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The Biological Sources of the Organic Matter in Poyang Lake Sediments

We conducts a systematic study on the biological sources of the sediment organic matter through the analysis of the organic carbon and nitrogen content in the sediments of Poyang Lake, the n-alkanes as biomarker and the characteristics of the compound-specific isotope of n-alkanes. It is found that the C/N ratio of organic matter is less than 10 in Poyang Lake and that the organic matter mainly originates from lacustrine aquatic organism. The short-chain hydrocarbon takes absolute advantage in the n-alkanes. The value of C21-/C22+ is greater than 1, which shows that the biomass of bacteria and algae is greater than the sum of the aquatic submerged plants and terrigenous organisms biomass. The value of (nC15+nC17)/(nC23+nC25) of n-alkanes is greater than 2, which reveals that bacteria and algae have an absolute predominance in aquatic organism. The high carbon n-alkanes come from terrigenous plants and their compound-specific carbon isotope demonstrates that C3 plant is the main biological source.