青藏高原更尕海水—气界面CO_(2)交换通量及其影响因素

Variations in CO2 fluxes at the water-air interface and its influencing factors in the Genggahai Lake on the Qinghai-Tibetan Plateau

湖泊作为陆地水生生态系统的重要组成部分,对全球碳收支有着重要作用。理解湖泊水—气界面CO_(2)交换通量(F(CO_(2)))及影响因素是探讨湖泊碳收支的重要基础和前提。为探究青藏高原湖泊水—气界面碳收支及其影响因素,课题组于2021年7月23日、8月8日、8月28日、9月25日、9月26日8:00~17:00采用静态箱法对更尕海湖泊水深10、20、30、80和150 cm水—气界面F(CO_(2))开展连续、定点监测,初步探讨了该湖泊水—气界面CO_(2)交换特征及其影响因素。结果表明,更尕海水—气界面F(CO_(2))变化介于-19.44~22.29 mg·m^(-2)·h^(-1)之间,平均值为-2.89 mg·m^(-2)·h^(-1),因此,更尕海为大气CO_(2)的汇。特别是在12:00~14:00之间,湖泊“汇”的功能表现得更为明显,这可能主要与强烈的水生植物光合作用带来的水体pH值较高有关。此外,湖泊内水—气界面F(CO_(2))具有明显的空间差异。水深30 cm处水—气界面F(CO_(2))平均值为正值,呈现出CO_(2)释放状态;其余4个监测点水—气界面F(CO_(2))平均值均为负值,呈现出CO_(2)吸收状态。这主要与水深30 cm监测点周围生长有大量黄苔,可能抑制了其他浮游植物、水生植物的繁殖有关。青藏高原湖泊水—气界面F(CO_(2))存在明显的时间和空间差异,未来评估其碳源汇潜力时应综合考虑湖泊内部和不同时间湖泊碳收支通量,以提高评估的准确性。

Lake is an important component of terrestrial aquatic ecosystems,which plays an important role in global carbon balance.Investigating the CO_(2)exchange flux(F(CO_(2)))at the water-air interface and its influencing factors in lakes is fundamental for assessing the carbon budget of lakes.To explore the carbon budget at the water-air interface in Qinghai-Tibetan Plateau(QTP)lakes,the F(CO_(2))at the water-air interface in the Genggahai Lake were observed continuously from 8:00 a.m.to 17:00 p.m.on 23 July,8 and 28 August,and 25 and 26 September in 2021 based on the floating chamber method.The depth of water at the monitoring sites was 10 cm,20 cm,30 cm,80 cm,and 150 cm respectively.The results show that the F(CO_(2))varied from-19.44 to 22.29 mg·m^(-2)·h^(-1),and the average daily F(CO_(2))was-2.89 mg·m^(-2)·h^(-1).The Genggahai Lake was a sink of the atmospheric CO_(2),especially between 12:00 and 14:00.The daily variations in F(CO_(2))was mostly influenced by the high pH value,which was related to the photosynthesis of submerged plants.In addition,there were significant spatial differences in the F(CO_(2))within the lake.The average F(CO_(2))value in the yellow moss distribution area was positive,suggesting that this area was a carbon source;The average F(CO_(2))values of the other four monitoring points were negative,suggesting that these four monitoring areas were carbon sinks.The F(CO_(2))in QTP lakes showed distinct temporal and spatial differences.To obtain accurate evaluation results of carbon source/sink potential of QTP lakes,we should take carbon budget within the lakes and at different temporal scales into account.