Minor methane emissions from an Alpine hydropower reservoir based on monitoring of diel and seasonal variability,Environmental Science: Processes & Impacts

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Minor methane emissions from an Alpine hydropower reservoir based on monitoring of diel and seasonal variability
Environmental Science: Processes & Impacts ( IF 4.3 ) Pub Date : 2017-08-11 00:00:00 , DOI: 10.1039/c7em00232g
Sébastien Sollberger _{1,

2,

3,

4,

5} , Bernhard Wehrli _{1,

2,

3,

4,

5} , Carsten J. Schubert _{1,

2,

3,

4,

5} , Tonya DelSontro _{1,

2,

3,

4,

5} , Werner Eugster _{5,

6,

7,

8,

9}

Affiliation

We monitored CH₄ emissions during the ice-free period of an Alpine hydropower reservoir in the Swiss Alps, Lake Klöntal, to investigate mechanisms responsible for CH₄ variability and to estimate overall emissions to the atmosphere. A floating eddy-covariance platform yielded total CH₄ and CO₂ emission rates at high temporal resolution, while hydroacoustic surveys provided no indication of CH₄ ebullition. Higher CH₄ fluxes (2.9 ± 0.1 mg CH₄ per m² per day) occurred during the day when surface water temperatures were warmer and wind speeds higher than at night. Piston velocity estimates (k₆₀₀) showed an upper limit at high wind speeds that may be more generally valid also for other lakes and reservoirs with limited CH₄ dissolved in the water body: above 2.0 m s⁻¹ a further increase in wind speed did not lead to higher CH₄ fluxes, because under such conditions it is not the turbulent mixing and transport that limits effluxes, but the resupply of CH₄ to the lake surface. Increasing CH₄ fluxes during the warm season showed a clear spatial gradient once the reservoir started to fill up and flood additional surface area. The warm period contributed 27% of the total CH₄ emissions (2.6 t CH₄ per year) estimated for the full year and CH₄ accounted for 63% of carbonic greenhouse gas emissions. Overall, the average CH₄ emissions (1.7 to 2.2 mg CH₄ per m² per day determined independently from surface water samplings and eddy covariance, respectively) were small compared to most tropical and some temperate reservoirs. The resulting greenhouse gas (GHG) emissions in CO₂-equivalents revealed that electricity produced in the Lake Klöntal power plant was relatively climate-friendly with a low GHG-to-power output ratio of 1.24 kg CO_2,eq per MW h compared to 6.5 and 8.1 kg CO_2,eq per MW h associated with the operation of solar photovoltaics and wind energy, respectively, or about 980 kg CO_2,eq per MW h for coal-fired power plants.

中文翻译：

基于监测迪尔和季节性变化的高山水电站的少量甲烷排放

我们在瑞士阿尔卑斯山克伦塔尔湖的一座高山水库无冰期期间监测了CH _4的排放，以调查造成CH ₄变异的机制，并估算向大气的总体排放。漂浮的涡度协方差平台在高时间分辨率下产生了总的CH ₄和CO ₂排放率，而水声调查没有提供CH ₄沸腾的迹象。白天，当地表水温度升高且风速高于夜间时，发生了更高的CH ₄通量（每天每m ²为2.9±0.1 mg CH ₄）。活塞速度估算值（k ₆₀₀）在高风速下显示上限，这对于在水体中溶解有有限CH _4的其他湖泊和水库也可能更普遍有效：在2.0 ms ^-1以上，风速的进一步提高并未导致更高的CH ₄通量，因为在这样的条件下，不是湍流的混合和传输限制了流出，而是CH ₄向湖泊表面的再供应。一旦储层开始注满并淹没额外的表面积，在暖季期间增加的CH ₄通量就显示出明显的空间梯度。温暖期占全年估计的CH ₄排放总量（每年2.6 t CH ₄）和CH ₄排放总量的27％。占碳温室气体排放量的63％。总体而言，与大多数热带水库和一些温带水库相比，平均CH ₄排放量（每天每m ² 1.7至2.2 mg CH ₄分别独立于地表水采样和涡动协方差确定）很小。产生的以CO ₂当量表示的温室气体（GHG）排放量表明，克伦塔尔湖发电厂生产的电力相对气候友好，温室气体发电比为1.24千克二氧化碳_2当量/兆瓦时，与每兆瓦时6.5和8.1千克二氧化碳_当量，与太阳能光伏发电和风能的运行相关，或约980千克二氧化碳_当量燃煤电厂的每兆瓦时。

更新日期：2017-08-25

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