【Paper】
Adsorption of Basic Ca Ions by the Soil Layer in Landfill Sites
Yusaku Ono* and Nobutoshi Tanaka**
* Group of Waste Management, Center for Environmental Science in Saitama
** Graduate School of Engineering, Hokkaido University
† Correspondence should be addressed to Yusaku Ono:
Group of Waste Management, Center for Environmental Science in Saitama
（914 Kamitanadare, kisai-machi, Saitama, 347-0115 Japan）


Abstract
Landfill leachate contains high concentrations of Ca ions from incineration ash. This investigation was carried out to study the adsorption of Ca ions through various soil column tests. In the case of Ca（OH）2 solutions passing through the various soil columns, the humic volcanic ash soil had the highest adsorption capacity of Ca ions at 300meq/100g-soil or more at the breakthrough point（C/Co＝0.05）. This phenomenon is estimated to result from neutralization and adsorption of Ca ions through the dissociation of H＋ from soil substances, including clay-OH and humin-COOH at alkali conditions. In cases when incinerator ash extraction was passed through the soil columns, Ca ions passed through all of the columns until about C/Co＝0.4, and Ca ions were adsorbed until the breakthrough point. The amount of OH- ions in ash extraction was a 0.6 equivalent amount lower than that of Ca ions, and another 0.4 equivalent amount was leached out as neutral salts including CaCl2.
According to the results, it is estimated that a depth of about 0.5m is needed for Ca adsorption by humic volcanic ash soil when incineration ash is disposed of at a depth of 3m.


Key words: c