Fluoride geochemistry in groundwater at regulated industrial sites.

Few studies apply geochemical concepts governing fluoride fate and transport in natural waters to geochemical conditions at contaminated industrial sites. This has negative implications for designing sampling and compliance monitoring programs and informing remediation decision-making. We compiled geochemical data for 566 groundwater samples from industrial waste streams associated with elevated fluoride and that span a range of geochemical conditions, including alkaline spent potliner, near-neutral pH coal combustion, and acidic gypsum stack impoundments. Like natural systems, elevated fluoride (hundreds to thousands of ppm) exists at the pH extremes and is generally tens of ppm at near-neutral pH conditions. Geochemical models identify pH-dependent fluoride complexation at low pH and carbonate stability at high pH as dominant processes controlling fluoride mobility. Limitations in available thermochemical, kinetic rate, and adsorption/desorption data and lack of complete analyses present uncertainties in quantitative models used to assess fluoride mobility at industrial sites. PRACTITIONER POINTS: Geochemical fundamentals of fluoride fate and transport in groundwater are communicated for environmental practitioners. Fluoride is a reactive constituent in groundwater, and factors that govern attenuation are identified. Geochemical models are useful for identifying fluoride attenuation processes, but quantitative use is limited by thermodynamic data uncertainties.

Discarded substrates from soilless hydroponic horticulture as potential amendments for metal-contaminated soils.

Soil contamination with metals is a major threat for the environment and public health since most metals are toxic to humans and to non-human biota, even at low concentrations. Thus, new sustainable remediation approaches are currently needed to immobilize metals in soils to decrease their mobility and bioavailability. In this work, we explore the application of discarded substrates from hydroponic cultivation, namely coconut shell and a mixture of coconut shell and pine bark, for immobilization of metals (Cd, Cr, Ni, Cu, Pb, Hg, Sb and As) in a naturally contaminated soil from a mining region in Portugal. The immobilization capacity of substrates (added to the soil at 5% mass ratio) was assessed both individually and also combined with other traditional agriculture soil additives (limestone and gypsum, at 2% mass ratio) and nanoparticles of zero-valent iron (nZVI) at 1-3% mass ratio. The overall results obtained after a 30-d incubation showed that the discarded substrates are a viable, economic, and environmental-friendly solution for metal remediation in soils, with the capacity of immobilization ranging from 20 to 91% for the metals and metalloids studied. Furthermore, they showed the capacity to reduce the soil toxicity (EC50 ∼ 6000 mg/L) to non-toxic levels (EC50 > 10000 mg/L) to the bacteria Aliivrio fischeri.

Nutritional convergence in plants growing on gypsum soils in two distinct climatic regions.

BACKGROUND AND AIMS: Soil endemics have long fascinated botanists due to the insights they can provide about plant ecology and evolution. Often, these species have unique foliar nutrient composition patterns that reflect potential physiological adaptations to these harsh soil types. However, understanding global nutritional patterns to unique soil types can be complicated by the influence of recent and ancient evolutionary events. Our goal was to understand whether plant specialization to unique soils is a stronger determinant of plant nutrient composition than climate or evolutionary constraints. METHODS: We worked on gypsum soils. We analyzed whole-plant nutrient composition (leaves, stems, coarse roots and fine roots) of 36 native species of gypsophilous lineages from the Chihuahuan Desert (North America) and the Iberian Peninsula (Europe) regions, including widely distributed gypsum endemics, as specialists, and narrowly distributed endemics and non-endemics, as non-specialists. We evaluated the impact of evolutionary events and soil composition on the whole-plant composition, comparing the three categories of gypsum plants. KEY RESULTS: Our findings reveal nutritional convergence of widely distributed gypsum endemics. These taxa displayed higher foliar Sulfur and higher whole-plant Magnesium than their non-endemic relatives, irrespective of geographic location or phylogenetic history. Sulfur and Magnesium concentrations were mainly explained by non-phylogenetic variation among species related to gypsum specialization. Other nutrient concentrations were determined by more ancient evolutionary events. For example, Caryophyllales usually displayed high foliar Calcium, whereas Poaceae did not. In contrast, plant concentrations of Phosphorus was mainly explained by species-specific physiology not related to gypsum specialization or evolutionary constraints. CONCLUSIONS: Plant specialization to a unique soil may strongly influence plant nutritional strategies, as we described for gypsophilous lineages. Taking a whole-plant perspective (all organs) within a phylogenetic framework has enabled us to gain a better understanding of plant adaptation to unique soils when studying taxa from distinct regions.

