Hydrogeochemistry and isotope hydrology were carried out to investigate the spatial distribution of fluoride (F−) and the mechanisms responsible for its enrichment in the western region of the Ordos basin, northwestern China. Sixty-two groundwater samples from the unconfined aquifer and fifty-six from confined aquifer were collected during the pre-monsoon (June 2016). Over 77% of groundwater samples from the unconfined aquifer (F− concentration up to 13.30 mg/L) and approximately 66% from confined aquifer (with a maximum F− concentration of 3.90 mg/L) exhibit F− concentrations higher than the Chinese safe drinking limit (1.0 mg/L). High-F− groundwater presents a distinctive hydrochemical characteristic: a high pH value and HCO3− concentration with Ca-poor and Na-rich. Mineral dissolution (e.g., feldspar, calcite, dolomite, fluorite), cation exchange and evaporation in the aquifers predominate the formation of groundwater chemistry, which are also important for F− enrichment in groundwater. Mixing with unconfined groundwater is a significant mechanism resulting in the occurrence of high-F− groundwater in confined aquifer. These findings indicate that physicochemical processes play crucial roles in driving F− enrichment and that may be useful for studying F− occurrence in groundwater in arid and semi-arid areas.

The main purpose of this study focused on the feasibility of geologic CO2 sequestration within the actual geological conditions of the first Carbon Capture and Storage (CCS) project in China. This study investigated CO2–water–rock interactions under simulated hydrothermal conditions via physicochemical analyses and scanning electron microscopy (SEM). Mass loss measurement and SEM showed that corrosion of feldspars, silica, and clay minerals increased with increasing temperature. Corrosion of sandstone samples in the CO2-containing fluid showed a positive correlation with temperature. During reaction at 70°C, 85°C, and 100°C, gibbsite (an intermediate mineral product) formed on the sample surface. This demonstrated mineral capture of CO2 and supported the feasibility of geologic CO2 sequestration. Chemical analyses suggested a dissolution–reprecipitation mechanism underlying the CO2–water–rock interactions. The results of this study suggested that mineral dissolution, new mineral precipitation, and carbonic acid formation-dissociation are closely interrelated in CO2–water–rock interactions.

The presence of potentially hazardous elements (PHEs) in playground soils is generally associated with anthropogenic sources such as vehicle traffic, industries, construction sites, and biomass burning. Studies indicate that PHEs are harmful to human health and may even be carcinogenic. Therefore, the aim of this study was to evaluate the physicochemical, morphological, and mineralogical properties of soil samples from three public playgrounds located in the cities of Bogota, Medellin, and Barranquilla. Besides, the possible impacts caused by the aerodynamics of particles in Colombian cities were verified. The morphology, composition, and structure of the nanoparticles (NPs) (< 100 nm) present in these soils were evaluated by field emission scanning electron microscopy (FE-SEM) equipped with high-precision field emission (FE) and high-resolution transmission electron microscopy (HR-TEM). Soil samples were predominantly feldspar, quartz, and, to a lesser extent, clay minerals, carbonates, and hematites. The average content of PHEs was anthropogenically enriched in relation to the upper continental crust. As and Sn showed a large spatial variation, indicating the influence of local sources, such as vehicle traffic and industries. There is an inverse relationship between the total concentrations of some elements and their leachable fractions. The accumulation of traffic-derived PHEs has a negative impact on human health and the environment, which is alarming, especially for elements such as Pb, Sb, or As. Therefore, the presence of PHEs should receive greater attention from public health professionals, and limits should be set and exposures controlled. This study includes the construction of a baseline that provides basic information on pollution, its sources, and exposure routes for humans in the vicinity of Colombia’s major cities, characterized by their increasing urbanization and industrialization.

