Compositions of sedimentary organic matter of surface sediments in the northern South China Sea

This dataset includes total organic carbon (TOC), stable carbon isotope (δ13C), and radiocarbon activity (expressed as Fm) of TOC, as well as mineral surface area (SA), mean grain size, and calcium carbonate (CaCO3) of 89 surface sediment samples from the northern South China Sea. The samples were collected through the German R/V SONNE cruises SO50, SO72A, SO95, and SO132 during July–September 1987, October–November 1990, April–June 1994, and June–July 1998, respectively. TOC and stable carbon isotope (δ13C) of the decarbonated samples were measured by an elemental analyzer interfaced with an isotope ratio mass spectrometer (EA-IRMS; Flash EA 1112 HT-Delta V Advantage). The standard deviations of TOC content and δ13C were 0.03% and 0.08‰, respectively, by replicate measurements of the same acetanilide standard samples. Radiocarbon activity of carbonate free sediment were measured using a Mini Carbon Dating System (MICADAS) accelerated mass spectrometry at the Laboratory of Ion Beam Physics, ETH Zürich. Radiocarbon data are reported as \"fraction modern\" (Fm), representing the deviations of the 14C/12C ratio from 95% modern oxalic acid standard. The absolute error of Fm is better than ±0.01. The conventional radiocarbon ages are calculated based on the equation of t = –8033 ln (Fm), in years Before Present (yr BP, where present is 1950 AD). Organic-free mineral surface area (SA) was measured using a 5-point Brunauer-Emmett-Teller (BET) nitrogen adsorption method on NOVA 4000 SA analyzer (Quantachrome Instrument). The standard deviations of two reference minerals are 0.03 and 0.14 m2 g–1, respectively. The sample was then performed for mean grain size analysis using a laser Particle Size Analyzer (Malvern Mastersizer 2000). The calcium carbonate content of the samples was determined by a vacuum-gasometric system with a relative accuracy of ±0.7%.本数据集涵盖南海北部89个表层沉积物样品的总有机碳（total organic carbon, TOC）、稳定碳同位素（stable carbon isotope, δ¹³C）及总有机碳的放射性碳活度（以现代碳分数Fm表示），同时包含样品的矿物比表面积（mineral surface area, SA）、平均粒径与碳酸钙（calcium carbonate, CaCO₃）含量。该批次样品分别由德国R/V SONNE号科考船于1987年7—9月、1990年10—11月、1994年4—6月及1998年6—7月执行的SO50、SO72A、SO95和SO132航次采集。脱碳酸盐化处理后样品的总有机碳与稳定碳同位素（δ¹³C）采用元素分析仪-同位素比质谱联用法（EA-IRMS；Flash EA 1112 HT-Delta V Advantage）进行测定；通过对同一乙酰苯胺标准样品的重复测定，总有机碳含量与稳定碳同位素值的标准偏差分别为0.03%与0.08‰。不含碳酸盐沉积物的放射性碳活度采用迷你碳测年系统（MICADAS）加速器质谱法，于苏黎世联邦理工学院（ETH Zürich）离子束物理实验室完成测定。放射性碳数据以“现代碳分数”（Fm）形式报告，其表征的是¹⁴C/¹²C比值与95%现代草酸标准的偏差，现代碳分数的绝对误差优于±0.01。常规放射性碳年龄基于公式t = -8033 ln(Fm)计算，单位为距今年（yr BP，其中“距今”指公元1950年）。无有机质矿物比表面积（SA）采用5点布鲁瑙厄-埃梅特-泰勒（Brunauer-Emmett-Teller, BET）氮气吸附法，在NOVA 4000 SA比表面积分析仪（Quantachrome Instruments）上完成测定；两种标准参考矿物的测定标准偏差分别为0.03与0.14 m²·g⁻¹。随后采用激光粒度分析仪（Malvern Mastersizer 2000）对样品开展平均粒径分析。样品的碳酸钙含量采用真空气体分析法测定，相对精度为±0.7%。