Deterioration of sandstones: Insights from experimental weathering in acidic, neutral and biotic solutions with Acidithiobacillus thiooxidans

The susceptibility of sandstones to deteriorative factors when used for construction requires detailed experimental evaluation. This study investigated the (bio)weathering behaviour of Lower-Silesian Cretaceous sandstones (quartz arenites) to quantify the deteriorative effect of bacterium Acidithiobacillus thiooxidans. For controls, ultrapure water (in undersaturated conditions) and sterile acidic medium (in abiotic acidic conditions pH 2.5) were used. Sandstone exposure to A. thiooxidans mimicked the extremely acidic conditions (pH up to 0.9) that may develop under long-term weathering, which promote microbial activity and acidic metabolite production. Element release was assessed using triple quadrupole inductively coupled plasma mass spectrometry (QQQ4CP-MS) and identifying potential element donor minerals through scanning electron microscopy, coupled with energy dispersive spectrometer (SEM-EDS). The results demonstrated that sandstones were relatively susceptible to weathering, especially when exposed to aggressive acidic conditions, where the presence of bacteria apparently acts as an accelerating factor in deterioration. Based on Si release, sandstone degradation under biotic conditions was 0.27% within 86 days, whereas the dissolution achieved in ultrapure water did not exceed 0.02%. A highly pronounced weathering feature observed on sandstones was the dissolution of goethite and/or kaolinite cement, whereas quartz was less susceptible to weathering under the conditions studied. Bioweathering investigations may help solve deterioration issues in sandstone building materials. (C) 2020 Elsevier Ltd. All rights reserved.