地球化学模拟方法确定黏性土孔隙水化学组分

发布时间：2018-06-15 04:30

本文选题：黏性土 + 孔隙水　；参考：《水文地质工程地质》2017年01期

【摘要】：黏性土孔隙水的地球化学行为对于弱透水层水质水量研究、污染物在黏性土中的迁移、核废物储存场址评价及油气储层的盖层评价等均具有重要作用。受低渗透性限制,传统方法提取黏性土孔隙水非常困难。通过实验测定黏性土的物化特性,利用PHREEQC软件模拟计算了孔隙水组成。通过浸提实验,利用阴离子可通过孔隙度(50%总孔隙度)确定模型中孔隙水的Cl-和SO2-4含量;根据岩土的阳离子交换量及各离子的交换选择系数,矿物沉淀-溶解平衡,确定了孔隙水的主要化学组分。结果显示,模拟的孔隙水化学组分与压榨液(相当于原位孔隙水)相近,不同于浸提液。传统的浸提方法不可直接换算为孔隙水,受矿物可交换点阳离子的释出与矿物溶解影响,各离子含量被明显高估。模拟所得天津滨海区黏性土阳离子交换量为13.4~37.8 meq/100g土,可交换离子以Na、Mg、Ca为主。所得孔隙水为还原环境,且随着深度增加,还原性增强。模型中所选矿物均为平衡状态,溶液中可能存在的矿物大部分为未饱和或平衡状态,仅部分含Fe、Al矿物过饱和。由结果可知Fe含量偏高,对控制Fe元素的矿物需进一步精确测定。本方法在低渗透,超固结,低含水量介质的孔隙水相关研究中将发挥重要作用。
[Abstract]:The geochemical behavior of pore water in clay soil plays an important role in the study of water quality and quantity of weak permeable layer, the migration of pollutants in clay soil, the evaluation of nuclear waste storage site and the evaluation of oil and gas reservoir caprock. Due to the limitation of low permeability, it is very difficult to extract pore water from clay soil by traditional methods. The physical and chemical properties of clay were measured and the pore water composition was simulated by using PHREEQC software. Through extraction experiment, the content of Cl- and SO2-4 in pore water in the model can be determined by using anion through porosity of 50% total porosity, and mineral precipitation-dissolution equilibrium can be obtained according to the cation exchange capacity of rock and soil and the exchange selectivity coefficient of each ion. The main chemical components of pore water were determined. The results show that the simulated pore water chemical composition is similar to the press fluid (equivalent to in-situ pore water) and is different from the extraction solution. The traditional extraction method can not be directly converted into pore water. The ion content is obviously overestimated due to the release of exchangeable cations and dissolution of minerals. The cationic exchange capacity of clay soil in Tianjin Binhai area is 13.4 ~ 37.8 meq/100g soil, and the main exchangeable ion is Na _ 2O _ (mg _ (2) _ (Ca). The pore water obtained is a reductive environment and increases with the increase of depth. All the minerals selected in the model are in equilibrium state. Most of the minerals that may exist in the solution are unsaturated or equilibrium, and only a part of the Feanal minerals are supersaturated. The results show that the content of Fe is on the high side and the minerals controlling Fe need to be determined accurately. This method will play an important role in the study of pore water correlation in medium with low permeability, overconsolidation and low water content.
【作者单位】：中国地质大学(武汉)环境学院;中国地质大学(武汉)湿地演化与生态恢复湖北省重点实验室;水利部长江勘测技术研究所;天津地质矿产研究所;
【基金】：国家自然科学基金(41272258,41502231) 中央高校基本科研业务费专项基金(CUGL1500824) 湖北省自然科学基金(KZ15K380) 博士后基金(1231536)
【分类号】：P641.3

【相似文献】