The sedimentary C/N and δ13C in six Yangtze floodplain (China) lake sediment cores since 1800s CE. The sediment cores were dated using lead-210. C/N ratios and δ13C were analysed at the National Environmental Isotope Facility at the British Geological Survey, after preliminary treatment (HCl (5%) to remove calcites) in the School of Geography at the University of Nottingham, using Costech Elemental Analyser (EA) and on-line VG TripleTrap and Optima dual-inlet mass spectrometer. TOC and TN content were calibrated using the acetanilide standard. δ13C was calibrated to the Vienna Pee Dee Belemnite (VPDB) using laboratory standards which were calibrated against NBS-18, NBS-19 and NBS-22.