裂隙介质中Pu迁移的连续时间随机游走模拟  

Transport simulation of Pu through fractured media based on continuous time random walk model

作　　者：黄诗棋 胡立堂[1] 刘东旭[2] 林剑锋[2] 田蕾 王道 HUANG Shi-qi;HU Li-tang;LIU Dong-xu;LIN Jian-feng;TIAN Lei;WANG Dao(College of Water Sciences,Beijing Normal University,Engineering Research Center of Groundwater Pollution Control and Remediation of Ministry of Education,Beijing 100875,China;Northwest Institute of Nuclear Technology,Xi'an 710024,China)

机构地区：[1]北京师范大学水科学研究院,地下水污染控制与修复教育部工程研究中心,北京100875 [2]西北核技术研究所,陕西西安710024

出　　处：《中国环境科学》2023年第12期6321-6328,共8页China Environmental Science

基　　金：国家自然科学基金核技术创新联合基金资助项目(U2167211)。

摘　　要：为更准确地模拟核素的非菲克迁移行为并寻求一种更合理的建模方法,根据一维裂隙岩柱中Pu(钚)迁移试验资料,利用基于不同联合概率密度的连续时间随机游走(CTRW)模型和传统对流-弥散方程(ADE)对Pu迁移的穿透曲线(BTC)进行了过程模拟,对比分析了ADE模型、CTRW-TPL模型、CTRW-TPLA模型和CTRW-ETA模型的拟合程度及适用性,进而选择出最优的模型对不同胶体浓度下Pu在裂隙介质中的迁移进行模拟研究.结果表明,相较于传统ADE模型,参数拟合后考虑吸附作用的CTRW-TPL模型能有效地描述非菲克迁移行为特征,CTRW-ETA拟合过程更易实现,但能为迁移行为的刻画提供的信息较少.研究还发现胶体的存在显著提高了Pu在裂隙介质中的迁移性,但胶体浓度超过某个临界值后,随着浓度升高Pu的迁移性反而减弱,在CTRW理论框架中,该过程表现为表征广义运移速度和弥散系数的参数值先增大后减小,而介质对溶质颗粒的平均吸附率先减小后增大.Non-Fickian dispersion occurs in the migration of nuclides in groundwater,which is influenced by geological media heterogeneity and physicochemical processes.To improve the accuracy of the simulation of this phenomenon,an alternative model is required.To analyze Pu(plutonium)migration in one-dimensional fractured rock columns,we employed the continuous time random walk(CTRW)model together with the traditional advection-dispersion equation(ADE)to effectively represent Pu breakthrough curves(BTCs).The goodness of fit and feasibility of the ADE,CTRW-TPL,CTRW-TPLA,and CTRW-ETA models were later compared to identify the superior model for simulating Pu transport in fractured media with varying colloidal concentrations.The results indicated that the CTRW-TPL model,which incorporated adsorption,outperformed the traditional ADE in describing non-Fickian migration characteristics.Although the CTRW-ETA model lacked comprehensive migration characterization,its inversion process was more feasible.Furthermore,the migration capacity of Pu in fractured media was significantly enhanced due to colloidal effects.However,beyond a certain concentration threshold,the migration capacity of Pu decreased with increasing colloidal concentrations.Regarding the theoretical framework of the CTRW model,our analysis showed that the generalized transport velocity and dispersion coefficient first increased and then decreased,while the average adsorption rate of solute particles first decreased and then increased.These findings serve as a valuable reference for future research on the parameters of the CTRW model in fractured media.

关 键 词：核素 非菲克迁移 连续时间随机游走(CTRW) 对流-弥散方程(ADE) PU 胶体促进迁移 

分 类 号：X591[环境科学与工程—环境工程]