The formation of silt from quartz dune sand by salt-weathering processes in deserts

1979 ◽  
Vol 2 (2) ◽  
pp. 105-112 ◽  
Author(s):  
A.S. Goudie ◽  
R.U. Cooke ◽  
J.C. Doornkamp
Keyword(s):  
Salt Weathering ◽  
Dune Sand ◽  
Weathering Processes

scholarly journals Weathering Processes and Mechanisms Caused by Capillary Waters and Pigeon Droppings on Porous Limestones

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 18
Author(s):  
David Benavente ◽  
Marli de Jongh ◽  
Juan Carlos Cañaveras
Keyword(s):  
Chemical Effect ◽  
Salt Weathering ◽  
Capillary Water ◽  
Material Loss ◽  
Weathering Processes ◽  
Geochemical Study ◽  
Pigeon Droppings ◽  
Deterioration Process ◽  
Dehydration Processes ◽  
Physical And Chemical

This investigation studies the physical and chemical effect of salt weathering on biocalcarenites and biocalcrudites in the Basilica of Our Lady of Succour (Aspe, Spain). Weathering patterns are the result of salty rising capillary water and water lixiviated from pigeon droppings. Surface modifications and features induced by material loss are observable in the monument. Formation of gypsum, hexahydrite, halite, aphthitalite and arcanite is associated with rising capillary water, and niter, hydroxyapatite, brushite, struvite, weddellite, oxammite and halite with pigeon droppings. Humberstonite is related to the interaction of both types of waters. Analysis of crystal shapes reveals different saturation degree conditions. Single salts show non-equilibrium shapes, implying higher crystallisation pressures. Single salts have undergone dissolution and/or dehydration processes enhancing the deterioration process, particularly in the presence of magnesium sulphate. Double salts (humberstonite) have crystals corresponding to near-equilibrium form, implying lower crystallisation pressures. This geochemical study suggests salts precipitate via incongruent reactions rather than congruent precipitation, where hexahydrite is the precursor and limiting reactant of humberstonite. Chemical dissolution of limestone is driven mainly by the presence of acidic water lixiviated from pigeon droppings and is a critical weathering process affecting the most valuable architectural elements present in the façades.

Impacts of climatic seasonality on weathering of rock-cut structures at Lalibela, Ethiopia

2021 ◽  
Author(s):  
Blen Taye ◽  
Heather Viles
Keyword(s):  
Climatic Conditions ◽  
Rock Surface ◽  
Salt Weathering ◽  
Northern Ethiopia ◽  
Climate Data ◽  
Climate Trends ◽  
Weathering Processes ◽  
North East ◽  
The North ◽  
Diurnal Range

<p>Weathering of rock-cut structures exposed to the environment is strongly influenced by fluctuations in climatic variables. Both macro and microclimate data are needed to identify key weathering types and rates likely to affect rock-cut structures in a specific region. The aim of this paper is to study the macro and micro climatic conditions affecting the rock-cut churches in Lalibela, Ethiopia to determine how the climate influences weathering at this site. Macro climate data collected over a 26-year period and microclimate data monitored on the north, east, south and west walls at one of the churches in the Lalibela church complex (Bete Mariam) are used to make these assessments. Microclimate data was monitored during the long rains (Kiremt), short rains (Belg) and dry (Bega) seasons in 2018 and 2019. The results showed a high seasonal variation in macro climatic conditions like rainfall and ambient relative humidity. The micro climatic (rock surface) conditions also tended to vary seasonally. The diurnal range of rock surface temperature during Bega varied significantly depending on which cardinal directions the walls were facing, with south and west facing walls having high diurnal thermal ranges. The influence of aspect was less pronounced in Belg and Kiremt, but cloud cover played an important role in varying the range of diurnal thermal and humidity cycles from day to day during these seasons. These climate trends are likely to cause seasonal variations in wetting and drying cycles, deep wetting, increased time of wetness and thermal cycling. These wetting/drying and heating/cooling characteristics affect weathering processes. During Kiremt, biological weathering, salt weathering and clay swelling are more likely to occur than in Belg and Bega. High diurnal thermal ranges in Bega are likely to cause thermal fatigue in this season. This is the first paper to address the macro and micro climatic trends that influence rock weathering at the rock-cut churches in Lalibela. The results of this study also have implications for rock-cut structures in northern Ethiopia having similar environmental conditions as Lalibela.</p>

