Geochemical characterization and material properties of coastal permafrost near Drew Point, Alaska

Permafrost cores (4.5-7.5 m long) were collected April 10th-19th, 2018, along a geomorphic gradient near Drew Point, Alaska to characterize active layer and permafrost geochemistry and material properties. Cores were collected from a young drained lake basin, an ancient drained lake basin, and primary surface that has not been reworked by thaw lake cycles. Measurements of total organic carbon (TOC) and total nitrogen (TN) content, stable carbon isotope ratios (δ13C) and radiocarbon (14C) analyses of bulk soils/sediments were conducted on 45 samples from 3 permafrost cores. Porewaters were extracted from these same core sections and used to measure salinity, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), anion (Cl-, Br-, SO4
2-, NO3
-), and trace metal (Ca, Mn, Al, Ba, Sr, Si, and Fe) concentrations. Radiogenic strontium (87Sr/86Sr) was measured on a subset of porewater samples. Cores were also sampled for material property measurements such as dry bulk density, water content, and grain size fractions.

2018年4月10日至19日，沿阿拉斯加德鲁角附近的地貌梯度，采集了长度4.5~7.5米的永久冻土岩芯（permafrost cores），以表征活动层（active layer）与永久冻土的地球化学特征及物质属性。本次采样分别选取了年轻疏干湖盆、古老疏干湖盆，以及未被热融湖循环改造的原生地表三类位点。针对3根永久冻土岩芯的45个样品，开展了总有机碳（total organic carbon, TOC）、总氮（total nitrogen, TN）含量、稳定碳同位素比值（stable carbon isotope ratios, δ¹³C）分析，以及整体土壤/沉积物的放射性碳（radiocarbon, ¹⁴C）测定。从上述相同岩芯段中提取孔隙水，用于测定盐度、溶解性有机碳（dissolved organic carbon, DOC）、总溶解氮（total dissolved nitrogen, TDN）、阴离子（Cl⁻、Br⁻、SO₄²⁻、NO₃⁻）及痕量金属（Ca、Mn、Al、Ba、Sr、Si、Fe）浓度；同时在部分孔隙水样品中完成了放射性锶（radiogenic strontium, ⁸⁷Sr/⁸⁶Sr）的测定。此外，还对岩芯开展了物质属性检测的采样工作，测定指标包括干容重（dry bulk density）、含水量（water content）与粒度组分（grain size fractions）。