Comparative analysis of cyanobacterial communities in gypsum outcrops: insights from sites in Israel and Poland.

Today, the biodiversity of endolithic microbial colonisations are only partly understood. In this study, we used a combination of molecular community metabarcoding using the 16S rRNA gene, light microscopy, CT-scan analysis, and Raman spectroscopy to describe gypsum endolithic communities in 2 sites-southern Poland and northern Israel. The obtained results have shown that despite different geographical areas, climatic conditions, and also physical features of colonized gypsum outcrops, both of these sites have remarkably similar microbial and pigment compositions. Cyanobacteria dominate both of the gypsum habitats, followed by Chloroflexi and Pseudomonadota. Among cyanobacteria, Thermosynechococcaceae were more abundant in Israel while Chroococcidiopsidaceae in Poland. Interestingly, no Gloeobacteraceae sequences have been found in Poland, only in Israel. Some of the obtained 16S rRNA gene sequences of cyanobacteria matched previously detected sequences from endolithic communities in various substrates and geographical regions, supporting the hypothesis of global metacommunity, but more data are still needed. Using Raman spectroscopy, cyanobacterial UV-screening pigments-scytonemin and gloeocapsin have been detected alongside carotenoids, chlorophyll a and melanin. These pigments can serve as potential biomarkers for basic taxonomic identification of cyanobacteria. Overall, this study provides more insight into the diversity of cyanobacterial endolithic colonisations in gypsum across different areas.

Gypsum Cave Biofilm Communities are Strongly Influenced by Bat- And Arthropod-Related Fungi.

The Gypsum Karst of Sorbas, Almeria, southeast Spain, includes a few caves whose entrances are open and allow the entry and roosting of numerous bats. Caves are characterized by their diversity of gypsum speleothems, such as stalactites, coralloids, gypsum crusts, etc. Colored biofilms can be observed on the walls of most caves, among which the Covadura and C3 caves were studied. The objective was to determine the influence that bat mycobiomes may have on the fungal communities of biofilms. The results indicate that the fungi retrieved from white and yellow biofilms in Covadura Cave (Ascomycota, Mortierellomycota, Basidiomycota) showed a wide diversity, depending on their location, and were highly influenced by the bat population, the guano and the arthropods that thrive in the guano, while C3 Cave was more strongly influenced by soil- and arthropod-related fungi (Ascomycota, Mortierellomycota), due to the absence of roosting bats.

Chemical improvement of soluble rocks: Foundation of Mosul Dam as case study.

The dissolution of soluble rocks (gypsum/anhydrite) beneath the Mosul Dam by water seepage has been observed upon the initial impoundment; consequently, several sinkholes have been manifested in the vicinity of the dam site. Traditional grouting has been envisaged as a potential remedy; however this measure has not eradicated the problem. The main purpose of this study is to overcome the solubility of the gypsum/anhydrite rocks using chemical grouts. Rock samples were acquired from the Fatha Formation outcrop and problematic layers of brecciated gypsum situated at varying depths beneath the Mosul Dam. Two commercially available liquid polymers, polyurethane (PU) and a mixture of acrylic and cement (ARC) were used to investigate their sealing performance in halting of the solubility of the rocks (gypsum/anhydrite). To simulate the dissolution phenomenon under the influence of artificial hydraulic pressure of the dam and the water flow in its abutments, two distinct laboratory models were devised. The outcomes from the experimental study on both untreated and treated samples revealed that the acrylic-cement composite (ARC) and polyurethane (PU) are influential polymers in halting the solubility of the gypsum rock samples under both factors of water pressure and high-velocity water flow.

