天津地区典型土壤剖面饱和烃分布特征及环境意义

分析了天津地区不同环境功能区7 条土壤剖面中饱和烃含量、组成及部分地球化学参数 的变化规律, 比较了不同土壤剖面饱和烃在纵向上的变化特征。结果表明, 市区( 南开区) 及近郊 区( 武清区, 北辰区和宁河县交界处) 表层土饱和烃含量最高, 其他剖面含量较低; 随深度增大, 饱 和烃含量均有所降低, 但不同剖面变化幅度不同, 表层含量较高的剖面随深度增大, 饱和烃含量 降低幅度较大, 反之则较小。根据部分典型地球化学参数的纵向变化特征, 推测表层土壤饱和烃 主要为石油源和植物源的混合源, 且市区和郊区主要受石油源控制。不同土壤剖面表层土污染源 存在差别。同一剖面表层土壤( <30cm) 不同层次的样品的饱和烃污染源较为接近; 剖面深部( > 30cm) 不同层次样品中正构烷烃不同于表层, 且成因复杂, 既受来源于土壤中有机质降解产物的 影响, 又受表层土中饱和烃纵向迁移作用的影响。对于甾、萜类化合物, 表层土壤中饱和烃含量较 高的剖面, 深层土壤受表层土壤甾、萜类污染物迁移作用的影响; 表层土壤中饱和烃含量较低的 剖面, 深层土壤受表层土壤甾、萜类污染物影响较小。

Ver tical Distr ibution and Environmental Significance of Saturated Hydrocarbons in Soil Samples Collected from Tianjin

The vertical distribution of both the concentration and composition characteristics of saturated hydrocarbons in soil samples collected from 7 soil profiles in Tianjin has been investigated.The vertical variation patterns of saturated hydrocarbons composition along the soil profiles with different environmental conditions have been discussed.The results showed that the concentrations and chemical compositions of saturated hydrocarbons were significantly different in the surface soil of different locations.The concentrations were higher in the soil samples from suburban area than rural area.Generally,concentrations of saturated hydrocarbons in the upper horizons from 0 to 30cm were much higher than those in the bottom soils where concentrations were constant.The concentration of saturated hydrocarbons changes dramatically along the profile,reaching a higher concentration in the topsoil.The composition changes of normal alkanes,sterane and terpane in soil with the depth were complex.It also reveals that the primary sources of saturated hydrocarbons in the surface soils were from a mixture of petroleum(including diesel,gasoline and their products of uncompleted combustion) and higher plants,and the petroleum is the primary source of the suburban area.The surface soil of different soil profiles had different contamination sources.The different horizons had similar composition characteri-stics,indicating the similar contamination sources.However,in the bottom soils,the composition characteristics and geochemical indices of normal alkanes were significantly distinct.The sources were different with the surface soils and complex for the normal alkanes in the bottom soils,which may be in connection with both the degradation of soil organic matter and the moving down of saturated hydrocarbons in the topsoil.For sterane and terpane in the profiles which had a high concentration of saturated hydrocarbons in the topsoil,the character of sterane and terpane compositions were similar.Accordingly,in the profiles with a high concentration of saturated hydrocarbons in the topsoil,the bottom soil was influenced by down-moving of the terane and terpane from the topsoil.