西北干旱区水中氟的分布规律及环境特征

The Distributing Regularity of Fluorine and Its Environmental Characteristics in Arid Area of Northwest China

中国科学院寒区旱区环境与工程研究所冻土工程国家重点实验室，甘肃兰州７３００００摘要：西北干旱区天然水体中广泛分布以ＮａＦ和ＫＦ为主的氟物质。随干旱区内陆水系的产生、径流消亡，从山区至山前细土平原，Ｆ~－的迁移分布具有显著的淋溶－径流、径流－蒸发与溶滤－蒸发浓缩富集３个水文化学分带；在白垩系及第四系下更新统以来湖相沉积的湖盆洼地以及沙漠边缘地区，地下水中Ｆ~－相对富集，且具有深部地下水Ｆ~－含量大于浅层地下水及地表水的垂直分带性；Ｆ~－的富集与贫化与水化学特征关系密切，一般情况下，低ＳＯ_４^(２－)的贫钙碱性水环境有利于Ｆ~－的溶解与富集。干旱区内陆流域丰富的氟物质来源、相对封闭的水文环境与干旱的气候条件为Ｆ~－在水中溶解、迁移和富集提供了有利条件。

In arid area of northwest China, the NaF and KF are extensively distributed in the natural water, such as rivers, lakes and groundwater. From mountains to silt plain along with the formation, runoff and disappear of inland rivers, the distributing regularity of F^- can be markedly divided into three hydrochemical zones: drench and dissolution-runoff zone, runoff-evaporation zone, dissolution- evaporation zone. In the low- lying land and desertification edge with Lacustrine sediments deposited from Cretaceous and lower Pleistocene of Quaternary period, the contains of F^- in groundwater was high with the vertical distributing pattern of larger in lower and letter in upper. There are close relationship between high F^- and the hydro-chemical characteristics. Generally, in the alkali water with lower contains of So_4^(2-) such as Cl·HCO_3 - Na or HCO_3 - Na types, the F^- can be easily dissolved and rich in water. The arid climatic conditions, rich source of Fluorine and relatively close hydrological environment provide the advantage of F^- to dissolution, transformation and rich in some regions.