A critical review on the use of flue gas desulfurization gypsum to ameliorate saline-alkali soils and its prospect for reducing carbon emissions.

Flue gas desulfurization gypsum (FGDG), a solid waste produced during sulfur removal in coal-fired power plants, has applications in saline-alkali soil amelioration due to its function of calcium­sodium ion exchange. Existing research has focused on the use of gypsum to improve saline-alkali soils in non-coastal areas. However, coastal areas are not only extensively salinized, but an important source of methane, and surprisingly, FGDG may assist to decrease methane formation mainly by the action of sulfate radical. This is the first critical review to systematically discuss the effects of FGDG on both saline-alkali soil improvement and carbon emission control in tidal flats, including application status, amendment principles, environmental risks and methane emission control. After adding FGDG, soil salinization degree was weakened via adjusting soil structure, pH, exchangeable sodium percentage and electric conductivity, introduction of nutrients also promotes crop growth. The optimal FGDG dosage in tidal flats seems to be higher (>2 %) than that in non-coastal areas (<1 %). Its environmental risks regarding heavy metals and eutrophication are evaluated safe. In tidal areas, more methane is produced in hot seasons and ebb tides. Plants and invertebrates also promote methane release. FGDG controls methane production by promoting the activity of sulfate-reducing bacteria and inhibiting methanogens. Considering methane flux levels and seawater erosion, FGDG use in low tidal beach needs more research, while that in high and middle tidal beach is recommended. This review will expand applications and appropriate use of FGDG for reducing carbon emission and improving ecological services in coastal areas.

MgO-based supersulfated cement with different industrial by-product gypsum: Experiments and molecular dynamics simulation.

Super sulfate cement (SSC) emerges as a sustainable alternative to ordinary Portland cement, boasting minimal carbon emissions and exceptional performance. As the quest for eco-friendly alternatives intensifies, there's a growing focus on exploring alkaline and sulfate activators conducive to SSC's environmental goals. This study delves into the viability of utilizing MgO as an alkaline activator in producing MgO-based supersulfated cement, while also investigating the impact of various industrial by-product gypsums on its performance. Findings reveal that employing MgO as an alkaline activator yields favorable hydration properties and mechanical strength in SSC. The optimized formulation comprises 15 % industrial by-product gypsum, 83 % granulated blast furnace slag (GGBFS), and 2 % MgO. Incorporating building gypsum and flue gas desulfurization (FGD) gypsum demonstrates superior unconfined compressive strength (UCS) growth compared to citric gypsum and phosphogypsum. Notably, gel-pores below 20 nm dominate the matrix, with variations in their distribution linked to the gypsum type used. The pH level and crystal structure of the industrial by-product gypsum emerge as pivotal factors dictating the hydration process. The interaction energy between hydrated building gypsum crystal planes and water molecules proves lower, contributing to the root cause of its high sulfate activating capability. Compared to traditional SSC, MgO-based supersulfated cement requires less alkaline activator content and accommodates more industrial by-product gypsums, thus reducing costs, CO2 emissions, and promoting the efficient utilization of these solid wastes.

Effect of Fiber Loading on Mechanical and Flame-Retardant Properties of Poplar-Fiber-Reinforced Gypsum Composites.

Gypsum-based composites were prepared via a slurry casting process using construction gypsum as the binding material and poplar fibers as reinforcing material. The effects of different fiber content and curing time on the mechanical properties, water resistance, and flame retardancy of these composites were investigated, and the influence mechanism was characterized by infrared spectroscopy, scanning electron microscopy, and X-ray diffractometry. The results showed that the best composite mechanical strength was achieved with 10% poplar fiber- content, and the absolute dry flexural and compressive strengths reached 3.59 and 8.06 MPa, respectively. Compared with pure gypsum, the flexural strength and compressive strength increased by 10% and 19%, respectively. The inclusion of fibers somewhat prevented the migration of free water within the composites and enhanced their water resistance. At 10% fiber content, the composite's 24 h water absorption rate was 34.3%, 8% lower than that of pure gypsum, with a softening coefficient of 0.55. However, fiber content increases the porosity of gypsum-based composites. When heated, this increased porosity accelerates' heat conduction within the matrix, raising the peak and total exothermic rates, thereby weakening the composites' inherently flame-retardant properties. Poplar-fiber-reinforced gypsum-based composites offered superior performance in commercial applications, compared to pure gypsum board, providing a sustainable and green alternative for ceilings, partitions, and other applications, while broadening the prospects for gypsum-based composites in the engineering field.

