海洋混凝土结构表面自由氯离子含量时变规律及对其寿命影响

表面氯离子含量(C_s)是研究海洋环境条件下混凝土结构耐久性和服役寿命的氯离子扩散方程的边界条件,是海洋混凝土结构耐久性分析和定量设计的重要参数。依据国内外大量自然暴露试验与工程实测数据,通过采用Excel、Origin等数据分析软件进行数据统计和回归分析,确定了海洋混凝土结构表面自由氯离子含量(C_(sf))与表面总氯离子含量(C_(st))之间的相互关系,探讨了海洋混凝土结构的C_(sf)时变规律,建立了C_(sf)与暴露时间之间的关系表达式及其取值范围,并运用可靠度理论和修正氯离子扩散理论分析了C_(sf)时变性对海洋混凝土结构寿命的影响。结果表明:C_(sf)与C_(st)线性相关,且C_(sf)随着暴露时间的延长呈指数或者幂函数的增长关系;采用不同的C_(sf)时变性规律,对海洋混凝土结构寿命具有重大的影响。     

Chloride as a signature indicator of soil textural and hydrologic stratigraphies in variable charge deep profiles

Soil properties that influence water movement through profiles are important for determining flow paths, reactions between soil and solute, and the ultimate destination of solutes. This is particularly important in high rainfall environments. For highly weathered deep profiles, we hypothesize that abrupt changes in the distribution of the quotient [QT = (silt + sand)/clay] reflect the boundaries between textural units or textural (TS) and hydrologic (HS) stratigraphies. As a result, QT can be used as a parameter to characterize TS and as a surrogate for HS. Secondly, we propose that if chloride distributions were correlated with QT, under non‐limiting anion exchange, then chloride distributions can be used as a signature indicator of TS and HS. Soil cores to a depth of 12·5 m were taken from 16 locations in the wet tropical Johnstone River catchment of northeast Queensland, Australia. The cores belong to nine variable charge soil types and were under sugarcane (Saccharum officinarum‐S) production, which included the use of potassium chloride, for several decades. The cores were segmented at 1 m depth increments and subsamples were analysed for chloride, pH, soil water content (θ), clay, silt and sand contents. Selected bores were capped to serve as piezometers to monitor groundwater dynamics. Depth incremented QT, θ and chloride correlated, each individually, significantly with the corresponding profile depth increments, indicating the presence of textural, hydrologic and chloride gradients in profiles. However, rapid increases in QT down the profile indicated abrupt changes in TS, suggesting that QT can be used as a parameter to characterize TS and as a surrogate for HS. Abrupt changes in chloride distributions were similar to QT, suggesting that chloride distributions can be used as a signature indicator of QT (TS) and HS. Groundwater data indicated that chloride distributions depended, at least partially, on groundwater dynamics, providing further support to our hypothesis that chloride distribution can be used as a signature indicator of HS. Copyright © 2005 John Wiley & Sons, Ltd.     

Retention of chloride in soil and cycling of organic matter‐bound chlorine

Chloride (Cl_inorg) is generally considered to be a hydrologically and chemically inert substance. Past research suggests that Cl_inorg participates in a complex biogeochemical cycle involving the formation of organically bound chlorine (Cl_org). The present study examines whether Cl_org cycling is sufficiently extensive as to influence the geochemical cycling of Cl_inorg. Undisturbed soil cores were collected in a coniferous forest soil in SE Sweden. The cores were stored in climate chambers for three months, irrigated with artificial rain, and the leachate was collected and analysed. The water balance of the lysimeters could be well described, and we found that 20–50% of the chlorine leached from the lysimeters was organically bound and that the amounts lost did not decrease with time. This strongly suggests that a substantial amount of Cl_org forms in topsoil, and that subsequent leaching to deeper layers causes a considerable withdrawal of Cl_inorg. The concentration of both organic carbon and Cl_org in the leachate was considerably higher than concentrations observed in the runoff in the actual catchment, suggesting that organic matter precipitates or is mineralized on its way through the soil. Copyright © 2005 John Wiley & Sons, Ltd.     

