K-axis dissolved iron (dFe) data from the Kerguelen-Axis region of the Southern Ocean

Sampling was conducted according to GEOTRACES protocols. Samples for trace element analyses, including dissolved iron (dFe), were filtered through acid-cleaned 0.2 um cartridge filters (Pall Acropak) under constant airflow from several ISO class 5 HEPA units. All plastic ware was acid-cleaned prior to use, following GEOTRACES protocols. Samples were collected into low-density polyethylene (LDPE) bottles, acidified immediately to pH 1.7 with Seastar Baseline hydrochloric acid (HCl), double-bagged and stored at room temperature until analysis on shore. Samples for dFe analysis were pre-concentrated offline (factor 40) on a SeaFAST S2 pico (ESI, Elemental Scientific, USA) flow injection system with a Nobias Chelate-PA1 column. Samples were eluted from the column in 10% distilled nitric acid (HNO3), with calibration based on the method of standard additions in seawater (made using multi-element standards in a 10% HNO3 matrix, rather than an HCl matrix). Pre-concentrated samples were analysed using Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICP-MS, Thermo Fisher Scientific, Inc.). Data were blank-corrected by subtracting an average acidified milli-Q blank that was treated similarly to the samples. The dFe detection limit for a given analysis run on the SeaFAST/SF-ICP-MS was calculated as 3 x standard deviation of the milli-Q blank on that run. Detection limits ranged from 0.016 to 0.067 nmol kg-1, with a median of 0.026 nmol kg-1 (n=12). GEOTRACES reference materials were analyzed along with samples and results were in good agreement with consensus values: SAFe D1 was measured at 0.69 +/- 0.05 nmol kg-1 (n=7; consensus value = 0.67 +/- 0.04 nmol kg-1) and GD was measured at 1.02 +/- 0.01 nmol kg-1 (n=6; consensus value = 1.00 +/- 0.1 nmol kg-1). Comments regarding the data spreadsheet:NaN = no sampledFe QC flags:      1 = high confidence in data quality 2 = detection limit 3 = low confidence in data qualitydetection limits: dFe data that were below the daily detection limit were replaced with the respective detection limit. They are flagged with the number 2 in the dFe QC flag column.

本研究采样严格遵循GEOTRACES规程执行。用于痕量元素分析（含溶解态铁dFe）的样品，在数台ISO 5级高效微粒空气（HEPA）过滤单元提供的恒流空气环境中，经酸清洗的0.2 μm筒式过滤器（Pall Acropak）完成过滤。所有塑料耗材均依照GEOTRACES规程，在使用前完成酸清洗处理。样品采集至低密度聚乙烯（LDPE）瓶中，即刻使用SeaStar Baseline级盐酸（HCl）酸化至pH 1.7，随后双层封装并于室温下保存，直至送至陆地实验室开展分析。针对溶解态铁分析的样品，通过Nobias Chelate-PA1富集柱，在SeaFAST S2 pico（ESI, Elemental Scientific, 美国）流动注射系统上完成离线预富集，富集倍数为40倍。样品经10%蒸馏硝酸（HNO3）从富集柱上洗脱，校准采用海水基体标准加入法——校准曲线由10%硝酸基体中的多元素标准溶液配制，而非盐酸基体。预富集后的样品采用扇形磁场电感耦合等离子体质谱（SF-ICP-MS, Thermo Fisher Scientific, Inc.）进行分析。数据分析通过扣除经相同处理流程的酸化超纯水（milli-Q）空白平均值，完成空白校正。单次分析批次的溶解态铁检测限，按该批次酸化超纯水空白的3倍标准偏差计算得出。本次分析的检测限区间为0.016~0.067 nmol·kg⁻¹，中位值为0.026 nmol·kg⁻¹（样本量n=12）。分析过程同步搭载GEOTRACES标准参考物质，测定结果与共识值吻合度良好：SAFe D1的测定值为0.69±0.05 nmol·kg⁻¹（n=7；共识值为0.67±0.04 nmol·kg⁻¹），GD的测定值为1.02±0.01 nmol·kg⁻¹（n=6；共识值为1.00±0.1 nmol·kg⁻¹）。关于数据电子表格的备注：
NaN表示未采集溶解态铁样品；
溶解态铁质量控制（QC）标记：
1 = 数据质量置信度高
2 = 结果低于当日检测限
3 = 数据质量置信度低
检测限说明：低于当日检测限的溶解态铁数据将替换为对应批次的检测限值，并在溶解态铁QC标记列中以数值2标注。