| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1995: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1994: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
Japanese forest soil acidification was investigated by experimental and theoretical approach. From the ecological point of view, Special accounts were taken to the aluminum dissolution and ion exchange process derived from soil acidification. Dynamic behavior of aluminum (Al) and base cation (Ca, Mg, K,Na) in soil systems were evaluated and predicted.
An ion chromatographic method in which Al is quantitatively determined via postcolumn derivatization with PCV (pyrocatechol violet) was evaluated for its utility as a method for speciating Al in aqueous solutions. oxalato- and humic aluminum complexes were identified by distinct peaks within chromatograms of Al solutions. Quantitative agreement between predicted species concentrations via thermodynamic data and determined by ion chromatography was obtained for oxalate and aluminum solution samples.
Using the simulated acid incident precipitation or throughfall, saturated soil column experiments were carried out. Total ion concentration of t
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hroughfall is higher than that of incident precipitation. As compared with incident precipitaion, Simulated throughfall reduced acid neutralization by cation exchange in soil, and raised Al concentration in effluent. Among co-existing cation in simulated throughfall, the effect of calcium ion and potassium ion on soil acidification were more important than that of sodium ion.
Another column experiments, using inorganic forest soil (A-horizon) and forest floor (O-horizon), were carried out. Cation exchage capacity of forest floor was much higher than that of inorganic soil (A-horizon). It was indicated that forest floor retarded the aluminum dissolution in inorganic forest soil and change aluminum species to organic complexes at the condition of relatively high pH (4.5-5.15) in soil solution.
SMART Model proposed by De Vries et al.is often referred as a general model for estimate soil acidification. SMART model was simplified only to include the physicochemical processes such as the aluminum dissolution and some exchange reactions. The structured model were applied to column experiments which were carried out by using simulated acid incident precipitation or throughfall (pH3.3 or 4.0). The structured model could explain the experimental results especially at the case of both simulated acid incident precipitation and throughfall. of PH3.3. Also we discussed about the validity of each parameter value. Using this model, future changes of chemical property of forest soil in Japan were predicted for one hundred years. Less
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