天津市海河温室气体排放特征与影响因素研究

Patterns and Influencing Factors of Greenhouse Gas Emission from Haihe River in Tianjin

河流生态系统是内陆水体温室气体重要的排放源,城市河流由于受人为活动干扰较大其温室气体排放特征及控制因子与自然河流不同。为探讨人为活动对城市河流温室气体的排放的影响,选择天津市海河为研究对象,于2019年12月(冬季)及2020年7月(夏季),对水体温室气体溶存浓度及扩散通量进行监测,分析海河温室气体排放时空特征及关键驱动因素。结果表明,冬季海河水体CH_(4)、CO_(2)、N_(2)O平均浓度分别为(0.32±0.42)μmol·L^(−1)、(102.19±64.07)μmol·L^(−1)、(63.78±34.21)nmol·L^(−1),其平均通量分别为(5.54±9.72)μmol·m^(−2)·h^(−1)、(865.85±394.74)μmol·m^(−2)·h^(−1)、(965.87±844.63)nmol·m^(−2)·h^(−1)。夏季海河水体CH_(4)、CO_(2)、N_(2)O平均浓度分别为(0.72±0.81)μmol·L^(−1)、(75.00±57.87)μmol·L^(−1)、(19.43±6.23)nmol·L^(−1),其平均通量分别为(27.99±29.60)μmol·m^(−2)·h^(−1)、(3281.88±3425.55)μmol·m^(−2)·h^(−1)、(558.73±298.67)nmol·m^(−2)·h^(−1)。在海河水体中CO_(2)浓度和通量呈现出上游大于下游的空间特征,而CH_(4)、N_(2)O浓度和通量呈现出上游小于下游的空间特征。海河二道闸的存在及人为调控对海河上下游水质及温室气体排放影响较大。在季节特征上,除CO_(2)通量、CH_(4)浓度和通量外,均呈现冬季大于夏季的季节分布特征。海河水体中DO、NO_(3)^(−)-N、DOC和CODMn是控制海河中温室气体浓度和通量的关键影响因子。海河水体中温室气体的产生不仅与水体中微生物功能有关,还与富含氮、磷等营养物质的工农业废水和生活污水的排放有关,人为活动影响和决定了海河温室气体排放模式及主要控制因子。

River ecosystem is an important source of greenhouse gas emissions in inland water.Urban rivers are different from natural rivers in terms of their emission characteristics and control factors due to the influence of human activities.In order to explore the impact of human activities on greenhouse gas emissions in urban rivers.In December 2019 and July 2020,the concentrations and diffusion fluxes of greenhouse gases in surface water were determined to clarify the spatio-temporal pattern and key driving factors of greenhouse gas emissions in Haihe River.In winter,the mean concentrations of CH_(4),CO_(2),N_(2)O were(0.32±0.42)μmol·L^(−1),(102.19±64.07)μmol·L^(−1),(63.78±34.21)nmol·L^(−1),respectively,and their mean diffusion fluxes were(5.54±9.72)μmol·m^(−2)·h^(−1),(865.85±394.74)μmol·m^(−2)·h^(−1),(965.87±844.63)nmol·m^(−2)·h^(−1),respectively.In summer,the mean concentrations of CH_(4),CO_(2),N_(2)O were(0.72±0.81)μmol·L^(−1),(75.00±57.87)μmol·L^(−1),(19.43±6.23)nmol·L^(−1),respectively,and their mean diffusion fluxes were(27.99±29.60)μmol·m^(−2)·h^(−1),(3281.88±3425.55)μmol·m^(−2)·h^(−1),(558.73±298.67)nmol·m^(−2)·h^(−1),respectively.The concentration and flux of CO_(2) in the upstream was higher than that in the downstream of Haihe River,while the concentrations and fluxes of CH_(4) and N_(2)O were smaller in the upstream than in the downstream.The existence and artificial regulation of the second tide gate of Haihe River had significant influence on the water quality and greenhouse gas emission of the upstream and downstream of Haihe River.In terms of seasonal pattern,exception for CO_(2) flux,CH_(4) concentration and flux,the seasonal distribution in winter was larger than those in summer.DO,NO_(3)^(−)-N,DOC and CODMn in the water column were the key factors to control the concentration and flux of greenhouse gas in Haihe River.The production of greenhouse gas in Haihe River was not only related to the microbial function in the water body,but also to the discharge of industrial and agricultural wastewater and domestic sewage rich in nutrients such as nitrogen and phosphorus.Human activities affect and determine the pattern and main control factors of greenhouse gas emissions in Haihe River.