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Influence of allophane and organic matter contents on surface properties of Andosols
Author(s) -
Bartoli F.,
Poulenard A. J.,
Schouller B. E.
Publication year - 2007
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2007.00899.x
Subject(s) - allophane , bet theory , andosol , chemistry , microporous material , adsorption , organic matter , carbon fibers , materials science , soil water , organic chemistry , soil science , geology , composite material , composite number
Summary The aim of this study was to use nitrogen gas adsorption to study the complex surface properties of a wide range of Andosol Ah and Bw horizons; N 2 gas adsorption not only provides specific surface area, SSA , but it also yields complementary information about micropore volume and hydrophilic and/or hydrophobic surface properties. Total SSA s were positively related to micropore SSA which was, in its turn, positively interrelated to the dimensionless parameter C of the Brunauer‐Emmett‐Teller (BET) equation (micropore N 2 filling) and microporous allophane content. The more allophanic the Andosol horizon sample, the larger were its total, micropore and mesopore SSA s. On the other hand, strong negative exponential relationships were obtained between either total or micropore or mesopore SSA and soil organic carbon content, with a SSA threshold at an organic carbon content of c . 8–10%, the SSA s being extremely small at larger organic carbon content values. Both SSA BET and C BET decreased non‐linearly as a function of the organic C/allophane ratio, with either a SSA BET or a C BET threshold at an organic C/allophane ratio value of 3–5, above which both SSA BET and C BET were very small (mostly the aluandic Andosol Ah horizons). The more the soil allophanes are assumed to be coated, the more hydrophobic the soil surfaces become and the smaller both SSA BET and C BET become; nitrogen gas has a permanent quadrupole moment and therefore acts as a polar probe when surfaces are sufficiently hydrophobic. The antagonistic roles played by allophanes and organic matter in both the SSA s and the values of the dimensionless parameter C in the BET equation were also highlighted by (i) multiple linear regressions between the SSA s and both allophane and organic carbon contents and (ii) principal‐component analysis of SSA BET , C BET and soil constituent (allophane, ferrihydrite and organic C) contents.