Estimates of regional and global freshwater N2 O emissions have remained inaccurate due to scarce data and complexity of the multiple processes driving N2 O fluxes the focus predominantly being on summer time measurements from emission hot spots, agricultural streams. Here, we present four-season data of N2 O concentrations in the water columns of randomly selected boreal lakes covering a large variation in latitude, lake type, area, depth, water chemistry, and land use cover. Nitrate was the key driver for N2 O dynamics, explaining as much as 78% of the variation of the seasonal mean N2 O concentrations across all lakes. Nitrate concentrations varied among seasons being highest in winter and lowest in summer. Of the surface water samples, 71% were oversaturated with N2 O relative to the atmosphere. Largest oversaturation was measured in winter and lowest in summer stressing the importance to include full year N2 O measurements in annual emission estimates. Including winter data resulted in fourfold annual N2 O emission estimates compared to summer only measurements. Nutrient-rich calcareous and large humic lakes had the highest annual N2 O emissions. Our emission estimates for Finnish and boreal lakes are 0.6 and 29 Gg N2 O-N/year, respectively. The global warming potential of N2 O from lakes cannot be neglected in the boreal landscape, being 35% of that of diffusive CH4 emission in Finnish lakes.

中文翻译：

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湖泊是北方景观中的一氧化二氮源。

由于缺乏数据以及驱动N2 O通量的多个过程的复杂性，对区域和全球淡水N2 O排放量的估算仍然不准确，重点主要放在排放热点，农业溪流的夏季时间测量上。在这里，我们介绍了随机选择的北方湖泊水柱中N2 O浓度的四个季节数据，这些数据涵盖了纬度，湖泊类型，面积，深度，水化学和土地利用覆盖率的巨大变化。硝酸盐是N2 O动态的关键驱动因素，解释了所有湖泊中季节性N2 O浓度平均变化的78％。硝酸盐浓度随季节的变化而变化，冬季最高，夏季最低。在地表水样品中，有71％的N2 O相对于大气过饱和。在冬天测得最大的过饱和度，在夏天测得最低的过饱和度，这强调了将全年N2 O测量值包括在年度排放估算中的重要性。包括冬季数据在内，与仅夏季测量相比，年度N2 O排放估算值是原来的四倍。富含营养的钙质和大型腐殖质湖泊的年度N2 O排放量最高。我们对芬兰和北方湖泊的排放估算分别为每年0.6 Gg和29 Gg N2 ON。在北方地区，湖泊中N2 O的全球变暖潜力不可忽视，是芬兰湖泊中CH4扩散排放量的35％。富含营养的钙质和大型腐殖质湖泊的年度N2 O排放量最高。我们对芬兰和北方湖泊的排放估算分别为每年0.6 Gg和29 Gg N2 ON。在北方地区，湖泊中N2 O的全球变暖潜力不可忽视，是芬兰湖泊中CH4扩散排放量的35％。富含营养的钙质和大型腐殖质湖泊的年度N2 O排放量最高。我们对芬兰和北方湖泊的排放估算分别为每年0.6 Gg和29 Gg N2 ON。在北方地区，湖泊中N2 O的全球变暖潜力不可忽视，是芬兰湖泊中CH4扩散排放量的35％。