Similarities and Differences in Behavior of ¹³⁷Cs, ⁴⁰K and ⁷Be in Natural Ecosystems

1. Abstract

Fallout-derived ¹³⁷Cs and naturally occurring radionuclides, such as ⁴⁰K and ⁴⁰Be in soils and grass were measured in Thessaloniki area, Northern Greece, at temperate zone (40°), in order to examine their behaviour in natural ecosystems. For long-term measurements over a 15-y period, ¹³⁷Cs concentrations ranged from 3.73 to 1307 Bq kg⁻¹ (avg. 210.5 Bq kg⁻¹) in soils and from 0.4 to 334.9 Bq kg ⁻¹(avg. 14.5 Bq kg⁻¹) for grass. Potassium-40 concentrations ranged from 141.4 to 580.2 Bq ^kg−1 (avg. 224.4 Bq kg⁻¹) in soils and from 66.3 to 1480 Bq kg⁻¹ (avg. 399.8 Bq kg⁻¹) for grass. Beryllium-7 concentrations ranged from 0.53 to 39.6 Bq kg⁻¹ (avg. 14.4 Bq kg⁻¹) in the soils and from 2.1 to 348.0 Bq kg⁻¹ (avg. 54.4 Bq kg⁻¹) for grass. Cesium-137 transfer coefficients, TF from soil to plants (grass) ranged from 0.002 to 7.42 (avg. 0.20). Potassium-40 TF values from soil to plants (grass) ranged from 0.16 to 2.42 (avg. 0.73). Beryllium-7 TF values from soil to plants (grass) ranged from 0.027 to 2.37 (avg. 0.42) 137 An ecological half-life, T_ec for ¹³⁷Cs in grassland 3 1/3 y could be derived, when TF values varied between 0.1 and 0.01 in an 11-y elapsed time since contamination (May 1986). An almost similar T_ec value (3 2/3 y) was derived for ⁴⁰K in grassland.