Sulfur and iron speciation in recently recovered timbers of the Mary Rose revealed via X-ray absorption spectroscopy

This paper reports the results of an investigation into the mechanisms that have led to the build up of sulfuric acid in the timbers of the Mary Rose, with a particular focus on recently recovered timbers. Measurements have been made by sulfur and iron K-edge X-ray absorption near edge spectroscopy (XANES), X-ray microscopy and by X-ray diffraction (XRD). Results from S K-edge XANES studies reveal that the concentration of highly oxidised S decreases with depth into the timber, from ∼15 at.% of S at the surface to negligible levels after approximately 50 mm. Fe K-edge XANES reveals little variation with depth in which Fe3+ ions are dominant. This sheds some light on the sulfur oxidation path, and indicates Fe3+ ions are produced by the oxidation mechanisms that are currently underway. XRD studies have identified several mineral components that may form part of the oxidation chain. These are magnetite (Fe3O4), jarosite (KFe3(SO4)2(OH)6) and calcite (CaCO3).