ELSEVIER zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA J. Environ. Radioactivify, Vol. 35, No. 2, 203-219, 1997 pp. 0 1997 Else&r Science Limited Printed in Ireland. All rights reserved PII: SO265-931X(96)00040-9 0265-931X/97 $17.00 + 0.00 zyxwvuts The Interactions of =Mn with Humic Substances of Freshwater Sediment Origin Marijana Erk,* Ljerka Musani & Biserka Raspor Center for Marine Research Zagreb, Ruder Bo5koviC Institute, PO Box 1016; HR- 10000 Zagreb, Croatia (Received 5 November 1995; accepted 16 April 1996) ABSTRACT The interactions of j4Mrt radionuclide with humic (HAB) andfulvic acid (FAB) isolated from freshwater sediment of the Butoniga impoundment were studied in a freshwater system from Butoniga impoundment, and in a diluted seawater system from the RasYa Bay at elevatedpH by high-voltage paper electrophoresis. In this way, it was possible to detect cationic, anionic and immobile 54Mn species, and to calculate their electrophoretic mobilities. The interaction of 54Mn with humic substances (HS) in a freshwater system is demonstrated by the formation of an electrophoretically immobile zone and the formation of the cationic forms of “Mn having smaller electro- phoretic mobilities than cationic forms of 54Mn in a freshwater system without HS added. The amount of cationic forms decreases in the zyxwvutsrqponmlkjih presence of HS. This effect is enhanced with an increase in HS concentration in the range 5-100 mg 1-t and in an increase in pHfrom 9.5 to 10.5. The addition of HAB up to IOOmgt’ and the increase of pH from 7.9 to 9.0 in diluted seawater systems do not cause significant changes of cationic electrophoretic mobilities of j4Mn, nor the formation of an electrophoretically immobile -form of “Mn. 0 1997 Elsevier Science Limited. All rights reserved zyxwvutsrqponml INTRODUCTION Manganese-54 is a neutron activation product, and, by the controlled discharge of activated cooling water from nuclear and fuel processing *To whom correspondence should be addresed. E-mail address: erk@olimp.irb.hr A part of M.Sc. Thesis, University of Zagreb, Croatia, 1995. 203