Stable isotopic composition (d13C and d15N) of sinking particulate matter measured from short-term sediment traps in the northern Barents Sea during May 2021, Nansen Legacy cruise 2021704 Q2

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 May 2021 as part of the Nansen Legacy project (cruise 2021704, Q2). 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 12 to 27 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. At selected stations, single trap cylinders were deployed by divers 1m below the sea ice. 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.

2021年5月，作为南森遗产计划（航次2021704，Q2）的一部分，研究团队依托“哈康国王号”（R/V Kronprins Haakon）科考船，在巴伦支海北部75°N至85°N海域，利用短期漂流沉积物捕获器采集了沉降有机质的碳、氮同位素组成样品。在站位处采集高密度底层海水，经Whatman GF/F 0.7μm滤膜过滤后，注入沉积物捕获器的采样筒（丹麦KC公司制造，长径比>6），随后开展布放作业。此后，沉积物捕获器在30、40、60、90、120、200m各深度层以2或4个采样筒的配置进行布放，布放时长为12至27小时。根据海冰状况，沉积物捕获器布放于开阔水域、固定于海冰浮块或布置于冰间水道内。在选定站位，潜水员在海冰下方1米处布放单个采样筒。回收后，将各深度层采样筒内的样品合并，于4℃避光保存，以待后续分析。取250~1000mL样品过滤至经预灼烧处理的Whatman GF/F 0.7μm滤膜上（滤膜于450℃灼烧7小时），用于碳、氮稳定同位素组成分析。随后将滤膜封装于灼烧过的铝箔中，于-80℃保存。在实验室中，将滤膜于60℃烘干24小时，随后封装至5×9规格的锡胶囊（Elemental Microanalysis出品）中，采用赛默飞世尔科技（Thermo Fisher Scientific）EA IsoLink同位素比值质谱系统进行测试；该系统由赛默飞世尔科技Flash元素分析仪与DeltaV同位素比值质谱仪组成。样品在奥斯陆大学（UiO）CLIPT稳定同位素生物地球化学实验室完成分析，该实验室由挪威研究理事会通过其卓越中心资助计划#223272（地球演化与动力学中心）资助。碳、氮同位素比值的标准物质分别为维也纳佩德德箭石（Vienna PeeDee belemnite，VPDB）与大气氮。采用丙氨酸（JALA，飞世尔科技（Fischer Scientific））作为内部质量控制物质，其分析精度分别为δ¹³C_VPDB = -20.59±0.05‰（n=47次测试）与δ¹⁵N_大气 = -3.16±0.10‰（n=57次测试）。采用L-谷氨酸（JGLUT，飞世尔科技（Fischer Scientific））与甘氨酸（POPPGLY，飞世尔科技（Fischer Scientific））作为内部参考物质。δ¹³C_VPDB的内部参考物质与质量控制结果通过碳酸钙（NBS19）和碳酸锂（LSVEC）进行校准，其标准参考值分别为1.95‰与-46.6‰；δ¹⁵N_大气的校准则采用L-谷氨酸（USGS40与USGS41），标准参考值分别为-4.52‰与47.57‰。