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Distinctive, dark-coloured, glaze-like mineral accretions are common on low-angle surfaces in sandstone rock shelters in the Kimberley region of north-western Australia, where they provide an attractive medium for the production of deep engravings, and occasionally, are associated with painted rock art. These accretions form within the shelter dripline and are similar to those reported from other sites around the world, where they have been used for radiocarbon dating of associated rock art. This study uses extensive field observations and mineralogical analysis of 77 such oxalate-rich accretions collected at 41 different sites across a wide area of the north Kimberley region. The mineralogy of these accretions is dominated by well-crystallised calcium oxalate and sulphate minerals, most commonly whewellite and gypsum, with significant occurrences of phosphates in some samples. The accretions are typically several millimetres thick and characterised by distinctive internal laminations that show regular stacked undulations, giving a stromatolitic appearance under the microscope. Together with other apparently microbial features observed under the scanning electron microscope, these features provide strong support for a microbiological origin for these oxalate-rich accretions. The well-crystallised nature of the oxalates and the preservation of fine laminar features within the accretions supports their use for radiocarbon dating.

Ancient salt deposits preserve a record of highly specific environmental, climatic and biological conditions, including past surface water chemistry and water depths, local air temperatures, atmospheric composition and halophilic microorganisms. This paper presents the first sedimentological study of the mid‐Late Permian Belfast Harbour Evaporite Formation of Northern Ireland. This formation is dominated by bedded halite, contains some siliciclastic mudstone and bedded anhydrite, and is cross‐cut by intrusive igneous rocks. The bedded halite lithology contains bottom‐growth chevron and cornet crystals, efflorescent crusts and dissolution pipes, which are evidence of a saline surface brine that underwent periods of evapoconcentration, desiccation and flooding. The mudstone lithology contains dewatering structures, intraclasts and mudcracks, which indicate flooding and desiccation in dry mudflats. Bedded anhydrite was deposited as beds of gypsum cumulate crystals in saline surface waters. The Belfast Harbour Evaporite Formation was formed by saline lakes with associated mudflats, based on sedimentary characteristics and supported by mineralogical, geochemical and stratigraphic context. Diagenetic features reflect dissolution and cementation at the surface and shallow subsurface in the depositional environment and limited late‐stage alterations. Syndepositional dissolution pipes in bedded halite were formed by flooding events. Early halite cement is present in dissolution pipes and mudstones. Gypsum/anhydrite repeatedly dehydrated and rehydrated to form an interlocking crystal mosaic. Later features include fluid migration and the intrusion of mafic rocks. The Belfast Harbour Evaporite Formation was deposited by an ephemeral saline lake and dry mudflat system in an arid climate. This study, when compared to age‐equivalent continental deposits elsewhere, suggests that arid settings with saline lakes existed across much of Pangea during the Permo‐Triassic. The Belfast Harbour Evaporite Formation stratigraphically underlies the extremely low pH saline lakes of the Mercia Mudstone Group, implying that it aids in understanding the formation of Pangean acid brine lakes.

The treatment of flue‐gas desulfurization (FGD) gypsum, a common solid waste material that is often affected by chloride ions, typically occupies large amounts of land, causes resource waste, and results in environmental pollution. An emission reduction process involving the dechlorination of FGD gypsum and reducing its emissions has been proposed to solve these problems. Laboratory experiments were conducted to verify the feasibility of the emission reduction process and study any differences from the conventional process. The test results indicated that the average dechlorination rate of the emission reduction process was 80.4%, which is equivalent to 97.5% of the conventional process. The average dechlorination wastewater volume of the emission reduction process was 0.22 L, which is equivalent to 4.9% of the conventional process. The results show that the emission reduction process can effectively reduce the chlorine content of FGD gypsum and its related wastewater discharge. This novel gypsum dechlorination process effectively reduces the chlorine content of FGD gypsum and related wastewater. In addition, the emission reduction process can lead to greater recovery of renewable resources and can result in a cleaner energy conversion process. This process is an alternative method for recovering residues and resources without secondary pollution. Therefore, if this technology is integrated into existing FGD facilities, costly chemical processes could be replaced by those that recover a renewable resource and incorporate a clean energy conversion process.

A study was conducted to test the suitability of a range of organic and inorganic residuals mixed with municipal biosolids to create a soil amendment effective for a broad range of end uses. Biosolids suitable for unrestricted use were sourced from San Francisco, CA. Residuals including urban wood and yard waste, nut shells, biochar, and sawdust were sourced from nearby producers. Existing biosolids based soil products, peat, and a yard-food compost were used as controls. Experimental mixtures were tested for a range of soil properties, appearance, odor, germination, and growth response. Several mixtures performed as well as or better than the yard-food compost, and several performed comparably to the biosolids soil controls. Yard waste fines blended with biosolids in a 50:50 ratio by volume or yard waste fines blended with biosolids and 20% sand at 40:40:20 were highly effective across all measured indices. Mixed yard and recycled lumber fines blended with biosolids at these same ratios performed similarly well. Blends with a high percentage of char performed poorly in germination and growth response, likely as a result of elevated electrical conductivity. Certain blends such as gypsum and redwood shavings failed to mix well with biosolids to create a uniform looking material and were less visually appealing. In general, blends that met established quality control parameters for compost performed well on the measured indices. These results suggest that blending Class A biosolids with organic and inorganic feedstocks to meet quality criteria developed for compost will create marketable soil products.

