A possible iron-dominated catalytic oxidation mechanism in waterlogged archaeological wood from the Mengxihe Palaeolithic site

Abstract

In marine shipwrecks, wood degradation is described by the sulfur-iron model, in which pyrite forms during burial and then oxidizes to sulfuric acid after excavation. Whether this model applies to freshwater environments remains unclear. Here, we analyzed waterlogged archaeological wood from the Paleolithic Mengxihe site in China. The wood exhibited strong acidity (pH 1.71–4.80), high iron content (7.17–32.31 wt%), extensive polysaccharide loss, and lignin modification. Unlike in marine wood, sulfur occurs mainly as sulfates, and the iron-to-sulfur ratio far exceeds that of pyrite. We therefore propose an iron-mediated Fenton-like oxidative degradation as a plausible mechanism for freshwater archaeological wood, providing new insights for the conservation of such materials.