AUTHOR=Yang Rongjie , Chen Yingying , Du Jie , Pei Xiangjun , Li Jinghua , Zou Zan , Song Huixing 

TITLE=Daily Variations in pCO2 and fCO2 in a Subtropical Urbanizing Lake

JOURNAL=Frontiers in Earth Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2021.805276

DOI=10.3389/feart.2021.805276

ISSN=2296-6463

ABSTRACT=<p>The transfer of CO<sub>2</sub> from lakes to the atmosphere is a component of the global carbon equilibrium, while the quantification of the CO<sub>2</sub> partial pressure (<italic>p</italic>CO<sub>2</sub>) is critical for exploring the contribution of freshwater CO<sub>2</sub> emissions in the regional/global carbon budget. To investigate the daily variability of <italic>p</italic>CO<sub>2</sub> and CO<sub>2</sub> fluxes (<italic>f</italic>CO<sub>2</sub>), we conducted <italic>in situ</italic> biweekly <italic>p</italic>CO<sub>2</sub> detection at 7:00, 10:00, 14:00, and 17:00 China Standard Time (CST) from Jan. to Sept. 2020 in the subtropical urbanizing Qinglonghu Lake in Chengdu, Sichuan, China. The <italic>p</italic>CO<sub>2</sub> during the daytime varied greatly from 8.3 to 1,061.3 μatm, with an average of 137.7 μatm, while the average <italic>p</italic>CO<sub>2</sub> (<italic>n</italic> = 11) clearly gradually decreased from 7:00 CST (204.9 ± 295.7 μatm) to 17:00 CST (93.5 ± 105.5 μatm). Similarly, the average <italic>f</italic>CO<sub>2</sub> values were −19.3 (±27.5), −24.8 (±20.7), −29.2 (±9.1) and −30.4 (±10.7) mmol m<sup>2</sup> h<sup>−1</sup> at 7:00–17:00 CST, respectively. Further, we observed a negative correlation between <italic>p</italic>CO<sub>2</sub> and water temperature and dissolved oxygen, but a positive correlation between <italic>p</italic>CO<sub>2</sub> and total organic carbon and chlorophyll <italic>a</italic>. By a systematic overview of previously published data, we also discussed the differences and uncertainties in <italic>p</italic>CO<sub>2</sub> and <italic>f</italic>CO<sub>2</sub> estimates at regional and global scales. We therefore speculate that uncertainties may exist in the contributions of CO<sub>2</sub> balance on lake surface in regional/global carbon budgets due to this daily <italic>p</italic>CO<sub>2</sub> variation.</p>