The distribution characteristics of normal alkane in the lake sediments can be used to indicate well the organic sources and deposition environments. In this paper, some surface sediments on lake bottom in Koh Xil area, high altitude cold area in the northern part of Qinghai-Xizang ( Tibet) Plateau, were collected. After analyzing the n-alkane in the sediments, the n-alkane distribution characteristics and the environmental significances are abtained. It is shown that the distribution of n-alkane can be controlled by terrestrial and aquatic plants and lake salinity, n-alkane C31 predominance from terrestrial plants has been existed in almost all lakes in this area. Mid-chain length n-alkanes ( C23 - C25 ) have been shown in the lake sediments with aquatic plants developing and have a high-carbon number n-alkane (C27, C29, C31) contribution, n-alkane from aquatic plants of Potamogeton malaianus has an predominance C23 peak and C31, C29, C27 peaks. In the salt and brackish water lakes, high Ph exists. That different mid-chain-length re-alkanes and no even carbon n-alkanes in the high salt lakes is the reason of the different component and distribution of n-alkanes in the lake sediments. At the same time, C27 and C29 predominance peaks do not always come from terrestrial woody plants, but with the same characteristic from aquatic plants.%湖泊沉积物中有机质正构烷烃分布特征对有机质母源、沉积环境等有较好的指示作用.本文通过对青藏高原高寒地区可可西里不同盐度的现代湖泊表层沉积物样中有机质正构烷烃的分析,表明正构烷烃分布主要受陆生植被、水生植物和水体盐度的控制.结果表明,有机质以眼子菜为主的沉水植物来源的正构烷烃有较高的C23正构烷烃峰和高丰度中等链长正构烷烃,以及高丰度C31、C29、C27正构烷烃峰；而没有C23正构烷烃峰,仅有高丰度C31、C29、C27正构烷烃峰,代表了陆生草本植物来源的特征.咸水、微咸水还原环境有明显高Ph丰度.C17的高丰度代表了藻类植物来源特征.不同的中等碳数正构烷烃、高盐度沉积物中未见偶碳数正构烷烃特征表明有机母质的差异是沉积物中正构烷烃组成和分布差异的主要原因.同时,C27、C29的存在不一定就是陆生木本植物来源有机质,水生植物也具有相似的特征.
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