Dataset: Particulate Th data from samples collected on 5 cruises at Station ALOHA off Hawaii and Station M off California from 2019 to 2020

Particulate sample collection methods are similar to those described by Roca-Marti et al. (2021). Briefly, 142 mm diameter, 0.3 micron (µm) pore-size GF75 filters, 1 µm pore-size QMA filters, and 53 µm pore-size Nitex filters were cleaned according to trace metal clean protocols. Filters were mounted sequentially by size on metal-free mini-MLVFS filter holders attached to the in situ pumps and deployed at depths between 10 and 4000 depending on the cruise. Between ~500-2000 L of water were filtered per deployment at a rate of 8 L/minute. High flow rates of ~20 L/minute were used to filter large volumes of water (~5000-7000 L) required for capturing sufficient > 53 µm particles for isotopic and compound specific analyses.

Small particles collected using QMA and GF75 filters were subsampled using a ~22 mm Delrin punch for particulate 234Th, total carbon (C), and bulk C and nitrogen (N) isotopic analyses under trace metal clean conditions. Large particle (> 53 µm) samples for 234Th, C, and bulk N were rinsed onto 25 mm QMA filters using 0.2 µm filtered seawater and visible swimmers were removed. Samples were then dried, mounted onto RISO discs, and stored at 4˚C prior to and immediately following counting. All samples were counted on a low level RISO beta counter using a helium/1%butane gas mixture.