A multi‑media biogeochemical dataset from Lake Dian, a shallow eutrophic plateau lake in southwest China

This dataset comprises a comprehensive multi‑media biogeochemical dataset from Lake Dian, a shallow eutrophic plateau lake in southwest China. It was collected to address the lack of long‑term, high‑resolution observations in plateau lake systems and to support research on eutrophication, carbon cycling, and nutrient dynamics.The dataset includes the following components:Sediment coresEight sediment cores (0.3–1.5 m in length) with210Pb‑137Cs chronologies and high‑resolution (0.5 cm interval) measurements of total organic carbon (TOC), inorganic carbon (IC), stable carbon isotopes (δ13C), stable nitrogen isotopes (δ15N), C/N ratios, and phosphorus fractions.Surface sediments100 surface sediment samples (0–2 cm) analyzed for the same parameters (TOC, IC, δ13C, δ15N, C/N, and phosphorus fractions).Water samplesWater samples collected during the rainy season (October 2023) and dry season (April 2024), including surface water, bottom water, and 19 water column profiles. Measurements include nutrients (TN, DTN, NO3−3−​‑N, NH4+4+​‑N, TP, DTP, PO43−43−​‑P), carbon components (TC, TOC, IC), and chlorophyll a.Pore waterNutrient concentrations and spectral data from sediment pore water extracted from surface sediments and sediment cores.Source end‑membersδ13C, δ15N, and C/N data for potential organic matter sources (algae, aquatic plants, C3​plants, sewage, and soil organic matter) collected within the Dianchi watershed.Model outputsOrganic matter source contribution estimates derived from the MixSIAR Bayesian mixing model.All data have undergone rigorous quality control, including standard reference material comparisons, replicate sample analyses, blank tests, and validation of sediment chronologies using137Cs time markers. Data are provided in CSV format to facilitate use in statistical software (R, Python, MATLAB) and spreadsheet applications.This dataset is freely available under a Creative Commons Attribution 4.0 International (CC BY 4.0) license and can be used for studies on lake eutrophication history, carbon cycle modeling, organic matter source apportionment, internal nutrient loading, and cross‑lake comparative analyses.