Search Results (24)

Urban air pollution poses significant risks to cultural heritage buildings, particularly in polluted megacities like Delhi, India. The Red Fort, a UNESCO World Heritage Site and a symbol of India’s rich history, is highly susceptible to degradation caused by air pollutants. Despite its great importance as an Indian and world heritage site, no studies have focused on characterizing its constituent materials or the degradation phenomena taking place. This study was developed in the framework of the MAECI (Italian Ministry of Foreign Affairs) and the Department of Science and Technology under the Ministry of Science and Technology, India, project: Indo—Italian Centre of Excellence for Restoration and Assessment of Environmental Impacts on Cultural Heritage Monuments. To understand their composition and degradation, Vindhyan sandstone and black crust samples were studied. Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) indicated that the red sandstone predominantly consisted of quartz and microcline, while the black crusts mainly comprised gypsum, bassanite, weddellite, quartz, and microcline. The analysis attributed the formation of gypsum to exogenous sources, such as construction activities and cement factory emissions. This pioneering study provides a basis for further research into the impacts of air pollution on Indian patrimony and promotes conservation strategies. Full article

Background: Different types of kidney stones are associated with distinct changes in urine chemistry. Methods: We assessed urinary parameters of 98 patients with calcium oxalate (CaOx) stones one month following endoscopic stone removal. The 24 h urine analysis encompassed the assessment of various parameters, including volume, sodium, chloride, sulfate, nitrate, fluoride, phosphate, calcium, potassium, magnesium, oxalate, uric acid, citrate, creatinine, and pH levels. Results: Hypocitraturia was the most prevalent urinary abnormality (61.2%, n = 63), followed by low urine volume (53%, n = 52) and hypercalciuria (50%, n = 49). We did not find any statistically significant differences between patients with whewellite (COM) (n = 69) and weddellite (COD) stones (n = 29) (p > 0.05). However, oxalate concentration was the only parameter with a statistically significant intergroup difference (p = 0.0297). Additionally, in univariate linear regression analysis, urinary phosphate levels ≥ 48.0 mmol/d showed a trend towards significance (OR 0.17, 95% CI 0.02–1.15, p = 0.0692), indicating that phosphaturia is associated with a significant increase in the odds ratio of COD stones. To further explore metabolic heterogeneity among stone formers, we conducted cluster analysis, which revealed three distinct metabolic subgroups. Cluster 1 was predominantly associated with COM stones (80.5%) and exhibited significantly higher urinary excretion of sodium, calcium, oxalate, phosphate, and uric acid compared to Cluster 2, which had a more balanced distribution of monohydrate and dihydrate stones. Conclusions: These findings suggest that a specific metabolic phenotype may be linked to COM stone formation, providing a framework for risk stratification and personalized prevention strategies in calcium oxalate stone formers. Full article

A comprehensive analysis of kidney stones is essential for the future treatment of patients. Almost all of the methods available for kidney stone analysis were used in this study. The chemical analysis included powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA-DSC). Following the chemical analysis, a detailed morphological analysis was carried out using stereoscopic microscopy, scanning electron microscopy (SEM-EDX), and micro-computed tomography (micro-CT). These investigations showed that the sixteen kidney stones analyzed in detail had a heterogeneous mineralogical structure, consisting of at least two different minerals. Kidney stones consist mainly of calcium oxalate (whewellite or weddellite) but also contain significant amounts of phosphate (mainly apatite and struvite). A thorough analysis of kidney stones can determine the cause of their formation and investigate possible treatments. Full article

