Weathering Mechanisms Research Articles

Weathering assessment approach for building sandstone using hyperspectral imaging technique

Weathering is one of the most common causes of building sandstone damage. The evolution of building sandstone in various weathering behaviors is critical for research. An intelligent assessment approach for classifying weathering degree of building sandstone in a humid environment is presented in this study. This synthesis method relates to three parts: microscopic observation of weathering characteristics, hyperspectral acquisition of weathered samples, and machine learning technology for a classification model. At first, weathering process is divided into initial weathered stage, accelerated weathered stage, and stable weathered stage according to the causes and mechanisms of weathering. Secondly, a novel classification method of weathering degree is proposed based on the weathering stage. Then, the mapping relationship between microscopic characteristics and hyperspectral image of shedding samples can be established in the visible and near-infrared spectral ranges (400–1000 nm) according to the change law of spectral absorption feature. Next, the spectral data of building sandstone with different weathering degrees are classified using Random Forest model. Furthermore, the hyperparameters of Random Forest model are optimized by Gray Wolf Optimizer algorithm for better performance. The trained model is finally applied to evaluate the weathering degree of large-scale sandstone walls quantitatively. The whole weathering assessment process is worth recommending for diagnosing and monitoring the building sandstone.

Degradation characteristics of SBS polymer and its contribution to weathering aging of modified asphalt

Under the weathering environment, the aging behavior of SBS-modified asphalt (SBSMA) is complex, including oxidation of matrix asphalt, degradation of SBS, and disruption of SBS-asphalt interaction. However, most studies on the weathering mechanism of SBS-modified asphalt have mainly been considered from its overall perspective and based on environmental variables. In order to investigate the aging mechanism of SBSMA more clearly, the paper proposes a novel method of SBS-independent weathering to determine the aging behavior of SBS under accelerated weathering conditions and its effect on the performance of modified asphalt. Finally, by correlating its samples (M1) with the behavior of different fresh SBSMA(M2) and weathering aged SBSMA(M3), the SBS effective content equation under weathering conditions and the conversion coefficient between different aging methods were determined. Furthermore, by analyzing the physicochemical properties of SBS polymers before and after weathering and comparing them with the calculated results of SBS effective content within modified asphalt, it is discussed that the swelling effect of SBS under this method differs due to different aging levels, which affects the complete separation of matrix asphalt oxidation and SBS degradation. The macroscopic rheological behavior of samples was evaluated by dynamic shear rheology experiments (DSR), the variation of their chemical component and molecular weight were analyzed by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC), and the microscopic network was observed by fluorescence microscopy (FM). The results illustrate that the degradation pattern of weathering SBS follows a single exponential decay function. The SBS effective content decreases to 66.7 %, 50 %, and 33.3 % after accelerated weathering for 5.8 h, 10.5 h, and 14.5 h, respectively. In addition, the conversion relationship between the effective content of SBS under two modes of SBS independent weathering aging and SBSMA weathering aging was established. The effective content of SBS within SBSMA at different service stages and its remaining modification capacity can be reasonably predicted by simple SBS weathering tests.

Li isotopic seasonality in a small catchment at the northeastern Tibetan Plateau: Roles of hydrology and temperature dependency

Silicate weathering is critical to sustain our habitable planet. Lithium (Li) isotopes enable us to investigate the nature of silicate weathering. A number of riverine Li isotope (δ7Lirw) investigations have been made from polar to equatorial terrains, but there remains no consensus about the controlling mechanisms of both weathering and δ7Lirw. Here we investigated δ7Lirw response to climate by collecting weekly river water samples in a small catchment (the Buha River within the Lake Qinghai basin) on the northeastern Tibetan Plateau, with stable tectonic, lithology, and topography. In the hydrology year of 2007 of the Buha River, we find that during the dry seasons, δ7Lirw ratios show temperature dependency typically, when the groundwater fed the river. During the monsoon seasons, δ7Lirw were obviously lower than the temperature dependency predicted values, when abundant rock dissolved and thereby fresh Li release into rivers. We propose that the hydrology and temperature dependency together play important roles in regulating δ7Lirw ratios in such an alpine small catchment. The mechanism is that long residence time facilitates the equilibrium chemical and Li isotopic fractionation during the dry seasons, so a temperature dependency of δ7Lirw is achieved. In contrast, rapid erosion and weathering contribution of fresh rock-like δ7Li to river water would significantly decrease δ7Lirw ratios during the monsoon seasons. This hypothesis can better interpret previously reported data of seasonal δ7Lirw variation, as a superposition between temperature dependency and hydrology regulation on silicates weathering in the small catchments besides tectonics.

