Авторы: Kopacek J., Klementova S., Norton S.

2005 г.

Envir.Sci.Techn.

   Photochemical liberation of allochthonous organically bound aluminum (Al) and iron (Fe) and in-lake hydroxide precipitation are important sources of these metals to lake sediments. Mass budgets of ionic Al and Fe (Al_i, Fe_i), organically bound Al and Fe (Al_o, Fe_o), and particulate Al and Fe (Al_p, Fe_p) were measured for two western Czech Republic forest lakes (Plesˇne´ and Cÿertovo) in the 2000-2003 hydrological years. The lakes were net sinks of Ali, Alo, and Feo and net sources of Alp and Fep. The average Al_o and Fe_o inputs from terrestrial sources (66-110 and 12-17 mmol m-2 yr-1, respectively, on a lake area basis) were reduced 45% and 25% in the lakes. Mass budgets of dissolved organic carbon, particulate organic C, and Al species indicated that only a minor part of the observed in-lake retention of Alo could be explained by coagulation and sedimentation of organic matter, or from Ali hydrolysis and formation of Alp. Laboratory experiments with a short-time irradiation (300 nm, 800 W m-2) of water from inlets to Plesˇne´ Lake showed the importance of photochemical processes in the liberation of Al and Fe from Alo and Feo. After 12 h of irradiation, Alo and Feo concentrations decreased 54 ( 6% and 70 ( 16%, respectively, compared to those of the dark controls. The photoliberated Alo and Feo increased the Ali and Fei concentrations reciprocally, on a 1:1 mass basis. The subsequent hydrolysis of Ali and Fei in lakes forms insoluble hydroxides, increasing the sediment concentrations of Al and Fe.

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