Distribution Characteristics of n-alkanes in Sediment Core and Implication of Environment in Different Lakes of Dianchi

Abstract

In order to study the composition and environment significance of the organic matter in Lake Dianchi, samples from two sediment cores from the northern and southern parts of the lake were collected in July, 2014. Meanwhile, the vertical distributions of total organiccarbon (TOC), total nitrogen (TN), n-alkanes fractions were investigated. The results showed that ① the concentrations of TOC and TN had been clearly increasing since the 1970s, which implied that the primary productivity of Lake Dianchi was continuously enhanced; ② The values of the parameter n-C27/n-C31, Paqand CPI indicated the alternation between herbs and woody plants from the bottom up in Lake Dianchi sediments. Besides, the high carbon number of organic matter in sediments mainly originated from endogenous submerged floating and large plants; ③ The index of C/N and distribution characteristics of n-alkanes suggested differences in the various sources of organic matter in different lakes. In detail, organic matter came from terrigenous organic matter of anthropogenic sources and endogenous bacteria in the sediments of northern Dianchi, while organic matter was derived from endogenous aquatic and terrestrial higher plants mixed source in the sediments of southern Dianchi. Finally, it is worthwhile to emphasize further research on organic matter in different lakes of Lake Dianchi.