Influence of physical properties of soil on (137)Cs mobility

Abstract

Išnagrinėti radiocezio pasiskirstymo dirvožemyje profiliai ir, remiantis gautaisiais rezultatais, pasiūlytas būdas, kaip atsižvelgti į radiocezio mobilumą dirvožemyje. Pateiktu modeliu rastais rezultatais parodyta, kad cezio migraciją dirvožemyje lemia stačioji mobilios cezio fazės konvekcija, tuo tarpu molekulinė difuzija pasireiškia silpnai. Stačiosios mobilios cezio fazės pernešimo koeficientą galima laikyti pastoviu, nes didžiausią įtaką turi radiocezio surišimas dirvožemyje. Parodyta, kad radiocezio surišimas stipriausiai pasireiškia organika praturtintuose sausuose dirvožemiuose su maža mineralinių medžiagų koncentracija

A model to account for the mobility of radiocesium in soil is presented. The model requires a minimal set of coefficients that describe radiocesium migration and fixation rates, which can be related to physical soil properties. The peculiarities of experimental radiocesium profiles in soil are explained by the composition of soil, which affects the radiocesium fixation rate. It is shown that the migration of radiocesium in soil is governed by vertical convection of a mobile form, whereas diffusion is a slower process due to strong fixation. The results show that the velocity of vertical migration downward of mobile radiocesium can be set constant, because the overall migration rate depends on fixation. Modelling of experimental radiocesium soil profiles suggests that organic (humic) layers with reduced mineral content and humidity have a high radiocesium fixation rate. Soil structure that maintains high soil humidity and mineral content has an increased cesium exchangeability and, consequently, a higher radiocesium mobility