Spatial distributions of 137Cs in surface soil in Jing-Jin-Ji Region, North China.

Artificial Radiocaesium ((137)Cs) has been widely deposited over global soils. In this study, we measured (137)Cs activity concentrations in the soil samples taken from Jing-Jin-Ji Region, North China, during 2007-2008. The surface soil (0-20 cm) samples were collected from 452 sites in this region. The activity concentration of (137)Cs in the samples was measured using a GEM series HPGe (high-purity germanium) coaxial detector system (ADCOM-100). The main findings are as following. (1) The activity concentration of (137)Cs in surface soils in the region of study fluctuates within 0.3±0.1 to 12.9±0.4 Bq/kg with mean value of 3.7 Bq/kg. Compared to other regions located at roughly the same latitude, the (137)Cs activity is relatively low. The results indicate that there are no new inputs of the radionuclides into the area at that time and the data obtained could serve as baseline levels of (137)Cs in Jing-Jin-Ji Region. (2) Considering land use types, surface soil in woodland mostly shows high (137)Cs activities with rare natural erosion and anthropogenic activities, and the surface soil with relatively low (137)Cs activities appears in the areas of intensive anthropogenic activities, especially in the cities, river banks, reservoirs and the strongly eroded areas. The findings suggest that the varying distribution of (137)Cs activities in surface soil corresponds with land use types.