This study reports on experimental observations during fungi–mineral substrate interactions. Selected mineral substrates of biotite, muscovite, bauxite, chromite, galena, malachite, manganite, and plagioclase were exposed in vitro to free fungal growth under open conditions. The interaction produced strong biochemical and biomechanical alterations to the mineral substrates. Specifically, reported here is a three-dimensional thigmotropic colonization pattern of the mineral surfaces that suggested a possible pattern of fungal metalophagus behavior. Authigenic secondary mineral biomineralization occurred: Ca- and Mg-Oxalates such as weddellite: CaC₂O₄·2H₂O, whewellite: CaC₂O4·H₂O, and glushinskite: MgC₂O₄·₂H₂O; struvite: (NH₄) MgPO₄·6H₂O; gibbsite: Al(OH)₃; and gypsum: CaSO₄·2H₂O. The bioleached elements included Fe, Pb, S, Cu, and Al, which formed single crystals or aggregates, amorphous layers, amorphous aggregates, and linear forms influenced by the fungal filaments. The fungi bioleached Fe and Al from bauxite and Mn from manganite and deposited the metals as separate mineral species. Gypsum was deposited during the interaction with the manganite substrate, indicating a source of Ca and S either within manganite impurities or within the fungal growth environment. Other biochemical and biomechanical features such as tunneling, strong pitting, exfoliation, dissolution, perforations, and fragmentation of the mineral surfaces were also produced. The results of this study, besides emphasizing the role of fungi in bioweathering and mineral alteration, also show that, to produce these alterations, fungi employ a 3D fungal colonization pattern of mineral surfaces guided by thigmotropic and possible metalophagus behavior. Full article

In this paper, the chromatic alteration of various types of paints, present on mural painting fragments derived from the vaults of The Upper Basilica of Saint Francis of Assisi in Italy (12th–13th century), is studied using synchrotron radiation. Six painted mural fragments, several square centimeters in size, were available for analysis, originating from the ceiling paintings attributed to Cimabue and Giotto; they correspond to originally white, blue/green, and brown/yellow/orange areas showing discoloration. As well as collecting macroscopic X-ray fluorescence and diffraction maps from the entire fragments in the laboratory and at the SOLEIL synchrotron, corresponding paint cross-sections were also analyzed using microscopic X-ray fluorescence and powder diffraction mapping at the PETRA-III synchrotron. Numerous secondary products were observed on the painted surfaces, such as (a) copper tri-hydroxychloride in green/blue areas; (b) corderoite and calomel in vermillion red/cinnabar-rich paints; (c) plattnerite and/or scrutinyite assumed to be oxidation products of (hydro)cerussite (2PbCO₃·Pb(OH)₂) in the white areas, and (d) the calcium oxalates whewellite and weddellite. An extensive presence of chlorinated metal salts points to the central role of chlorine-containing compounds during the degradation of the 800-year-old paint, leading to, among other things, the formation of the rare mineral cumengeite (21PbCl₂·20Cu(OH)₂·6H₂O). Full article

Ammonium N-(pyridin-2-ylmethyl)oxamate (AmPicOxam), synthesized from O-methyl-N-(pyridin-2-ylmethyl)oxamate, was spectroscopically and structurally characterized and assayed as a novel precursor for the protection and consolidation of carbonate stone substrates. An in-depth characterization of treated and untreated biomicritic limestone and white Carrara marble samples was carried out by means of SEM microscopy, X-ray powder diffraction, helium pycnometry, determination of water transport properties, and pull-off tests. The improved solubility (1.00 M, 16.5% w/w) of the title compound with respect to ammonium oxalate (0.4 M, 5% w/w) results in the formation of a thicker protective coating of calcium oxalate (CaOx) dihydrate (weddellite) on marble and biomicrite samples after the treatment with 5% and 12% w/w water solutions, producing a reduction in the stone porosity and increased cohesion. Theoretical calculations were carried out at the DFT level to investigate both the electronic structure of the N-(pyridin-2-ylmethyl)oxamate anion and the hydrolysis reaction leading from AmPicOxam to CaOx. Full article