scholarly journals Weathering Stability and Durability of Birch Plywood Modified with Different Molecular Weight Phenol-Formaldehyde Oligomers

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 175
Author(s):  
Juris Grinins ◽  
Vladimirs Biziks ◽  
Brendan Nicholas Marais ◽  
Janis Rizikovs ◽  
Holger Militz
Keyword(s):  
Uv Light ◽  
Phenol Formaldehyde ◽  
Wood Decay ◽  
Soft Rot ◽  
Solid Wood ◽  
Solid Content ◽  
Molecular Weights ◽  
Weathering Processes ◽  
Commercial Resin ◽  
D 20

This study investigated the effect of phenol-formaldehyde (PF) resin treatment on the weathering stability and biological durability of birch plywood. Silver birch (Betula pendula) veneers were vacuum-pressure impregnated with four different PF resins with average molecular weights (Mw) of 292 (resin A), 528 (resin B), 703 (resin C), and 884 g/mol (resin D). The aging properties of PF resin modified birch plywood were analyzed using artificial weathering with ultraviolet (UV) light, UV and water spray, and weathering under outdoor conditions. The same combinations of PF-treated plywood specimens were then tested in soil-bed tests to determine their resistance against soft-rot wood decay. It was not possible to compare weathering processes under artificial conditions to processes under outdoor conditions. However, the weathering stability of birch plywood treated with PF resins A, B, and C, scored better than plywood treated with commercial resin D (regardless of solid content concentration [%]). Results from unsterile soil bed tests showed improvements in resistance to soft-rot wood decay compared to untreated plywood and solid wood. Mass loss [%] was lowest for birch plywood specimens treated with resin of highest solid content concentration (resin D, 20%). Provisional durability ratings delivered durability class (DC) ratings of 2–3, considerably improved over untreated solid wood and untreated birch plywood (DC 5).

scholarly journals Soluble Salts Quantitative Characterization and Thermodynamic Modeling on Roman Bricks to Assess the Origin of Their Formation

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2866
Author(s):  
Claudia Scatigno ◽  
Nagore Prieto-Taboada ◽  
Giulia Festa ◽  
Juan Manuel Madariaga
Keyword(s):  
Archaeological Site ◽  
Risk Level ◽  
Salt Weathering ◽  
Soluble Salts ◽  
High Concentration ◽  
Quantitative Characterization ◽  
Chromatography Analysis ◽  
Acidic Gases ◽  
Hygroscopic Moisture ◽  
Ostia Antica

The environmental weathering and the formation of efflorescences on the brick walls are studied at the “Casa di Diana” Mithraeum at Ostia Antica archaeological site. Previous studies on subsoil, bedrock, hydrological systems and environmental conditions, and new ion chromatography analysis combined with ECOS-RUNSALT and Medusa-Hydra thermodynamic modelling software, had allowed us to identify the subsoil contamination related to soluble salts. The atmospheric acidic gases, CO2 and SO2, are determined as the main salt weathering species. A dry deposition after a subsequent hydration action from the shallow freshwater aquifer that reaches up to 1 m on the walls is identified as the mechanism of salt formation. An evaluation of potential sources such as the nearby Fiumicino airport, CO2-rich gases inputs from fumaroles and CO2 inputs was also debated. The risk level of contamination the surfaces of the materials should be considered mildly/very polluted with a medium/high risk of hygroscopic moisture due to the high concentration of sulphates.

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