Residual β activity of particulate 234Th as a novel proxy for tracking sediment resuspension in the ocean

• Published in: Scientific Reports
• Main Authors: Lin, Wuhui, Chen, Liqi, Zeng, Shi, Li, Tao, Wang, Yinghui, Yu, Kefu
• Format: Text
• Language: English
• Published: Nature Publishing Group 2016
• Subjects: Article; Arctic; Arctic Ocean; Southern Ocean; Climate change
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4890035/; http://www.ncbi.nlm.nih.gov/pubmed/27252085; https://doi.org/10.1038/srep27069

Sediment resuspension occurs in the global ocean, which greatly affects material exchange between the sediment and the overlying seawater. The behaviours of carbon, nutrients, heavy metals, and other pollutants at the sediment-seawater boundary will further link to climate change, eutrophication, and marine pollution. Residual β activity of particulate 234Th (RAP234) is used as a novel proxy to track sediment resuspension in different marine environments, including the western Arctic Ocean, the South China Sea, and the Southern Ocean. Sediment resuspension identified by high activity of RAP234 is supported by different lines of evidence including seawater turbidity, residence time of total 234Th, Goldschmidt’s classification, and ratio of RAP234 to particulate organic carbon. A conceptual model is proposed to elucidate the mechanism for RAP234 with dominant contributions from 234Th-238U and 212Bi-228Th. The ‘slope assumption’ for RAP234 indicated increasing intensity of sediment resuspension from spring to autumn under the influence of the East Asian monsoon system. RAP234 can shed new light on 234Th-based particle dynamics and should benefit the interpretation of historical 234Th-238U database. RAP234 resembles lithophile elements and has broad implications for investigating particle dynamics in the estuary-shelf-slope-ocean continuum and linkage of the atmosphere-ocean-sediment system.