Abstract
During the period of Apr., 1984 to Feb., 1985, aerosol samples were collected by Andersen sampler in four seasons in Nara city, inland rural city area and then the atmospheric concentration and particle size distribution of aerosols and their inorganic ion components (SO42-, NO3-, Cl-, F-, NH4+, Na+, K+, Ca2+, Mg2+) were derived.
Together with seasonal variation of these atmospheric concentration and particle size distribution, the removal of these ionic components by rainfall were investigated.
The particle size distribution of aerosols in Nara city exhibited bimodal pattern throughout a year and the particle size distribution of each ionic components was roughly divided into three main patterns, that was, (1) Distribution was concentrated to fine particles over a year such as SO42-, F-, NH4+and K+ components (FF (Fine fraction): 65-95%), (2) Distribution was predominated in coarse particles fraction over a year such as Na+, Ca2+and Mg2+ components (FF: 5-45%), (3) Distribution was differed in different seasons such as NO3-and Cl- components (FF: 16-67%).
These differences of particle size distribution of ionic components were mainly caused by their sources and NO3-, Cl- components were largely related to stability of NH4+ salts that were secondary products in the atmosphere, the coarse particles of NO3- was estimated to contain Ca (NO3) 2 as well as NaNO3.
The relationship between FF of ionic components and removal rate by rainfall was shown to be correlated significantly and it was recognized that coarse fraction of aerosols and their ionic components were liable to be removed by rainfall.
