Assessment of natural radionuclide transfer factors and partition coefficients in some Syrian soils

Abstract

Transfer factors of radium 226(²²⁶Ra), lead 210(²¹⁰Pb), polonium 210 (²¹⁰Po), uranium 238 (²³⁸U) and thorium 234(²³⁴Th) from five different agricultural soils in Syria to coriander, parsley and mint were investigated in a pot culture experiment. Geometric means of transfer factors (TF)were²²⁶Ra (0.13),²¹⁰Pb(0.03), ²¹⁰Po (0.02) and ²³⁸U (1.76) were within worldwide values, while TF values for ²³⁴Th (1.35) were higher than those recorded globally. The available transfer factor (ATF) values ranged between 0.03 and 1.45, 0.33 and 3.2, 0.10 and 3.36, 1.30 and 16.2 and 1.0 and 6.95 for²²⁶Ra,²¹⁰Pb,²¹⁰Po, ²³⁸U and ²³⁴Th, respectively. However, it is worth mentioning that the data from pot experiments may not represent field conditions. Liquid/solid partition coefficients (K_d)of ²²⁶Ra, U, ²¹⁰Pb and ²¹⁰Po for55 soils representing the dominant types of soils in Syria were also determined. Geometric means of K_d values ranged from 280 to1200, 750 to1600, 350to 4800 and 100-120 L kg^-1 for ²²⁶Ra, ²³⁸U, ²¹⁰Pb and ²¹⁰Po, respectively at pH = 4.0, and from 200 to 6700, 670 to 2400, 150 to 2100 and 100 to 160Lkg^-1at pH = 5.5, and from 370 to 790, 130 to 550, 60 to 330 and370 to 920Lkg^-1at pH = 7.0. The effects of soil mineral content, CEC, ECE, pH and soluble ions on the K_d values were investigated. In general, there were logarithmic relationships between the activity concentrations in soil and the K_d values (R² ranged from 0.59 to 1.00 at pH 4.0). There were no relationships between the K_d values and soil pH.

Keywords: (210)Pb; (210)Po; (226)Ra; (234)Th; (238)U; Available transfer factor; Factor value; Partition coefficient.