TY - JOUR

T1 - Vivianite precipitation and phosphate sorption following iron reduction in anoxic soils

AU - Heiberg, Lisa

AU - Bender Koch, Christian

AU - Kjærgaard, Charlotte

AU - Jensen, Henning S.

AU - Hansen, Hans Chr. Bruun

PY - 2012

Y1 - 2012

N2 - Phosphorus retention in lowland soils depends on redox conditions. The aim of this study was to evaluate how the Fe(III) reduction degree affects phosphate adsorption and precipitation. Two similarly P-saturated, ferric Fe-rich lowland soils, a sandy and a peat soil, were incubated under anaerobic conditions. Mossbauer spectroscopy demonstrated that Fe(III) in the sandy soil was present as goethite and phyllosilicates, whereas Fe(III) in the peat soil was mainly present as polynuclear, Fe-humic complexes. Following anoxic incubation, extensive formation of Fe(II) in the solids occurred. After 100 d, the Fe(II) production reached its maximum and 34% of the citrate-bicarbonate-dithionite extractable Fe (Fe-CBD) was reduced to Fe(II) in the sandy soil. The peat soil showed a much faster reduction of Fe(III) and the maximum reduction of 89% of Fe-CBD was reached after 200 d. Neoformation of a metavivianite/vivianite phase under anoxic conditions was identified by X-ray diffraction in the peat. The sandy soil exhibited small changes in the point of zero net sorption (EPC0) and P-i desorption with increasing Fe(III) reduction, whereas in the peat soil P-i desorption increased from 80 to 3100 mu mol kg(-1) and EPC0 increased from 1.7 to 83 mu M, after 322 d of anoxic incubation. The fast Fe(III) reduction made the peat soils particularly vulnerable to changes in redox conditions. However, the precipitation of vivianite/metavivianite minerals may control soluble P-i concentrations to between 2 and 3 mu M in the long term if the soil is not disturbed.

AB - Phosphorus retention in lowland soils depends on redox conditions. The aim of this study was to evaluate how the Fe(III) reduction degree affects phosphate adsorption and precipitation. Two similarly P-saturated, ferric Fe-rich lowland soils, a sandy and a peat soil, were incubated under anaerobic conditions. Mossbauer spectroscopy demonstrated that Fe(III) in the sandy soil was present as goethite and phyllosilicates, whereas Fe(III) in the peat soil was mainly present as polynuclear, Fe-humic complexes. Following anoxic incubation, extensive formation of Fe(II) in the solids occurred. After 100 d, the Fe(II) production reached its maximum and 34% of the citrate-bicarbonate-dithionite extractable Fe (Fe-CBD) was reduced to Fe(II) in the sandy soil. The peat soil showed a much faster reduction of Fe(III) and the maximum reduction of 89% of Fe-CBD was reached after 200 d. Neoformation of a metavivianite/vivianite phase under anoxic conditions was identified by X-ray diffraction in the peat. The sandy soil exhibited small changes in the point of zero net sorption (EPC0) and P-i desorption with increasing Fe(III) reduction, whereas in the peat soil P-i desorption increased from 80 to 3100 mu mol kg(-1) and EPC0 increased from 1.7 to 83 mu M, after 322 d of anoxic incubation. The fast Fe(III) reduction made the peat soils particularly vulnerable to changes in redox conditions. However, the precipitation of vivianite/metavivianite minerals may control soluble P-i concentrations to between 2 and 3 mu M in the long term if the soil is not disturbed.

U2 - 10.2134/jeq2011.0067

DO - 10.2134/jeq2011.0067

M3 - Journal article

C2 - 22565275

VL - 41

SP - 938

EP - 949

JO - Journal of Environmental Quality

JF - Journal of Environmental Quality

SN - 0047-2425

IS - 3

ER -