Actinium-227 (227Ac), radium-226 (226Ra) and radium-228 (228Ra) profiles in sediments were measured and modeled at 5 stations in the Northeast Pacific. Data allowed the distribution coefficient (Kd) between the solid and liquid phases for Ac and Ra.
A strong positive correlation is observed between Ra and 227Ac kd values, with 227Ac being almost 6.6 times higher than Ra kd values, and both co-varying with the MnO2 in solid phases.
The source function of 227Ac in the Northeast Pacific was determined by two independent methods: core incubation and reaction transport models. The authors also established the Ra fluxes.
The largest 227Ac and Ra isotope fluxes are near the center of the Northeast Pacific (~37ºN). Smaller 227Ac, 228Ra and 226Ra fluxes occur north of 40ºN, primarily due to dilution of their protactinium and thorium ancestors by higher sediment accumulation rates.
Kemnitz, N., Hammond, D. E., Henderson, P., Le Roy, E., Charette, M., Moore, W., Anderson, R. F., Fleisher, M. Q., Leal, A., Black, E., Hayes, C. T., Adkins, J., Berelson, W., & Bian, X. (2023). Actinium and radium fluxes from the seabed in the northeast Pacific Basin. Marine Chemistry, 250, 104180. Access the paper: 10.1016/j.marchem.2022.104180