Speaker
Description
Subaerial biofilms (SABs) are microbial communities colonizing air-exposed mineral surfaces, where water availability is crucial for their metabolic activity. Located at the interface between the mineral substrate and the air atmosphere, SABs interact directly with both environments. Although precipitation and dew contribute to SAB hydration, water availability is largely controlled by evaporation and condensation closely linked to the fluctuating temperature and humidity conditions. As a result, variations in external conditions affect the interaction of SABs with the air and the mineral substrate, and thereby its internal organization.
A mathematical model describing the water dynamics in the SAB, the ambient air and the underlying stone is proposed. Based on thermodynamic principles, the model captures changes in water content by accounting for the evaporation and condensation through gradients in water chemical potential. It considers the SAB capacity to delay water loss, while enabling the biofilm to draw water from stone pores to compensate for atmospheric evaporation.
The key components of the model are validated by using experimental data reported in literature on water transport in limestone samples with and without SAB. Additional numerical simulations are performed under variable environmental conditions featuring daily fluctuations. Several scenarios are explored by considering different permeability conditions of the stone and the presence or absence of the SAB.
