Identification of ^137Cs Reference Sites in Southeastern China

The ^137Cs vertical distributions in uncultivated and cultivated soils, developed from Quaternary red clay, granite, argillaceous shale, and red sandstone, were studied to develop reliable guidelines for selecting reference sites in southeastern China, which is dominated by strong acidic and/or clay-textured soils, and examine their reliability by comparing them to the reported ^137Cs reference inventory data to see whether they agreed with the global distribution pattern. It was observed that a relatively high proportion of ^137Cs was concentrated in the surface layers of soils with relatively high clay content. In the paddy soils developed from granite more ^137Cs penetrated to depths below the plow layer （about 45.3%）, when compared to those from the other three parent materials. The relatively low soil ^137Cs inventories on crests excluded using the crest as the ^137Cs reference site; instead the paddy field on the hillock plain was selected. Furthermore, within a specific county characterized by great systematic spatial variations of rainfall and topography across the landscape, a significant （P 〈 0.01） and positive linear relationship （r^2 = 0.81） between local ^137Cs inventory and corresponding local annual rainfall was observed. Thus, for areas with large variations in rainfall, a single uniform value of local ^137Cs reference inventory should be used with caution.