Premium
THE HIGH‐ AND LOW‐ENERGY PHOSPHATE ADSORBING SURFACES IN CALCAREOUS SOILS
Author(s) -
HOLFORDI I. C. R,
MATTINGLY G. E. G.
Publication year - 1975
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1975.tb01964.x
Subject(s) - adsorption , calcareous , soil water , chemistry , dithionite , phosphate , langmuir equation , sorption , bicarbonate , organic matter , langmuir , environmental chemistry , inorganic chemistry , geology , soil science , organic chemistry , paleontology , enzyme
Summary The two‐surface Langmuir equation was used to study P adsorption by 24 calcareous soils (pH 7.2‐7.6; 0.8‐24.2 per cent CaCO 3 ) from the Sherborne soil series, which are derived from Jurassic limestone. High‐energy P adsorption capacities ( x ″ m ) ranged from 140–345 μg P/g and were most closely correlated with dithionite‐soluble Fe. Hydrous oxides therefore appear to provide the principal sites, even in calcareous soils, on which P is strongly adsorbed ( x ″ m 6–51 ml/μg P). The low‐energy adsorption capacities ( x ″ m ) ranged from 400–663 μg P/g and were correlated with organic matter contents and the total surface areas of CaCO 3 but not with per cent CaCO 3 , pH, or dithionite‐soluble Fe. Total surface areas of CaCO 3 in the soils ranged from 4.0 to 8.5 m 2 /g soil. Low‐energy P adsorption capacities agree reasonably with values (100 pg P/m 2 ) for the sorption of phosphate on Jurassic limestones but phosphate was bonded much less strongly by soil carbonates ( k ″= 0.08–0.45 ml/μg P) than by limestones ( k ∼10.0 ml/μg P). Low‐energy P adsorption in these soils is tentatively ascribed to adsorption on sites already occupied by organic anions (and probably also by bicarbonate and silicate ions) which lessen the bonding energy of co‐adsorbed P.