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Phosphorus Transport during Transient, Unsaturated Water Flow in an Acid Sandy Soil
Author(s) -
Chen J. S.,
Mansell R. S.,
NkediKizza P.,
Burgoa B. A.
Publication year - 1996
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1996.03615995006000010009x
Subject(s) - sorption , chemistry , soil water , sorbent , aqueous solution , water flow , volumetric flow rate , freundlich equation , reaction rate constant , soil science , analytical chemistry (journal) , environmental chemistry , kinetics , adsorption , thermodynamics , environmental science , organic chemistry , physics , quantum mechanics
Sorbent‐sorbate interactions heavily retard the movement of P during water flow in most soils. The effect of soil/solution ratio on sorption kinetics and movement of P during unsteady unsaturated water flow were investigated. A series of batch experiments with soil/solution ratios ranging from 0.1 to 6.4 Mg m ‐3 were conducted to obtain sorption rate coefficients. Aqueous P solutions (100–800 g m ‐3 ) were applied at two constant fluxes (1.4 × 10 ‐6 and 6.9 × 10 ‐6 m s ‐1 ) to columns of an air‐dry spodic soil. The experimental data were simulated with a parallel two‐site nonlinear, nonequilibrium transport model during unsteady, unsaturated water flow. Phosphorous sorption followed Freundlich‐type reversible kinetics with a very fast reaction occurring in Type I sites and a slow reaction occurring in Type II sites. The sorption reaction of P in batch experiments was satisfactorily described by the model but the rate coefficients varied with the soil/solution ratio. Experimentally determined rate coefficients described P movement in column experiments at an influx rate of 6.9 × 10 ‐6 m s ‐1 , but not for the slower influx rate of 1.4 × 10 ‐6 m s ‐1 , hence calibration of rate coefficients was necessary for describing P movement during the slower water influx. We developed a technique for determining rate coefficients under water saturated‐unsaturated conditions that provides a way to validate P transport models during transient, unsaturated water flow.