Organic carbon fractions and estimation of organic carbon storage in the lake sediments in Inner Mongolia Plateau, China

Abstract

Organic carbon (OC) in lake sediments plays an important role in terrestrial ecosystem carbon cycle. The Inner Mongolia Plateau contains a number of shallow and freshwater lakes, with a total lake area of more than 8,000 km2, accounting for an approximate 10 % of the total lake area in China. The Inner Mongolia Plateau lakes act as important OC sink in mid-high latitude regions. In this study, heavy and light fractions of OC and OC species were analyzed in sediments from four typical lakes in the Inner Mongolia Plateau. Meanwhile, to identify OC origins, allochthonous and autochthonous OC were calculated based on a binary model. Furthermore, total organic carbon (TOC) storage, active carbon pool (ACP), and stable carbon pool (SCP) over the past 150 years were estimated in the Inner Mongolia Plateau. The dominating direct findings of the current research are that heavy fraction OC plays a key role as carbon sink in mid-high latitude regions due to its percentage of more than 90 % in TOC. The percentages of allochthonous OC in TOC are high, 86.4, 66.7 and 72.5 %, in Daihai Lake (DH), Dalinuoer Lake (DLNE), and Hulunhu Lake (HLH), respectively, which indicates that allochthonous OC is dominant in DH, DLNE, and HLH. The range of humin is 62.15–84.03 % in these four lakes. The average OC accumulation rate calculated in this work is 1.37 g C m−2 year−1 in these four lakes. Comparatively, OC storages in sediments from lakes in the Inner Mongolia Plateau are relatively more stable than from those lakes located in tropical and sub-tropical regions. An estimate of the TOC burial, SCP and ACP in lake sediments would be 1.64 × 1012, 1.52 × 1012, and 1.20 × 1011 g C, respectively, over the past 150 years in the Inner Mongolia Plateau.