An understanding of P transformations in altered wetlands has mainly developed from temperate and humid regions with neutral to acidic soils. Little is known regarding downstream water quality impact of P transformations in semiarid wetlands that undergone repeated cycles of drying and rewetting. The P geochemistry was studied using the Hedley fractionation scheme in the altered peat soils of the Hula Valley, Israel. The peat soils were sampled according to the peat depth and redox potential characteristics. The mean total P concentration (Pt) in the surface peat horizons (1190 ± 300 mg kg−1) was significantly higher than in the anaerobic (EH < −220 mV) peat layers (650 ± 260 mg kg−1). The concentrations of P in all fractions except the most labile P were significantly higher in the aerobic (EH = 400 mV) peat layers. The predominant extractable fractions in the surface peat horizons were Ca‐P extracted by 1 M HCl (21–60% of Pt), Iron‐P extracted by 0.5 M NaOH (11–41% of Pt), and residual P extracted by H2SO4 (20–40% of Pt). The source of the Ca in the Ca‐P fraction was mainly from gypsum dissolution following the rewetting cycles. The results clearly showed that the drainage of these wetlands facilitated rapid organic matter (OM) oxidation, release of organically bound metals and P followed by sesquioxides and gypsum precipitation. These geochemical transformations enhanced the Pt concentration per mass of altered peat soil and changed the P distribution among the different pools. Most of the P is currently associated with Fe oxides and hydroxides and/or coprecipitated with Ca.

downstream Lake Kinneret (Serruya et al., 1969; Serruya and Berman, 1976). The observed increase in phosphorus (P) loading into the JordanThe behavior of P in the peat soils of the Hula Valley River could increase eutrophication processes in Lake Kinneret, the is complex, partly because most of the 54 soil series only freshwater lake in Israel, which provides 25% of the country's identified in the valley have not yet reached a steady drinking water. The P may originate from the peat soils of the highly altered Hula Valley's semiarid wetland ecosystem through which the state (Israel Ministry of Agriculture, 1986). In the past Jordan River runs. The objectives of this research were to ascertain 40 yr, since the drainage of the Hula Valley, the soil the sorption capacity of these soils and to identify areas with high pH has increased steadily from 5 to 7, while the organic potential for P release from soils to ground water. We extracted 80 matter content has decreased from 50 to 70% before soil samples collected across the valley with ammonium oxalate and the drainage to 25 to 30% in 200030% in (Litaor et al., 2003a. determined the ratio of extractable P to Fe and Al, from which we The steady change in pH and organic matter content has derived the degree of phosphorus saturation (DPS). A relatively low undoubtedly affected the physico-chemical behavior of DPS (Ͻ15%) was observed in Histosols compared with the high DPS

The observed increase in phosphorus (P) loading into the Jordan River could increase eutrophication processes in Lake Kinneret, the only freshwater lake in Israel, which provides 25% of the country's drinking water. The P may originate from the peat soils of the highly altered Hula Valley's semiarid wetland ecosystem through which the Jordan River runs. The objectives of this research were to ascertain the sorption capacity of these soils and to identify areas with high potential for P release from soils to ground water. We extracted 80 soil samples collected across the valley with ammonium oxalate and determined the ratio of extractable P to Fe and Al, from which we derived the degree of phosphorus saturation (DPS). A relatively low DPS (<15%) was observed in Histosols compared with the high DPS (>30%) observed in many of the hydromorphic organo-mineral soils. We used a sequential Gaussian simulation technique to assess the spatial pattern of the DPS and found that the Histosols have a low probability (<10%) of exceeding the widely used environmental DPS threshold of 25%. The areas characterized by mineral soils, such as hydromorphic Vertisols and various marl redoximorphic soils, have a high probability (>60%) of exceeding the threshold value. The ability to predict the concentrations of dissolved P in ground water based on DPS values was somewhat impaired because of the preferential flow characteristics in this altered wetland.

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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.