Soil 137Cs background values in monsoon region of china

Land degradation,, which is resulted from the soil erosion, is one of the major environmental problems. It severely affects the food supplies, environmental safety and the sustainable development in China. Some areas in the monsoon region are suffering from the acute soil erosion. To find out the degree of soil erosion, the proven technique of 137Cs tracer is definitely one of the best methods, and the key is to ascertain the accuracy of soil 137Cs background value. The distributions of 137Cs were explored in soil profiles by detecting the 137Cs of soil cores from the Yimeng mountain area in Shandong Province, hills in the southern area of Jiangsu Province and Dianchi catchment in Yunnan Province, respectively. We found that the depth of 137Cs distribution is not the same in the soils of various areas. But the 137Cs activity shows an exponential distribution in the uncultivated soil and demonstrates a strong correlation with the soil depth, while the 137Cs activity proves uniform in the soil plowing layer of the cultivated land. The study shows the 137Cs background values of three areas: 1737.1 Bq/m2 in Yimeng mountain area, 1847.6 Bq/m2 in southern area of hills in Jiangsu, 918.0 Bq/m2 in Dianchi catchment. The certainty of 137Cs background value can technically support the use of 137Cs technique to study the spatial pattern of soil erosion, deposition and the land degradation, which provides the support for the sustainable utilization of soil resource, the assessment of economical benefit and loss and the evaluation of water and soil conservation measures. (authors)