Cement has been widely used for low- to intermediate-level radioactive waste management; however, the long-term modelling of multiple mineral transfer between the cement leachate and the host rock of a geological disposal facility remains a challenge due to the strong physical-chemical interactions within the chemically disturbed zone. This paper presents a modelling study for a 15-year experiment simulating the reaction of crystalline basement rock with evolved near-field groundwater (pH = 10.8). A mixed kinetic equilibrium (MKE) modelling approach was employed to study the dolomite-rich fracture-filling assemblage reacting with intermediate cement leachate. The study found that the mineralogical and geochemical transformation of the system was driven by the kinetically controlled dissolution of the primary minerals (dolomite, calcite, quartz, k-feldspar and muscovite). The initial high concentration of calcium ions appeared to be the main driving force initiating the dedolomitization process, which played a significant role in the precipitation of secondary talc, brucite and Mg-aluminosilicate minerals. The modelling study also showed that most of the initially precipitated calcium silicon hydrate phases redissolved and formed more stable calcium silicon aluminium hydrate phases. The findings highlight the importance of a deep and insightful understanding of the geochemical transformations based on the type and characteristics of the host rock, where the system is under out of equilibrium conditions, and the rates of mineral reactions.

Investigations were undertaken to study sorption of heavy metal ions from aqueous solution onto coal bottom ash. X-ray diffraction analysis of coal bottom ash indicated presence of feldspar (KAlSi₃O₈–NaAlSi₃O₈–CaAl₂Si₂O₈), mullite (Al₆Si₂O₁₃), and magnetite (Fe²⁺Fe³⁺₂O₄). Toxicity characteristics leaching procedure (TCLP) revealed that heavy metal ions such as Fe(II), Fe(III), Mn(II), Cu(II), Zn(II), As(III), As(V), Pb(II), and Cd(II) could be leached out from coal bottom ash. Continuous column test with the bottom ash showed negligible heavy metal ion leach-out at pH 6.0, although at pH 4.2 some heavy metal ion leaching, mainly of Mn(II), was observed. Batch sorption studies with individual heavy metal ions (Fe(II), Cu(II), Zn(II) and Mn(II)) revealed that the heavy metal ion sorption onto coal bottom ash could be described by pseudo-second-order kinetics. Sorption isotherm studies revealed that Langmuir isotherm could adequately describe the heavy metal ion sorption onto coal bottom ash with maximum adsorption capacity (qₘ) ranging from 1.00 to 25.00 mg/g for various heavy metal ions. Removal of heavy metal ions by coal bottom ash is attributed to both adsorption and hydroxide precipitation of heavy metals due to the presence of different oxides (i.e., SiO₂, Al₂O₃, Fe₂O₃, CaO) in coal bottom ash.

The present work elucidates the effective application of multivariate statistics in understanding the probable relations between surface water hydrochemistry and aquatic macrophyte productivity and their underlying seasonal dynamics in a remote mountainous lake of northeast India. The result of hierarchical cluster analysis revealed three distinct clusters corresponding to the pre-monsoon (35.42%), post-monsoon (52.08%), and monsoon (12.50%) seasons. The factor analysis yielded three principal components suggesting the sediment flux, farming discharge, domestic waste, bacterial oxidation of sulfur compounds, and dissolution of plant matters associated with dissolved feldspar minerals as the influential factors. The lake hydrochemistry also varied significantly, both spatially and temporally implying geogenic weathering processes from rock-soil-water interactions. Overall, sixteen aquatic macrophytes were identified, and their monthly and daily net primary productivity varied considerably in different seasons. Regression analysis highlighted the effect of temperature, total dissolved solids, electrical conductivity, and turbidity on the seasonal fluctuations in macrophyte productivity. Overall, the study provides insights into seasonal variation in the lake water chemistry and highlights the role of statistical tools in understanding the fragile aquatic ecosystems over cost-, labor-, and time-intensive inventory studies.

Accumulation of excess potentially toxic elements (PTEs) in soils poses a threat to human health as the agricultural ecosystem is closely related to the food chain. Accordingly, soil samples and groundwater samples were collected, and the soil samples were examined for pH, EC, As, Fe, Mn, Co, Cr, Cu, Al, Zn, Ni, Ba, B and F. The mean concentration of As, Co, Cr, Cu, Zn, Ni and Fe exceeded their geochemical background values impacting contamination from these toxic elements in the agricultural soils within study area. The PTEs-based various pollution indices are employed to aggregate and assess the toxic element pollution in the study area which indicates minor enrichment to moderately severe enrichment of Al, Ba, Cu, Zn, Fe, Mn, Ni and As within soils. This could be attributed to the accumulation of these elements from weathering of parent materials such as amphibolite, feldspar, hematite and ilmenite with partial input from the anthropogenic source like pesticides and fertilizers. Similarly, Nemerow comprehensive index also suggests that 60% of locations represent seriously contaminated class (Ps ≥ 5), due to the elevated concentrations of Cu, As and Zn. Likewise, the potential ecological risk with a mean value of 130.89, appears to be characterized by “considerable (100–200) to high contamination” (> 200) at about 53.33% locations. Hierarchical cluster analysis results also confirm that association of PTEs such as Cr, Ni, Fe, Mn, Zn, Ba and As in a cluster is indicative of anthropogenic source, and on the other hand, weathering of aluminosilicates of parent rock is mainly responsible for contamination of Co, Al, Cu and B. Above all, pH and F in soils have a close association with F in groundwater indicating the influence of soil in enriching F in groundwater, perhaps due to excessive drawdown of groundwater for agricultural activity.

