核化学与放射化学2026，Vol.48Issue(2)：139-148,10.DOI:10.7538/hhx.2026.48.02.0139
90Sr和99Tc在某近地表处置场地下水中的种态分布和吸附特性
Speciation Distribution and Sorption Characteristics of 90Sr and 99Tc in Groundwater of Near Surface Disposal Facility in China
摘要
Abstract
This study focuses on the speciation distribution and sorption characteristics of 90Sr and 99Tc at a near surface disposal facility in Northwest China.The primary geological medium in the study area is metamorphic quartz sandstone,whose main mineral components are quartz and mica.The surface potential of metamorphic quartz sandstone is negative when pH ranges from 3 to 11,and the surface potential decreases as the pH increases.The groundwater in the study area has a pH of 7.37 and an Eh of 125.7 mV;the water type is of SO4·HCO3-Na·Ca type.Based on the chemical compositions of groundwater in the study area,geochemical simulation software GWB was employed to simulate the chemical species of 90Sr and 99Tc in groundwater,and to evaluate the effect of pH,Eh and major anion concentrations on their speciation distribution.The simulation results indicate that speciation distribution of 90Sr is mainly governed by groundwater pH,with Sr2+being the predominant form in the groundwater.Besides,among the major anions(Cl-,SO42-,HCO3-and F-)of groundwater,SO42-has the most significant impact on Sr speciation distribution.In contrast,speciation distribution of 99Tc is mainly controlled by Eh,with TcO4-being the primary species in oxidized environments.Batch sorption tests were performed to determine the adsorption equilibrium time and distribution coefficient Kd for 90Sr and 99Tc in metamorphic quartz sandstone.The test results show that adsorption equilibrium time for both 90Sr and 99Tc are approximately 30 days.90Sr exhibits a higher Kd value(1.68 mL/g)than 99Tc(0.68 mL/g),which indicates that metamorphic quartz sandstone has a stronger adsorption capacity for 90Sr than 99Tc.This is attributed to the negative charge on the surface of the metamorphosed quartz sandstone,making it prone to adsorbing Sr2+but difficult to adsorb TcO4.Batch sorption tests were also carried out to study the effect of aqueous pH on nuclide adsorption.The results show that trend in Kd values for 90Sr and 99Tc as a function of pH is closely related to the pH-dependent speciation distribution of nuclide.Kd values for 90Sr firstly increase and then decrease with rising pH,reaching a maximus at pH of 8.This is primarily due to the presence of a large amount of H+in the solution under low pH conditions,which occupies a portion of the surface adsorption sites of the geological medium;under high pH conditions,the concentrations of OH-and CO3-in the solution increase significantly,forming complexes SrOH+and SrCO3(aq)with Sr2+,thereby hindering the adsorption of 90Sr and leading to a decrease in its Kd.However,Kd values for 99Tc decrease with increasing pH under the experimental conditions of oxidizing environment.This is due to that 99Tc primarily exists as TcO4-across most of the pH range in the oxidizing condition and the surface electron egativity of metamorphic quartz sandstone increases with rising pH.This leads to enhanced electrostatic repulsion between TcO4-and the surface of the metamorphic quartz sandstone as pH increases,further hindering the adsorption of 99Tc and causing its Kd to decrease as pH increases.关键词
90Sr/99Tc/GWB软件/种态分布/批式实验Key words
90Sr/99Tc/software GWB/speciation distribution/batch sorption test分类
化学化工引用本文复制引用
吕敏,康明亮,王旭宏,吕涛,夏加国,李星宇,刘兴伟,李昶,王馨,胡立堂..90Sr和99Tc在某近地表处置场地下水中的种态分布和吸附特性[J].核化学与放射化学,2026,48(2):139-148,10.基金项目
中核联合基金(U2167211) （U2167211）
