Soil-to-plant transfer of 137Cs, 40K and 7Be

Measurements of fallout-derived 137Cs and of naturally occurring radionuclides, such as 40K and 7Be, in soils and grass were made in the Thessaloniki area of northern Greece, in the temperate zone (40°N), in order to determine their transfer factors from soil to plants. Long-term measurements over an 11-year period showed 137Cs concentrations ranging from 3.73 to 1307 Bq kg-1 (avge. 210.5 Bq kg-1) in soils and from 0.4 to 334.9 Bq kg-1 (avge. 14.5 Bq kg-1) in grass. Potassium-40 concentrations ranged from 141.4 to 580.2 Bq kg-1 (avge. 224.4 Bq kg-1) in soils and from 66.3 to 1480 Bq kg-1 (avge. 399.8 Bq kg-1) in grass. Beryllium-7 concentrations ranged from 0.53 to 39.6 Bq kg-1 (avge. 14.4 Bq kg-1) in soils and from 2.1 to 348.0 Bq kg-1 (avge. 54.4 Bq kg-1) in grass. Cesium-137 transfer coefficients, TF, from soil to plants (grass) ranged from 0.002 to 7.42 (avge. 0.20). Potassium-40 TF values from soil to plants (grass) ranged from 0.25 to 2.42 (avge. 0.73). Beryllium-7 TF values from soil to plants (grass) ranged from 0.027 to 2.37 (avge. 0.42). An ecological half-life, Tec, for 137Cs in grassland of years could be derived, while TF values varied between 0.1 and 0.01 over an 11-year period since the contamination event (May 1986). An almost similar Tec value ( years) was derived for 40K in grassland.