Biomarker and stable carbon isotopic signatures for 100-200 year sediment record in the Chaihe catchment in southwest China.

Natural inputs and anthropogenic influences on lakes and their catchments are reflected in the sediment record. In the present study, the extractable organic compounds from sediments in the Chaihe catchment of the Dianchi watershed were analyzed to characterize source inputs. Results show that the sediments are dominated by odd numbered n-alkanes (n-C16-n-C33), maximizing at n-C17, n-C29 and n-C31. Aliphatic hydrocarbon may be composed of terrestrial plants and bacteria. The values of δ(13)C27, δ(13)C29 and δ(13)C31 of n-alkanes exhibit a range from -33.27‰ to -25.46‰, from -35.76‰ to -28.47‰ and from -33.67‰ to -27.42‰, respectively and three records strongly covary with depth, falling within the range of C3 plants in the study area. An isotopic model revealed C3 plant contribution to sedimentary organic matter (OM) ranging from 40.75% to 97.22%. The values of ACL27-33, CPI27-33, OEP, Paq, Pr/Ph, (C27+C29)/2C31, (C21+C23+C25)/3C17 and nC26(-)/nC27(+) are consistent with the C3 plant predominance. A constant CRS model gave the accumulation rates ranging from 2.69 to 8.46mma(-1) spanning 1885-2010. It was concluded that OM transport in the Chaihe catchment was influenced strongly by human activities resulting in enhanced eutrophication.