Dissolved and Particulate Organic Carbon and its isotopic composition in the Lena Delta in winter 2019 and in summer 2019, 2017 and 2016

Dissolved and particulate Organic Carbon (DOC and POC) and their isotopic composition were measured in water samples from the Lena Delta (Sardakhskaya branch). Samples were taken in winter (April) and summer (August) 2019 during the CACOON expedition (Fuchs et al., 2021a, b and 2022) and in the summer 2017 and 2016 during previous Lena Delta sampling campaigns. Water was filtered through pre-combusted (4.5 hours, 450 °C) and pre-weighed glass fiber filters (GF/F Whatman, 0.75 µm membrane, Ø 2.5 cm) for DOC analyses, filters with rest suspended matter on it were used to analyse POC. δ13C of DOC and POC was measured by Sercon 20-20 isotope ratio mass spectrometer coupled to an Automated Nitrogen Carbon Analyzer, ∆14C of DOC and POC by accelerator mass spectrometer achieved on a Mini Carbon Dating System. Our aim was to highlight the variability in quantity and composition between seasons and suggest that permafrost deposits are degrading year around, impacting the release of organic matter through the Lena Delta.

溶解性有机碳（Dissolved Organic Carbon, DOC）与颗粒性有机碳（Particulate Organic Carbon, POC）及其同位素组成在勒拿河三角洲（萨达赫斯卡亚分支）的水样中进行了测定。样本采集于2019年冬季（4月）和夏季（8月）的CACOON考察期间（Fuchs等，2021a、b及2022），以及2016年和2017年夏季此前开展的勒拿河三角洲采样活动中。为进行DOC分析，水样经预燃烧（4.5小时，450℃）并预称重的玻璃纤维滤膜（glass fiber filters，Whatman GF/F型，膜孔径0.75μm，直径2.5cm）过滤；滤膜上留存的悬浮物用于POC分析。DOC与POC的δ¹³C值通过Sercon 20-20型同位素比值质谱仪（isotope ratio mass spectrometer）结合自动氮碳分析仪（Automated Nitrogen Carbon Analyzer）测定；DOC与POC的∆¹⁴C值通过Mini Carbon Dating System上的加速器质谱仪（accelerator mass spectrometer）测定。本研究旨在揭示季节间有机碳含量与组成的变化规律，并提出永久冻土沉积层（permafrost deposits）全年均在退化、通过勒拿河三角洲影响有机质（organic matter）释放的观点。