Estimation of soil specific surface area from adsorbed soil water content
Chong Chen, Emmanuel Arthur, Markus Tuller, Hu Zhou, Xiang Wang, Jianying Shang, Kelin Hu, Tusheng Ren
Abstract
Abstract The adsorbed water content is an attractive predictor for estimation of soil specific surface area (SSA) as its measurement is less laborious and more cost effective than standard laboratory techniques. We analysed the effects of total specific surface area (SSA tot ), external specific surface area (SSA ex ) and internal specific surface area (SSA in ) on water vapour sorption on 21 soil samples, and proposed models for estimating SSA ex , SSA tot and SSA in from organic carbon content and the slope of soil water vapour sorption isotherm ( SL 0.5 ) and water content ( WC 0.5 ) at a water activity of 0.5. The results indicated that the variation of correlation coefficients between water content change at 0.05 water activity interval (WCC 0.05 ) and SSA tot with water activity was mainly due to the differences in water vapour adsorption in interlayer spaces at different water activity levels. Furthermore, in the soil water content range from ~0.001 to ~0.03 g g −1 (within the water activity range from ~0.45 to ~0.75), water vapour adsorption was related closely to SSA ex . Cross‐validation results on estimated SSA ex , SSA tot and SSA in of the 21 samples produced root mean square error (RMSE) values less than 9.39 m 2 g −1 and Nash‐Sutcliffe model efficiency coefficients (E) greater than 0.93, suggesting that the proposed models provided reasonable estimates of SSA components. Thus, soil water vapour adsorption data can be applied to simultaneously estimate SSA ex , SSA tot and SSA in . Variation of correlation between WCC 0.05 and SSA tot with water activity depended on SSA in . Soil water vapour sorption is related closely to SSA ex at water activities from ~0.45 to ~0.75. The proposed models yield reasonable estimates of SSA tot , SSA ex and SSA in . Adsorbed water content can be used as a predictor for SSA estimation. Highlights Variation of correlation between WCC 0.05 and SSA tot with water activity depended on SSA in . Soil water vapor sorption relates closely to SSA ex at water activities from ~0.45 to ~0.75. The proposed models yield reasonable estimates of SSA tot , SSA ex , and SSA in . Adsorbed water content can be used as a predictor for SSA estimation.