夏季金沙江下游水-气界面CO2、CH4通量特征初探

CO_2 and CH_4 flux across water-air interface in summer in the downstream of Jinsha River,Southwest China

河流是连接大陆和海洋两大碳库的桥梁,在全球碳循环中的作用举足轻重.金沙江作为长江的上游段,对区域碳循环及区域化学风化的影响非常重要.于2015年8月8-18日对金沙江下游水-气界面CO_2与CH_4通量特征进行监测与分析.采用顶空平衡法结合薄边界层模型估算法计算表层水体CO_2与CH_4的分压以及水-气界面的交换通量,并分析环境变量与其之间的相关性.研究发现,金沙江下游表层水体p(CO_2)平均值为2724.84±477.18μatm,表层水体p(CH_4)平均值为59.96±6.74μatm;水-气界面CO_2通量平均值为2.24±0.50 mmol/(m2·h),CH_4通量平均值为0.000163±0.00009 mmol/(m2·h),通量与分压趋势基本保持一致.表层水体p(CO_2)与溶解性无机碳浓度、碱度均呈显著正相关,而p(CH_4)与水温、叶绿素a浓度均呈显著正相关,CO_2通量与p(CO_2)、溶解性无机碳浓度、碱度均呈正相关,CH_4通量与p(CH_4)、风速均呈正相关,其他环境因素对通量的影响不明显,仍需进一步研究.金沙江下游水-气界面CH_4扩散通量较低,而CO_2扩散通量在世界主要河流中属于中等水平.

Rivers connect continent and ocean, the two major carbon pools, which play an important role in global carbon cycling. Jinsha River is the upstream of Yangtze River and significantly influences carbon cycle and chemical weathering in the watershed. Water-air CO2 and Cl[ 4 fluxes were measured from August 8 to 18, 2015 in the downstream of Jinsha River. The study used the headspace equilibrium method and thin boundary layer method to estimate p（ CO2） and p（ CU4） in surface water and exchange flu-xes between water and air. Results showed that in summer p（CO2） and CO2 fluxes were 2724.84±477.18 patm and 2.24±0.50 mmol/（m2 -h） , respectively, thep（C l4） and CU4 fluxes were 59.96±6.74 patm and 0.000163±0.00009 mmol/（m2 h）, and the trend of differential pressure was consistent with flux. p（ CO2） has significant positive correlation with dissolved inorganic carbon and total alkalinity. p（ Cl[ 4） has significant positive correlation with water temperature and chlorophyll- a. Air-water CO2 flu-xes was mainly impacted by p （CO2 ） , dissolved inorganic carbon and total alkalinity. Cl fluxes was significantly impacted by p（ Cl4） and wind speed. Impacts from other environmental factors such as nutrients were not obvious, and more studies shall be conducted to elucidate the variance of flux and its controlling factors. The air-water C l4 fluxes of Jinsha River was low, and the airwater CO2 fluxes was in medium level, comparing to other major rivers in the world.