Beyond traditional stratigraphy: Depth-resolved laser-induced breakdown spectroscopy for assessing fungal biodeterioration in heritage wood

Wooden cultural heritage materials are highly vulnerable to biodeterioration, with fungal colonization driving complex biochemical degradation processes. In this study, fungal biodeterioration of historic wood from Al-Qazdughli Palace (Cairo, Egypt) was investigated using an integrated microbiological, spectroscopic, and depth-resolved analytical approach. Dominant fungal taxa ( Aspergillus flavus, Aspergillus niger, Penicillium sp., and Rhizopus sp.) were isolated and identified by microscopic analysis, and pure cultures were subsequently analyzed using Laser-Induced Breakdown Spectroscopy (LIBS) to assess their characteristic spectral signatures. Multivariate analysis based on Principal Component Analysis (PCA) enabled successful discrimination among the isolated fungal cultures, establishing a spectral basis for fungal differentiation. Depth-resolved LIBS profiling of biodeteriorated wood further revealed stratigraphic variations in nitrogen-rich CN molecular emissions associated with fungal biomass, and manganese distributions linked to oxidative lignin degradation processes. Stoichiometric relationships between CN, Mn, and phosphorus provided additional insight into the functional decoupling between fungal biomass distribution and oxidative metabolic activity. Crater depth analysis confirmed the reliability of laser ablation for stratigraphic interpretation. Collectively, the results demonstrate that depth-resolved LIBS, combined with chemometric analysis, offers a rapid and reliable alternative to traditional stratigraphic methods, providing mechanistic insight and reliable diagnostics for fungal biodeterioration and targeted conservation of heritage wood.