Analysis on Disease Types and Deterioration Mechanisms of Pig Mandibles from Huangshan Site in Nanyang

Abstract

Natural pig mandibles excavated from the Huangshan Site, Nanyang, feature rich pores and high organic content and undergo serious composite deterioration under burial and post-excavation environments. Targeting bone relic conservation, this study selects fragmented pig mandible samples to identify disease types and microscopic deterioration mechanisms. Field surveys classify diseases into five categories: mechanical degradation, hygrothermal deformation, discoloration, mildew corrosion and salt efflorescence, with obvious coupled deterioration features. Multiple testing methods including ultra-depth-of-field microscopy, SEM, XRF, ion chromatography, XRD, FTIR, nitrogen adsorption and mercury intrusion porosimetry are adopted to characterize micromorphology, elements, anions, mineral phases, pore structure and water content. The results show the samples are dominated by carbonated hydroxyapatite with interconnected pores and an average water content of 39.86%; Cl⁻ and SO₄²⁻ are major corrosive anions. Bone deterioration follows a two-stage mechanism: preferential collagen degradation accompanied by synchronous dissolution of inorganic minerals. Weakly acidic groundwater and soil components induce latent underground damage, whereas drastic post-excavation humidity-temperature fluctuations and cyclic salt crystallization accelerate visible deterioration. This research reveals the complete deterioration evolution of prehistoric bone relics and offers theoretical and technical support for emergency field treatment and long-term museum preservation of analogous animal bone artifacts.