Impact of Superplasticizers on the Performance of Low-Grade Limestone-Based Cement Mixes.

Low-grade limestone (LGL) is not used to produce cement clinker, but this leftover material in cement quarries increases the water demand when used as a filler in concrete production. In this study, the effect of six commercial superplasticizers on the performance of cement mixes containing 35% LGL and 2% gypsum was investigated. The optimal doses of these superplasticizers were found in a range of different water/binder (w/b) ratios by conducting several Marsh cone and mini-slump tests. The addition of a superplasticizer with a higher active solid content produced a maximum cement flow, regardless of the w/b ratios. The LGL-based mortar samples admixed with this superplasticizer obtained a maximum compressive strength of about 36 MPa at the end of 28 days. SEM and XRD results showed the formation of a new calcium-rich mineral in their microstructure. These findings highlight the impact of the type and properties of superplasticizers on the performance of concrete mixes containing LGL as a supplementary cementitious material.

[Effects of Different Modified Materials on Soil Fungal Community Structure in Saline-Alkali Soil].

Studying the effects of different modified materials on the physicochemical properties and fungal community structure of saline-alkali soil can provide theoretical basis for reasonable improvement of saline-alkali soil. High-throughput sequencing technology was used to explore the effects of five treatments, namely, control (CK), desulfurization gypsum (T1), soil ameliorant (T2), organic fertilizer (T3), and desulfurization gypsum compounds soil ameliorant and organic fertilizer (T4), on soil physicochemical properties and fungal community diversity, composition, and structure of saline-alkali soil in Hetao Plain, Inner Mongolia. The results showed that compared with those in CK, the contents of available phosphorus, available potassium, organic matter, and alkali hydrolysis nitrogen were significantly increased in modified material treatments, and the T4 treatment significantly decreased soil pH. Modified treatments increased the Simpson and Shannon indexes of fungi but decreased the Chao1 index. The dominant fungi were Ascomycota, Basidiomycota, and Mortierellomycota, and the dominant genera were Mortierella, Conocybe, Botryotrichum, Fusarium, and Pseudogymnoascus. The application of modified materials increased the relative abundance of Ascomycota, Basidiomycota, Fusarium, and Pseudogymnoascus, while decreasing the relative abundance of Mortierellomycota, Chytridiomycota, and Mortierella. LEfSe analysis showed that modified treatments altered the fungal community biomarkers. Correlation analysis showed that pH and available potassium were the main environmental factors affecting fungal community structure. The results can provide scientific basis for improving saline-alkali soil and increasing soil nutrients in Hetao Plain, Inner Mongolia.

The Roles of Oil-Water Interfaces in Forming Ultrasmall CaSO4 Nanoparticles.

In natural and engineered environmental systems, calcium sulfate (CaSO4) nucleation commonly occurs at dynamic liquid-liquid interfaces. Although CaSO4 is one of the most common minerals in oil spills and oil-water separation, the mechanisms driving its nucleation at these liquid-liquid interfaces remain poorly understood. In this study, using in situ small-angle X-ray scattering (SAXS), we examined CaSO4 nucleation at oil-water interfaces and found that within 60 minutes of reaction, short rod-shaped nanoparticles (with a radius of gyration (Rg) of 17.2 ± 2.7 nm and a length of 38.2 ± 5.8 nm) had formed preferentially at the interfaces. Wide-angle X-ray scattering (WAXS) analysis identified these nanoparticles as gypsum (CaSO4·2H2O). In addition, spherial nanoparticles measuring 4.1 nm in diameter were observed at oil-water interfaces, where surface-enhanced Raman spectroscopy (SERS) revealed an elevated pH compared to the bulk solution. The negatively charged oil-water interfaces preferentially adsorb calcium ions, collectively promoting CaSO4 formation there. CaSO4 particle formation at the oil-water interface follows a nonclassical nucleation (N-CNT) pathway by forming ultrasmall amorphous spherical particles which then aggregate to form intermediate nanoparticles, subsequently growing into nanorod-shaped gypsum. These findings of this study provide insights into mineral scaling during membrane separation and can inform more efficient oil transport in energy recovery systems.

