A new approach to analysis of relationships between ¹³⁷Cs activity concentrations in forest soil horizons

The measurements results of ¹³⁷Cs activity concentrations in forest soil profiles are discussed. In studies some simplifications were considered. First of them concerns disregarding of soil subtype in data analysis. However initially this parameter was considered in data analysis, it was finally ignored. The second assumption drops information about specific soil horizon. Description of ¹³⁷Cs accumulation is based on relationships between its relative activity concentrations in soil layers. The model formulation was based on the results of exploratory data analysis of the relative ¹³⁷Cs activity concentrations. In studies the methods designed for compositional data analysis were used. The results of analysis showed that the relationships between the relative activity concentrations of ¹³⁷Cs in soil layers, due to their nature, might be divided into two groups. The first of them concerns layers located close to soil surface. The relative activity concentrations of ¹³⁷Cs in these layers are proportional to each other, and distribution mechanism of cesium within them has the characteristics of the process leading to thermodynamic equilibrium. The second group is related to layers that are located deeper. The calculation results suggest lack of thermodynamic equilibrium between these layers and layers situated above. Utilization of a linear model for description of changes in relative activity concentrations of ¹³⁷Cs in deeper layers supposes that these changes occur much slower than in layers lying above.