Using(137)Cs and(210)Pb(ex) to trace the impact of soil erosion on soil organic carbon at a slope farmland in the black soil region

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.