The antipyretic effect of the famous classical formula Qingwanzi Pills on a rabbit model and its serum metabolomic study.

Qingwanzi Pills (QP) were first mentioned in the "Puji Fang" of the Ming Dynasty, with a history of approximately 600 years. The formula consisted of Gypsum Fibrosum and Indigo Naturalis. It is a famous classical formula with antipyretic effects frequently utilized in ancient China, although our knowledge about the overall antipyretic mechanism of QP remains limited. Therefore, we replicated the fever model in New Zealand rabbits induced by lipopolysaccharide, performed the pharmacodynamic evaluation of QP, identified the differential metabolites among QP groups, and performed pathway enrichment analysis to comparatively analyze the effects of QP on fever-related metabolic pathways by ultra-performance liquid chromatography-mass spectrometry. The results showed that the antipyretic effect of QP was superior to that of each disassembled prescription, with Gypsum Fibrosum primarily contributing to the efficacy, followed by Indigo Naturalis and Junci Medulla. QP had an effective antipyretic effect, which was related to lowering the levels of TNF-α, IL-6, IL-1ß, and calcium in rabbit serum, lowering the levels of PGE2 and cAMP in rabbit cerebrospinal fluid, and increasing the level of calcium in rabbit cerebrospinal fluid. A total of 27 endogenous biomarkers were screened by serum metabolomics for the treatment of fever with QP. It is hypothesized that the antipyretic mechanism of QP may be related to regulating α-linolenic acid, sphingolipid, tryptophan, and bile acid metabolism. In summary, QP exhibited a significant antipyretic effect in rabbits with lipopolysaccharide-induced fever.

Synergistic effect of biochar with gypsum, lime, and farm manure on the growth and tolerance in rice plants under different salt-affected soils.

Soil salinization and sodication harm soil fertility and crop production, especially in dry regions. To combat this, using biochar combined with gypsum, lime, and farm manure is a promising solution for improving salt-affected soils. In a pot experiment, cotton stick biochar (BC) was applied at a rate of 20 t/ha in combination with gypsum (G), lime (L), and farm manure (F) at rates of 5 and 10 t/ha. These were denoted as BCG-5, BCL-5, BCF-5, BCG-10, BCL-10, and BCF-10. Three different types of soils with electrical conductivity (EC) to sodium adsorption ratio (SAR) ratios of 2.45:13.7, 9.45:22, and 11.56:40 were used for experimentation. The application of BCG-10 led to significant improvements in rice biomass, chlorophyll content, and overall growth. It was observed that applying BCG-10 to soils increased the membrane stability index by 75% in EC:SAR (2.45:13.7), 97% in EC:SAR (9.45:22), and 40% in EC:SAR (11.56:40) compared to respective control treatments. After BCG-10 was applied, the hydrogen peroxide in leaves dropped by 29%, 23%, and 21% in EC:SAR (2.45:13.7), EC:SAR (9.45:22), and EC:SAR (11.56:40) soils, relative to their controls, respectively. The application of BCG-10 resulted in glycine betaine increases of 60, 119, and 165% in EC: SAR (2.45:13.7), EC: SAR (9.45:22), and EC: SAR (11.56:40) soils. EC: SAR (2.45:13.7), EC: SAR (9.45:22), and EC: SAR (11.56:40) soils all had 70, 109, and 130% more ascorbic acid in BCG-10 applied treatment, respectively. The results of this experiment show that BCG-10 increased the growth and physiological traits of rice plants were exposed to different levels of salt stress. This was achieved by lowering hydrogen peroxide levels, making plant cells more stable, and increasing non-enzymatic activity.

