Ammonium sulfate or ammonium nitrate solution was added repetitiously in volcanic ash soil. The difference in amount of anion adsorption or cation desorption, and the change in pH were compared with the simulated results by the four plane model. pH of soil solution was lowered by the addition of the ammonium nitrate solution, and pH was increased in the ammonium sulfate solution. The amount of desorption of the base cation in the ammonium nitrate solution was large than that of ammonium sulfate solution addition. The adsorbed amount of sulfate ion was increased, even if pH rose in the ammonium sulfate solution addition. The amount of sulfate ion adsorption was depended on concentration, and that didn’t depend on hydrogen ion concentration by adaptation of regression equation that composed with anion and hydrogen ion concentration. Sulfate and nitrate ion adsorption calculated by the four plain model were corresponded to the measurements well. Comparing the simulated charge density at each plain, addition of ammonium sulfate solution was large than that of ammonium nitrate solution addition. In the case of ammonium sulfate solution addtion, amount of hydrogen ion adsorption on S plain was large than that of hydroxyl ion compared with ammonium nitrate solution addition. These simulated results correspond with the pH measurements.
The purpose of this study was to appreciate the spatial variability of upland soil profile on
complex hillslope and to consider the adequacy of geomorphological information to explain the
soil profile distribution. On a 1.2-ha upland field of central Hokkaido, Soil profile was investigated
at 154 locations on a 14-m grid. Apparent differences were recognized according to
the location on a slope position. In the landsurface model units of Interfluve and Convex Creep
Slope, horizon sequence was Ap/C-type, the color of Ap-horizon soil in this area was relatively
bright and coarse texture. In the units of Colluvial Footslope and Alluvial Toeslope, horizon
sequence was Ap/Ab/B/C-type, the Ap-horizon soil color was relatively dark and fine texture
influenced by sedimentation. Terrain attributes, slope gradient, slope curvature, specific catchment
area etc, calculated from the 7m-digital elevation model were highly correlated with
A-horizon thickness except for slope gradient. Thick A-horizon was observed at the location
which topographic conditions were convex slope, low altitude and high specific catchment area.
The multiple regression model of A-horizon thickness by terrain attributes didn’t have sufficient
result for quantitative tool. However landsurface model units identified the A-horizon thickness
distribution. Geomorphological analisys is useful to guide soil management system with consideration
of spatial variability.
The prediction method of ion concentration in the effluent during permeation of acid solutions involving multiple anionic species into volcanic ash soil was examined in this study. The method for prediction was composed of chemical reactions between acid solution and soil, and Mixing cell model, which approximately describe solute transport in soil. The results were summarized in the following.
1) The model could simulate well pH and monovalent anions (NO3- + Cl-) in the effluent during permeation of acid solutions involving NO3-, Cl- and SO42- into soil column. This shows that it is possible to handle sum of NO3_ and Cl- as a monovalent anion.
2) The simulation results agreed well with the measured values of pH and concentration of anions and BC2+ (sum total of Ca2+, Mg2+, K+ and Na+) in the effluent. Therefore, it seemed that simulation model used in this study is useful for predicting the main effects when acid rain including multiple anionic species deposited on the Kanto loam subsoil.
In this study, soil surveys and water retention measurements were conducted on a wide range of soil textures sampled from thirty one locations in the central hinterland of Horqin sandy land. Because the measured water retention curves belong to intermediate scanning curves between the main desorption and sorption processes, some precautions on measurement and application of the water retention curves were suggested. All soils in survey sites were classified into nine soil types. The average water retention curve of each soil type could be sufficiently approximated by using van Genuchten formula (vG-I). Their saturated and residual volumetric water contents (θs, θr) increased with clay contents of soil groups. It was confirmed that the shape of their water retention curves are reflected precisely by the parameters ε and ν that describe the degree of the first and second inflection curvatures of vG-I, respectively. Pedotransfer functions in the survey area were estimated using the water retention curves for the nine soil types by the function parameter regression method. The parameters of the fittedwater retention curves using vG-1 and vG-II (assumed m =l in vG-I)were known to have quite good regression relations with the indexes of soil physical and chemical properties. Particularly, the accuracy of estimation was found to increase when the regression formulas of ε and ν were substituted for m and n in vG-I. Therefore, PTF is an efficient method for estimating the water retention curves for different sites in the survey area.