Molecular biomarkers for sources of organic matter in lacustrine sediments in a subtropical lake in China

摘要

N-alkanes distributions and stable isotopic compositions δ~(13)C and δ~(15)N) in the lacustrine sediments of Shijiu lake were measured to assess whether biological source information was recorded in the molecular biomarker. Results showed regular unimodal n-alkanes distribution in range of C_(16)-C_(33) with strong predominance of odd-numbered n-alkanes, maximizing at C_(29). The δ~(15)N for SON were uniformly low, ranging from -6.7‰ to 3.8‰ and C/N ratios ranged from 6.6 to 10.0, suggesting that most of organic matter was influenced by terrestrial characteristics of the watershed. The δ~(13)C for C_(27) to C_(31) n-alkanes and for SOC varied from -32.9‰ to -26.6‰ and -23.4‰ to -21.6‰ respectively, falling within the range of corresponding n-alkanes in leaves mainly from C3 land plants. The values of C/N, CPI, OEP, ACL and C_(27)/C_(31) exhibit similar temporal changes with the primary production, showing enhanced eutro-phication resulted from increased anthropogenic activities in Shijiu lake from 1852 to 2010.