异戊二烯在大气光化学过程中的能量作用

Isoprene and Its Energy Role in the Atmospheric Photochemical Processes

2002年夏季在内蒙古草原进行了太阳辐射、异戊二烯排放的综合观测,根据紫外辐射(UV)的传输规律以及对观测数据的统计分析,发展了实际天气条件下UV的经验模型,该模型考虑了影响UV的异戊二烯、光化学、散射等因子的能量作用,对地面和大气顶的UV均有较好的模拟。对数据的统计分析发现,实际天气条件下异戊二烯与UV之间的关系表现为负的能量关系,其揭示的机制是异戊二烯对UV能量的利用,即异戊二烯利用了其他具有UV吸收物质中的能量,进而参与大气中的化学和光化学反应。在冠层尺度上,异戊二烯与PAR也表现出负的能量关系。敏感性分析表明,实际天气条件下,UV对于异戊二烯的变化最敏感,其次是光化学因子、散射因子,这揭示了内蒙古草原实际天气条件下,异戊二烯及其光化学产物等的变化将引起UV最大的变化。内蒙古草原散射辐射与总辐射之比为0.32,表明其大气中的物质含量相对较低。

The integrated measurements of solar radiation and isoprene emission were carried out at the Inner Mongolia Grassland during the summer season in 2002. Based on the principles of solar UV transmission and the statistical analysis on the observation data, an empirical model for calculating UV under all sky conditions was developed. This model considers the energy roles of isoprene, photochemical and scattering factors, shows reasonable results for UV at the ground and the top of the atmosphere. Based on the statistical analysis of observation data, it is found that isoprene and UV exhibit a negative energy relationship under all sky conditions, which implies the mechanism of isoprene utilizing UV energy, i.e., isoprene utilizes the energy from the substances that have direct UV absorption, then takes part in chemical and photochemical reactions in the atmosphere. Isoprene and PAR (Photosynthetically Active Radiation) also exhibit a negative energy relationship on a canopy level. The sensitivity test shows that UV is more sensitive to isoprene factor, then photochemical factor, and scattering factor, under all sky conditions. It implies that the variation of isoprene and its oxidation products would cause the biggest change of UV at the Inner Mongolia grassland under all sky conditions. The ratio of solar scattering radiation to solar global radiation is 0.32, which means the total substances in the atmospheric column are in relatively low level at the Inner Mongolia grassland.