Diel variation of CH4 emission fluxes in a small artificial lake: Toward more accurate methods of observation
Diel variation of CH4 emission fluxes in a small artificial lake: Toward more accurate methods of observation
复制标题
小型人工湖 CH4 排放通量的昼夜变化：寻求更准确的观测方法
DOI：
10.1016/j.scitotenv.2021.147146
复制
发表时间：
2021
影响因子：
9.8
通讯作者：
Yuchun Wang
中科院分区：
文献类型：
--
作者：
Di Tan;Qingguang Li;Shilu Wang;Kevin M. Yeager;Mingwei Guo;Kun Liu;Yuchun Wang
湖泊是全球甲烷（CH4）预算的重要来源。然而，由于观测时间、方法和气体传输速度（k）参数化等方面的数据存在不确定性，对全球湖泊CH4排放量的估计可能存在很大偏差。在这里，我们进行了连续48小时的测量CH4通量使用浮箱法季节性在百花湖，在中国西南部的一个小水库，并比较结果与来自边界层模式的估计。结果表明，有一个弱的依赖于风速，表明风速不是主要因素调节气体交换在这样的小湖泊。因此，风速依赖边界层模式方法不适合中小湖泊CH4通量观测，建议采用浮箱法。CH4通量的日变化规律明显，因此用单一观测值来代表日平均值具有不可接受的不确定性。一个合理的替代方法是将日出和日落时的观测值取平均值，以表示每日值，其不确定性要小得多（范围从0.8%到13.6%）。地下水中CH4和叶绿素浓度的峰值重合表明CH4主要来源于好氧甲烷生成。太阳辐射可能是调节CH4产生和排放的主要因素之一，通过增加CH4的产生，抑制CH4的氧化，并可能改变水动力条件。因此，在观测湖泊CH4通量时，应将辐照作为一个关键因素加以考虑。由于采样时间有限，应按比例包括晴天和阴天的观测结果。据我们所知，这是第一次提出太阳辐射是湖泊CH4排放的主要驱动因素。
Lakes are significant sources in global methane (CH4) budgets. However, estimations of the magnitude of global CH4emissions from lakes may be highly biased owing to the uncertainties in data originating from observation times, methods, and parameterizations of the gas transfer velocity (k). Here, we conducted continuous 48-hour measurements of CH4fluxes using the floating chamber method seasonally at Lake Baihua, a small reservoir in southwestern China, and compared the results with estimates derived from boundary layer models. Results showed that there was a weak dependency ofkon wind speed, indicating that wind speed was not the major factor regulating gas exchange in such small lakes. It is thus concluded that the wind speed-dependent boundary layer model method is not suitable for CH4flux observations in small and medium-sized lake, and that the floating chamber method is recommended for use instead. The measured CH4fluxes displayed remarkably diurnal patterns, therefore the use of single observations to represent daily average values comes with unacceptably large uncertainties. A reasonable alternative is averaging observations made at sunrise and at sunset to represent daily values, which has a much smaller uncertainty (ranging from 0.8% to 13.6%). The coincident peaks of CH4and chlorophyll concentrations in the subsurface indicate that CH4originated mainly from aerobic methanogenesis. Solar radiation is likely one of the major factors regulating CH4production and emissions in the lake through enhancing CH4production, inhibiting CH4oxidation, and probably changing hydrodynamics conditions. Therefore, irradiation should be taken into consideration as a key factor in observing CH4fluxes in lakes. As sampling times are limited, observations during both sunny and cloudy weather should be proportionally included. This is the first time, to the best of our knowledge, that solar radiation has been proposed as a key driver of CH4emissions from lakes.