Artificial weathering of plastics used in oyster farming

With the omnipresence of plastic litter from oyster farming in marine coastal areas, the objective of this work was to better understand the weathering of plastics used in this field, focusing on oyster spat collectors. During their use, around fifteen years, collectors made of polypropylene (PP) undergo numerous degradations, alternatively submerged, emerged in seawater, and stored outdoor until the next cycle. They weaken, crack, break, end up fragmenting and disseminated in the environment as microplastics associated to persistent organic pollutants. In this work, a comparison of 55 months of in situ weathering with five months of artificial weathering in air or in artificial seawater in a homemade UV chamber was conducted to better understand the mechanisms involved. Chemical, thermal and surface characterizations of virgin and weathered samples were conducted using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Environmental Scanning Electron Microscopy (ESEM). After 55 months of in situ weathering, collectors were notably damaged with large fissures and loss of microplastics (MPs) associated with an increase of carbonyl index values and a decrease of melting temperatures and crystallinity rates. Considering only UV irradiation, five months of artificial weathering at 30 °C under continuous irradiation of 6.9 W/m2 under UV lamps (295–400 nm) reproduced approximately 4.4 months of natural sunlight. Artificial weathering confirmed that photooxidation by combined effects of UV rays and oxygen was the main weathering mechanism and was reduced in seawater. These results help to understand the mechanisms involved in the weathering of these collectors in the marine environment and provide valuable information for industrials and professionals. Our study suggests a better storage away from UV rays and a reduction of the duration of use compared to current practices.

Weathering Mechanisms of Porous Marl Stones in Coastal Environments and Evaluation of Conservation Treatments as Potential Adaptation Action for Facing Climate Change Impact

This work presents the methodological approach followed for the study of the interaction of natural stone monuments with the local microclimate (exposure to RH, temperature alterations, wind, marine aerosol). This was implemented with the documentation of the associated weathering phenomena and the study of historic climate data of the area. The paper is focused on the main weathering mechanisms of the marly limestone at the Hellenistic theater of Zea in Piraeus, Greece. Based on the weathering phenomena identified, the development of the appropriate mitigation strategy was based on the physical, chemical and mechanical characterization of the natural stones, along with the evaluation of different conservation treatments, considering the characteristics of the coastal environment. Considering the mineralogy of marly limestones, silane-based materials were selected for providing both consolidation and water repellency effects. The evaluation of the conservation treatments was based on the modification of microstructural and water-related properties of natural stone samples, along with their consequent effect on their durability against accelerated aging tests. The results indicated that the design of migration actions proved to be multivariable parameter, depending on the intrinsic stone properties, the environmental parameters and the conservation efficacy of the treatments.

Hydrogeo-Chemical Processess and Evaluation of Groundwater Quality for Drinking and Irrigation Purposes in Afzalpur Taluk, Karnataka, India.

To determine the geochemical processes impacting groundwater geochemistry and its appropriateness for drinking and irrigational uses, a thorough examination of groundwater is conducted in some areas of the Afzalpur taluk. According to the results of a thorough chemical analysis, the research area's groundwater has a pH average between 6.7 and 6.3, making it fairly acidic. Mg2+ and Ca2+ cations and HCO3- anions are also present in high amounts. Ion-exchange and rock weathering mechanisms were perceived to dominate the groundwater chemistry, with anthropogenic sources playing a minor role. Particularly, the electrical conductivity, total hardness (TH), and concentrations of Na+ and HCO3- exceeded the BIS and WHO water quality standards' acceptable limits. Groundwater suitability for irrigation was assessed on the basis of sodium adsorption ratio, Na%, magnesium hazard (MH), residual sodium carbonate (RSC), and Kelley's index (KI). Above parameters revealed that nearly 40 to 50 % of the groundwater in the sampling sites was of high-quality for irrigation purpose.

