抄録
Desertification is the process of land degradation in arid, semiarid and some sub-humid areas, due to adverse climate and human activities. The dust storms in the area are frequently observed in the atmosphere over Japan following the dust falls in the Asian continent, well known as “Kosa” . In this study, in order to monitor Kosa aerosols and to analyze the trend of them, deposition was weekly collected at two points in Ishikawa Prefecture, Japan, where located near the coast of the Sea of Japan. The deposition was collected by using bulk samplers. After the collection, the deposition was immediately filtered through a membrane filter to remove course particles, analyzed to determine its water-soluble chemical composition. All samples were analyzed for anions, such as NO3-, SO42-, and Cl-, and cations, such as NH4+, Ca2+, Mg2+, K+ and Na+. According to the analyses of the deposition, it was found that non-sea-salt (nss-) calcium ion and sea-salt components indicated seasonal changes. The nss-calcium ion concentration was higher during March to June than the other seasons as well as to indicate increasing trend year by year. It is suggested from the results that the mass of nss-calcium ion in the deposition was definitely increasing.
