Miyamoto,T., Hamamoto,R. and Yanagi,T.(2010): Sr and Nd isotope compositions of atmospheric mineral dust at the summit of Mt. Sefuri, north Kyushu, southwest Japan: A marker of the dust provenance and seasonal variability. Geochimica et Cosmochimica Acta, 74, 1471-1484.

『南西日本の北部九州の背振山頂での大気鉱物質風塵のストロンチウムとネオジム同位体組成:風塵の起源と季節変動の標識』


Abstract
 We analyzed Rb-Sr-Nd isotope ratios of mineral dust in total aerosol load collected with rainwater continuously from 1998 to 2006 at the summit of Mt. Sefuri, northern Kyushu, southwestern Japan. During this period, the total mass of the dust generally increased in late winter, peaked in early spring, and then decreased.
 87Sr/86Sr in atmospheric mineral dust varied from 0.7096 to 0.7180, and εNd(0)CHUR from -19.9 to -3.5. During heavy deposition periods, the dust had high 87Sr/86Sr isotope ratios and low to middle εNd(0)CHUR values, respectively. These compositions are comparable to those of sand and loess in arid areas of Northeast China, Takla Makan and Western Beijing. Such particles were transported by westerlies from those areas to northern Kyushu in winter and spring. In summer and autumn, the isotopic compositions of the dust varied greatly; however, during light deposition periods, the Sr isotope composition was low. In these seasons, the contributions to the dust from Japanese soils and volcanic ash, transported by southern winds, were relatively larger than in winter and spring because of decreased mineral dust particle transport from the continent. Nevertheless, fine sandy desert particles and loess in general accounted for most mineral dust deposition in northern Kyushu year-round, even in summer. Local soils derived from weathered granite and volcanic ash were minor components only.
 The net mass of water-insoluble inorganic matter in the collected mineral dust fluctuated from year-to-year; deposition on Mt. Sefuri was relatively large before 2001, decreased from 2002 to 2005, and increased greatly in spring 2006. These year-to-year differences probably reflected changes in the strength of the westerlies and in climate conditions in the arid source areas.』

1. Introduction
2. Geography and climate in northern Kyushu, southwestern Japan
3. Analytical methods
4. Analytical results
5. Discussion
 5.1. Isotopic characteristics of atmospheric mineral dust on Mt. Sefuri during regular and heavy deposition periods
 5.2. Seasonal variation of isotope compositions of atmospheric mineral dust
 5.3. Interannual variation in aerosol amounts and compositions
6. Concluding remarks
Acknowledgements
References


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