2015 年 30 巻 4 号 p. 262-269
Abstract CaCO3 in mineral dusts can be converted to highly hygroscopic substances, which affect the formation of clouds, by reactions with gaseous oxidative species in the atmosphere. It is important to investigate CaCO3 reactions in the presence of various kinds of gaseous oxidative species in order to improve the understanding of climate change. In this study, heterogeneous chemical reaction of CaCO3 particles in the presence of HCl, NO2 and O3 was evaluated using the Raman microscope coupled with aerosol reaction chamber. The reaction of CaCO3 particles with HCl and NO2 resulted in the formation of internal mixtures of Ca(NO3)2 and CaCl2, both of which were very hygroscopic and undergoes deliquescence at low relative humidity. Ca(NO3)2 did not change into CaCl2 by the subsequent reactions with HCl, whereas the produced CaCl2 reacted partially with NO2 and O3 to form Ca(NO3)2. Mixed particles including large amounts of Ca(NO3)2 were most frequently seen in microscope observation and existed in the state of supersaturated droplets under a low humidity condition. On the other hand, the particles containing large amount of CaCl2 were observed as transparent particles with wrinkled surfaces, which included CaCl2・2H2O hydrate under low humidity condition.