ABSTRACT

Molecular distribution and compound-specific hydrogen isotopic ratios (δD) of n-alkanes in shallow-water surface sediments from the Chaka salt lake and from various terrestrial plants in the surrounding area were measured to obtain a better understanding of the relationship between sedimentary n-alkanes in salt lakes and their biological sources. The n-alkanes in the terrestrial plants exhibited a modal distribution, maximizing at n-C₂₅ or n-C₂₇ with average chain length (ACL) values ranging from 26.6 to 27.7. The ACL values of the sediments were similar to those of terrestrial herbaceous plants from the study area. The average n-alkane δD value (-81.7‰) for the woody-plant leaves was higher than that for terrestrial herbaceous plants (-164.3‰). The average δD values of n-alkanes in the sediments ranged from -163.8‰ to -127.7‰, which fall between the δD values in herbaceous and woody plants, but closer to those in terrestrial herbaceous plants from the study area. This similarity of the n-alkane distributions, and δD values of sediments and plants suggests that n-alkanes in the sediments are likely to be derived mainly from terrestrial herbaceous and partly from woody plants.