贵阳市某岩溶地区地下汽油污染物运移特征分析

Analysis on the characteristics of underground gasoline pollutants migration in a certain karst region in Guiyang City

岩溶地区地质环境脆弱,防污能力差,特别是浅埋藏岩溶发育地区,地下水具有易污染性。本文以贵阳市某加油站10年前发生的油灌泄漏污染为例,分析了汽油污染物在岩溶水中的运移特征。调查结果表明(1)汽油污染物运移受包气带的岩性、结构、厚度以及地形坡度、地下水流速等的影响,主要沿岩溶管道、基岩面、裂隙运移;(2)汽油污染物优先在断裂、裂隙、溶缝、溶洞等通道中迁移扩散,以侧向运移为主,垂向次之;(3)有机污染物除了随地下水流动而迁移外,还会发生弥散作用,在基岩隆起部位或地形较高部位,这种现象更为明显;(4)受限于红粘土本身对污染物的拦截吸附作用,污染物向上浸染扩散程度并不高,只有最靠近基岩面的那一部分才会遭受油类污染物的浸染;(5)汽油污染物长期着在岩溶管道壁、岩溶裂隙、土岩接触面上,具有难迁移、难消除的特点。

The geological environment in karst area is vulnerable,especially in the shallowly buried karst region,the groundwater there is easily to be polluted.The characteristics of groundwater gasoline pollutants migration is analyzed by studying instance of petrol leakage at a gas station 10 years ago in Guiyang City in this article.The results is as follows：（1）Influenced by the lithology,construction,thickness of aeration zone,heterogeneous characters such as ground gradient,groundwater velocity,the gasoline pollutants migrate mainly through karst tube,bedrock surface,fracture,and cracked top strata of the bedrock.（2）The gasoline pollutants migrate and diffuse preferentially through fault,fracture,karst cave,and lateral migration is stronger than the vertical one.（3）Other than migrate with groundwater flow,organic pollutants also disperse apparently in those bedrock uplifted part and high topography part.（4）As red clay has high sorption to pollutants,pollutants mainly contaminate the nearby bedrock,only very few can contaminate the upper part.（5）The gasoline pollutants are buried in karst tube,karst fracture and the contact surface between the soil and the rock which made it quite difficult to migrate and eliminate.