水化学揭示的弱透水层孔隙水演化特征及其古气候指示意义  

Hydro-Geochemistry Implications of Evolution of Pore Water in Low-Penetrability Aquifer and Significance of Paleoclimate

作　　者：李静[1] 梁杏[2] 毛绪美[1] 王聪[1] 柳富田[3] 

机构地区：[1]中国地质大学环境学院,湖北武汉430074 [2]中国地质大学生物地质与环境地质国家重点实验室,湖北武汉430074 [3]天津地质调查中心,天津300170

出　　处：《地球科学（中国地质大学学报）》2012年第3期612-620,共9页Earth Science-Journal of China University of Geosciences

基　　金：国家重点基础研究发展计划"973"项目(No.2010CB428802);国家自然科学青年基金项目(No.40602031)

摘　　要：地下水开采、弱透水层释水,以及污染物迁移转化、高危废物深埋选址等水文地质和工程地质活动中,弱透水层的作用越来越受到重视.了解弱透水层孔隙水的演化特征是认识弱透水层作用的首要问题.采用机械压榨法提取了曹妃甸地区某钻孔0～100m粘性土孔隙水,对孔隙水化学特征进行了分析.结果显示钻孔粘性土孔隙水呈碱性,总溶解固体为7.26～26.89g/L,从浅到深逐渐减小;陆相沉积层Cl/Br比趋向无穷大,而海相沉积层仅为279～289.分析得出弱透水层孔隙水基本为岩层沉积水,陆相和海相沉积层孔隙水分别显示出淡水和海水起源特征,没有后期海水入侵影响迹象;Cl-、Na+变化趋势主要受蒸发浓缩作用影响,SO42-受硫酸盐的还原作用和石膏的溶解作用共同控制,Ca2+、Na+、K+还受到沉积过程中阳离子交换与吸附作用影响;由δ18O重建晚更新世古气温为5.21～5.81℃,浅部40m以内计算的气温偏高是由于全新世气候变暖、孔隙水向下扩散迁移混合的影响.The low-penetrability aquifer plays an important role in hydrogeology and engineering geology activities, including groundwater exploitation, porewater release from aquitard, migration and transformation of pollutants, and reposition of high radioactive waste. For understanding the low-penetrability aquifer, it＇s important to investigate the evolution of pore water. In this paper, pore water was extracted by mechanical squeeze in a bore of Caofeidian with a depth of 0--100 m. The analysis of porewater indicates that the pore water is alkaline, and the total dissolved solid is between 7.26 and 26.89 g/L, decreasing with depth; and Cl/Br in continental sediment tends to infinity, while that in marine sediment is 279--280. It can be concluded that the pore water is sedimentary water revealing the freshwater and seawater characteristics in continental and marine sediment re spectively with no clear signs of modern seawater intrusion. The trend of Cl , Na4 is dominated by evaporation; SO42 is con trolled both by sulfate reduction and gypsum dissolution; cation exchange and adsorption mainly influence Ca2＋ , K＋ and Na＋ . The reconstruction of Late Pleistocene temperature is 5.21--5.81 ℃ using δ18 O, with much higher temperatures calculated by shallow data within 40 m attributed to mixing and diffusion of modern pore water.

关 键 词：弱透水层 孔隙水 地球化学 氢氧同位素 水文地质学 

分 类 号：X641.3[环境科学与工程]