Millennial-aged peat carbon outgassed by large humic lakes in the Congo Basin

1. Analysis Code (DIC_monte_carlo.R) This R script performs the End-Member Mixing Analysis (EMMA) used to quantify the contribution of ancient peat carbon to the dissolved inorganic carbon (DIC) pool. The script executes a Monte Carlo simulation (n = 100,000 iterations) to solve for source fractions under two scenarios: a three-source "Equilibration" model (Peat, Modern, Atmosphere) and a two-source "Outgassing" model (Peat, Modern). It processes data for four locations (Lakes Mai-Ndombe and Tumba, Fimi and Ruki Rivers), calculates summary statistics (mean +/- SD), generates weighted averages, and produces the violin plots presented in Extended Data Fig. 3. 2. Model Input Data (DIC_monte_carlo.csv) This comma-separated value file serves as the direct input for the R analysis script. It contains the aggregated isotopic data required to define the end-members (Peat/SOC, Modern DOC/POC, Atmosphere) and the DIC mixtures for each study location.