Nobuko Kanamori

Kosa aerosol as eolian carrier of anthropogenic material

Abstract Nine samples of three Kosa aerosols (Asian dust) were collected at Yaku Island located ∼900 km southeast off the coast of China, during winter and spring 1988. Aluminum, Mg, Ca and Fe were present in highest concentration, but, as reported previously, high levels of NO 3 and SO 4 2 were also found. The increase in NO 3 and SO 4 2 levels in Kosa aerosol compared with normal aerosol during non-Kosa events were associated with the coarse size fraction, whereas no increase was found in the fine size fraction. The high correlation coefficient between NO 3 , non-sea-salt SO 4 2 , and total surface area of aerosol particles for all size fractions of the coarse fraction indicate that these ions are deposited on and transported with the Kosa aerosol.

Behaviour of magnesium and strontium during the transformation of coral aragonite to calcite in aquatic environments

Abstract Some coral aragonites transform easily to calcite in aquatic environments. The behaviour of magnesium and strontium in the coral aragonite-to-calcite transformation process was examined through laboratory experiments and field observations; the coral aragonite samples came from Okinawa and Kagoshima prefectures. When powdered coral aragonite is suspended in aqueous solution, hydrophobic and hydrophilic suspensions are observed. The transformation rate of hydrophilic aragonite is higher than that of hydrophobic. The release of strontium from hydrophilic aragonite into solution is very active; it increases with increasing transformation of aragonite to calcite. Magnesium is dissolved very rapidly into solution. The strontium content of calcite transformed from coral aragonite is 1500 ppm or more. These experimental results are supported by the analytical results of natural coral samples collected from Okinawa islands and Kagoshima prefecture, which suggests that the transformation from aragonite to calcite does not occur through the complete dissolution of aragonite and the complete recrystallization of calcite in aqueous solutions.