A Fault and Capacity Loss Prediction Method of Wind Power Station under Extreme Weather

Extreme weather events can severely affect the operation and power generation of wind farms and threaten the stability and safety of grids with high penetration of renewable energy. Therefore, it is crucial to forecast the failure and capacity loss of wind farms under extreme weather conditions. To this end, considering the disaster‐causing mechanism of severe weather and the operational characteristics of wind farms, this paper first uses the density‐based spatial clustering of applications with noise algorithm to cluster the units in the wind farm based on the operating characteristics affected by the weather, and uses correlation analysis methods to extract key disaster‐causing factors in extreme weather; then proposes a prediction model based on feature‐weighted stacking integration. The model adopts the stacking‐integrated learning architecture to support multiple learners and performs feature weighting according to the prediction accuracy of each learner in the base learner, thereby improving the training effect of the meta‐learner and improving the prediction accuracy of the model. The prediction model is used to predict each wind turbine group based on the extracted key features and to predict the failure and capacity loss of the wind farm. Finally, an example analysis is performed based on actual data from a wind farm, and the results show that the proposed prediction method can effectively predict the operational reliability of wind farms.

High-speed and high-resolution 2D and 3D elemental imaging of corroded ancient glass by laser ablation-ICP-MS

Optimizing the LA-ICP-MS procedure to obtain 2D and 3D high-resolution multi-elemental imaging of heavily degraded Roman glass for studying glass weathering mechanisms by monitoring the lateral and in-depth distribution of elements.

Characteristics and a mechanism of dust weather in Northern China

Characteristics and a mechanism of dust weather in Northern China

A Mineral-Doped Micromodel Platform Demonstrates Fungal Bridging of Carbon Hot Spots and Hyphal Transport of Mineral-Derived Nutrients.

Soil fungi facilitate the translocation of inorganic nutrients from soil minerals to other microorganisms and plants. This ability is particularly advantageous in impoverished soils because fungal mycelial networks can bridge otherwise spatially disconnected and inaccessible nutrient hot spots. However, the molecular mechanisms underlying fungal mineral weathering and transport through soil remains poorly understood primarily due to the lack of a platform for spatially resolved analysis of biotic-driven mineral weathering. Here, we addressed this knowledge gap by demonstrating a mineral-doped soil micromodel platform where mineral weathering mechanisms can be studied. We directly visualize acquisition and transport of inorganic nutrients from minerals through fungal hyphae in the micromodel using a multimodal imaging approach. We found that Fusarium sp. strain DS 682, a representative of common saprotrophic soil fungus, exhibited a mechanosensory response (thigmotropism) around obstacles and through pore spaces (~12 μm) in the presence of minerals. The fungus incorporated and translocated potassium (K) from K-rich mineral interfaces, as evidenced by visualization of mineral-derived nutrient transport and unique K chemical moieties following fungus-induced mineral weathering. Specific membrane transport proteins were expressed in the fungus in the presence of minerals, including those involved in oxidative phosphorylation pathways and the transmembrane transport of small-molecular-weight organic acids. This study establishes the significance of a spatial visualization platform for investigating microbial induced mineral weathering at microbially relevant scales. Moreover, we demonstrate the importance of fungal biology and nutrient translocation in maintaining fungal growth under water and carbon limitations in a reduced-complexity soil-like microenvironment. IMPORTANCE Fungal species are foundational members of soil microbiomes, where their contributions in accessing and transporting vital nutrients is key for community resilience. To date, the molecular mechanisms underlying fungal mineral weathering and nutrient translocation in low-nutrient environments remain poorly resolved due to the lack of a platform for spatial analysis of biotic weathering processes. Here, we addressed this knowledge gap by developing a mineral-doped soil micromodel platform. We demonstrate the function of this platform by directly probing fungal growth using spatially resolved optical and chemical imaging methodologies. We found the presence of minerals was required for fungal thigmotropism around obstacles and through soil-like pore spaces, and this was related to fungal transport of potassium (K) and corresponding K speciation from K-rich minerals. These findings provide new evidence and visualization into hyphal transport of mineral-derived nutrients under nutrient and water stresses.

