Rain water was collected in the rural area close to Kobe area (Moshi, Sanda-city, mountainious area, about 40 km to the north of Kobe area), and main ions in the water were determined and compared with that in Kobe area.
The concentrations of the ions in the rain water in Moshi were almost lower than those in Kobe, i.e. NO
3-, Cl
-, H
+ and NH
4+: slightly lower, SO
42-and Na
+: considerably lower, and NO
2-: very markedly lower (Fig.10) . The molar concentrations of the cations in Moshi were found in the order: H
+>NH
4+>Na
+, similar to that in Kobe, and those of the anions in the order: NO
3->SO
42->Cl
- in summer (SO
42->Cl
->NO
3- in Kobe, Fig.6, 7) . The NO
3-/NH
4+ molar ratio was identical with the ratio calculated as NH
4NO
3 (Fig.4), and the Cl
-/Na
+ molar ratio was higher than that of sea water (Na
+ loss, Fig.5) .
These results suggest that, in the transport process of air pollutants from urban to rural area, the coarse particles (containing NaCl and NaNO
3 etc.) and reactive gases (such as NO
2) are partially excluded from air, whereas the fine particles (containing NH
4NO
3etc.), the less reactive gases (such as HCl) and the gases emitted also from natural sources (such as NH
3) are scarcely reduced, and that these behaviors are reflected to the ionic composition of the rain water in the rural area (Fig.11) .
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