华北农村区域夏季大气中异戊二烯未知来源的探究

植物排放的异戊二烯是大气中一种重要的挥发性有机物，是二次有机气溶胶及臭氧的重要前体物，对区域乃至全球环境具有重要的影响。申请者基于所在课题组及北京大学在华北农村站点玉米季均观测到大气中异戊二烯傍晚峰值（3-4ppbv）的异常现象，推测玉米作物是大气异戊二烯的主要来源，且其排放特征与树木异戊二烯的常规排放特征可能显著不同。为此，本项目拟选择河北省望都县东白陀玉米作物为研究对象，采用双动态箱法测量玉米整个生长季节异戊二烯的排放通量，获得玉米不同生长阶段异戊二烯排放的日变化特征，阐明农村观测站点大气中异戊二烯异常日变化特征的原因；同步测定箱体内光合有效辐射及温度，探寻玉米作物异戊二烯排放量与它们之间的定量关系；同步测定二氧化碳的交换通量，揭示玉米光合休眠期与玉米作物异戊二烯排放通量的关系；基于所测异戊二烯的排放通量，估算华北玉米作物异戊二烯的排放总量。

As an important volatile organic compound emitted from plant species, isoprene has been shown to be the precursor of SOA and ozone, and have an important impact on regional and global environment. Base on the abnormal phenomenon of the peak concentration of atmospheric isoprene (3-4 ppbv) at dusk obtained both from the study group of the applicant and the Peking university, we suggest that maize is the main atmospheric isoprene source in the study site and have obviously different emission characteristics with trees. And hence, with the maize (planted in the Wangdu County, Hebei province) as the study object, the exchange fluxes and the emission characteristics of isoprene at different growth stages are obtained by using dynamic chambers, which would be used to explain the abnormal phenomenon of the diurnal variation of atmospheric isoprene. Simultaneous recording of the photosynthetically active radiation and the temperature in the dynamic chamber to seek the quantitative relation between the isoprene emission and these impact factors, and simultaneous determination the exchange fluxes of carbon dioxide to reveal the relationship between the isoprene emission and the unphotosynthetic. Finally, based on the obtained isoprene emission fluxes, we estimate the total isoprene emissions from maize.