The range dataset of P fractions in the sediments of Huguangyan Maar Lake.

Two sediment cores HG-1 (96 cm) and HG-3 (184.8 cm) were drilled from the depocenter of Huguangyan Maar Lake (HML) using a 90-mm diameter percussion piston coring system in December 2019. They were divided into 0.2 cm intervals, sealed in numbered bags, and freeze-dried for the subsequent radiometric dating and P fraction analysis. The freeze-dried were grounded and filtered through a 200-mesh (~75 μm) sieve. The freeze-dried sediments of HML sediments were ground and filtered through a 200-mesh (~75 μm) sieve. Then, the phosphorus (P) fractions were extracted, and a phosphorus fractions range dataset was obtained. P is sequentially extracted from dry sediments (0.2 g) using 40 mL of extractant for F1-F4 and 20 mL of extractant F5. 0.46 M sodium chloride (NaCl) was used to extract F1, and F2 is extracted by the buffer solution (NaBD, pH 7.0) made by 0.11 M sodium dithionite (Na2S2O4) and 0.11 M sodium bicarbonate (NaHCO3). The F3 is extracted by 1.0 M sodium hydroxide (NaOH) while F4 is extracted with 0.5 M hydrochloric acid (HCl). The rest of samples was freeze-dried, calcined in a muffle furnace at 550°C for 2 hours, and then treated with 1.0 M HCl to obtain the F5. All extractions utilized AR (analytical reagent)-grade reagents in ultrapure water, which were stirred with orbital oscillator in room temperature. Post-extraction, residues were rinsed with 0.46 M NaCl (15 min) and centrifuged (4,000 rpm, 15 min, room temperature). Other than the extraction of F1 which takes 1 hour, the process of obtaining each P fraction takes 16 hours. Supernatants were collected for spectrophotometric analysis of P fractions.