Insights into particle formation and remineralization using the short-lived radionuclide, Thoruim-234

Simple mass balance models are applied to a high resolution Th-234 profile from the northwest Pacific to examine the magnitude, rate, and depth distribution of particle remineralization processes below the euphotic zone (E-z). Here, excess Th-234 (Th-234 > U-238) below the E-z is attributed to fragmentation processes that result in the conversion of sinking to non-sinking particles. By considering particulate organic carbon (POC) to Th-234 ratios on particles, we show that POC flux attenuation is larger than for Th-234, which we attribute to bacterial and zooplankton consumption of sinking POC. Three case studies are used to demonstrate how different combinations of particle fragmentation and POC respiration impact flux attenuation below the E-z. When sampled with high vertical resolution and precision, Th-234 and POC/Th-234 ratios provide insights into both export from the E-z and the extent to which sinking particle fluxes and associated minerals are attenuated with depth. Citation: Maiti, K., C. R. Benitez-Nelson, and K. O. Buesseler (2010), Insights into particle formation and remineralization using the short-lived radionuclide, Thoruim-234, Geophys. Res. Lett., 37, L15608, doi: 10.1029/2010GL044063.