土壤发生性碳酸盐碳稳定性同位素模型及其应用  

Modeling and Application of Stable Carbon Isotope of Pedogenic Carbonate

作　　者：杨黎芳[1] 李贵桐[1] 李保国[1] 

机构地区：[1]中国农业大学资源与环境学院土壤与水农业部重点实验室土壤植物相互作用教育部重点实验室,北京100094

出　　处：《地球科学进展》2006年第9期973-981,共9页Advances in Earth Science

基　　金：国家自然科学基金项目"微生物在栗钙土无机碳转化与迁移中的作用"(编号:40303015)资助

摘　　要：干旱、半干旱地区土壤无机碳库比有机碳库大2～5倍，无机碳库及其周转在该地区土壤碳平衡中具有重要意义。土壤发生性碳酸盐是土壤发育过程的产物，与岩生性碳酸盐溶解／沉积平衡、土壤有机碳分解CO2的再转化密切相关。发生性碳酸盐碳稳定性同位素主要由土壤CO2的碳同位素组成决定，可以用描述不饱和层气体质量传递的扩散-生成模型模拟。在土壤碳酸盐体系（土壤CO2（g）、碳酸盐和土壤溶液）处于同位素平衡状态时，根据生物过程产生的分子扩散以及碳酸盐化学平衡反应的分馏模型，发生性碳酸盐δ^13 C值比有机质δ^13 C值大14‰～16‰。扩散-生成模型和／或分馏模型可以用于鉴定和定量化分散态发生性碳酸盐组分、区分土壤碳酸盐悬膜上发生性碳酸盐的比例，并可用于定量评价土地利用管理措施对碳酸盐溶解／沉积平衡的影响，这在全球碳循环研究中具有重要意义。In arid and semiarid zones, soil inorganic carbon pool is about 2-5 times more than soil organic carbon pool. For these regions, size and turnover of soil inorganic carbon pool play important role in soil carbon balance. Pedogenic carbonate is product of soil genesis process. It is closely related with the solution/deposition balance of soil lithogenic carbonate and the CO2 re-turnover of the decomposition of soil organic carbon. Stable carbon isotope composition of pedogenic carbonate is controlled by the isotopic values of soil CO2 , which can be stimulated by unsaturated zone gas steady-state diffusion-production model. Under the carbonate system （soil CO2 （g） , carbonate, and soil solution） isotopic equilibrium condition, simulation result, from molecular diffusion of biologically produced CO2 and carbonate chemical equilibria reaction model, shows that pedogenic carbonate is enriched by approximately 14‰ - 16‰ stable C isotope compared to the value of soil organic matter. The diffusion-production model and/or fractionation model can been used to quantify disseminated pedogenic carbonate accumulations, to partition the proportion of pedogenic carbonate in laminations, and to assess quantificationally the effect of land use practices on carbonate solution/deposition balance. That application makes the model very useful in understanding the global carbon cycle.

关 键 词：土壤发生性碳酸盐 扩散-生成模型 分馏模型 土壤CO2 δ^13C值 

分 类 号：P597[天文地球—地球化学] S153[天文地球—地质学]