『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