Sorption Characteristics of Phosphorus in Peat Soils of a Semiarid Altered Wetland

Abstract

We studied the adsorption characteristics of P in altered peat soils of the Hula Valley, Israel, which has undergone repeated drying and rewetting cycles. As a result, the water quality of Lake Kinneret, the only freshwater lake in Israel, may have been adversely affected. Peat sample collection was based on pedogenic evaluation of the wetland's history and on the redox potential of aerobic (Eh = 450 mV) and anaerobic (Eh < −220 mV) conditions. Extractable citrate–bicarbonate–dithionite iron (FeCBD) was a dominant mineral phase in the aerobic layers (29 ± 5 g kg−1). Mössbauer spectra suggested that hematite, goethite, ferrihydrite, and magnetite are the main Fe minerals in these peat soils. The sorption maximum (Smax) of the aerobic layers ranged from 670 to 1750 mg P kg−1, with a mean value of 1250 mg P kg−1, whereas the anaerobic layers ranged from 625 to 975 mg P kg−1, with a mean value of 775 mg P kg−1 The equilibrium phosphorus concentration (EPC0) values in the most anaerobic peat layers were several orders of magnitude higher (0.31 mg L−1) than in the aerobic layers (0.01 mg L−1). Only a weak to moderate correlation was found between the sorption attributes and the Fe content due to precipitation of Ca‐P phases. The main source of Ca in these soils is gypsum. Rewetting of the peat soils leads to a decrease in Smax and the buffer capacity, and an increase in EPC0, which could lead to higher P mobility. The increased potential of P mobility declined with a concurrent increase in Ca‐P precipitation due to enhanced dissolution of gypsum.

Relation between various soil phosphorus extraction methods and sorption parameters in calcareous soils with different texture

“…The P buffer capacity (PBC) (L kg − 1 ) of the soil was estimated from the product of the Langmuir constant k and Q max (Holford, 1979;Litaor et al, 2005). Equilibrium P concentration at the point of zero sorption (EPC 0 ) was calculated from Langmuir equation.…”

Hydrogeological characterization of an altered wetland

“…This flow mechanism is especially important in the context of the water quality of the JR. Soluble reactive P (SRP) concentrations in the JR are normally below 0.02 mg L À1 (Salingar et al, 1993;Rom, 1999). However, the soils and sediments of the marl subaquifer are characterized by high equilibrium P concentration (EPC 0 = 0.1 mg L À1 , Litaor et al, 2005). This value represents the equilibrium dissolved P concentration, at which net P adsorption is zero (Reddy et al, 1998).…”

Phosphorus mobilization in rewetted peat and sand at variable flow rate and redox regimes

“…Litaor et al, 2004;Richardson, 1985;Sah and Mikkelsen, 1986;Schlicting et al, 2002). During anoxic conditions redox sensitive Fe(III) oxides are subjected to microbial induced reductive dissolution, which may lead to changes in sorption properties (Heiberg et al, 2010), and concurrent release of Fe(II) and dissolved P. Numerous investigations have reported increased Fe and P concentrations in soil pore water following reduction in soil redox potential Meissner et al, 2008;Moore and Reddy, 1994;Pant et al, 2002;Rupp et al, 2004;Sallade and Sims, 1997;Scalenghe et al, 2002;Young and Ross, 2001).…”