Evaluating The Protective Effect of Calcium Carbonate Coating On Sandstone Cultural Heritage

The purpose of this work is to use different surfactants to deposit different crystal forms of calcium carbonate film on the surface of sandstone through a simple double replacement reaction. The protective effect of calcium carbonate coatings was evaluated through water absorption, water vapor permeability and weather resistance tests. The results show that the stone treated with vaterite calcium carbonate has excellent water absorption and permeability. Compared with untreated stone, the water absorption rate is reduced by 0.5 times, and the weather resistance is increased by 4 times, effectively hindering the erosion of water and soluble salts. These findings are expected to provide useful suggestions for the protection of stone cultural heritage.

Alpha-particle fluence in radiobiological experiments

Two methods were proposed for determining alpha-particle fluence for radiobiological experiments. The first involved calculating the probabilities of hitting the target for alpha particles emitted from a source through Monte Carlo simulations, which when multiplied by the activity of the source gave the fluence at the target. The second relied on the number of chemically etched alpha-particle tracks developed on a solid-state nuclear track detector (SSNTD) that was irradiated by an alpha-particle source. The etching efficiencies (defined as percentages of latent tracks created by alpha particles from the source that could develop to become visible tracks upon chemical etching) were computed through Monte Carlo simulations, which when multiplied by the experimentally counted number of visible tracks would also give the fluence at the target. We studied alpha particles with an energy of 5.486 MeV emitted from an 241Am source, and considered the alpha-particle tracks developed on polyallyldiglycol carbonate film, which is a common SSNTD. Our results showed that the etching efficiencies were equal to one for source–film distances of from 0.6 to 3.5 cm for a circular film of radius of 1 cm, and for source–film distances of from 1 to 3 cm for circular film of radius of 2 cm. For circular film with a radius of 3 cm, the etching efficiencies never reached 1. On the other hand, the hit probability decreased monotonically with increase in the source–target distance, and fell to zero when the source–target distance was larger than the particle range in air.

Corrosion control using hydroxide and bicarbonate alkalising agents in water drinking processes

<p><strong>Abstract.</strong> The water supply industry is faced with three phenomena of great importance: the aggressiveness, corrosion, and incrustation of water distribution systems (WDS), which are primarily due to the low alkalinity of water sources and the addition of chemicals used in water treatment processes, which require pH adjustments during the last stage of the treatment process before going into the WDS. This article presents the results of using Ca(OH)₂ and NaOH with doses between 2 and 20 mg L⁻¹ and NaHCO₃ and Na₂CO₃ between 10 and 250 mg L⁻¹ to adjust the pH of water treated from the Cauca River, which is located in Cali, Colombia, using stabilisation indices normally used in water treatment plants for pH monitoring processes and to better predict the behaviour of water in the WDS. The results indicate that for the case of the surface water source studied, which exhibits low alkalinity levels, the evaluated alkalising agents, with the exception of NaHCO₃, can create conditions that lead to the precipitation of a~protective calcium carbonate film. Because the pH values that guarantee an adequate pH adjustment are higher (8.7–9.0) than those specified by the Colombian water code and because other international rules indicate that these values do not compromise the health of consumers, it is advisable to review and adjust the code in this respect.</p>