嘉陵江四川段平水期CH_(4)、CO_(2)排放通量空间分布特征及影响因素

Spatial Distribution Characteristics and Influencing Factors of CH_(4),CO_(2)Emission Fluxes in Jialing River(the Section of Sichuan)during Normal Season

河流是陆地生态系统中内陆水域温室气体的重要排放源。以嘉陵江四川段为研究对象,于2021年10月采集表层水样,运用改良顶空法采集表层水体溶存的CH_(4)、CO_(2),分析了研究区域平水期CH_(4)、CO_(2)溶存浓度与排放通量的空间分布特征,并探究水体理化性质和土地利用类型对温室气体排放的响应。结果表明,嘉陵江四川段人类活动主导了水质变化特征,城市和农业活动是氮素和磷素沿河流方向累积的重要原因。表层水体中CH_(4)和CO_(2)浓度分别为(16.87±15.55)nmol·L^(-1)和(836.11±132.68)μmol·L^(-1),排放通量分别为(68.39±81.26)nmol·m^(-2)·d^(-1)和(1596.08±1291.61)μmol·m^(-2)·d^(-1)。CH_(4)、CO_(2)浓度和排放通量具有较大空间异质性,不同土地利用类型条件下,耕地主导河段接收了较多的非点源污染和陆源碳。这些污染物质的输入导致水体理化性质发生改变,影响水生植物和浮游植物生长以及微生物活动,进而给CH_(4)和CO_(2)产生和释放造成影响。总氮(TN)、磷酸盐(PO_(4)^(3-)-P)和耕地面积占比是影响嘉陵江四川段温室气体排放的关键因子,表明温室气体排放不仅受河流生态环境的影响,还受不同土地利用类型条件下人类活动的影响。

Rivers are important sources of greenhouse gas emissions in inland waters of terrestrial ecosystems.In recent years,the emission of greenhouse gases has increased the seriousness of environmental problems.This paper focuses on the Sichuan section of the Jialing River as the research subject to explore the spatial distribution characteristics of dissolved CH_(4)and CO_(2)concentrations and emission fluxes,and the response of the water physical and chemical properties and land use types to greenhouse gas emissions.Surface water samples were collected from the Jialing River in October 2021,and a modified headspace method was used to capture dissolved CH_(4)and CO_(2)in the water.Results indicate that human activities dominate the changes in water quality in the Sichuan section of the Jialing River,with urban and agricultural activities being the primary reasons for the accumulation of nitrogen and phosphorus along the river.The concentrations of CH_(4)and CO_(2)in the surface water were(16.87±15.55)nmol·L^(-1)and(836.11±132.68)μmol·L^(-1),respectively.The emission fluxes of CH_(4)and CO_(2)were(68.39±81.26)nmol·m^(-2)·d^(-1)and(1596.08±1291.61)μmol·m^(-2)·d^(-1),respectively.The concentration and emission fluxes of CH_(4)and CO_(2)exhibited significant spatial heterogeneity.Among the different land use types,the river reach dominated by cultivated land received significant amounts of non-point source pollution and terrigenous carbon.The input of these pollutants changed the physical and chemical properties of water bodies,the growth of aquatic plants and phytoplankton,and the microbial activities in the river,and further influenced the production and release of CH_(4)and CO_(2).TN,PO_(4)^(3-)-P,and area proportion of cultivated land are the key factors contributing to greenhouse gas emissions in the Sichuan section of the Jialing River,which indicating that Greenhouse gas emissions are not only influenced by the ecological environment of the river but also by human activities under different land use types.