A comparison of measured 137Cs and excess 210Pb levels in the cultivated brown and cinnamon soils of the Yimeng Mountain area

This contribution analyzes the similarities and differences between the measured activities of ¹³⁷Cs and excess ²¹⁰Pb (²¹⁰Pb_ex) in the cultivated brown and cinnamon soils of the Yimeng Mountain area, discusses the influence of soil texture on the measurement of ²¹⁰Pb_ex, and presents differences between the two types of soils. Fields A and B were selected to represent the fields that contain cultivated brown and cinnamon soils, respectively. From either study field, one site of sectioned core and six bulk cores were collected to measure ¹³⁷Cs levels, ²¹⁰Pb_ex levels, and the particle-size composition of soil samples. Three undisturbed soil samples were collected to measure capillary and aeration porosities. The ¹³⁷Cs inventories for the two study fields are very similar. The ¹³⁷Cs is a man-made radionuclide, which means that its measured levels for soils are unaffected by soil texture. In contrast, levels of the naturally occurring ²¹⁰Pb_ex of soils from Field A were lower than those of Field B by about 50%. In contrast to aquatic sediments, levels of ²¹⁰Pb_ex in terrestrial surface soils are affected by the emanation of ²²²Rn from the soils. It can be assumed that the coarser the soils, the greater the emanation of ²²²Rn; in addition, the lower the measured ²¹⁰Pb_ex, the greater the underestimate of this value. The cultivated brown soils in Field A are coarser than the cultivated cinnamon soils in Field B. As a result, ²²²Rn in Field A will diffuse more easily into the atmosphere than that in Field B. As a consequence, the measured ²¹⁰Pb_ex in soils from Field A is much lower than the actual value, whereas the value measured for Field B is much closer to the actual value.