We're glad to announce the release of our newly produced SFB 1313 film. This time we focused on evaporation processes in porous media and salt precipitation. Our experts Sander Huisman (project leader of SFB 1313 research project C05) and Stefanie Kiemle (associated SFB 1313 research project C-X5) explain the topic. The film was again produced by with "aha! film GmbH".
Vision Topic "Salt Precipitation"
Understanding evaporation of water in porous media in the presence of soluble salts plays a key role in many environmental and hydraulic applications, such as water management, the global water cycle, plant growth, plant yield and vegetation, agriculture, rock weathering, soil and groundwater salinization, as well as in other fields such as the construction of porous building materials. In many arid and semi-arid regions, evaporation from porous media induces salt deposition and crystallization on the surface or within the porous matrix, resulting in the degradation of soil productivity. This problem concerns a wide range of soils worldwide, for example in Tunisia, where the salt-affected soils make up more than 10% of the entire country’s surface; hence, the understanding of such phenomena is of great importance.
Cooperation with the Ecole Nationale d'Ingénieurs de Tunis
The Ecole Nationale d'Ingénieurs de Tunis (ENIT) is one of SFB 1313's international partners. In the framework of this cooperation, Dr. Emna Mejri, former researcher at the ENIT and now researcher at the Helmut Schmidt Universität Hamburg (Germany), was several times a guest researcher at the Department of Hydromechanics and Modelling of Hydrosystems (LH2) and within SFB 1313. Together with SFB 1313 spokesman Rainer Helmig, Emna was leading a DAAD project entitled "EVASAL: Environmental applications of evaporative salt precipitation in porous media: numerical modelling and experimental investigations". In the framework of a research internship, the two doctoral researchers Aroua Manai and Safa Maiza from the ENIT visited the LH2 twice in 2019 and 2022 as well, to further develop their doctoral theses.
About Emna Mejri's research interest
As an Environment and Water Science Engineer, she was motivated by research works dealing with environmental issues such as water management, soil and groundwater pollution and global water cycle. That conducted her to focus her research interests on understanding and modelling multiphase multicomponent flow and transport in porous media.
She started her research career ten years ago at the Department of Hydromechanics and Modelling of Hydrosystems working on modelling and analysis of salt precipitation on evaporation processes in the unsaturated zone. The main focus of that project was to analyze the evaporative salinization processes driven by the exchange between the free-flow and porous media flow interface and to produce sequences of evaporation and salt precipitation related to hydroclimatic conditions in Tunisia. After she successfully achieved her PhD project, she went back to her home country and continued working on the research topic. Thanks to the financial support from the DAAD, she implemented together with Prof. Rainer Helmig a research project called EvaSal at the National Engineering School of Tunis. This project was considered as a continuity of her PhD research work with a main focus on environmental and civil engineering applications of evaporative salt precipitation in porous media. Numerical and also experimental investigations have been done in the framework of this project in order to understand and evaluate soil and groundwater salinization influenced by salt recycling due to irrigation practices in an arid Tunisian area and also to study the influence of evaporative salt precipitation on the alteration and damage of monuments in archaeological sites in Tunisia.
About Aroua Manai's research interest
She is an industrial chemical engineer holding a master's in hydraulics and environmental modeling. She started her PhD on “Salt Crystallization in Building Materials: Numerical Modeling and Experimental Investigations” under the project Evasal. The crystallization of evaporites within and on rock surfaces frequently damages the host rock; this is known as salt weathering. The latter is frequently observed as a significant contributor to the degradation of building materials and historical architecture. Environmental changes, particularly variations in relative humidity and temperature, can induce alterations in the occurrence and manner of salt crystallization and growth. This can lead to the development of efflorescence or the generation of sub-florescence, which causes stone degradation due to increased crystallization pressures. The main objective of her work is to model the salt crystallization process in building materials under drying conditions by implementing geochemistry, which takes into account ionic interactions in solution and faithfully reproduces the precipitation sequence induced by evaporation. The model also takes into account the mechanical effect of salt crystallization in the porous medium. In addition, a field survey was carried out on the historical monument of Romain in Tunisia to assess the state of degradation of the monuments and identify the type of salts responsible for the degradation of the stones.
J. A. (Sander) Huisman
Prof. Dr.Principal Investigator, Research Project C05
Stefanie Kiemle
M. Sc.Doctoral Researcher C-X5, Project MGK