Synergy of chemical and isotopic signatures data for environmental fate studies

Abstract

Environmental fate study conducted for case of uranium contamination of the environment have been described and discussed in the paper as an example of combined application of radiochemical separation methods, spectrometric analytical techniques and elemental speciation procedures to obtain the most complete set of data for investigation of their correlations. As a result, isotopic and chemical composition, ratios of activities concentrations and indication of probable physicochemical forms and bonding with different substrates were obtained. Radiochemical ion-exchange separation procedures followed by alpha spectrometry analysis have shown the isotopic ratios of 238U, 234U and 235U activity concentrations characteristic for depleted uranium. The isotopic signature of contaminant was determined on the basis of activity ratios 235U/238U and 234U/238U. These isotopic ratios differ for natural and depleted uranium and their values in the soil samples or their components are corresponding to the amount of depleted uranium in total uranium content of the sample. In the fractions obtained after the soil samples underwent a series of successive solid/liquid chemical extractions simulating environmental conditions, depleted uranium contribution to the total uranium contents was calculated and analyzed together with data on chemical composition of fractions. Correlations derived from isotopic and stable elements concentrations determined in extraction phases after multistep sequential extraction indicated potential substrates and bonding potential. Although contamination was not widespread, on the basis of obtained data, environmental fate of contaminant in terms of geochemical fractionation and mobility may be indicated.