利用^(137)Cs技术研究黑土坡耕地土壤再分布特征

Redistribution patterns of black soil in hillslope landform of Northeast China:A ^(137)Cs study

利用^(137)Cs示踪技术和不同的理论模型研究典型的东北漫岗地形的黑土土壤再分布状况 .通过野外采样和模型分析 ,得出研究区^(137)背景值为 2 2 32 75Bq·m- 2 ,介于长江三角洲和黄土高原背景值之间 ,表明^(137)沉降与纬度和降水相关 .研究区各地貌部位^(137)含量在水平方向和深度分布上有很大的分异 .坡肩部位^(137)含量最低 ,土壤侵蚀最为强烈 ;坡顶和坡背侵蚀较为微弱 ;坡脚和坡足基本上表现土壤沉积 .^(137)分布深度从坡肩 2 0cm到坡足 80cm土层 ,表现出该区经历了强烈的侵蚀和沉积过程 .文中采用 4种常用的^(137)土壤侵蚀模型估计研究区的土壤侵蚀速率 ,结果表明 ,PM模型明显低估了土壤侵蚀速率 ,MBM1明显高估了土壤侵蚀速率 ,MBM2 和MBM3估计的结果较为相近的合理结果 .

In the black soil region of Northeast China,soil and water loss is quite serious,but not fully investigated due to the lack of reliable methods. 137 Cs technology is a good one to study the medium and long term erosion and sedimentation rates and the spatial redistribution of soil.With this technology and the existing calibration models,this paper studied the redistribution patterns of black soil in a typical hillslope landform of Northeast China.The results showed that in the study area,the reference 137 Cs value was 2232.75 Bq·m -2 ,intervenient the background values in the Yangtse River Delta and Loess Plateau;and the 137 Cs areal activity had a great differentiation in horizontal and vertical directions,being the lowest in the shoulder slope positions,which suggested that the summits and back slope positions suffered weak erosion,and some of the eroded soils were re deposited in foot slope and toe slope positions.The vertical distribution of 137 Cs in soil profile ranged from 20 cm on a shoulder slope to 80 cm on a toe slope position,indicating a significant erosion and deposition.Estimations with four existing calibration models showed that PM model underestimated while MBM 1 model overestimated the soil erosion rates very obviously,and both MBM 2 and MBM 3 gave similar and reasonable estimations.