Pellerin André, Lotem Noam, Walter Anthony Katey, Eliani Russak Efrat, Hasson Nicholas, Røy Hans, Chanton Jeffrey P, Sivan Orit
Department of Earth and Environmental Sciences, Ben Gurion University of the Negev, Beersheva, Israel.
Water and Environmental Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, USA.
Glob Chang Biol. 2022 May;28(10):3206-3221. doi: 10.1111/gcb.16151. Epub 2022 Mar 18.
Methane (CH ) release to the atmosphere from thawing permafrost contributes significantly to global CH emissions. However, constraining the effects of thaw that control the production and emission of CH is needed to anticipate future Arctic emissions. Here are presented robust rate measurements of CH production and cycling in a region of rapidly degrading permafrost. Big Trail Lake, located in central Alaska, is a young, actively expanding thermokarst lake. The lake was investigated by taking two 1 m cores of sediment from different regions. Two independent methods of measuring microbial CH production, long term (CH accumulation) and short term ( C tracer), produced similar average rates of 11 ± 3.5 and 9 ± 3.6 nmol cm d , respectively. The rates had small variations between the different lithological units, indicating homogeneous CH production despite heterogeneous lithology in the surface ~1 m of sediment. To estimate the total CH production, the CH production rates were multiplied through the 10-15 m deep talik (thaw bulb). This estimate suggests that CH production is higher than emission by a maximum factor of ~2, which is less than previous estimates. Stable and radioactive carbon isotope measurements showed that 50% of dissolved CH in the first meter was produced further below. Interestingly, labeled C incubations with 2- C acetate and C CO indicate that variations in the pathway used by microbes to produce CH depends on the age and type of organic matter in the sediment, but did not appear to influence the rates at which CH was produced. This study demonstrates that at least half of the CH produced by microbial breakdown of organic matter in actively expanding thermokarst is emitted to the atmosphere, and that the majority of this CH is produced in the deep sediment.
永久冻土融化向大气释放甲烷（CH₄）对全球CH₄排放有显著贡献。然而，为预测未来北极地区的排放情况，需要确定控制CH₄产生和排放的融化效应。本文给出了在快速退化的永久冻土区域CH₄产生和循环的可靠速率测量结果。位于阿拉斯加中部的大径湖是一个年轻且正在积极扩张的热喀斯特湖。通过从不同区域采集两个1米长的沉积物岩芯对该湖进行了研究。两种测量微生物CH₄产生的独立方法，即长期（CH₄积累）和短期（¹³C示踪），分别得出了相似的平均速率，即11±3.5和9±3.6 nmol cm⁻³ d⁻¹。不同岩性单元之间的速率变化较小，这表明尽管沉积物表层约1米的岩性不均一，但CH₄产生是均匀的。为估算CH₄的总产生量，将CH₄产生速率乘以10 - 15米深的融区（融化球）。该估算表明CH₄产生量比排放量最多高约2倍，这低于先前的估算。稳定和放射性碳同位素测量表明，在第一米深度内溶解的CH₄中有50%是在更深层产生的。有趣的是，用²-¹³C乙酸盐和¹³C CO₂进行的¹³C标记培养表明，微生物产生CH₄所使用的途径变化取决于沉积物中有机质的年龄和类型，但似乎并未影响CH₄的产生速率。这项研究表明，在正在积极扩张的热喀斯特中，由微生物分解有机质产生的CH₄至少有一半排放到了大气中，并且这些CH₄的大部分是在深层沉积物中产生的。
