Stable isotopic composition (d13C and d15N) of sinking particulate matter measured from short-term sediment traps in the northern Barents Sea during August 2019, Nansen Legacy cruise 2019706 Q3

Samples for carbon and nitrogen isotopic composition of sinking organic matter were collected with short-term drifting sediment traps between 75° and 85°N in the northern Barents Sea with R/V Kronprins Haakon in August 2019 as part of the Nansen Legacy project (cruise 2019706, Q3). High-density bottom water was collected at the station and filtered (Whatman GF/F 0.7µm), and then filled into the trap cylinders (KC Denmark, aspect ratio >6) prior to their deployment. Afterwards, the sediment traps were deployed with 2 or 4 cylinders at each depth (30, 40, 60, 90, 120, 200m) for a duration between 18 to 25 hours. Depending on the sea ice conditions, the sediment traps were deployed in open water, anchored to a sea ice floe or within an ice lead. Upon retrieval, the content of the cylinders from each depth was pooled and stored at 4°C in dark until further analyses. Between 250-1000ml were filtered onto pre-combusted 0.7µm GF/F filters (Whatman, combusted for 7h at 450°C) for the analysis of carbon and nitrogen stable isotopic composition. The filters were then packed in combusted aluminium foil and stored at -80°C. In the lab, the filters were dried for 24h at 60°C and subsequently packed 5x9 tin capsules (Elemental Microanalysis), and then measured with a Thermo Fisher Scientific EA IsoLink IRMS System, which consists of a Thermo Fisher Scientific Flash Elemental Analyzer and a Thermo Fisher Scientific DeltaV Isotope Ratio Mass Spectrometer. Samples were analyzed at the CLIPT stable isotope biogeochemistry lab at UiO, funded by the Research Council of Norway through its Centers of Excellence funding scheme #223272 (Centre for Earth Evolution and Dynamics). Standards for isotopic ratios for carbon and nitrogen were Vienna PeeDee belemnite and air, respectively. Alanine (JALA, Fischer Scientific) was used for internal quality assurance with an analytical precision of δ¹³CVPDB = -20.59 +- 0.05 ‰ (n = 47 runs) and δ15NAIR = -3.16 +- 0.10 ‰ (n = 57), respectively. L-glutamic acid (JGLUT, Fischer Scientific) and glycine (POPPGLY, Fischer Scientific) were used as internal reference material. Internal references and quality assurance for δ13CVPDB were calibrated against calcium carbonate (NBS19) and lithium carbonate (LSVEC) with consensus values 1.95 ‰ and -46.6 ‰, respectively, and for δ15NAIR against L-glutamic acid (USGS40 and USGS41) with consensus values -4.52 ‰ and 47.57 ‰, respectively.

本数据集的沉降有机质碳、氮同位素组成样品，采集于2019年8月巴伦支海北部北纬75°至85°海域，依托“哈康王储号”（R/V Kronprins Haakon）科考船，作为南森遗产计划（Nansen Legacy project，航次编号2019706、航段Q3）的组成部分，通过短期漂流沉积物捕集器（short-term drifting sediment traps）获取。

科考站位处采集了高密度底层水，经沃特曼GF/F型0.7微米滤膜（Whatman GF/F 0.7µm）过滤后，注入捕集器圆柱舱（丹麦KC公司（KC Denmark）生产，长径比＞6）待用。随后，沉积物捕集器按每站位2或4个圆柱舱的配置，在30、40、60、90、120、200米深度布设，布设时长为18至25小时。根据海冰状况，捕集器可部署于开阔水域、锚定于浮冰块（sea ice floe）或冰间水道（ice lead）中。

回收后，将各深度舱内的样品混合，于4℃避光环境保存以待后续分析。取250~1000毫升样品，经预先灼烧的0.7微米沃特曼GF/F滤膜（Whatman，450℃灼烧7小时）过滤，用于碳、氮稳定同位素组成分析。随后将滤膜封装于灼烧铝箔中，于-80℃低温保存。

实验室环节中，滤膜经60℃烘干24小时后，装入5×9规格的锡囊（Elemental Microanalysis公司生产），通过赛默飞世尔科技（Thermo Fisher Scientific）EA IsoLink同位素比值质谱系统（EA IsoLink IRMS System，由赛默飞世尔科技Flash元素分析仪与赛默飞世尔科技DeltaV同位素比值质谱仪组成）完成测试。样品分析工作在奥斯陆大学（UiO，University of Oslo）CLIPT稳定同位素生物地球化学实验室（CLIPT stable isotope biogeochemistry lab）完成，该项目由挪威研究理事会（Research Council of Norway）通过其卓越中心资助计划#223272（Centers of Excellence funding scheme #223272，地球演化与动力学中心（Centre for Earth Evolution and Dynamics））资助。

碳、氮同位素比值的国际标准分别为维也纳佩迪箭石（Vienna PeeDee belemnite）与大气空气。采用丙氨酸（Alanine，货号JALA，飞世尔科技（Fischer Scientific））作为内部质控样品，其分析精密度为δ¹³C_(VPDB) = -20.59 ± 0.05 ‰（n=47组测试），δ¹⁵N_(AIR) = -3.16 ± 0.10 ‰（n=57组测试）。采用L-谷氨酸（L-glutamic acid，货号JGLUT，飞世尔科技（Fischer Scientific））与甘氨酸（glycine，货号POPPGLY，飞世尔科技（Fischer Scientific））作为内部参考物质。碳同位素δ¹³C_(VPDB)的内部参考物质与质控样品，通过碳酸钙标准物质NBS19（标准定值1.95 ‰）与碳酸锂标准物质LSVEC（标准定值-46.6 ‰）校准；氮同位素δ¹⁵N_(AIR)则通过L-谷氨酸标准物质USGS40（标准定值-4.52 ‰）与USGS41（标准定值47.57 ‰）校准。