Methodology improvement of radiocaesium sorption determinations on bottom sediments from Chernobyl contaminated areas

¹ ITN/Departamento de Protecçao Radiologica e Segurança Nuclear, EN 10, Apartado 21, 2686-953 Sacavém, Portugal
² SPA Typhoon Institute, Obninsk, Russia

Abstract

Characteristics of radiocaesium selective sorption on soils and bottom sediments from Chernobyl contaminated areas, such as, capacity of selective sorption sites (frayed edge sites-[FES] and high affinity sites-[HAS]) and radiocaesium interception potential (RIP) are determined, allowing to predict radiocaesium distribution in the soil-water systems. Experimental methods based on masking of the regular exchange sites (RES) by silver thiourea (AgTU) were carried out. To extent the potential of these methods, the methodology was slightly modified by introduction of additional ammonium extraction of exchangeable radiocaesium after equilibrium time. To obtain [FES] and [HAS] linear form of Langmuir equation was used. Application of linear form of Langmuir equation allows to determine the capacity of selective sorption sites [FES] for organic bottom sediments for which maximum of caesium isotherm does not take place as a result of lattice interlayers collapse. Capacity of high affinity sites [HAS] was determined using Langmuir linearisation of the initial piece of sorption isotherm. In the case of RIP determinations fixation leads to overestimation the value of RIP. The notion of RIP^ex (exchangeable RIP-after ammonium acetate extraction) was introduced.