长春城市水体夏秋季温室气体排放特征

为掌握我国东北地区城市湖泊水体温室气体的释放/吸收特征,本研究分别于夏季和秋季,对位于吉林省长春市的7个城市湖泊(南湖、北湖、雁鸣湖、胜利公园、地理所内湖、天嘉公园和长春公园)表层水中的CO_2和CH_4分压p(CO_2)和p(CH_4)]进行了监测,并对影响p(CO_2)和p(CH_4)季节变化的相关环境和水质参数进行了分析.研究结果表明在夏季和秋季这7个城市湖泊表层水体中CH_4都处于过饱和状态;除夏季的南湖和胜利公园内湖,其它湖泊CO_2也都处于过饱和状态,且不同湖泊间的温室气体分压具有显著性差异(P0.05),通量也同样具有显著性差异(P0.05).除了南湖和胜利公园内湖外,其它各湖泊在夏秋季节都是大气CO_2和CH_4的"源",且对大气中温室气体的贡献都以CO_2为主.环境参数与p(CO_2)或p(CH_4)之间的相关性分析表明,在夏季,城市湖泊表层水体中p(CO_2)和p(CH_4)都与日照时数呈显著负相关(r_(p(CO_2))=-0.48,P0.05;r_(p(CH_4))=-0.63,P0.01),日照时数通过影响水生植物的光合作用进而影响水体中CO_2和溶解氧浓度,p(CH_4)还与降水量呈显著正相关(r_(p(CH_4))=0.44,P0.05);在秋季,p(CO_2)与气温呈显著负相关(r_(p(CO_2))=-0.39,P0.05).另外,水质参数与p(CO_2)和p(CH_4)的相关性分析表明,这些城市湖泊表层水体的p(CO_2)和p(CH_4)都与水体pH显著负相关(r_(p(CO_2))=-0.51,r_(p(CH_4))=-0.82,P0.01),与盐度显著正相关(r_(p(CO_2))=0.38,P0.05;r_(p(CH_4))=0.75,P0.01),p(CH_4)还与水体DOC、TN和TP均具有显著相关性(P0.01).从研究结果可以推测在这7个富营养城市湖泊中,水体的营养物水平及其所决定的浮游植物生物量并不是影响表层水体p(CO_2)的最主要因素,而日照时数、水体pH和盐度与夏秋季表层水体中的p(CO_2)和p(CH_4)有较大关联.

Seasonal Variability of Greenhouse Gas Emissions in the Urban Lakes in Changchun, China

The partial pressures of carbon dioxide p(CO₂) and methane p(CH₄) in the surface water of seven urban lakes in Changchun city, China (Nan Lake, Bei Lake, Yanming Lake, Shengli, Dilisuo, Changchun, Tianjia), have been studied in both summer and autumn related to the environment and water quality parameters. The results indicated that both in summer and autumn, CH₄ of seven lakes was all supersaturated, and CO₂ was all supersaturated except in Nan lake and Shengli lake. For either p(CO₂) or p(CH₄), there was a significant difference among different urban lakes (P < 0.05), and there was almost no obvious difference in the same lake between summer and autumn. The gas flux also had a significant difference among different urban lakes (P < 0.05). Except for Nan Lake and Shengli, all other lakes were the sources of atmospheric CO₂ and CH₄ both in summer and fall, and the discharge of CO₂ to atmosphere by lakes was more than that of CH₄. According to the correlation analysis, there was a significant negative relationship between p(CO₂, CH₄) and sunshine duration in summer (r_p(CO₂)=-0.48, P < 0.05; r_p(CH₄)=-0.63, P < 0.01). The sunshine duration could affect the concentrations of CO₂ and dissolved oxygen in the water by influencing the photosynthesis of aquatic plants. There was also a significant negative relationship between p(CH₄) and precipitation in summer (r_p(CH₄)=0.44,P < 0.05), and between p(CO₂) and air temperature in autumn (r_p(CO₂)=-0.39,P < 0.05). The correlation analysis between water quality parameters and p(CO₂, CH₄) showed that both p(CO₂) and p(CH₄) were negatively correlated with pH (r_p(CO₂)=-0.51, r_p(CH₄)=-0.82, P < 0.01), while they were positively correlated with salinity (r_p(CO₂)=0.38, P < 0.05; r_p(CH₄)=0.75, P < 0.01). The results suggested that the levels of nutrients in these urban lakes, which were related to the phytoplankton biomass, were not the main influencing factors for p(CO₂) in surface water, and sunshine duration, pH, and salinity all had a greater impact on p(CO₂) and p(CH₄) in summer and autumn.