Data from: Seasonal and spatial dynamics of gas ebullition in a temperate water-storage reservoir

Gas ebullition of river impoundments plays an increasingly significant role, particularly in transporting methane CH4 from their sediments to the atmosphere, and contributing to the global carbon budget and global warming. Quantifying stochastic and episodic nature of gas ebullition is complicated especially when conventionally conducted by using coverage-limited gas traps. Current knowledge of seasonality in a reservoir’s gas ebullition is lacking in the literature. For this reason, advanced acoustic surveying was intensively applied to determine spatiotemporal distributions of gas ebullition in a European water-storage reservoir for two years. Additionally, the sampling was accompanied with gas collecting for analyzing gas composition. The gas released from the reservoir was primarily composed of CH4 (on average 52%, up to 94%). The longitudinal distribution of gas ebullition was mainly determined by a proximity to the river inflow as a source of organic matter. A magnitude of ebullitive fluxes within the reservoir varied up to 1,300 mL m-2 d-1(30 mmol CH4 m-2 d-1). The most significant period of ebullition has turned out to be in fall, on average reaching a sevenfold ebullitive flux (70 mL m-2 d-1, 1.6 mmol CH4 m-2 d-1) higher than in the rest of the season. A substantial contribution to the fall peak was induced by an expansion of gas ebullition into greater depths, covering two thirds of the reservoir in late fall. The study demonstrates that the ebullitive fluxes of the temperate water storage reservoir were correlated to season, depth, and inflow proximity.河流蓄水水库的气体冒泡释出正发挥着日益重要的作用，尤其是在将沉积物中的甲烷（CH4）输送至大气，并对全球碳收支与全球变暖产生贡献方面。量化气体冒泡释出的随机性与突发性特征极具挑战性，尤其是在使用覆盖范围有限的气体收集阱进行常规监测时。当前学界对水库气体冒泡释出的季节变化规律仍缺乏充分认知。为此，研究团队连续两年采用先进声学探测技术，对某欧洲蓄水水库的气体冒泡释出时空分布特征展开了密集监测。此外，本次监测同步开展气体采集工作，以分析释出气体的组分。该水库释出的气体主要成分为甲烷，平均占比达52%，最高可达94%。气体冒泡释出的纵向分布主要取决于其与作为有机质来源的河流入水口的距离。水库内的冒泡释气通量最高可达1300 mL·m⁻²·d⁻¹（对应30 mmol CH4·m⁻²·d⁻¹）。研究发现，释气活动最活跃的时段为秋季，其冒泡通量平均可达其他季节的7倍（分别为70 mL·m⁻²·d⁻¹与1.6 mmol CH4·m⁻²·d⁻¹）。秋季释气峰值的出现，主要源于冒泡释出活动向更深水域扩张，在晚秋时期，释气区域覆盖了水库三分之二的水域。本研究表明，该温带蓄水水库的冒泡释气通量与季节、水深以及与入水口的距离显著相关。