Flue gas desulphurization (FGD) gypsum can effectively remediate sodic soils through improving two‐dimensional/three‐dimensional (3D) soil pore characteristics, especially vertical macroporosity. Understanding the response pattern of pore characteristics of sodic soils with different textures to FGD gypsum reclamation measures is critical to formulating appropriate improvement strategies for addressing growing challenges of land degradation. The objectives of this study were (a) to quantify the effect of FGD gypsum on two‐dimensional/three‐dimensional pore characteristics of amended sodic soils using X‐ray computed tomography (CT); and (b) to investigate the response pattern of different sodic soils to reclamation measures. Three types of intact sodic soils (sandy loam, silty loam, and silt soil) were collected from different sodic fields in north China for X‐ray CT image scan, and soil pore characteristic parameters (including porosity, pore network density, pore length density, and tortuosity) were measured. The results indicate that the high proportion of horizontal pores and lower pore length density are typical features in the sodic soils investigated. The responses of three sodic soils to reclamation measures demonstrate obvious variations that the 3D macroporosity of silt sodic soils was significantly increased (p

To elucidate the effects of salts on the properties of citric acid‐induced tofu gel, gelation was induced in the presence of KCl, CaCl₂ or CaSO₄, and gypsum tofu was used as a reference. The textural properties, water‐holding capacity (WHC), rheological behaviour, aggregate size distribution and microstructure of the tofu were evaluated. The results indicated that the addition of 0.10 g/100 mL KCl,0.05 g/100 mL CaCl₂ and 0.15 g/100 mL CaSO₄ yields more elastic tofu with high water‐holding capacity. The WHC of tofu induced in the presence of salts was similar to that of gypsum tofu, while the tofu was firmer and less elastic than gypsum tofu. The maximum elasticity of citric acid‐induced tofu was obtained with addition of 0.15 g/100 mL CaSO₄. These results are useful to understand the effects of different salts on soymilk gelation and provide a theoretical base for the quality improvement of citric acid‐induced tofu.

Knowledge of S fertilizer reaction products following application is needed to predict the ability of different fertilizer forms to provide sufficient plant-available S to crops. K-edge X-ray absorption near-edge structure (XANES) spectroscopy and wet chemical analysis techniques were used to identify the soil S species formed week to months after fertilization in the field on Brown Chernozem and Black Chernozem soils in Saskatchewan, Canada. The S fertilizer forms were ammonium sulfate, liquid ammonium thiosulfate, gypsum, elemental S, and a zero-S control treatment. Treatments were applied at seeding at 20 kg S ha⁻¹. Sulfur as ammonium sulfate, ammonium thiosulfate, and gypsum increased the extractable SO₄–S in the seed row 1 wk after application; thereafter, it decreased through plant uptake and runoff. For all fertilizers, total S concentration in the seed row increased after application and decreased over time. The XANES results showed that the highly oxidized sulfate form of S was dominant (45–55%) in ammonium sulfate- and gypsum-treated soils 1 wk following application. Thereafter, the proportion as sulfate decreased over time while the reduced and intermediate S forms increased. The proportion of reduced S was highest in the elemental S and ammonium thiosulfate treatments and the proportion in oxidized forms increased from Week 1 to Week 8. Overall, the highly oxidized fertilizer S forms applied (sulfates) transformed to intermediate and reduced S species via immobilization and reduction processes, whereas the highly reduced forms (e.g., elemental S) underwent some oxidation as reduced S decreased and highly oxidized sulfate increased.

Soil mineral composition affects soil behavior, but field estimation of mineral composition has proved difficult. To investigate the potential of predicting soil mineral composition in situ, 15 soils representing diverse mineral composition from New South Wales, Australia, were scanned with visible near-infrared (VisNIR) and portable X-ray fluorescence (pXRF) spectrometers to a depth of 1 m at 2.5-cm scanning increments. The presence of phyllosilicate and Fe oxides was assessed using a pattern-matching algorithm with VisNIR spectra from mineral end-member libraries. Rule-based iterative partitioning was then applied on pXRF elemental compositions based on mineral stoichiometry to determine the abundance of kaolinite, smectite, illite, hematite, goethite, calcite, gypsum, and quartz. This fusion model correctly identified the most abundant mineral in a sample with 72% accuracy. Mineral predictions were stable under variable moisture and surface conditions, as experienced when scanning samples in situ and under air-dry and ground conditions in the laboratory. Relative changes in mineral composition within a profile and across horizon boundaries were accurately expressed. The fusion model accurately quantified the abundance of quartz (Cohen’s kappa coefficient, 0.67), and CaCO₃ (Cohen’s kappa coefficient, 0.76; Lin’s concordance correlation coefficient, 0.96; RMSE, 20.9 g kg⁻¹). The dominant phyllosilicate mineral was identified correctly with 86% accuracy, although accurate quantification of phyllosilicates and Fe oxides was not achieved. Conjoint use of VisNIR and pXRF spectroscopy as part of a fusion model approach showed great potential to provide comprehensive estimation of soil mineral composition in situ.

