COMPLEXATION OF SOIL HUMIC-ACID WITH TRIVALENT CURIUM AND EUROPIUM IONS - A COMPARATIVE-STUDY

The complexation between a well characterized soil humic acid (OkchunH A) and trivalent metal ions (Cm3+, Eu3+) was compared with that by the Gorleben aquatic humic acid (GohyHA) by carrying out the investigatio n under the same experimental conditions and with the use of the same instrumentation (time resolved laser fluorescence spectroscopy: TRLFS) . The emission spectra (peak maxima: 601.2 nm) and two time components for the lifetime of fluorescence (70 mu s and 142 mu s) were found to be nearly the same, suggesting that the two Cm(III)-humates formed fr om two different humic acids are made of the similar chemical species. The calculated stability constants (Cm(III)-humate: log beta = 6.01+/ -0.05 1 mol(-1); Eu(III)-humate: log beta = 6.05+/-0.23 1 mol(-1)) wer e found to be in good agreement with those obtained earlier in the Goh yHA study, suggesting that the same thermodynamic description can be a pplied to both humic acids, provided 1:1 complex formation is assumed.