RELATIONS BETWEEN SPECIFIC SURFACE-AREA AND SOIL PHYSICAL AND CHEMICAL-PROPERTIES

The total specific surface area (SA) is a factor that can relate grain -scale properties to macro-scale physical and chemical properties of a porous medium, It is, therefore, advantageous to establish the relati onships between SA and general soil physical properties, In this study we investigated the relationship between SA and properties such as so il texture, cation exchange capacity (CEC), volatile organic vapor ads orption, water retention, and saturated hydraulic conductivity. Total specific surface area was highly correlated to the clay-size fraction of the soil and negatively correlated to the soil organic matter (SOM) of the soil, Both the CEC and the soil-water content at -15 bars (the wilting point) were highly correlated to SA, However, a steadily decr easing degree of correlation between SA and water contents at seven in creasing matric potentials was seen, suggesting that only the tightly bound water is directly related to SA, Using the measured specific sur face area, the soil-water contents at -15 bars were converted into equ ivalent molecular layers of water coverage, This revealed that the soi l-water content at -15 bars was consistently between four and eight mo lecular layers of water coverage for most soils, This equals the water coverage below which volatile organic chemical vapor/solid partitioni ng becomes significant,The soil-water content at the wilting point, th erefore, seems promising as a simple measure for the lower water conte nt at which Henry's Law and the aqueous/solid partition coefficient ca n be used to predict VOC adsorption, The Campbell water retention mode l parameter, b, was highly correlated to the volumetric specific surfa ce area, S-0, potentially making S-0 useful for predicting the soil-wa ter characteristic curve,The Kozeny-Carman equation was applied to des cribe the relationship between S-0 and the saturated hydraulic conduct ivity,The equation did not relate well to the measured data,This may b e explained by the heterogeneity of all of the investigated soils, whe reas the Kozeny-Carman equation was originally developed for structure less soils.