干旱区典型湖泊CH_(4)扩散排放特征及其影响因素

Characteristics and influencing factors of CH4 diffusion emissions from a typical lake in arid area

湖泊等水体CH_(4)的排放是全球温室气体的主要组成部分,但目前对干旱区湖泊CH_(4)扩散排放特征及其影响因素的研究却鲜有报道.本文选取干旱区典型湖泊—博斯腾湖为研究对象,分别于2021年6月、9月、10月采集水样,并测定其生物地球化学参数及溶解CH_(4)浓度,确定其水-气界面CH_(4)扩散排放通量.结果表明,博斯腾湖CH_(4)扩散通量均值为(0.305±0.080)mmol·m^(-2)·d^(-1),表现为大气CH_(4)的排放源;在空间上,受外源输送影响,入湖河口为CH_(4)的扩散排放热点区域;在不同月份,CH_(4)扩散通量变化受营养状态影响显著,与综合富营养化指数、叶绿素a浓度等呈显著正相关(富营养化指数:r=0.67,p<0.01;叶绿素a:r=0.54,p<0.01),但其对温度的依赖性较低(p>0.05).另外,受外源输送、水动力特征、内部生物化学过程等影响,博斯腾湖CH_(4)扩散通量在不同湖区的控制因子表现出较大差异,其具体控制机制还需进一步明晰.

CH_(4) emissions from lakes and other water bodies are a major component of global greenhouse gases,but the diffusion efflux of CH_(4) and its influencing factors in lakes of arid regions are rarely reported.Bosten Lake,a typical lake in the arid area northwestern China,is chosen as the sampled lake.Water samples were collected in June,September,and October 2021 to determine water chemistry and the surface dissolved CH_(4) concentration,and then the CH_(4) diffusion efflux was calculated.The results showed that the mean CH_(4) diffusion efflux in Bosten Lake was(0.305±0.080)mmol·m^(-2)·d^(-1),indicating the lake was a source of atmospheric CH_(4).Spatially,the river mouth of the lake was a hot spot for CH_(4) diffusion efflux due to external loadings input.Temporally,the CH_(4) diffusion efflux was significantly affected by trophic status,and the CH_(4) efflux was positively correlated with Chl a(r=0.54,p<0.01)and TSI(r=0.67,p<0.01).However,weak relationship was found between CH_(4) efflux and water temperature.In addition,factors controlling the CH_(4) diffusion efflux varied among sub-zones of the lake,among which external input,hydrodynamic characteristics,and internal biochemical processes are the primary influencing factors.The specific control mechanism of CH_(4) emission in the lake needs to be further clarified.