Production rates and radiocarbon signatures of greenhouse gases from incubations of thermokarst lake sediments in Kuujjuarapik

This dataset presents results from anoxic incubations of thermokarst lake surficial sediments from northern Quebec (Kuujjuarapik) across a range of temperatures (4, 12, and 22˚C). We measured methane (CH4) and carbon dioxide (CO2) production rates and associated radiocarbon values. In the summers of 2019 and 2021, sediment samples were collected from five lakes two different sites. The first lake (KWK1), located in the KWK valley, was formed due to mineral soil permafrost collapse. The remaining four lakes are situated in the SAS2 peatland. Permafrost in this region is found in palsa permafrost mounds, while permafrost-free areas consist of bogs with peat moss and sedges, along with numerous thermokarst lakes. The lakes sampled include SAS2X, SAS2C, SAS2A, and SAS2B. Sampling involved collecting the upper 5–10 cm of surface sediments from the central regions of the lakes using an Eckman dredge. In 2019, samples were stored in sealed 0.5 L Nalgene bottles, while in 2021, Whirlpak bags were used. The sediments were stored at 4 °C until utilized for the subsequent incubation experiments. Experiments were prepared by combining ~10 grams of homogenized sediment from the sites with 20 mL of M9 growth medium in anaerobic conditions. The slurries were sealed in serum bottles, flushed with pure Nitrogen, and incubated at three temperatures (4 °C, 12 °C, and 22 °C) with duplicates or triplicates for each site. Controls were added to assess abiotic CH4 production and verify the absence of CH4 sources other than sediment. Incubations were terminated when there was sufficient CH4 for radiocarbon measurements, approximately 1 mg of carbon or 3% CH4 in the headspace. Three sets of incubations were conducted. The first involved sediment collected in August 2019 from SAS2B, SAS2C, and KWK1 lasting 105 days. The second set, assembled eight months later due to COVID-19 restrictions, used the same sediment and extended the incubation to 219 days. The third set utilized sediment collected in August 2021 from SAS2X, SAS2C, and SAS2A for 260 days. Results in this dataset include then, production rates of CH4 and CO2, radiocarbon values of CH4 and CO2, and geochemical and isotopic characteristics of the sediment used for the incubations.本数据集收录了魁北克北部库朱阿拉皮克（Kuujjuarapik）区域热喀斯特湖（thermokarst lake）表层沉积物在4、12、22℃梯度温度下的厌氧培养实验结果。本研究测定了甲烷（CH₄）与二氧化碳（CO₂）的产生速率及其配套的放射性碳同位素数值。2019年与2021年夏季，研究团队从两处不同点位的5个湖泊中采集沉积物样本。首个湖泊KWK1坐落于KWK山谷，由矿质土壤多年冻土坍塌形成；其余4个湖泊均位于SAS2泥炭地内。该区域的多年冻土以 palsa 冻土丘（palsa permafrost mounds）形态分布，无冻土区域则为发育有泥炭藓与莎草的沼泽，伴生大量热喀斯特湖。本次采样覆盖的湖泊包括SAS2X、SAS2C、SAS2A与SAS2B。采样采用埃克曼采泥器（Eckman dredge）采集各湖泊中心区域表层5~10 cm的沉积物。2019年采集的样本储存于密封的0.5 L Nalgene瓶中，2021年的样本则使用Whirlpak袋封装，所有沉积物样品均保存于4℃环境，直至开展后续培养实验。实验将约10 g均质化原位沉积物与20 mL M9生长培养基（M9 growth medium）在厌氧条件下混合，将所得沉积物悬液密封于血清瓶（serum bottles）内，以纯氮气吹扫置换瓶内空气，随后分别在4℃、12℃、22℃三个温度下进行培养，每个点位设置2次或3次平行重复。同时设置对照组以评估非生物成因的甲烷产生量，并验证除沉积物外无其他额外甲烷来源。当顶空气体中甲烷含量达到可开展放射性碳测量的阈值（约1 mg碳或顶空体积占比3%）时，终止培养实验。本次实验共开展三组培养：第一组使用2019年8月采集自SAS2B、SAS2C与KWK1的沉积物，培养周期为105天；第二组受2019年新冠疫情（COVID-19）防控限制推迟8个月后启动，采用同一批次的沉积物，将培养周期延长至219天；第三组使用2021年8月采集自SAS2X、SAS2C与SAS2A的沉积物，培养周期为260天。本数据集收录的实验结果包括甲烷与二氧化碳的产生速率、甲烷与二氧化碳的放射性碳同位素值，以及用于培养实验的沉积物的地球化学与同位素特征。