The formation of oxalates in soils and rocks under conditions of cryoarid climate, permafrost and taiga vegetation was studied. Whewellite and weddellite were found in four areas associated with the mining industry: on the kimberlite deposit of the Daldyn territory, in the lower reaches of the Markha River of the Central Yakut Plain, and on the coastal outcrop of the Allah-Yun Sellah-Khotun ore cluster. Whewellite was found in the upper organic horizon of Skeletic Cryosol (Thixotropic) (sample 151) and as a film on the surface of plant remains of Humic Fluvisols (sample 1663). Weddellite was found as an extensive encrustation on the surface of the soil and vegetation cover of Stagnic Cryosols Reductaquic (sample 984) and on a siltstone outcrop (sample KM-6-21). Calcium oxalates were identified by X-ray phase analysis, photographs of the samples were taken on a polarizing microscope, and the crystal morphology was studied on a scanning electron microscope. To determine the chemical composition of soils and rocks, the classical wet-chemical method was used; the physical properties of the studied samples were studied using a pH meter, the photoelectric colorimetric method, and a synchrotron thermal analysis device. The source of calcium for the formation of salts is the parent layers of the studied soils, represented by carbonate and carbonate clastic rocks, which cause neutral and slightly alkaline environments. High humidity, which is provided by the seasonal thawing of the permafrost, has a key role in the formation of the studied oxalates in Yakutia with a sharply continental cryoarid climate. Based on the studies, it was found that the first two samples are the products of lichen activity, and the third and fourth are at the stage of initial soil formation by micromycetes. In addition, the formation of these oxalates, in our opinion, is the result of the protective function of vegetation, in the first two cases, with a sharp increase in the load on lichens under technogenic impact, and in the second and third cases, when favorable conditions arise for initial soil formation, but under conditions of toxic content of heavy metals and arsenic. Full article

The present work contributed to the patterns of crystallization affected by the metabolism of fungi and bacteria in various trophic conditions and specifically covers the case of Penicillium chrysogenum and P. chrysogenum with Bacillus subtilis. The cultivation of microorganisms was carried out on the dolomitic calcite marble in liquid Czapek–Dox nutrient medium with glucose concentrations of 1, 10 and 30 g/L. The study of the crystal component of mycelium formed on the marble surface was supported through powder X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy; the quantitative content of the extracellular polymer substance (EPS) and low-molecular-weight organic acids (LMWOAs) in the medium was determined through chromatography–mass spectrometry (GC-MS). The results obtained clearly demonstrated the unique ability of the fungus P. chrysogenum to not only release organic acids (primarily oxalic), but the EPS also which significantly affected the pH of the culture liquid and, accordingly, the carbonate and oxalate crystallization. Carbonate crystallization manifested in the presence of Bacillus subtilis as well. The transition from oxalate crystallization to carbonate and vice versa could occur with a change in the species composition of the microbial community as well as with a change in the nutritional value medium. Under the conditions closest to natural conditions (glucose content of 1 g/L), through the action of P. chrysogenum, oxalate crystallization occurred, and through the action of P. chrysogenum with B. subtilis, carbonate crystallization was observed. The identified patterns can be used to reveal the role of fungi and bacteria in the oxalate–carbonate pathway. Full article

The present investigation exposes the main results raised from an active collaboration started in 2018 with the San Pio Hospital (Benevento, Southern Italy), aiming at a detailed mineralogical investigation of urinary stones of patients from the Campania region. Forty-nine uroliths (both bladder and kidney stones) have been surgically collected from patients admitted between 2018 and 2020 at the Department of Urology of the San Pio Hospital and characterized for clinical purposes and environmental biomonitoring from a mineralogical point of view. Possible causes and environmental implications were inferred according to the morpho-constitutional classification of the uroliths carried out by means of a conventional analytical approach. The mineralogical frequency distribution of uroliths from the Campanian region can be discussed as a function of dietary, socio-demographic, and environmental risk factors. Whewellite [CaC₂O₄·H₂O] and weddellite [CaC₂O₄·(2+x)H₂O], along with anhydrous calcium oxalate, represent the main mineralogical phases forming the biominerals examined here. Worth to note is that the percentage of oxalates in the Campanian region (ca. 51%) is quite comparable to those of other Mediterranean areas. Frequent uricite [C₅H₄N₄O₃] (ca. 33%), mainly observed in bladder stones of older male patients, could be related to an incorrect lifestyle and dietary habits. Occurrence of lower percentages of phosphate (i.e., brushite [CaHPO₄·2(H₂O)] and carbonated apatite [Ca₁₀(PO₄CO₃)₆(OH)₈]) and mixed stones (such as, for example, a mixture of ammonium urate [NH₄C₅H₃N₄O₃] and calcium oxalates) indicates specific etiopathogenetic mechanisms, suggesting proper therapeutical approaches. Full article

