PARENT SESSION
Poster Session #23: Fish, Lakes, Streams, and Wetlands.
Wednesday, August 8, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
68
The geochemistry of phosphorus in the histosols of a semi-arid ecosystem, Israel.
Litaor, M. Iggy1, Reichmann, Oren2, Nishri, Ami3, Shenker, Moshe2, 1 2 3
ABSTRACT- The drainage of Lake Hula and surroundings swamps in the late 1950s resulted in numerous environmental problems, including significant land subsidence and re-flooding of the subsided areas. To mitigate some of the problems, the regional groundwater level was raised, and a shallow lake was created. The elevated groundwater resulted in highly anoxic conditions in the formally aerobic pedosphere. The anaerobic conditions yielded elevated concentrations of dissolved ferrous (x = 44 SD = 22 mg/L, n = 31) and variable amounts of dissolved P (x = 410 SD =320 ug/L, n = 31) across the study site. This could lead to an increase in P flux to the drainage system, depending on the geochemical attributes of the soils. Sequential extraction experiments have shown that the highest amount of P was associated with NaOH and 1M HCl extracts, which implied that P is mainly associated with Fe-oxides and Ca-P solid phases. The sorption experiments indicated that the oxidized peat horizons have high sorption capacity, probably due to their iron oxide mineral assemblages, whereas the calcareous layers are characterized by low to moderate sorption capacity. These results suggest that even under reducing conditions, peat horizons may still serve as a sink for P, thus limiting the leaching of phosphorous. On the other hand, calcareous layers that exhibit relative high equilibrium P concentration (EPC0) may allow P leaching, especially if the flowing interstitial water contains P concentrations lower than the EPC0. Although the anaerobic conditions yielded a considerable amount of ferrous and dissolved P, there was no spatial correlation between ferrous and phosphorous across the geochemical transect. We attribute the lack of spatial correlation to a myriad of processes that affect P solubility, such as adsorption-desorption, co-precipitation, and chemical equilibria of several chemical systems (Ca-P, Fe-P, and Fe-S-P).
KEY WORDS: wetland, semi-arid, Phosphorus, Histosols