| Summary: | Maintenance and Update Frequency: notPlanned Statement: Cleaning: All trace metal sampling and analyses techniques were based on the international GEOTRACES program’s cookbook (Cutter et al., 2017). Briefly, new 60 mL LDPE sample bottles were cleaned in 2% v:v Decon-90 for one week to remove any residue from manufacturing, after which bottles were rinsed four times with deionised water and thrice in ultra-high purity (UHP) water. The bottles were filled with 6M hydrochloric acid (HCl) and placed in a 1.2M HCl bath for one month. Bottles were rinsed again with UHP water, filled with trace metal grade 1.2M HCl and triple-bagged for transportation. Bottles were rinsed thrice with freshly collected seawater prior to sampling. Dissolved trace elements: Water profiles were sampled using a purpose-built Trace Metal Rosette (TMR; General Oceanics Inc.), comprising twelve 10L Teflon-lined Niskin bottles, each equipped with an external spring and automatic firing mechanism. The TMR was deployed from the ship with a Dyneema™ line to a maximum depth of 1,200 m. Bottles were programmed to fire at predetermined depths to sample the water column during the ascent. Once onboard, Niskin bottles were carefully transported to a trace-metal-clean laboratory equipped with an ISO 5 HEPA filtered air system. Sixty mL of seawater from each depth was sampled using acid-washed AcroPak 0.2 µm filters and acidified to pH 1.8 with ultrapure HCl (Seastar Baseline) for trace element analysis in Australia. Seawater samples were analysed for a suite of dissolved trace elements (including Fe, Mn, and Ti, among others) using a commercially available, offline seaFAST preconcentration system (SC-4 DX seaFAST S2/pico, ESI, USA) with sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) detection. Briefly, samples were loaded onto a Nobias PA1 resin column (200 µL) to retain metals of interest. Trace metals were then eluted with 0.75 mL of 1.6 M ultrapure nitric acid (HNO3; Seastar Baseline). This method allowed the seawater matrix ...
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