TY - JOUR
T1 - A comparative study of phosphate sorption in lowland soils under oxic and anoxic conditions
AU - Heiberg, Lisa
AU - Pedersen, Thomas Vils
AU - Jensen, Henning S.
AU - Kjærgaard, Charlotte
AU - Hansen, Hans Chr. Bruun
PY - 2010/3
Y1 - 2010/3
N2 - Phosphate (Pi) release due to FeIII oxide dissolution is well documented for soils undergoing reduction. The Pi sorption properties of soils in anoxic conditions are, however, still under consideration. In this investigation, Pi sorption to strictly anoxic soils was compared with oxic conditions to assess the potential of lowland soils to function as traps for Pi when flooded with drainage water. Batch sorption experiments were performed on seven minerogenic soils. Sorption to the anoxic soils was conducted after anoxic incubation, resulting in reduction of 36 to 93% of the dithionite-extractable FeIII (FeBD). Langmuir fitted Pi sorption isotherms showed a Pi release of up to 1.1 mmol kg-1 in six soils when Pi concentrations in the matrix (Psol) were lower than 10 μM. Phosphate desorption was attributed to dissolution of amorphous iron oxides, and higher pH under anoxic conditions. The point of zero net sorption (EPC0) increased 2- to 10-fold on reduction. Five soils showed higher Pi sorption capacities in the anoxic than in the oxic state at higher Psol concentrations. Solubility calculations indicated that precipitation of vivianite or similar FeII phosphates may have caused the higher sorption capacities. Use of maximum sorption capacity (Smax) is therefore misleading as a measure of Pi sorption at low Psol concentrations. The results demonstrate that none of the strongly anoxic soils, irrespective of the initial FeIII oxide content, the P saturation, and the degree of Fe III oxide reduction, could retain Pi at natural P sol concentrations in agricultural drainage water.
AB - Phosphate (Pi) release due to FeIII oxide dissolution is well documented for soils undergoing reduction. The Pi sorption properties of soils in anoxic conditions are, however, still under consideration. In this investigation, Pi sorption to strictly anoxic soils was compared with oxic conditions to assess the potential of lowland soils to function as traps for Pi when flooded with drainage water. Batch sorption experiments were performed on seven minerogenic soils. Sorption to the anoxic soils was conducted after anoxic incubation, resulting in reduction of 36 to 93% of the dithionite-extractable FeIII (FeBD). Langmuir fitted Pi sorption isotherms showed a Pi release of up to 1.1 mmol kg-1 in six soils when Pi concentrations in the matrix (Psol) were lower than 10 μM. Phosphate desorption was attributed to dissolution of amorphous iron oxides, and higher pH under anoxic conditions. The point of zero net sorption (EPC0) increased 2- to 10-fold on reduction. Five soils showed higher Pi sorption capacities in the anoxic than in the oxic state at higher Psol concentrations. Solubility calculations indicated that precipitation of vivianite or similar FeII phosphates may have caused the higher sorption capacities. Use of maximum sorption capacity (Smax) is therefore misleading as a measure of Pi sorption at low Psol concentrations. The results demonstrate that none of the strongly anoxic soils, irrespective of the initial FeIII oxide content, the P saturation, and the degree of Fe III oxide reduction, could retain Pi at natural P sol concentrations in agricultural drainage water.
U2 - 10.2134/jeq2009.0222
DO - 10.2134/jeq2009.0222
M3 - Journal article
C2 - 20176846
SN - 0047-2425
VL - 39
SP - 734
EP - 743
JO - Journal of Environmental Quality
JF - Journal of Environmental Quality
IS - 2
ER -