The second series of experiments was carried out at the confined aquifers in the eastern part of Osaka. The city water of 179, 000m
3 (supplied from the Yodo River) was artificially recharged into two wells for a period of Nov. 1973 to Jun. 1974. Then, 88, 000m
3 of water were pumped up from a well for the succeeding period of July to Oct. 1974. Its change of quality was investigated. The original groundwater in the well had been high in alkalinity, low in the chloride concentration, and contained 9-10me/
l of the total ions. Owing to the first recharge and pumping-up, the total ion content was reduced to less than 6me/
l, whereas that of the recharge water was around 2.4me/
l. With pumping-up, the followings were always increased : the specific conductance, alkalinity and the contents of ammonia, calcium, magnesium, sodium, potassium and silica. The iron content was reduced at first and increased later. The DO and sulfate contents decreased, and the latter increased at first and decreased later. The chloride content remained unchanged consistently. These results suggests the existence of the interactions which were induced not only by mixing with the original groundwater, but also by oxidation-reduction reactions as well as the geological environment.
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