Assessment of laser treatment on dolostones colonized by microorganisms and lichens

The preliminary results of the laser assessment for biofilms removal on rock surfaces are shown. The procedure consisted of laser irradiation (Nd:YAG, 1064 nm, 10 ns, 200 mJ) on a dolostone colonized by microorganisms (mainly cyanobacteria) and lichens. Samples were taken to assess the effectiveness of laser treatment on both the lichens thalli and microbial communities (SEM-BSE and TEM), and also on the stone substrate (SEM-SE + EDS). The results show that lichen thalli were eliminated only partially. The laser fluence applied was not enough to efficiently eliminate and/or damage the majority of lichen thalli, which is in accordance with previous laboratory results, where it was demonstrated that a higher fluence is necessary to clean and make inactive lichen symbionts. No damage was found in the dolomite crystals after laser radiation. Roughness and color were recorded before and after laser treatment. Continuous monitoring of the thermal processes during laser irradiation showed that thermal gradient is extremely high.