The dynamic redox chemistry of iron in the epilimnion of Lake Kinneret (Sea of Galilee).


Sivan O, Erel Y, Mandler D, Nishri A. The dynamic redox chemistry of iron in the epilimnion of Lake Kinneret (Sea of Galilee). Geochim. Cosmochim. ActaGeochimica et Cosmochimica Acta. 1998;62 (4) :565 - 576.

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Fe redox chem. was studied in Lake Kinneret (Sea of Galilee), a mesotrophic, monomictic lake in the central part of the Jordan Rift Valley, Israel. Fe2+ and total Fe concns. in the epilimnion and hypolimnion were measured; relationships between Fe2+ and other parameters (e.g., light, pH) were examd. In addn., lab. expts. were conducted where filtered (biota-free) Lake Kinneret water, sterile unfiltered Lake Kinneret water, and distd. water were spiked with various Fe3+ and Fe2+ concns. Fe3+ and Fe2+ concns. were measured as a function of time in water samples under a variety of pH, O2, and radiation conditions. Fe2+ concns. in the epilimnion were below detection limits (0.04 μM) during nighttime, whereas in daytime, Fe2+ concns. were always above detection limits and changed significantly throughout the year (0.05-0.15 μM). Fe2+:Fe(tot) ratios measured in the lake (3-99%) were higher than expected values for a high pH (pH ∼8), low ionic strength (∼10 mM) aquatic system. In addn. to photo-induced redn. of Fe3+, there was strong evidence that Fe2+ is stabilized in O2-satd. lake water, since Fe2+ concns. were detected at a depth of 10 m, where <10% of light penetrates. Results of oxidn. and photoredn. expts. suggested obsd. rates of Fe redox reactions in sterile lake water were consistent with known chem. (abiotic) rates, but that these rates cannot account for obsd. Fe2+ concns. in epilimnetic water. Therefore, it was proposed that the photo-induced Fe redox cycle in the epilimnion of Lake Kinneret is largely controlled by biol. activity and that abiotic photoredn. of Fe accounts for only a small fraction of Fe2+ in the epilimnion. [on SciFinder(R)]


CAPLUS AN 1998:283137(Journal)