The interactions of 54Mn with aminopolycarboxylic acids in aquatic systems

The interactions of 54Mn radionuclide with ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) were studied in freshwater system (Butoniga impoundment), and in diluted seawater system (the Ra a Bay) by high voltage paper electrophoresis. Depending on the EDTA or NTA concentrations it was possible to detect the distribution of cationic, anionic and immobile 54Mn species, and to calculate their electrophoretic mobilities. The apparent concentration stability constants of 54Mn-EDTA or 54Mn-NTA complexes were calculated from the respective titration curves. Logarithmic values of the apparent concentration stability constants for 54Mn-EDTA complex corrected for the influence of pH, Kc(αH), are in the range 6.20–7.38 in two different water types, while corrected for the effect of pH and Ca2+, Kc(αL), in 5% seawater amount from 11.29 to 11.89. Logarithmic values of the apparent concentration stability constants for 54Mn-NTA complex corrected for the influence of pH, Kc(αH), are in the range 6.42-5.21 in two different water types, while corrected for the effect of pH and Ca2+, Kc(αL), in 5% seawater amount from 6.92 to 6.47.