[pp.167-174]

‹Research Report›Modification of Prediction Model for Soil Acidification Risk Level by Acid Rain in Aoba W

Young-Sik HAM and Hiromi KOBORI （Musashi Institute of Technology）

Abstract:
The pH, acid neutralizing capacity (ANC), and critical acidification year of soil samples were measured throughout the Aoba Ward of Yokohama City, Central Japan. Soil pH in Aoba Ward soil samples (n = 18) ranged from extremely acid (pH 4.4) to mildly alkaline (pH 7.8); the average soil pH was slightly acid (pH 6.2). Average pH in urban area soil samples (n = 6) was neutral (pH 6.8 ± 0.8 (± SD)), which was less acid than the pH of green space area soil samples (pH 5.9 ± 0.8, medium acid; n = 12). The ANC of soils varied from 1.7 to 16.2 mmolc/100g in urban areas and from 3.2 to 5.7 mmolc/100g in green space areas; these ANC values were positively correlated to the samples’ pH values. This study terminologically defines critical acidification year as the estimated number of years required for undesirable soil acidification to occur. The critical acidification year for soil was estimated using a modified simple mass balance model for H+ budget in the soil system that accounts for the effects of runoff and soil percolation water. Also, the risk level for soil acidification in Aoba Ward was classified on a GIS Map, using the average critical acidification year in each land use. This study classified agricultural area, park/forest area and urban area as high, middle and low risk areas for soil acidification, respectively.

Key Word:
acid rain, Aoba Ward, critical acidification year, GIS, risk level, soil acidification

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