In situ continuous decoding of temperature-pH-strain variations in moss disease on sandstone

Moss-induced biocorrosion of stone heritage is a slow yet persistent deterioration process that alters the physicochemical conditions within porous stones, leading to structural damage and loss of cultural value. To conduct in-situ decoding of the pathogenic mechanism of mosses on sandstone, we developed a fiber Bragg grating (FBG)–based multi-parameter sensing system. The sensing system integrates three types of FBGs—temperature-sensing (T-FBG), strain-sensing (S-FBG), and polyacrylic acid–polyvinyl alcohol (PAA-PVA) coated pH-sensing FBG (H-FBG). The sensitivities and resolutions of T-FBG, S-FBG and H-FBG are 9.69 pm/℃ (0.01 ℃), 1.23 pm/με (0.1 με) and 38.63 pm/pH (0.02 pH units), respectively. A decoupling model based on a 3 × 3 sensitivity matrix was established to eliminate cross-sensitivity effects. During 60 days of Funaria hygrometrica colonization, the system captured dynamic variations including a maximal pH decrease of 0.5, a temperature fluctuation of 3.2 ℃, and an internal microstrain increase of 11.3 με. Microscopic and porosity analyses further confirmed the dual biochemical–mechanical degradation caused by metabolite secretion and rhizoid penetration. This work provides quantitative insights into moss-induced biocorrosion mechanisms and indicates the feasibility of optical fiber sensing as an early-warning strategy for preventive conservation of stone relics.