A Comparative Study of Phosphate Sorption in Lowland Soils under Oxic and Anoxic Conditions

Abstract

Phosphate (P(i)) release due to Fe(III) oxide dissolution is well documented for soils undergoing reduction. The P(i) sorption properties of soils in anoxic conditions are, however, still under consideration. In this investigation, P(i) sorption to strictly anoxic soils was compared with oxic conditions to assess the potential of lowland soils to function as traps for P(i) 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 Fe(III) (Fe(BD)). Langmuir fitted P(i) sorption isotherms showed a P(i) release of up to 1.1 mmol kg(-1) in six soils when P(i) concentrations in the matrix (P(sol)) were lower than 10 microM. Phosphate desorption was attributed to dissolution of amorphous iron oxides, and higher pH under anoxic conditions. The point of zero net sorption (EPC(0)) increased 2- to 10-fold on reduction. Five soils showed higher P(i) sorption capacities in the anoxic than in the oxic state at higher P(sol) concentrations. Solubility calculations indicated that precipitation of vivianite or similar Fe(II) phosphates may have caused the higher sorption capacities. Use of maximum sorption capacity (S(max)) is therefore misleading as a measure of P(i) sorption at low P(sol) concentrations. The results demonstrate that none of the strongly anoxic soils, irrespective of the initial Fe(III) oxide content, the P saturation, and the degree of Fe(III) oxide reduction, could retain P(i) at natural P(sol) concentrations in agricultural drainage water.

Phosphorus Retention in Intact and Drained Prairie Wetland Basins: Implications for Nutrient Export

“…Overall, S max was roughly 3.5 and 1.8 times higher for the basin center and midslope landscape position in intact wetlands than in drained wetlands. The range of maximum P sorption capacity we estimated for intact wetland sediments was similar to values previously reported for reservoirs, shallow polymictic lakes, pelagic sediments of subtropical palustrine forested wetlands (Lane and Autrey, 2016), stratified lakes (Cyr et al, 2009), and riverine wetlands (Bridgham et al, 2001) but were generally much higher than those reported for sediments of subtropical palustrine emergent wetlands (Lane and Autrey, 2016), stratified lakes (Cyr et al, 2009), riparian soils and stream sediments (Reddy et al, 1998; Dunne et al, 2006b; Heiberg et al, 2010; Agudelo et al, 2011), estuarine sediments (Sundareshwar and Morris, 1999; Pant and Reddy, 2001; Wang and Li, 2010), constructed wetlands (Jamieson et al, 2002; Lai and Lam, 2009), and eutrophic lakes (Olila and Reddy, 1993; Zhou et al, 2005; Belmont et al, 2009; Huang et al, 2015; Zhang et al, 2016). One possible explanation for the higher P sorption capacity observed in our wetland soils relative to the surrounding uplands may be due to the large biomass of submerged macrophytes present in these systems.…”

Effect of Soil Aeration and Phosphate Addition on the Microbial Bioavailability of Carbon-14-Glyphosate

“…The relatively higher clay content in the Drummer soil corroborates this line of reasoning (Table 1). Iron oxide dissolution in anoxic soils may be another possible explanation for the reduction in the number of adsorption sites and was implied in a comparative study of phosphate adsorption to oxic and anoxic soils (Heiberg et al, 2010). …”

Biomedicine in the environment: Cyclotides constitute potent natural toxins in plants and soil bacteria

“…For these experiments, an agricultural drained lowland soil from Skjern (Jutland, Denmark) with cereal crop rotation was sampled in April 2007 and kept at 58C in the dark. The soil pH (H2O) was 5.44, and the soil was classified as a sandy, mixed, mesic Eutrudept [32]. Before use, the soil was air-dried, sieved (2-mm mesh size), and manually mixed.…”