Composition and biodegradability of dissolved organic matter in supra-permafrost groundwater and surface waters near Simpson Lagoon, Alaska

Supra-permafrost groundwater (SPGW) is an important source of terrestrial dissolved organic matter (DOM) to the Arctic Ocean, yet few studies have investigated the quality or characteristics of this DOM. We sampled fresh SPGW, run-off, and rivers near Simpson Lagoon, Alaska during spring ice break-up (mid-June), summer open water (late July), and fall freeze-up (late September - early October). We measured dissolved organic carbon (DOC) concentrations in these samples and analyzed the composition of DOM using high-resolution mass spectrometry (Fourier transform ion cyclotron resonance mass spectrometry; FT-ICR MS). To measure biodegradable dissolved organic carbon (BDOC), we conducted an aerobic incubation experiment following the methods suggested by Vonk et al. (2015). Briefly, water samples were incubated at 20C for 28 days to measure DOC loss due to remineralization by in-situ microbial communities.

多年冻土上层地下水（Supra-permafrost groundwater, SPGW）是向北冰洋输入陆地溶解性有机质（dissolved organic matter, DOM）的重要来源，但目前鲜有研究探讨此类有机质的质量与组成特征。本研究于春季融冰期（六月中旬）、夏季无冰期（七月下旬）以及秋季封冻期（九月下旬至十月上旬），在阿拉斯加辛普森泻湖附近采集了新鲜的多年冻土上层地下水、径流与河水样品。随后测定了各样品中的溶解性有机碳（dissolved organic carbon, DOC）浓度，并采用高分辨质谱（傅里叶变换离子回旋共振质谱，Fourier transform ion cyclotron resonance mass spectrometry; FT-ICR MS）分析了溶解性有机质的组成。为测定可生物降解溶解性有机碳（biodegradable dissolved organic carbon, BDOC），本研究参照Vonk等人（2015）提出的方法开展了好氧培养实验：简要而言，将水样置于20℃下培养28天，以测定原位微生物群落矿化作用导致的溶解性有机碳损失量。