Annotated and filtered molecular formulas associated with dissolved organic matter molecular composition data of exemplary water masses resolved by online LC-FT-ICR-MS@en

The unique chromatographic behaviour of DOM was investigated on three exemplary water samples representing coastal DOM, oceanic surface DOM and oceanic refractory DOM. Weddell Sea surface (30 m depth, oceanic surface DOM) and deep water (1356 m depth, refractory DOM) was sampled with a rosette sampler on RV Polarstern during ANT XXII/2 (station PS67/006-130, latitude -67.5633, longitude -55.3448) and are described elsewhere (El Naggar et al., 2007; Koch et al., 2008). Coastal DOM is routinely extracted from southern North Sea (latitude 54.1447, longitude 7.8711) and used as an in-house laboratory standard. Mass spectra were obtained with liquid chromatography coupled to a Fourier-transform ion cyclotron resonance mass spectrometer (LC-FT-ICR-MS) with negative electrospray ionisation. A 7 Tesla scimaX MRMS system (Bruker Daltonics GmbH & Co. KG, Bremen, Germany) was coupled to an ultra-performance liquid chromatography system (UPLC, Elute LC, Bruker Daltonics GmbH & Co. KG, Bremen, Germany). Reversed phase chromatography was done with a C18 column (Waters AQUITY 2 x 100 mm, 1.7 µm) column at 0.3 mL min 1 and a linear gradient: A (ultrapure water, 4 mmol L 1 ammonium formate) 2 min: 99 %, 11 min: 0 %, 14.9 min: 99 %; B (MeOH, 4 mmol L 1 ammonium formate) 2 min: 1 %, 11 min: 100 %, 14.5 min 100 %, 14.9 min 1 %. The exact mass lists and intensities of the 1.1 min binned scans were exported with the DataAnalysis 5.3 software package (Bruker Daltonics GmbH & Co. KG, Bremen, Germany). Scans were calibrated with an in-house script. Molecular formulas were assigned with the following elemental composition: 12C≤∞1H≤∞16O≤∞14N≤232S≤1 within 0.3 ppm mass deviation, and filtered with the Ultra Mass Explorer (UME, www.awi.de/en/ume, (Leefmann et al., 2019)).本研究针对三类典型水体样品——沿海溶解有机质（Dissolved Organic Matter, DOM）、海洋表层溶解有机质与海洋难降解溶解有机质，探究了DOM独特的色谱行为。威德尔海表层水样（水深30 m，对应海洋表层DOM）与深层水样（水深1356 m，对应海洋难降解DOM），于ANT XXII/2航次（站位PS67/006-130，纬度-67.5633，经度-55.3448）中搭载“极星号”（RV Polarstern）科考船通过罗塞塔采样器采集完成，相关细节已在既往文献中报道（El Naggar等，2007；Koch等，2008）。沿海DOM常规提取自北海南部海域（纬度54.1447，经度7.8711），并作为实验室内部标准品使用。本研究采用液相色谱-傅里叶变换离子回旋共振质谱（liquid chromatography coupled to a Fourier-transform ion cyclotron resonance mass spectrometer, LC-FT-ICR-MS）结合负电喷雾电离模式获取质谱数据，实验联用7 T scimaX MRMS系统（德国不来梅布鲁克道尔顿股份有限公司&两合公司）与超高效液相色谱系统（Ultra-performance liquid chromatography, UPLC, Elute LC，德国不来梅布鲁克道尔顿股份有限公司&两合公司）。反相色谱分离采用C18色谱柱（Waters AQUITY 2 × 100 mm，1.7 μm），流速设置为0.3 mL·min⁻¹，采用线性梯度洗脱程序：流动相A为超纯水（含4 mmol·L⁻¹甲酸铵），2 min时占比99%，11 min时降至0%，14.9 min时恢复至99%；流动相B为甲醇（含4 mmol·L⁻¹甲酸铵），2 min时占比1%，11 min时升至100%，14.5 min维持100%，14.9 min降至1%。以1.1 min为分箱间隔的扫描数据的精确质荷比列表与峰强度，通过"DataAnalysis 5.3"软件包（德国不来梅布鲁克道尔顿股份有限公司&两合公司）导出。扫描数据通过内部自编脚本完成校准。分子分子式指派基于以下元素组成约束：¹²C≤∞、¹H≤∞、¹⁶O≤∞、¹⁴N≤232、³²S≤1，质量偏差阈值为0.3 ppm，并通过Ultra Mass Explorer（UME, "www.awi.de/en/ume", Leefmann等，2019）进行过滤。