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- Arsenie, Irina, et al.
(författare)
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Effects of Gamma Irradiation on an Aquatic Fulvic Acid
- 1991
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Ingår i: Humic substances in the aquatic and terrestrial environment : proceedings of an international symposium, Linköping, Sweden, August 21-23, 1989. - Berlin Heidelberg New York : Springer. - 3540537023 ; , s. 233-241
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Bokkapitel (refereegranskat)abstract
- An aquatic fulvic acid was irradiated with gamma radiation from a 60Co-source (dose range 0-48 Mrad), as part of a larger study of the transformation and decomposition of humic substances in natura! aquatic systems. Experiments were performed at two concentrations (1000 mg/l and 100 mg/l) and at various pH-values (2-10). The fulvic acid transformation was studied by monitoring optical density (UV-spectroscopy ), molecular weight distribution (GPC-technique) and total dissolved organic carbon (TOC). A general decrease in TOC with increasing radiation dose was observed: the initial G-value of about 5 decreased with the increasing dose to a minimum value of 0.2-0.3. A simultaneous increase in molecular weight (Mn rose from approximately 2000 to a maximum of about 4000) was observed in the acidic samples (pH 2-4) at a dose below 10 Mrad. Natural background radiation can significantly contribute to the degradation of dissolved humic substances in deep groundwaters, considering the observed G-value for low doses (about 5) and the otherwise high chemical stability of the fulvic acid fraction even after long residence times (103-104 y) in the ground.
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