中文摘要：

通过在野外28．5hm2的坡耕地上采集土壤样品，定量评价了利用137Cs和210Pbex，研究土壤有机碳（SOC）动态的潜力，以探讨东北黑土区土壤侵蚀对土壤有机碳的影响．结果表明：农耕地土壤137Cs、210Pbex和SOC在平面和垂直深度上均具有相似的分布特征．在平面上，尽管受土壤侵蚀沉积的影响，137Cs、210Pbex面积活度及SOC储量变异很大，但它们具有相同的变化趋势．在垂直断面上，侵蚀区137Cs、210Pbex和SOC在0～25cm耕层内分布均匀，25cm以下放射性活度减小，SOC含量也相应下降；沉积区0～100em深度上137Cs和210Pbex呈现先增加后减小的分布规律，SOC也具有类似的变化特征．农耕地SOC与137Cs、210Pbex呈显著线性相关，表明它们在黑土区农耕地上具有相似的物理运移特征，137Cs和210Pbex可直接用来定量评价黑土侵蚀下SOC的时空分布特点．

英文摘要：

Soil cores were collected from a 28.5 hm2 slope farmland in the black soil region of Northeast China. Based on the sampled data of 137Cs, 210Pbex and SOC, the potentials of applying 137Cs and 210Pbex, for assessing SOC redistribution were evaluated, aimed to approach the impact of soil erosion on soil organic carbon （SOC） in black soil region. At both planar and vertical directions, the 137Cs, 210Pbex and SOC in the farmland had similar distribution patterns. Although there were large planar variations in the 137Cs and 210Pbex areal activities and the SOC stock as affected by soil erosion and deposition, the 137Cs, 210Pbex and SOC had similar changing trends over the landscape. Two depth distribution profiles were also used to study the relations of 137Cs and 210pbex with SOC. At eroded site, the radioactivities of 137Cs and 210pbex and the SOC mass fraction did not show large variations in 0-25 cm soil layer, but decreased sharply below 25 cm. For the deposition sample, the radioactivities of 137Cs and 210Pbex in 0-100 cm soil increased firstly and then decreased. The SOC mass fraction also had similar depth distribution pattern in this soil layer. The 137Cs and 210pbex presented positive linear correlations with the SOC, indicating that 137Cs, 210Pbex and SOC moved with the same physical mechanism in the farmland, and fallout 137Cs and 210Pbex could be used to study spatio-temporal distribution characteristics of SOC in the black soil region under the condition of soil erosion.