Dataset: ETNP Dissolved and Particulate Ni Cd Fe Zn Cu
Deployment: SKQ201617S

Seawater and suspended particles were collected using 5 L acid‐cleaned Teflon‐coated external‐spring "Niskin‐type" bottles (Ocean Test Equipment) on a powder‐coated trace metal clean rosette (Sea‐Bird Electronics). After collection, seawater was filtered through acid-cleaned 47 mm-diameter 0.2 μm Supor polyethersulfone filters (Pall) into acid-washed 1 L low density polyethylene bottles (Nalgene). The filters with suspended particles (>0.2 μm) were stored in acid-washed 50 mL polyethylene centrifuge tubes. Size-fractionated marine particles were also collected at station P1 using a McLane pump (McLane Research Laboratories, Falmouth, MA, USA) equipped with a 4 mm mesh screen, a 142 mm-diameter Sefar polyester mesh prefilter (51 μm pore size) and a 142 mm-diameter 0.8 μm Pall Supor polyethersulfone filter at each sampling depth. All filters and filter holders were acid leached before use based.

Seawater samples (1L) were acidified to pH = 1.8 with 1 mL concentrated distilled HCl and added with 1 mL 30% H2O2, and left for over 1 month. For particulate samples, each 47 and 142 mm-diameter filter was digested by placing the filter in a 25 mL acid-washed Teflon vial containing 5 mL of 8 M HNO₃. HF was not used to digest the samples in order to minimize the decomposition of lithogenic materials. Samples were digested on a hot plate at 120°C for 12 h. After digestion, the filters were taken out, placed into acid-washed 15 mL centrifuge tubes and rinsed with 5 mL Milli-Q water. The Milli-Q water was transferred into the same digestion vials. The digested solution was then heated on a hot plate at 80°C in a trace-metal clean hood to nearly dry. Digested and dried particle samples were re-dissolved by adding 10 mL of 4 M HNO₃, transferred into acid-washed 15 mL centrifuge tubes, and then centrifuged at 2000 rpm for 5 mins to segregate insoluble particles and filter debris.

Seawater and particulate samples were then amended with double isotope spikes of 61Ni and 62Ni, 57Fe and 58Fe, 64Zn and 67Zn, and 110Cd and 112Cd in a spike-to-sample ratio of 2:1 for Fe, and 1:1 for Ni, Zn and Cd. Ni, Cd, Fe, Zn, and Cu in both types of samples were then extracted using Nobias PA1 resin. Metals of the seawater and particle extract were further separated and purified for isotopic analysis via anion exchange chromatography with AG-MP1 resin. As Fe, Zn and Cd samples were ready for analysis after the treatment, Cu required to be purified again by AG-MP1 resin and Ni required additional purification by Nobias PA-1 resin, followed by another separation using AG-MP1 to remove contaminants. Detailed information of the whole purification steps is described in Yang et al. (2020).

Isotopic measurements were performed using a multi-collector ICP-MS (Thermo Neptune) with a desolvator nebulizer as the sample introduction system (ESI Apex- IR), and the concentrations were determined using an high-resolution ICP-MS (Thermo Element 2) with a PC3 desolvation system.