Spatial distribution and sources of organic carbon in the surface sediment of Bosten Lake, China

Z T Yu,C Y Zhao,X J Wang,E L Zhang,X Q Liu

doi:10.5194/bg-12-6605-2015

Abstract

Abstract. Lake sediment is an important carbon reservoir. However, little is known on the dynamics and sources of sediment organic carbon in Bosten Lake. We collected 13 surface (0–2 cm) sediment samples in Bosten Lake and analyzed total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition in TOC (δ13Corg), and grain size. We found a large spatial variability in TOC content (1.8–4.4 %) and δ 13Corg value (−26.77 to −23.98 ‰). Using a three-end-member mixing model with measured TOC : TN ratio and δ13Corg, we estimated that 54–90 % of TOC was from autochthonous sources. Higher TOC content (> 3.7 %) was found in the east and central-north sections and near the mouth of the Kaidu River, which was attributable to allochthonous, autochthonous plus allochthonous, and autochthonous sources, respectively. The lowest TOC content was found in the mid-west section, which might be a result of high kinetic energy levels. Our study indicated that the spatial distribution of sediment TOC in the Bosten Lake was influenced by multiple and complex processes.

Highlights

Inland water bodies such as rivers and lakes are unique components on the Earth
Low total organic carbon (TOC) contents in the Tibetan Plateau lakes were a consequence of low biological productivity owing to the high altitude and low temperature (Lami et al, 2010)
Warm–humid climate in the Yangtze floodplain could promote decomposition of particulate organic carbon (POC) in the water column and TOC in the sediments (Gudasz et al, 2010), which led to less TOC storage in the surface sediments

Summary

Introduction

Inland water bodies such as rivers and lakes are unique components on the Earth. In spite of their relatively small coverage (Downing et al, 2006), lakes often receive a large amount of terrestrial materials from the watersheds (Battin et al, 2009; Anderson et al, 2013) and store a significant amount of carbon in the sediments (Ferland et al, 2012; Tranvik et al, 2009). There have been a number of studies from North America (Dean and Gorham, 1998), western Europe (Bechtel and Schubert, 2009; Woszczyk et al, 2011), eastern Asia (Khim et al, 2005; Wang et al, 2012), and other regions (Dunn et al, 2008), showing large spatial variability in total organic carbon (TOC) of lake sediment. Contributions of autochthonous and allochthonous sources have direct impacts on the spatial dis-

Methods

Results

Conclusion