The disposal of coal combustion fly ash (FA) generated from thermal power plants is a worldwide problem. However, its low bulk density and presence of calcium and iron–aluminium sesquioxide make it a prospective ameliorant alternative to gypsum for amending degraded sodic soils. A field experiment consisting of eight treatments with variable doses of FA and gypsum along with green manure (GM) was conducted for evaluating the amelioration mechanism by measuring changes in pH, exchangeable sodium percentage, zeta (ζ) potential, and properties of meso‐aggregates (0.5–2.0 mm). The results showed that compared with control, FA significantly reduced ζ‐potential, bulk density, and pH. The GM with FA further decreased ζ‐potential and increased hydraulic conductivity. The hydrolysis of iron and aluminium sesquioxide, present in FA, functioned to lower soil pH, whereas the reduction in exchangeable sodium percentage is attributed to bioavailable Ca (27.4%). A lower FA application rate produced better crop yields. FA 2.5% (w/w) alone, compared to the FA 5% (w/w), resulted in higher yield of rice (1.96 tonnes ha⁻¹), whereas 25% gypsum requirement (25GR) + FA 2.5% (w/w) and 25GR + FA 2.5% (w/w) + GM provided wheat yield on par with 50% gypsum requirement (50GR). The study identifies that where gypsum is scarce, the recommended amendment is 25GR + FA 2.5% or 25GR + FA 2.5% + GM when applied for sodic soil to achieve a similar yield response to standard 50GR. If gypsum is unavailable, a one‐time application of FA 2.5% (w/w) alone will improve the productivity of degraded sodic soils corresponding to more exchangeable calcium and organic carbon, which were found to be higher for meso‐aggregates (0.5–2.0 mm).

When used as a mineral binder, gypsum is thermally dehydrated and mixed with water, resulting in a paste hardening in the backreaction to calcium sulphate dihydrate (CaSO4 · 2 H2O). Although nowadays mainly hemihydratebased (CaSO4 · ½ H2O) binders are employed, higher firing temperatures in medieval kilns yielded anhydrite II (CaSO4). Except for the discrimination of the metastable phases anhydrite III and I due to different crystal structures, variations within the production temperature range of anhydrite II (approximately 300 to 1180°C) were not analytically accessible until recently. This study describes the development of an analytical technique, which is based on steady changes of band widths in room‐temperature Raman spectra of anhydrite II as a function of burning temperature. Raman microspectroscopic mapping experiments enable to pinpoint individual unreacted grains of thermal anhydrite in mortars and to discriminate them from natural anhydrites originating from the raw gypsum. The determination of band full widths at half maximum of down to 3 cm−1 and differences between them of a few tenths of wavenumbers is not a trivial task. Thus, a focus of this work is on peak fitting and strategies for correction of instrument‐dependent band broadening, which is often neglected also beyond the field of mortar analysis. Including other potential influences on band widths, burning temperatures of 400 to 900°C can be retraced in high‐fired medieval gypsum mortars with an uncertainty of approximately ± 50 K, as demonstrated with sample material of a stucco sculpture dated around 1400.

The effects of gypsum as a soil amendment and its interaction with nitrogen (N) applications in corn (Zea Mays L.) production are largely unknown. A 4-yr field study was conducted in Ohio, USA to evaluate (i) the effects of gypsum rates and rate frequencies at varying fertilizer N rates on corn grain yields, ear-leaf and grain nutrient concentrations, and on soil nutrients, and (ii) the interactive effects between N and gypsum applications. A split-plot experimental design was used with N rates (0, 84, 168, and 252 kg N ha–¹) as the main plot factor and either gypsum application rate (0, 1.1 and 2.2 Mg ha–¹) or application rate frequencies (i.e., 1.1 Mg ha–¹ annually, 2.2 Mg ha–¹ bi-annually, and 4.4 Mg ha–¹ once every four years) as subplot factors. Overall, corn yield response to gypsum applications was inconsistent. A positive corn yield response to gypsum application occurred only in 2017 at the Northwest site. Gypsum applied at 4.4 Mg ha–¹ significantly decreased yields at the Northwest site in 2017 and at the Wooster site in 2016 suggesting that the best management strategy may be to apply lower gypsum rates either annually or biannually. Gypsum applications did not improve corn response to N at either study site but significantly increased tissue, grain and extractable soil S concentrations with concentrations decreasing as the application frequency decreased. This suggests that where S deficiencies may occur, an annual rate of 1.1 Mg ha–¹ or a bi-annual application of 2.2 Mg ha–¹ would increase S availability.