Effect of Mineral Admixtures on Physical, Mechanical, and Microstructural Properties of Flue Gas Desulfurization Gypsum-Based Self-Leveling Mortar.

The production of flue gas desulfurization gypsum poses a serious threat to the environment. Thus, utilizing gypsum-based self-leveling mortar (GSLM) stands out as a promising and effective approach to address the issue. ß-hemihydrate gypsum, cement, polycarboxylate superplasticizer, hydroxypropyl methyl cellulose ether (HPMC), retarder, and defoamer were used to prepare GSLM. The impact of mineral admixtures (steel slag (SS), silica fume (SF), and fly ash (FA)) on the physical, mechanical, and microstructural properties of GSLM was examined through hydration heat, X-ray diffractometry (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) analyses. The GSLM benchmark mix ratio was determined as follows: 94% of desulfurization building gypsum, 6% of cement, 0.638% each of water reducer and retarder, 0.085% each of HPMC and defoamer (calculated additive ratio relative to gypsum), and 0.54 water-to-cement ratio. Although the initial fluidity decreased in the GSLM slurry with silica fume, there was minimal change in 30 min fluidity. Notably, at an SS content of 16%, the GSLM exhibited optimal flexural strength (6.6 MPa) and compressive strength (20.4 MPa). Hydration heat, XRD, and Raman analyses revealed that a small portion of SS actively participated in the hydration reaction, while the remaining SS served as a filler.

A Study of the Influence of Cement Addition and Humidity on the Mechanical Strength and Microstructure of Flue Gas Desulfurization Gypsum-Cement Plasters.

Over the last 20 years, flue gas desulfurization gypsum (FGD gypsum) has become a valuable and widely used substitute for a natural raw material to produce plasters, mortars, and many other construction products. The essential advantages of FGD gypsum include its high purity and stability, which allow for better technical parameters compared to natural gypsum, and, until recently, its low price and easy availability. This FGD gypsum is obtained in the process of desulfurization of flue gases and waste gases in power plants, thermal power plants, refineries, etc., using fossil fuels such as coal or oil. The gradual reduction in energy production from fossil raw materials implemented by European Union countries until its complete cessation in 2049 in favor of renewable energy sources significantly affects the availability of synthetic gypsum, and forces producers of mortars and other construction products to look for new solutions. The gypsum content in commonly used light plaster mortars is usually from 50 to 60% by mass. This work presents the results of tests on mortars wherein the authors reduced the amount of gypsum to 30%, and, to meet the strength requirements specified in the EN 13279-1:2008 standard, added Portland cement in the amount of 6-12% by mass. Such a significant reduction in the content of synthetic gypsum will reduce this raw material's consumption, thus extending its availability and developing other solutions. The study presented the test results on strength, density, porosity, pore size distribution, and changes in the microstructure of mortars during up to 180 days of maturation in conditions of increased relative humidity. The results show that decreased porosity and increased mechanical strength occur due to the densification of the microstructure caused by the formation of hydration products, such as C-S-H, ettringite, and thaumasite.

Eco-Design and Characterization of Sustainable Lightweight Gypsum Composites for Panel Manufacturing including End-of-Life Tyre Wastes.

The incorporation of rubber recycled aggregates from end-of-life tyres (ELT) in the manufacturing process of sustainable building materials has gained great interest in recent decades as a result of the large volume of this waste being generated annually. In this work, the objective is to make a contribution towards the circularity of construction products by carrying out a physico-mechanical characterisation of new gypsum composites made with the incorporation of these recycled rubber aggregates. To this end, up to 30% by volume of the original raw material has been substituted, analysing the mechanical resistance to bending and compression. Although lower than those of traditional gypsum material, both properties exceed the limits set at 1 and 2 MPa, respectively, by the current regulations. In addition, water absorption by capillarity significantly decreases, and thermal conductivity is reduced by more than 35% with respect to the reference material. Finally, in order to provide the research with a practical application, a prefabricated plate design has been proposed that incorporates the gypsum materials studied and an agglomerated rubber band that increases the thermal resistance and improves the efficiency of the designed construction system. In this way, this research reflects the potential of these novel building materials and explores new avenues for their application in building construction.

