Harmonized Sequential Extraction Parameters for Soil Organic Matter Fractions Across Contrasting Land-Use Soils: Optimization and Mass-Balance Assessment
Year: 2026
Type: article
Abstract: Fine fractionation of soil organic matter (SOM) underpins the interpretation of element speciation in different SOM pools, yet sequential extraction methods are mostly optimized for single soil types, limiting inter-study comparability. We optimized extraction time and concentration for six SOM fractions—exchangeable SOM (Ex), humic acid (HA), fulvic acid (FA), iron-bound humin (HMi), clay-bound humin (HMc), and insoluble humin (HMr)—using forest, vegetable, and farmland soils from Lincang, Yunnan, and characterized the extraction residues by FTIR, SEM, and EEM analyses. Optimal parameters fell within 8–12 h and 0.5–1.0 mol L−1: Ex, 1 mol L−1 NH4Ac (pH 5.0, 12 h); HA/FA, 1 mol L−1 NaOH + 0.05 mol L−1 Na4P2O7 (12 h); HMi, 0.5 mol L−1 H2SO4 (8 h), then 0.5 mol L−1 NaOH + saturated Na2SO4 (12 h); HMc, 1 mol L−1 H2SO4–HF (1:1, v/v, 12 h), then the same alkali extraction. Total SOM extraction rates reached 90.05% ± 1.12% to 96.97% ± 1.27% (n = 3); residues showed progressive stripping from weakly to strongly bound fractions, and fraction distributions differed consistently among land-use types. This framework provides a methodological basis for cross-soil SOM fractionation.
Source: Molecules
Institution: Kunming University
Language: English
Subfield: Soil Science
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $3,258
OpenAlex ID: W7223972494