Long-term transfer of 137Cs in sensitive agricultural environments after the Chornobyl fallout in Sweden

Abstract

In this study, the long-term transfer of ¹³⁷Cs from soil to grass on Swedish farms and fields, heavily contaminated after the 1986 radioactive fallout, was investigated. The study spans over 8–14 years, beginning in June 1986, and covers various soil types and agricultural practices. The transfer of ¹³⁷Cs from soil to grass was highly variable, with transfer factors ranging from 1.0 × 10⁻⁵ to 0.357 m² kg⁻¹. Higher values were observed on fields with sandy loam, loamy sand, and organic soils, and lower values on fields with a high clay content. The transfer of ¹³⁷Cs to grass generally exhibited an exponential decline across the majority of fields over the years. The rate of decrease was most pronounced in clay loam and silty loam soils, while it was least evident in sandy loam, sandy soils, and peat soils. The soil properties and farming practices were more important for ¹³⁷Cs uptake than the initial deposition density. The transfer factor had a negative correlation with soil pH, clay, and fine silt content. No significant relationships were found with other soil variables, such as soil organic matter content and plant available potassium concentration. The median effective half-life of ¹³⁷Cs in the grass was 4.5 years, with a range of 2–18 years. The uptake of ¹³⁷Cs by plants did not correlate with the potassium concentration in grass tissues; however, the activity concentration of ¹³⁷Cs in grass correlated negatively with the potassium content in the plants grown on fields with high deposition levels.