A Study of the Behavior of Cadmium in Soil–Soil Solution–Plant System in a Model Experiment Using the 109Cd Radioactive Tracer

This article discusses the processes of transition to the aqueous phase and uptake from it by plants of stable (Cd) and radioactive ( 109 Cd) isotopes. Regularities of the distribution of Cd/ 109 Cd between different forms of their chemical compounds in the soil were revealed by means of sequential extraction procedure (SEP) according to the Tessier–Förstner sceme. It was shown that the content of labile and conditionally labile forms of compounds (fraction F1-F3) of stable Cd was 1.2–1.8 times lower than that of radioactive 109 Cd and, conversely, fixed conservative forms of metal compounds (fraction F4–F6) by 2.4–5.3 times more. The Cd concentration, 109 Cd activity concentration, distribution and concentration coefficients of natural Cd and 109 Cd radionuclide, and accumulation and removal of metal by plants were evaluated. The values of enrichment factors of natural (stable) Cd contained in sequentially extracted chemical fractions by 109 Cd radioisotope were determined, and the value of pool of labile cadmium compounds in studied soil was calculated. Based on the results of solid-state 13 C NMR spectrometry, the qualitative composition of high-molecular organic compounds of the soil solution was determined and their ability to specifically sorb heavy-metal cations was assessed.