Assessing Past and Present Lead and Thorium Inventories and MARs Following the Deepwater Horizon Blowout

The 2010 DWH blowout caused a ~4x increase in sediment Mass Accumulation Rates (MAR) that were measured using excess 210Pb and 234Th inventories on a 10-year time series of sediment cores to determine the event impact(s) and recovery of the benthic system. This study continued the time series to determine how excess 210Pb and 234Th inventories and MARs continued to respond. Cores collected in May 2022 continued to show signs of stabilization up to 12 years after the DWH event. One Site (DSH-10) continued to show no return of bioturbation, whereas another (DWH-01) started to show signs of bioturbation 12 years after the blowout event. We suggest that Site DSH-10 either has yet to reach stabilization, or there was never bioturbation to begin with. Two sites (DSH-10 and PCB-06) continue to exhibit decreasing excess 210Pb inventories and MARs, while one site (DSH-08) remained stable over the time series, and another (MC-04) exhibited an increase in MAR in 2016. This seemingly complex pattern may reflect the different sedimentary systems, as DSH-10 and DSH-08 are on the western side of the Desoto Canyon, and have higher accumulation of siliciclastic sediments from the adjacent Mississippi River Delta. Sites PCB-06 and MC-04, on the other hand, reside in the carbonate sedimentary province east of DeSoto Canyon and reflect completely different sedimentary conditions, including much slower accumulation rates. Continued sampling and analyses will help determine if bioturbation, excess 210Pb and 234Th inventories, and MAR levels eventually stabilize, or continue to change.

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For more information: alhenes@eckerd.edu 

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