Using radon to quantify groundwater discharge and methane fluxes to a shallow, tundra lake on the Yukon-Kuskokwim Delta, Alaska
Using radon to quantify groundwater discharge and methane fluxes to a shallow, tundra lake on the Yukon-Kuskokwim Delta, Alaska
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DOI：
10.1007/s10533-020-00647-w
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发表时间：
2020-02-13
期刊：
影响因子：
4
通讯作者：
Henderson, Paul B.
中科院分区：
文献类型：
--
作者：
Dabrowski, Jessica S.;Charette, Matthew A.;Henderson, Paul B.
北方湖泊是向大气排放温室气体的一个来源，对全球碳收支贡献很大。然而，甲烷（CH 4）的来源，北方湖泊的制约很差，限制了我们的能力，以评估未来北极变化的影响。在这里，我们提出了测量的天然地下水示踪剂，氡，甲烷在浅湖的育空-Kuskokwim三角洲，AK和量化地下水排放率和地下水衍生的甲烷通量。我们发现，地下水中的氡和甲烷相对于湖水显着富集（2000%）。使用质量平衡方法，我们计算出平均地下水通量分别为1.2 +/- 0.6和4.3 +/- 2.0厘米/天（-1），作为保守估计和上限估计。地下水CH 4通量为7-24 mmol m（-2）day（-1），显著超过了从湖泊到大气的气-水扩散CH 4通量（1.3-2.3 mmol m（-2）day（-1）），这表明地下水是北极湖泊CH 4的重要来源，并可能驱动观测到的CH 4排放。地下水中甲烷的同位素特征被耗尽，与微生物的生产相一致。较高的甲烷浓度在地下水相比，其他高纬度湖泊可能的来源相对较高的CH 4扩散通量，相比以前报道的高纬度湖泊。这些研究结果表明，在温暖的永久冻土区的三角洲湖泊可能作为重要的热点CH 4释放整个北极景观。
Northern lakes are a source of greenhouse gases to the atmosphere and contribute substantially to the global carbon budget. However, the sources of methane (CH4) to northern lakes are poorly constrained limiting our ability to the assess impacts of future Arctic change. Here we present measurements of the natural groundwater tracer, radon, and CH4 in a shallow lake on the Yukon-Kuskokwim Delta, AK and quantify groundwater discharge rates and fluxes of groundwater-derived CH4. We found that groundwater was significantly enriched (2000%) in radon and CH4 relative to lake water. Using a mass balance approach, we calculated average groundwater fluxes of 1.2 +/- 0.6 and 4.3 +/- 2.0 cm day(-1), respectively as conservative and upper limit estimates. Groundwater CH4 fluxes were 7-24 mmol m(-2) day(-1) and significantly exceeded diffusive air-water CH4 fluxes (1.3-2.3 mmol m(-2) day(-1)) from the lake to the atmosphere, suggesting that groundwater is an important source of CH4 to Arctic lakes and may drive observed CH4 emissions. Isotopic signatures of CH4 were depleted in groundwaters, consistent with microbial production. Higher methane concentrations in groundwater compared to other high latitude lakes were likely the source of the comparatively higher CH4 diffusive fluxes, as compared to those reported previously in high latitude lakes. These findings indicate that deltaic lakes across warmer permafrost regions may act as important hotspots for CH4 release across Arctic landscapes.