Dataset: Particle bulk d15N values from EXPORTS cruises SR1812 on R/V Sally Ride and RR1813 on R/V Roger Revelle in August to September 2018

In situ pump filtration was performed using large volume pumps (WTS-LV; McLane Research Laboratories, Inc.) outfitted with mini-MULVFS (Multiple Unit Large Volume in-situ Filtration System) filter holders (Bishop et al. 2012). Pumps were loaded with filter stacks of either 3 filter pore sizes (51- and 5-um acid cleaned Nitex screens and 1 um pre-combusted quartz fiber filter) or 4 filter pore sizes (51- and 6-um acid cleaned Nitex screens, a double layer of 1 um pre-combusted quartz fiber filters, and a double layer of 0.3 um of pre-combusted glass fiber filters). Samples were frozen at -80 degrees Celsius until laboratory analysis. Sediment trap collection was performed using surface tethered sediment traps (STT) and neutrally buoyant sediment traps (NBST). Particles were collected in polycarbonate tubes with a collection area of 0.0113 m² and triggered to close at the end of the sampling period. Samples were collected in 500 mL of 70 ppt salinity, 0.1% formaldehyde-poisoned brine, buffered to pH 8.5 with borate and overlain with 1‑um filtered surface seawater. After collection and allowing particles to sink to the bottom of the tube on board the ship for an hour, brine was filtered through a 335‑um polyester screen and rotary wet split onto pre-combusted glass fiber filters with a pore size of 0.7 um. Samples were frozen at -80 degrees Celsius until laboratory analysis.

Subsamples were split gravimetrically and packed directly into tin capsules for elemental and isotopic composition.

Analyses were carried out using a Thermo Fisher Scientific Flash Elemental Analyzer (EA) coupled to a MAT 253 Plus Isotope Ratio Mass Spectrometer (IRMS) via a Conflo IV open split interface. The EA oxidation reactor was held at 980 degrees C, the reduction reactor at 650 degrees C, and the gas chromatography column at 65 degrees C.