The extraction of gold ore generates rejects called gold mining reject (GMR). This reject is considered a major environmental problem for the mining industry. In Amesmessa mine (Hoggar, Algeria), where mining have been carried out for over 15 years, about 2 million tons of mill tailings has been accumulated each year. The aim of this work is to study the reuse of GMR as raw material in ceramic field and its effect on microstructure, color, and mechanical and chemical properties. During investigation, the results show that GMR is mainly composed of quartz, hematite, pyrite, and dolomite. During sintering, mullite, quartz, anatase, and rutile were the mineralogical phases which composed the ceramic samples. As the temperature rises at 1200 °C, peaks of mullite increased, beside rutile and quartz phases. When 30 wt% of the reject was added, the crystalline phases as quartz and mullite diminished, giving rise to the glassy phase formation that is promoted by metal oxides playing a role as fluxing agents. Elastic property as Young’s modulus of the samples increased from 09.35 to 15.93 GPa and from 19.66 to 60.94 GPa at 1100 °C and 1200 °C respectively. The environmental study of the incorporation of GMR in ceramic matrix, rich in heavy metals (Fe, Zn, Ni), was evaluated by leaching tests of the fired products. The results indicated a successful immobilization of the heavy metals. These results suggested the use of gold mining reject in the ceramic field, as a substituent of feldspar, and might be an alternative and reliable method for the disposal of this reject.

We report on treatment and disposal of flue gas desulfurization (FGD) as a solid and hazardous waste. The effects of modified flue gas desulfurization residue (MFGDR) prepared by calcining a mixture of dry/semi-dry FGD residue, potassium feldspar, and/or limestone power on growth of plant and soil amelioration are investigated. The effect of MFGDR on the sweet potato was evaluated by analyzing the soil physiochemical properties and heavy metal speciation in the soil, and the yield, quality, and heavy metal concentrations of the sweet potato. The results indicated that applying MFGDR as soil ameliorant increased total yield by 53.38 %, safety, and the quality of sweet potato. The concentrations of Cd, Cr, Cu, Pb, and As in the sweet potato reduced by 31.34, 70.57, 22.17, 79.49, and 100 %, respectively. The improvements were attributed to enhancement of soil mineral composition contained in MFGDR. The MFGDR could also improve the soil physicochemical properties and decreased phytoavailability of heavy metals. The application of MFGDR in agriculture not only was a potential and useful technique for recycling and utilization of FGD residue, but also had potential benefits for soil amelioration, plant growth, and decrease of heavy metals in grown products.

Sediment, composed of a complex assemblage of minerals, controls the fate and behaviour of P in aqueous environments and affects trophic status. In this study, P adsorption was studied on minerals including quartz, hematite, potassium feldspar, montmorillonite, kaolin, and calcite (i.e., the main components of sediment) and sediment from the Guanting Reservoir. A general formula for P adsorption was proposed that considers mineral composition through the component additivity method, also incorporating the effects of environmental factors, including the aqueous P concentration (Cₑ), pH, sediment concentration (S), and ionic strength (IS). The P adsorption capacity gradually decreased with increasing particle size, and the contributions from kaolin and montmorillonite to P adsorption were significant despite representing only a small fraction of sediment (with a maximum amount of P adsorption of 0.92 and 0.36 mg/g, respectively). The content of quartz accounted for approximately 40–60% of sediment; however, its P adsorption capacity was only 0.13 mg/g. These minerals exhibited different adsorption characteristics due to their different surface morphologies and lattice structures. Multivariable regression analysis was used to show that the amount of P adsorption was strongly correlated with Cₑ, followed by S, IS, and pH.