Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot, 010021, China.
Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot, 010021, China; Key Laboratory of Mongolian Plateau Ecology and Resource Utilization, Ministry of Education, Hohhot, 010021, China; Autonomous Region Collaborative Innovation Center for Integrated Management of Water Resources and Water Environment in the Inner Mongolia Reaches of the Yellow River, Hohhot, 010018, China.
J Environ Manage. 2023 Dec 1;347:119093. doi: 10.1016/j.jenvman.2023.119093. Epub 2023 Sep 30.
Eutrophic lakes are a major source of the atmospheric greenhouse gas methane (CH), and CH ebullition emissions from inland lakes have important implications for the carbon cycle. However, the spatio-temporal heterogeneity of CH ebullition emission and its influencing factors in shallow eutrophic lakes of arid and semi-arid regions remain unclear. This study aimed to determine the mechanism of CH emission via eutrophication in Lake Ulansuhai, a large shallow eutrophic lake in a semi-arid region of China.To this end, monthly field surveys were conducted from May to October 2021, and gas chromatography was applied using the headspace equilibrium technique with an inverted funnel arrangement. The total CH fluxes ranged from 0.102 mmol m d to 59.296 mmol m d with an average value of 4.984 ± 1.82 mmol m d. CH ebullition emissions showed significant temporal and spatial variations. The highest CH ebullition emission was observed in July with a grand mean of 9.299 mmol m d, and the lowest CH ebullition emissions occurred in October with an average of 0.235 mmol m d. Among seven sites (S1-S7), the maximum (3.657 mmol m d) and minimum (1.297 mmol m d). CH ebullition emissions were observed at S2 and S7, respectively. As the main route of CH emission to the atmosphere in Lake Ulansuhai, the CH ebullition flux during May to October accounted for 69% of the total CH flux. Statistical analysis showed that CH ebullition was positively correlated with temperature (R = 0.391, P < 0.01) and negatively correlated with air pressure (R = 0.286, P < 0.00). Temperature and air pressure were found to strongly regulate the production and oxidation of CH. Moreover, nutritional status indicators such as TP and NH-N significantly affect CH ebullition emissions (R = 0.232, P < 0.01; R = -0.241, P < 0.01). This study reveals the influencing factors of CH ebullition emission in Lake Ulansuhai, and provides theoretical reference and data support for carbon emission from eutrophic lakes. Nevertheless, research on eutrophic shallow lakes needs to be further strengthened. Future research should incorporate improved flux measurement techniques with process-based models to improve the accuracy from regional to large-scale estimation of CH emissions and clarify the carbon budget of aquatic ecosystems. In this manner, the understanding and predictability of CH ebullition emission from shallow lakes can be improved.
富营养化湖泊是大气温室气体甲烷（CH）的主要来源，内陆湖泊的 CH 鼓泡排放对碳循环具有重要意义。然而，干旱和半干旱地区浅水富营养化湖泊 CH 鼓泡排放的时空异质性及其影响因素仍不清楚。本研究旨在确定中国半干旱地区大型浅水富营养化湖泊乌兰湖的富营养化过程中 CH 排放的机制。
为此，本研究于 2021 年 5 月至 10 月进行了每月的实地调查，并应用顶空平衡技术和倒漏斗装置进行气相色谱分析。总 CH 通量范围为 0.102mmol m d 至 59.296mmol m d，平均值为 4.984 ± 1.82mmol m d。CH 鼓泡排放表现出显著的时空变化。CH 鼓泡排放的最高值出现在 7 月，平均值为 9.299mmol m d，最低值出现在 10 月，平均值为 0.235mmol m d。在七个站点（S1-S7）中，最大值（3.657mmol m d）和最小值（1.297mmol m d）分别出现在 S2 和 S7。CH 鼓泡排放是乌兰湖向大气排放 CH 的主要途径，5 月至 10 月的 CH 鼓泡通量占总 CH 通量的 69%。统计分析表明，CH 鼓泡与温度呈正相关（R=0.391，P<0.01），与气压呈负相关（R=0.286，P<0.00）。温度和气压被发现对 CH 的产生和氧化具有强烈的调节作用。此外，TP 和 NH-N 等营养状况指标对 CH 鼓泡排放有显著影响（R=0.232，P<0.01；R=-0.241，P<0.01）。
本研究揭示了乌兰湖 CH 鼓泡排放的影响因素，为富营养化湖泊的碳排放提供了理论参考和数据支持。然而，富营养化浅水湖泊的研究仍需进一步加强。未来的研究应结合改进的通量测量技术和基于过程的模型，以提高从区域到大规模 CH 排放估算的准确性，并阐明水生态系统的碳预算。这样可以提高对浅水湖泊 CH 鼓泡排放的理解和可预测性。
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