Source characterization of organic carbon using elemental, isotopic and n-alkanes proxies in surface sediment from Lake Bosten, Xinjiang

Abstract

Lake sediment is an important carbon reservoir thus plays a role in the terrestrial carbon cycle. However,little is known on the dynamics and sources of organic carbon in the lake surface sediment from northwest China. In this paper,we applied element analyses,isotopic and n-alkanes approach to study the sources of organic carbon in the Lake Bosten,the largest inland lake in Xinjiang. We found that there was some spatial variability in C ∶ N( 4. 8-8. 5) and stable carbon isotopic composition in δ13Corg values(- 26. 7‰ to- 24. 1‰). The carbon numbers of n-alkanes ranged from C13 to C35,with the dominating compounds C17 and C23 in most samples. Further analyses showed that organic carbon in the surface sediments was generally from the autochthonous sources. There existed a relatively large spatial variability in contributions from different sources. According to the lake survey data and the spatial distribution characteristic of C ∶ N,δ13Corgand n-alkanes,we estimated that the organic carbon sources in the east near-shore lake area,central-east section and western shallow lake area,and the other lake parts were mainly attributable to allochthonous,autochthonous plus allochthonous,and autochthonous sources,respectively.