A 35-meter-long sediment core (DH-7B) was retrieved from Dahu Lake using a stainless-steel pipe mounted on a floating platform. The core was subsampled at 5-cm intervals with 1-cm thickness for diatom, stable isotope, and trace element analyses. For diatom analysis, 0.5 g of dry sediment was treated with 32% H₂O₂ and 10% HCl. The cleaned material was mounted on slides using Wako mounting medium, and 300 diatom valves were identified and counted under an optical microscope at 1000× magnification.