无侵蚀土壤垦殖后的^(210)Pb_(ex)深度分布变化理论模型  

Theoretical mode for ^(210)Pb_(ex) distribution of non-eroded soils after cultivation

作　　者：张云奇[1,2] 张信宝[1] 贺秀斌[1] 龙翼[1,2] 文安邦[1] 齐永青[1,2] 

机构地区：[1]中国科学院,水利部成都山地灾害与环境研究所,成都610041 [2]中国科学院研究生院

出　　处：《核技术》2007年第9期797-800,共4页Nuclear Techniques

基　　金：国家自然科学基金项目(90502002);中国科学院知识创新工程项目(KZCX3-SW422);973项目(2003CB415202);国际原子能机构CRP项目(12322/RO)资助

摘　　要：农耕地犁耕层土壤中的^(210)Pb_(ex)向犁底层土壤的扩散,相当于无限薄层扩散源向一维半无限介质的扩散。本文对无侵蚀土壤垦殖后土壤中^(210)Pb_(ex)的扩散、直至达到稳定态分布的物理过程给予了数学的描述。垦殖10年后(y=10.37a),土壤中的^(210)Pb_(ex)可以达到稳定态分布。根据四川内江无侵蚀紫色土农耕地土壤的^(210)Pb_(ex)深度分布,求得紫色土犁底层土壤的^(210)Pb_(ex)入渗系数(D)为0.676cm-2·a-1;计算了垦殖后不同时间犁底层中^(210)Pb_(ex)的积累扩散量;给出了犁底层土壤^(210)Pb_(ex)深度分布形态的时间变化。When uncultivated land without erosion is cultivated, the ^210Pbex in the depth of tillage, which decreases exponentially with depth, can be mixed in the plough layer. Subsequently, the ^210Pbex of the plough layer would gradually diffuse into the plough pan layer owing to the concentration grads of ^210Pbex between them, and finally a steady state would come forth as a result of balance between diffusion and decay of the ^210Pbex. This process can be considered as one-dimensional diffusion from a thin diffusion source layer with unlimited width to semi-infinite media. This paper describes the process in a quantitative way. The time of the process from initial cultivation to the steady state is about 10 years （y=10.37 a）. As in the case of cultivated purple soil of Neijiang in Sichuan province, the downward diffusion coefficient of soils of the plough pan layer is D=-0.676 cm^2.a^-1, which is achieved according to the ^210Pbex depth distribution of the soils. Subsequently, the ^210Pbex inventory of the plough pan layer of different time after initial cultivation are calculated, and ultimately the process of ^210Pbex distribution in the non-eroded purple soils after cultivation is figured out.

关 键 词：农耕地 ^210Pbex扩散 稳定态分布 入渗系数 

分 类 号：P595[天文地球—地球化学]