Abstract
In this study, 67 surface sediment samples collected from Nam Co in central Tibet were analyzed for total carbon, total organic carbon and total nitrogen, and 51 of these samples were also analyzed for n-alkanes. The origin and spatial distribution of organic matter were then investigated using these proxies, and the control factors responsible for the spatial distribution patterns and paleolimnological significance were discussed. The results indicated that the origin of organic matter in surface sediment of Nam Co is consistent with the sources of n-alkanes, which were primarily submerged plants, followed by terrestrial plants, and then aquatic algae and bacteria. The organic matter in surface sediments of the lake showed typical spatial variability. Because of the great influence of underwater topography, river inputs and water quality, the spatial distribution of organic matter is enriched from the source to the deposit center. This spatial variability of organic matter in the lake indicates that the sediments in different areas have different sensitivities to environmental changes, which is important to reconstruction of paleoenvironments and paleoclimate using lake sediment cores.
Highlights
Lake sediments are widely utilized for reconstruction of climatic and environmental changes because they possess continuous depositional sequences and rich proxies with apparent environmental significance [1]
The concentration, source and spatial distribution of total organic carbon (TOC), total nitrogen (TN) and n-alkanes were investigated in surface sediments of Nam Co on the central Tibetan Plateau
The results presented provide references that can be used to explain the paleoclimate changes in Nam Co and other lakes in the Tibetan Plateau
Summary
Lake sediments are widely utilized for reconstruction of climatic and environmental changes because they possess continuous depositional sequences and rich proxies with apparent environmental significance [1]. Lake sediments are being widely and thoroughly studied in this area, because there are more than 1000 lakes with areas greater than 1 km present on the plateau [7]. These lakes provide many natural environmental archives for past environmental changes [8,9,10,11,12,13,14], the explanations of the proxies are still based on lake studies of the lowland or other areas. The large central basin is the main basin of the lake, encompassing more than 80% of the entire lake and having a maximum water depth greater than 95 m. The dominant aquatic plant species are Cyperaceae, Ranunculaceae, Potamogetonaceae and Haloragaceae [26]
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