Visualizing the fibre texture of satin spar using laboratory 2D X-ray diffraction.

The suitability of point focus X-ray beam and area detector techniques for the determination of the uniaxial symmetry axis (fibre texture) of the natural mineral satin spar is demonstrated. Among the various diffraction techniques used in this report, including powder diffraction, 2D pole figures, rocking curves looped on φ and 2D X-ray diffraction, a single simple symmetric 2D scan collecting the reciprocal plane perpendicular to the apparent fibre axis provided sufficient information to determine the crystallographic orientation of the fibre axis. A geometrical explanation of the 'wing' feature formed by diffraction spots from the fibre-textured satin spar in 2D scans is provided. The technique of wide-range reciprocal space mapping restores the 'wing' featured diffraction spots on the 2D detector back to reciprocal space layers, revealing the nature of the fibre-textured samples.

Application of the Industrial Byproduct Gypsum in Building Materials: A Review.

The industrial byproduct gypsum is a general term for byproducts discharged from industrial production with calcium sulfate as the main ingredient. Due to the high number of impurities and production volume, the industrial byproduct gypsum is underutilized, leading to serious environmental problems. At present, only desulfurization gypsum and phosphogypsum have been partially utilized in cementitious materials, cement retarders, etc., while the prospects for the utilization of other byproduct gypsums remain worrying. This paper mainly focuses on the sources and physicochemical properties of various types of gypsum byproducts and summarizes the application scenarios of various gypsums in construction materials. Finally, some suggestions are proposed to solve the problem of the industrial byproduct gypsum. This review is informative for solving the environmental problems caused by gypsum accumulation.

Elucidating Amendment Resources for Reclaiming Efficacy of Sodic Soils around Abaya and Chamo Lakes, South Ethiopia Rift Valley.

BACKGROUND: Sodic soils are harmful to agricultural and natural environments in Ethiopia's semi-arid and arid regions, leading to soil degradation and reduced productivity. This study investigated how amendment resources could help improve the chemical properties of sodic soils around the Abaya and Chamo Lakes in the South Ethiopia Rift Valley. METHODS: A factorial experiment was conducted to study the effects of gypsum (GYP) and farmyard manure (FYM) on sodic soil reclamation. The experiment had four levels of GYP (0, 50, 100, and 150%) and four levels of FYM (0, 10, 20, and 30 tons ha-1), with three replications. The pots were incubated for three months and leached for one month, after which soil samples were collected and analyzed for chemical properties. ANOVA was performed to determine the optimal amendment level for sodic soil reclamation. RESULTS: The study found that applying 10 ton FYM ha-1 and gypsum at 100% gypsum required (GR) rate resulted in a 99.8% decrease in exchangeable sodium percentages (ESP) compared to untreated composite sodic soil and a 1.31% reduction over the control (GYP 0% + FYM 0 ton ha-1). As a result, this leads to a decrease in soil electrical conductivity, exchangeable sodium (Ex. Na), and ESP values. The results were confirmed by the LSD test at 0.05. It is fascinating to see how different treatments can have such a significant impact on soil properties. The prediction models indicate that ESP's sodic soil treatment effect (R2 = 0.95) determines the optimal amendment level for displacing Ex. Na from the exchange site. The best estimator models for ESP using sodic soil treatment levels were ESP = 1.65-0.33 GYP for sole gypsum application and ESP = 1.65-0.33 GYP + 0.28 FYM for combined GYP and FYM application, respectively. CONCLUSION: The study found that combined GYP and FYM applications reduced ESP to less than 10% in agriculture, but further research is needed to determine their effectiveness at the field level.