天津地区河流沉积物中中等分子量正构烷烃的分布特征

Composition and Distribution of Middle-Molecular Weight Normal Alkane Compounds in Sediments from Some Rivers in Tianjin,Northern China

分析了天津地区几条具不同环境功能特征的河流沉积物中正构烷烃的组成,重点介绍了中低分子量正构烷烃的分布特征,并通过与表层土壤、大气降尘及TSP中正构烷烃的分布特征的对比,分析了中等分子量正构烷烃的成因。分析表明,天津地区主要河流沉积物和大气降尘中正构烷烃普遍具有正十七烷(nC17)明显优势的特征,nC17单体烃同位素值也相对偏低,与来源于化石燃料的正构烷烃化合物存在明显的差别。在土壤和TSP中不存在这一现象,表明正十七烷化合物来源水体中的低等水生生物体,推测主要来源于藻类生物。由于这类化合物含量明显高于其他化合物,具有环境地球化学意义。

The composition and distribution of normal alkane compound in sediments from some rivers with different environmental condition in Tianjin city, northern China, have been investigated. The composition and distribution of middle-molecular weight normal alkane in sediments in different rivers was emphasized in this paper. The origins of middle-molecular weight normal alkane in sediments have been analyzed based on the comparison of normal paraffin hydrocarbon composition among sediment, topsoil, dust fall and TSP. The result shows that the relative content of nC17 or nC19 has obvious predominance compared with other normal paraffin hydrocarbon compound in sediments from different rivers and dust fall. The stable carbon isotope value of nC17 is lower, which is different from the value of normal alkane in fossil fuel （ such as oil and coal）. The composition predominance of nC17 in topsoil and TSP is not occurrence. It is suggested that the nC17 or nC19 in these samples are derived from aquatic organism, such as algae, in water and surface sediments.