The plant Saussurea costus (Falc) Lipsch has many biological activities and a strong curative and preventive power against a variety of diseases including cancer, diabetes, and hemorrhoids. In the current study, phytochemical screening was carried out as well as an investigation of the antilithiatic and antioxidant activities of aqueous and ethanolic extracts of this plant. The results showed that aqueous and ethanolic extracts were effective in reducing cystine stone mass and that the aqueous extract of Saussurea costus (Falc) Lipsch had the highest percentage of dissolution (6.756 ± 1.024) (p < 0.05). A turbidimetric method and a crystallization test were used to evaluate the antilithiatic activity of an aqueous and ethanolic extract of this plant on calcium oxalate crystallization. The results of these methods revealed that the ethanolic extract of this plant has a significant inhibitory effect on calcium oxalate crystallization, with a percentage inhibition of (91.017 ± 0.299) (p < 0.05) for a concentration of 2 mg mL⁻¹. The DPPH method revealed that the ethanolic extract of Saussurea costus (Falc) Lipsch with a concentration of (IC50 = 0.12325 mg mL⁻¹) had the highest IC50, whereas the FRAP method revealed that the aqueous extract of Saussurea costus (Falc) Lipsch with a concentration of 300 µg mL⁻¹ has the most significant reducing power with (OD = 0.56 ± 0.05). These findings indicate that aqueous and ethanolic extracts of Saussurea costus (Falc) Lipsch had a significant effect on whewellite and weddellite and a greater free radical scavenging effect but had no effect on cystine dissolution. Full article

Lichens are symbiotic organisms with an extraordinary capability to colonise areas of extreme climate and heavily contaminated sites, such as metal-rich habitats. Lichens have developed several mechanisms to overcome the toxicity of metals, including the ability to bind metal cations to extracellular sites of symbiotic partners and to subsequently form oxalates. Calcium is an essential alkaline earth element that is important in various cell processes. Calcium can serve as a metal ligand but can be toxic at elevated concentrations. This study investigated calcium-rich and calcium-poor sites and the lichen species that inhabit them (Cladonia sp.). The calcium content of these lichen species were analyzed, along with localized calcium oxalate formed in thalli collected from each site. The highest concentration of calcium was found in the lichen squamules, which can serve as a final deposit for detoxification. Interestingly, the highest content of calcium in Cladonia furcata was localized to the upper part of the thallus, which is the youngest. The produced calcium oxalates were species-specific. Whewellite (CaC₂O₄∙H₂O) was formed in the case of C. furcata and weddellite (CaC₂O₄∙2H₂O) was identified in C. foliacea. Full article

Powder mixtures with a given molar ratio of Ca/P = 1.67 were prepared under mechanical activation conditions from hydroxyapatite powder Ca₁₀(PO₄)₆(OH)₂ and a 1M aqueous solution of oxalic acid H₂C₂O₄ at a molar ratio of Ca₁₀(PO₄)₆(OH)₂/H₂C₂O₄ = 1:4. The phase composition of obtained powder mixture included brushite (calcium hydrophosphate dihydrate) CaHPO₄·2H₂O, calcium oxalate monohydrate CaC₂O₄·H₂O in form of whewellite and weddellite, and some quantity of quasi-amorphous phase. This powder mixture was used to produce microporous monophase ceramics based on hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ with apparent density of 1.25 g/cm³ after firing at 1200 °C. Microporosity of sintered ceramics was formed due to the presence of particles with plate-like morphology, restraining shrinkage during sintering. Microporous ceramics based on hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ with the roughness of the surface as a consequence of the created microporosity can be recommended as a biocompatible material for bone defects treatment and as a substrate for bone cell cultivation. Full article

