华北平原浅层含氟地下水演化特点及成因

以华北平原浅层地下水中氟为研究对象,在收集历史资料、实地水文地质调查、取样分析的基础上,运用水化学图解、统计分析、水文地球化学模拟等方法,对比分析了历史阶段(1980～1985年)和现阶段(2005～2010年)F^-质量浓度空间分布,探讨了现阶段华北平原浅层地下水中F^-的空间分布特征、演化特点及成因。结果表明:现阶段高氟水的区域范围相比历史阶段明显增加; 从山前冲洪积倾斜平原补给区(Ⅰ区),到中部冲积湖积平原缓慢径流区(Ⅱ区),最后到东部冲积海积滨海平原排泄区(Ⅲ区),浅层地下水中F^-质量浓度呈低→高→低的变化; 高氟水的水化学类型较为复杂,HCO^-₃和Na⁺富集的苏打型碱性水化学环境有利于F^-的富集,而Ca²⁺、Mg²⁺则会抑制F^-的富集; 高氟水的形成与其迁移、赋存的环境条件有关,在Ⅰ区地下水中F^-质量浓度主要受萤石溶解作用、F^-解吸作用控制,在Ⅱ区地下水中F^-质量浓度受蒸发浓缩作用、萤石溶解作用、方解石-白云石沉淀作用、F^-解吸作用等控制,而在Ⅲ区高氟水主要受方解石-白云石的沉淀作用、F^-解吸作用、阳离子交换吸附作用等控制。

Evolution Feature and Gensis of Fluoride Groundwater in Shallow Aquifer from North China Plain

Fluoride groundwater in shallow aquifer from North China Plain was taken as the object of study. Based on historic data, field hydrogeological investigation and groundwater sample analysis, spatial distributions of F^- concentrations at the historical stage(1980-1985)and the present stage(2005-2010)were compared, and spatial distribution, evolution feature and gensis of fluoride groundwater in shallow aquifer from North China Plain were discussed by means of hydrogeochemical plot, statistic analysis and geochemical modeling. The results showed that compared with the historical stage, the area of groundwater with high F^- concentration at the present stage significantly increased; North China Plain could be divided into alluvial-pluvial fans in the piedmont area(recharge area, Zone Ⅰ), alluvial-lacustrine plain in the central area(slow runoff area, Zone Ⅱ)and alluvial-marine plain in the coastal area(discharge area, Zone Ⅲ); F^- concentration of groundwater in shallow aquifer increased from Zone Ⅰ to Zone Ⅱ, and then declined from Zone Ⅱ to Zone Ⅲ; hydrochemical types of groundwater with high F^- concentration were relatively complex, soda alkaline water enriched in HCO^-₃ and Na⁺ was conducive to F^- enrichment, but Ca²⁺ and Mg²⁺ inhibited F^- enrichment; gensis of groundwater with high F^- concentration was closely related to the aquifer condition and F^- transportation; F^- concentrations of groundwater were mainly controlled by fluorite dissolution and F^- desorption in Zone Ⅰ, by evaporation-concentration, fluorite dissolution, calcite-dolomite precipitation and F^- desorption in Zone Ⅱ, and by calcite-dolomite precipitation, F^- desorption and cation exchange sorption in Zone Ⅲ.