Analysis of 230Th and 232Th were performed in clean laboratories of the Alfred-Wegener-Institute (AWI), following GEOTRACES methods (Anderson et al., 2012).Seawater samples were spiked with 229Th and 236U to prepare the isotope dilution analyses by ICP-MS. Spikes were calibrated against the reference standard material UREM11, a material in state of radioactive equilibrium (Hansen et al., 1983].Particles were sampled using in-situ pumps (McLane and Challenger Oceanic). 208 L to 772 L seawater were pumped through a 142 mm ᴓ, 0.45 µm pore size Supor® (polyether sulfone) filter (Anderson et al., 2012). Filters were cut aboard for subsamples under a laminar flow hood on a cutting board using tweezers and scalpels. 5/6 of the filters were used for Thorium and 231Pa (not shown in this study) analysis. A subsample (23mm ᴓ) was dried, placed onto plastic mounts, covered with Mylar and aluminum foil and directly measured by beta decay counting of 234Th (t1/2 = 24.1 days) for at least 12 h. Background measurements were performed six months later. Measurements were performed using an ICP-MS (Thermo Scientific™ ELEMENT-2™) equipped with an Apex-Q (Elemental Scientific®).===============Version comment:2020-01-28: Thorium 232, dissolved corrected