Measurements and calculations of seasonal evaporation rate from bare sandstone surfaces: Implications for rock weathering. Issue 12 (6th August 2020)

• Record Type: Journal Article
• Authors: Slavík, Martin; Bruthans, Jiří; Weiss, Tomáš; Schweigstillová, Jana
• Is Part Of: Earth surface processes and landforms. Volume 45:Issue 12(2020)
• Page Start: 2965
• Page End: 2981
• Publication Date: 2020-08-06
• Subjects: evaporation -- weathering -- drying -- sandstone -- vaporization plane -- surface resistance -- evaporation front -- dry surface layer -- uranine probe -- diffusion; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.4943
• Languages: English
• ISSNs: 0197-9337

Abstract

Abstract: Evaporation from porous rock plays an important role in weathering processes. In the case of salt weathering, the evaporation rate controls supersaturation of salt solutions within pores and the amount of precipitated aggressive salts, therefore weathering occurs mostly in places with intense evaporation. Evaporation also strongly affects frost, hydric and biogenic weathering, as these are influenced by water content and its temporal changes. Despite its importance, evaporation from porous rocks has seen little scientific focus. We present a study on evaporation from bare sandstone, one of the most common rocks affected by weathering. A new method that measures the evaporation rate from the surfaces of sandstone samples under field microclimate was developed and tested. Also, a simple calculation of 1D evaporation rate from bare sandstone surfaces based on Fick's law of diffusion is presented. The measurement was performed using sandstone cores (with a set depth of the vaporization plane) in a humid continental climate and measured on a roughly monthly interval for about 1 year. For the calculations, a laboratory‐measured water‐vapour diffusion coefficient of the sandstone, in‐situ seasonally measured vaporization plane depth, and values of air humidity and temperature were used. The sensitivity analyses showed that the most important factor controlling the evaporation rate was the vaporization plane depth, while seasonal and spatial changes of air humidity and temperature were of lesser importance. The calculated evaporation rate reasonably follows measured values. For its simplicity and the small number of parameters required, the proposed method has the potential to improve knowledge of weathering and living conditions of endolithic and epilithic organisms. Further research should focus on factors affecting the evaporation rate (wind, hygroscopicity, hydrophobicity, etc.) to improve the accuracy of the calculations, as well as to test the applicability of the method for other lithologies and climates. © 2020 John Wiley & Sons, Ltd. Abstract : A method to measure and calculate the evaporation rate from bare sandstone surfaces was introduced. The calculation of evaporation rate requires only: air temperature, relative humidity of air, water‐vapour diffusion coefficient of sandstone, and vaporization plane depth below sandstone's surface. The vaporization plane depth below the surface is the most important factor controlling the evaporation rate.