Calcium oxalates are naturally occurring biominerals and can be found as a byproduct of some industrial processes. Recently, a new and green method for carbon capture and sequestration in stable calcium oxalate from oxalic acid produced by carbon dioxide reduction was proposed. The reaction resulted in high-quality weddellite crystals. Assessing the stability of these weddellite crystals is crucial to forecast their reuse as solid-state reservoir of pure CO₂ and CaO in a circular economy perspective or, eventually, their disposal. The thermal decomposition of weddellite obtained from the new method of carbon capture and storage was studied by coupling in-situ high-temperature X-ray powder diffraction and thermogravimetric analysis, in order to evaluate the dehydration, decarbonation, and the possible production of unwanted volatile species during heating. At low temperature (119–255 °C), structural water release was superimposed to an early CO₂ feeble evolution, resulting in a water-carbon dioxide mixture that should be separated for reuse. Furthermore, the storage temperature limit must be considered bearing in mind this CO₂ release low-temperature event. In the range 390–550 °C, a two-component mixture of carbon monoxide and dioxide is evolved, requiring oxidation of the former or gas separation to reuse pure gases. Finally, the last decarbonation reaction produced pure CO₂ starting from 550 °C. Full article

The present study is focused on the effect of biofilm medium chemistry on oxalate crystallization and contributes to the study of the patterns of microbial biomineralization and the development of nature-like technologies, using the metabolism of microscopic fungi. Calcium oxalates (weddellite and whewellite in different ratios) were synthesized by chemical precipitation in a weakly acidic environment (pH = 4–6), as is typical for the stationary phase of micromycetes growth, with a ratio of Ca²⁺/C₂O₄²⁻ = 4.0–5.5, at room temperature. Additives, which are common for biofilms on the surface of stone in an urban environment (citric, malic, succinic and fumaric acids; and K⁺, Mg²⁺, Fe³⁺, Sr²⁺, SO₄²⁺, PO₄³⁺ and CO₃²⁺ ions), were added to the solutions. The resulting precipitates were studied via X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS). It was revealed that organic acids, excreted by micromicetes, and some environmental ions, as well as their combinations, significantly affect the weddellite/whewellite ratio and the morphology of their phases (including the appearance of tetragonal prism faces of weddellite). The strongest unique effect leading to intensive crystallization of weddellite was only caused by the presence of citric acid additive in the medium. Minor changes in the composition of the additive components can lead to significant changes in the weddellite/whewellite ratio. The effect of the combination of additives on this ratio does not obey the law of additivity. The content of weddellite in the systems containing a representative set of both organic acids and environmental ions is ~20 wt%, which is in good agreement with natural systems. Full article

The Alhambra Monumental Ensemble (Granada, Spain) is a unique well-preserved palatine city from the medieval Islamic period, and it constitutes the best example of Nasrid architecture. In this work, we focus on the study of one of its most unknown decorations: Wall paintings with the appearance of red bricks. These faux-brick decorations are found in many different locations within the Alhambra complex, including both exterior and interior walls, arches and vaults. We have considered locations from different Nasrid reigns to gain information about their characteristics in terms of materials, execution techniques and conservation state. They have been studied combining a non-invasive methodology using portable equipment (X-ray fluorescence (XRF) and Raman spectroscopy) with complementary studies on selected samples (Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) and Raman microimaging). In general, those located in the exterior are poorly preserved, in contrast with the good conservation state of the interior motifs. The red rectangles of these decorations were painted over a white finishing layer, which acted also as the edge lines between these false bricks. The red colour was always due to hematite (α-Fe₂O₃), as revealed by its characteristic Raman bands. The use of a natural red ochre pigment (very abundant in the region) could be hypothesised considering XRF and SEM-EDS results. In general, the white layer was made of lime mortar and the presence of CaCO₃ in the painting layers suggests the use of lime-based techniques (either fresco or mezzo fresco). Only in one of the indoor locations, a different execution technique, based on gypsum (CaSO₄·2H₂O) plaster, was used. The identification of calcium oxalate in this location, in the form of weddellite (CaC₂O₄·2H₂O), can be interpreted as the result of organic binder degradation. Furthermore, superficial contamination with gypsum was always detected in outdoor locations. Full article