砂塵ダスト発生地域における表層土壌の色彩および化学組成的特徴と日本に飛来した黄砂エアロゾルの発生源地域の推定  [in Japanese] Characteristics of Color and Chemical Composition of Surface Soils Collected in Source Regions of Asian Dusts and Identification of the Source of Kosa Aerosols Transported to Japan  [in Japanese]

<p>タクラマカン砂漠、ゴビ砂漠、黄土高原など砂塵嵐がよく発生する北東アジア地域の砂漠・乾燥地帯の8地域において、1998年から10年以上にわたり表層土64試料を採取した。その表層土から細粒試料（粒径＜100 μm）および微小試料 (＜10 μm) を分離し、化学組成分析を行った。ゴビ砂漠東地域の試料は、CO₃-C, Ca, Mgの含有量が他地域に比べ有意に低く、土壌色は最も明度が低く黄赤色を帯びていた。ゴビ砂漠東地域のCO₃-Cは＜0.5％、薄黄灰色の土壌色を呈すタクラマカン砂漠地域のCO₃-Cは1.8％と高く、8地域の土壌色と炭酸塩鉱物の含有量の間に明瞭な関係性が認められた。風化抵抗性が強くかつ土壌中の主成分元素であるAlを基準とする元素含有量比のばらつき（地域差と呼ぶ：RSD％）は地域間の特徴を表している。地域差が大きかった主要元素はCO₃-C, Ca, Mg, P, Sr (RSD；15–63％)、地域差が小さかった元素はK, Ti, Ba (RSD；7–9％) であった。地域差の大きかった主要元素Ca, Mg, P, Srを解析因子として、日本に飛来した典型的な黄砂16事例と本報告の8地域表層土によるクラスター解析を行い、その類似度による黄砂発生源地域の推定をした。クラスター解析による16事例の発生源地域の推定結果とSYNOP情報による砂塵嵐の観測地域と一致性が認められた。</p>

<p>Various desert and semi-arid areas in Northeast Asia that are susceptible to sandstorms and the generation of kosa aerosols have been investigated over a ten-year period commencing in 1998. Sixty-four samples of surface soils were collected from eight regions in the Taklamakan, Gobi deserts, the Hung tu (Chinese Loess) Plateau, and others. The grainy soil particulates (<100 μm) and the fine soil particulates (<10 μm) were classified by the sieve/cascade-impactor methods, and the chemical compositions of the particulates were determined. The darkest yellow-red colored samples were a group of surface soil samples from the Eastern Gobi region, and it was found that the CO₃-C, Ca and Mg contents were significantly less than those from the other areas. It was postulated that there was an underdeveloped formation/accumulation process of calcite mineralization in the surface soil layer of the Eastern Gobi. The concentration ratios of Ca, Mg, Sr and P to Al exhibited relatively large variations (15–52 RSD%), whereas the ratios, with respect to Al, for K, Ti, and Ba were significantly lower (7–9 RSD%). A cluster analysis based on the elemental ratios (with respect to Al) for Ca, Mg, Sr and P was used to identify the sources of the kosa aerosols which were transported to Japan (16 events studied). The estimated source regions of the kosa aerosols were substantiated using observational regions based on the SYNOP network reports about dust storms.</p>