name:
Woods Hole Open Access Server
Type:
Article
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