Determination of two‐dimensional laboratory‐scale dispersivities

A tracer test was conducted in a laboratory chamber representing a two‐dimensional aquifer to investigate the longitudinal dispersivity (α_L) and the ratio (α_T/α_L) of transverse to longitudinal dispersivity of sandy aquifer materials. Dispersive parameters were obtained by matching the observed chloride plumes at 9 hours and 16 hours after tracer injection with those simulated by a flow and transport model. The best match was found for α_L = 0·2 ? 0·25 cm and α_T/α_L = 0·2. The ratio of α_T/α_L = 0·2 was within the range of laboratory values reported in the literature. Sensitivity analysis revealed that the tracer plume concentration and shape were more sensitive to variations in longitudinal dispersivity than to the ratio of transverse to longitudinal dispersivity. This result contrasted with findings of others, showing that the dispersivity ratio greatly affects contaminant plume shape. However, our experimental boundary conditions restricted expansion of the plume normal to the direction of flow and thus affected the parameter estimation. Copyright © 2004 John Wiley & Sons, Ltd.     

马海盐湖浮选法生产氯化钾排放尾盐中钾资源的强制浸取技术研究

马海盐湖钾资源经过十几年的开发,在生产氯化钾过程中排放了大量的含钾尾盐,随着盐湖钾资源持续的开发,马海盐湖的钾资源已凸显日益枯竭的趋势,为高效利用马海盐湖的钾盐资源,近年来开展了对浮选法生产氯化钾过程所排放的含钾尾盐矿的开发利用技术研究。介绍了采用强制搅拌溶浸技术,溶浸马海盐湖含钾尾矿中钾资源的试验情况及所取得的试验结果,并对试验过程中出现的问题进行了讨论。     

利用盐湖老卤与元明粉制取七水硫酸镁工艺研究

氯化镁和硫酸钠作原料,以K~+,Na~+,Mg~(2+)//Cl~-,SO_4~2-H_2O及Na~+,Mg~(2+)//Cl~-,SO_4~2-H_2O水盐体系相图为理论依据,研究了氯化镁和硫酸钠分解转化—冷却结晶法生产七水硫酸镁的工艺路线。考察氯化镁和硫酸钠分解转化温度、分解转化时间、各物料配比关系等因素对制备七水硫酸镁的影响,确定了各试验因素对试验结果的影响主次顺序,得出了试验结果。     

氯化物中锂离子存在时EDTA质量滴定锶离子含量

锂共存时对EDTA络合滴定Sr2+离子产生较强的干扰,使分析结果偏高。根据被测液中氯化锂的大约含量,通过加入适量混合醇,可消除Li+离子的干扰,质量滴定法相对误差<0.3%。在锂锶质量比为0.100¹4.5范围内,被测样中LiCl质量与加入混合醇体积呈线性关系。混合醇掩蔽体积范围为314.5范围内,被测样中LiCl质量与加入混合醇体积呈线性关系。混合醇掩蔽体积范围为3⁵ mL。根据锂离子与水分子、短链醇形成蔟合物的键能,对消除Li+离子干扰络合滴定的机理进行探讨。     

黄河三角洲土壤氯离子空间变异特征及其控制因素

为了解黄河三角洲地区土壤盐渍化发生与发展的主要控制因素,通过采集土壤样品及潜水样,运用地统计学等方法,分析样品中优势离子Cl^-含量的空间分布特征及成因。结果表明:① 土壤Cl^-含量与潜水Cl^-质量浓度的空间分布表现出高度的相似性和相关性。② 潜水借助包气带自身的水势梯度或植物蒸腾作用向土壤输送水分,进而控制着土壤Cl^-的空间分布与变异。③ 地形地貌通过对水、气、热的再分配控制着包气带土层中Cl^-的迁移方向和富集区域。水文地质条件是对区域"饱和带-包气带"盐分迁移富集起决定作用的内部因素,而地形地貌条件是起控制作用的外部因素。     

海洋环境中混凝土结构服役寿命预测

通过参数定义对Fick定律的不合理假定进行修正,推导氯离子在混凝土中扩散的多因素修正模型,综合考虑氯离子扩散系数的时随效应、混凝土的氯离子结合能力和混凝土自身缺陷的影响.根据对大量数据的分析试算,给出模型中参数的取值.利用该扩散模型,进一步推导海洋环境下基于概率性能的混凝土结构服役寿命计算方法,有效解决混凝土结构服役寿命预测中氯离子扩散系数及混凝土保护层厚度的随机特性.最后给出实际工程算例,说明该预测方法的有效性.     

电感耦合等离子体发射光谱法快速测定氯化钾

用电感耦合等离子体发射光谱法对氯化钾产品进行杂质分析,利用配盐的方法将杂质离子配成盐,用总量100减去杂质盐分的含量即得氯化钾的含量。该方法快速准确,精密度和准确度都非常好,能代替原有的化学分析方法。