TROPOSPHERIC EOLIAN DUST ORIGIN OF RED-YELLOW SOILS IN NANSEI-SYOTO

对冲绳海槽、南海海沟和阿美高原的红黄土群、第四纪千枚岩和古生代千枚岩以及冲绳海槽的活塞岩和活塞芯的氧、碳同位素进行了研究。石英、白云母和方解石的氧、碳同位素组成表明，石英和白云母为风成尘来源。托亚火山灰(90~130ka)坠落后岩手岛火山特弗拉沉积的分析数据表明，风成尘主要沉积在20~34ka和50~70ka，末次冰期末期的风尘通量估计为4 cm/1000年。利用蛋白石植硅体组成和风尘含量估算了该区的植被和气候变化。近期中国中北部地区雨水的pH值和钙浓度均高于中国南部地区。我们的数据显示，风尘中的方解石被用来中和中国和韩国雨水中的酸性成分。近期从中国输送到日本的风尘中含有少量方解石，表明其对日本的酸雨中和能力较低。

Oxygen and carbon isotopic studies of the Red and Yellow soil Group, Quaternary and Paleozoic phyllite in the Nansei Syoto and piston cores in the Okinawa Trough, the Nansei Syoto Trench, and the Amami Plateau were carried out. The oxygen and carbon isotopic rations of quartz, muscovite and calcite indicated that quartz and muscovite were of eolian dust origin.Analytical data of the Iwate volcano tephra deposits after the fall of the Toya Ash (90-130ka) indicated that eolian dust was mainly deposited 20-34ka and 50-70ka and that the flux of eolian dust during the late period of the Last Glacial age was estimated to be 4cm/1,000 years. The changes of vegetation and climate were also estimated by using opal phytolith composition and eolian dust content.The recent rainwater in the central and northern regions of China shows higher pH values and Ca concentrations than southern region of China. Our data showed that calcite in the eolian dust was consumed to neutralize acidic components in Chinese and Korean rainwater. Recent eolian dust transported from China to Japan contains a small amount of calcite, suggesting that it has a low neutralization capacity to acid rain in Japan.