人工溴示踪法评价潜水蒸发可行性数值模拟  

Numerical simulation on applicability of bromide tracer method for evaluating groundwater evaporation

作　　者：王登 霍思远 孙芳[1] 曾娟 伊明启 WANG Deng;HUO Siyuan;SUN Fang;ZENG Juan;YI Mingqi(College of Resources and Environment,Yangtze University,Wuhan,Hubei 430100,China;International Institute of Water Ecology,Yangtze University,Wuhan,Hubei 430100,China)

机构地区：[1]长江大学资源与环境学院,湖北武汉430100 [2]长江大学国际水生态研究院,湖北武汉430100

出　　处：《水文地质工程地质》2020年第1期19-27,共9页Hydrogeology & Engineering Geology

基　　金：国家自然科学基金项目(41602246);长江大学大学生创新创业训练计划项目(2018226)

摘　　要：潜水蒸发是四水转换的重要环节。人工溴示踪法是指示非饱和带水流运动的有效手段,详细分析蒸发条件下包气带中溴离子运移规律以及示踪剂投放条件对潜水蒸发评价效果的影响,对于论证利用人工溴示踪法评价潜水蒸发的可行性,丰富潜水蒸发评价方法体系具有重要意义。利用HYDRUS软件构建多组一维非饱和水流-溶质运移模型,分析不同水位埋深、不同岩性条件下的溴离子运移规律,进而探究示踪剂投放深度、投放浓度对潜水蒸发评价的影响。结果表明:水位埋深越浅、包气带土壤颗粒越细,潜水蒸发强度越大,溴离子向上运移越快,其对不同包气带特征条件下的潜水蒸发过程响应显著,能够有效指示潜水蒸发规律及变化。示踪剂投放深度和投放浓度是影响评价结果的重要人为因素,投放深度越小,潜水蒸发计算值与实际值更为接近;示踪剂投放浓度决定其峰值浓度,弥散作用使示踪剂分布范围逐渐扩大,浓度分布趋于均一而难以确定浓度峰值位置,增大投放浓度有助于延长评价周期。Ground water evaporation is an important process in water cycling. The bromide tracer is an effective tool to indicate the unsaturated zone flow process. It is of great significance to analyze the transport process of bromide under continuous evaporation condition and to estimate the effects of tracer injection conditions on estimating groundwater evaporation,and then to prove the applicability of bromide tracer for evaluating groundwater evaporation. In this study,HYDRUS software is used to build multiple sets of onedimensional unsaturated water-solute transport models. Simulations were run to analyze the bromide transport under different conditions of water table depth and lithology,and to estimate the impact of tracer injection depth and concentration on evaluation of groundwater evaporation. The results show that: the bromide concentration peak moved upward fast due to the high intensity of groundwater evaporation when the vadose zone is thick and consisted of fine sediment. The different response of bromide transport to different conditions of vadose zone indicated the potential of bromide tracer to evaluate groundwater evaporation. The injection depth and concentration of tracer are important human factors affecting the evaluation results. The quantity of groundwater evaporation calculated by bromide tracer method was closer to the actual quantity when the injection depth is shallower. The injection concentration of tracer determines its peak concentration observed in the soil profile during the experiment period. The dispersion effect gradually enlarges the distribution range of tracer,thus the distribution of bromide concentration tends to be uniform in the profile and it is difficult to ascertain the position of bromide concentration peak. High injection concentration is conductive to prolong the evaluation period. Rainfall and the fluctuation of soil water content are potential negative factors affecting the evaluation results of field tracer test.

关 键 词：潜水蒸发 溴离子 示踪 数值模拟 HYDRUS 包气带 

分 类 号：P641[天文地球—地质矿产勘探]