Aerobic respiration controls on shale weathering

The weathering of shale exerts an important control on the hydrochemical fluxes to river systems, thus influencing the global carbon, nutrient, and geochemical cycles. However, the quantitative understanding of shale weathering and its impact on global biogeochemical cycles remains inadequate due to the complex interplay between hydrological, biogeochemical, and physical processes. In this study, we develop a novel modeling approach to quantitatively interpret the long-term chemical weathering of shale occurring since the last glaciation period (15,000 years) leading to the present geochemical conditions. The model explicitly considers processes occurring across multiple phases and involved in the weathering, including: (i) the infiltration of meteoric water, (ii) the interactions between the water and the mineral assemblage via dissolution/precipitation reactions, (iii) the microbially-mediated oxidation of organic matter, (iv) the evolution of porosity induced by mineral reactions, and (v) the exchange of gases between the subsurface and the atmosphere. To implement and test our model, we conduct this study at a well-instrumented hillslope underlain by Mancos Shale and located at the East River study site, Western Colorado. Consistent with field observations, the model successfully reproduces the stratified weathering front, the complex spatial distribution of organic carbon, and the gaseous emissions of carbon dioxide from the subsurface. Model simulations show that aerobic respiration exerts a fundamental control on the weathering of shale. While previous studies have highlighted the diffusion of oxygen from the atmosphere as the primary mechanism for shale weathering, our model simulations demonstrate that aerobic respiration limits the propagation of oxygen in the shallow subsurface, and thereby inhibits the dissolution of pyrite at depth. Aerobic respiration is particularly favored in the top soil horizon due to the constant flux of oxygen from the atmosphere, the replenishment of fresh litter/plant-derived organic matter, and to a lesser extent the presence of fossil shale-associated organic matter. The acidic pore water generated through aerobic respiration within the shallow subsurface is transported to greater depths, where it sustains the dissolution of carbonate (dolomite in this example). Overall, our results demonstrate that the evolution of pyrite and carbonate depletion fronts are significantly different, and primarily depend on the ability of microorganisms to carry out microbial respiration and the various transport pathways of reactants controlling the mineral reactions under partially saturated conditions.

A feasible strategy for deep arsenic removal and efficient tungsten recovery from hazardous tungsten residue waste with the concept of weathering process strengthening

Tungsten residue waste (TRW), generated by tungsten hydrometallurgy, is classified as a hazardous solid waste by Chinese government due to its high content and leaching toxicity of arsenic, but is also a typical critical metal secondary resource of tungsten. Deep arsenic removal and tungsten recovery of TRW are beneficial to waste harmless treatment and circular economy. However, the occurrence state and weathering mechanism of arsenic in TRW have not been investigated and reported, which is the fundamental reason why the harmless treatment of TRW has become a bottleneck problem. In this paper, a feasible and novel strategy for deep arsenic removal and efficient tungsten recovery from TRW was proposed based on the concept of weathering process strengthening. The results show that arsenic in TRW mainly exists in the form of arsenopyrite, and ionically bound arsenic (V) generated by weathering of arsenopyrite directly leads to leaching toxicity of arsenic in TRW exceeding 5 mg/L. The environmental risk of arsenic in TRW can be completely eliminated by strengthening the uncontrollable and slow weathering process of TRW into a controllable and efficient process. Over 98 % of arsenic and 84 % of tungsten were simultaneously leached from TRW under optimal conditions via an enhanced pressure oxidation leaching process in alkaline solutions based on the leaching thermodynamic and kinetic, resulting in only 0.07 mg/L of arsenic leaching toxicity in the secondary leach residue. Hydrated ferric oxide (HFO) generated by the leaching process provides the possibility for the diffusion of reactants and products, so that arsenic and tungsten can be high-efficiently leached. The harmless secondary leach residue can be used as a raw material for the production of building materials, cement, and glass. Taking into account the reduction of alkali consumption and recovery of tungsten and arsenic, the leach solution was recycled. The closed-loop strategy shows great promise for the harmless treatment and tungsten recovery of TRW on an industrial scale to promote circular economy and environmental protection.

Experimental thermo-hydric study to simulate natural weathering conditions

• Development of an experimental setup realistically reproducing thermo-hydric strain. • Estimation and localization of the generated thermo-hydric stress. • Comparison of stones through the assessment of long-term stone weathering. Laboratory aging tests allow to indirectly study stones behaviors on a monument. Classic aging tests are designed to compare materials resistance to different weathering mechanisms: they are more intense than the on-site conditions and do not reflect the real weathering intensity and kinetics. To study the real weathering on a monument and the materials behavior, an experimental setup using realistic experimental conditions was designed. The stones of a monument in Reims (France) were studied through this experimental setup: the Courville limestone (original stone) and the Savonnières limestone (restoration stone). The environmental variations were taken into account through a previous climatic monitoring of the monument. The realistic experimental setup was designed to reproduce, in a stone sample, the thermal and hydric strains experienced by a stone on a vertical wall. Temperature and humidity variations were applied unidirectionally through one surface, defined as the exposed surface. The temperature and humidity variations were based on typical variations identified with an in-situ monitoring of the basilica: sunny day, cold and warm rainy days, and frost day. The mild conditions, similar to the on-site conditions, did not visibly damage the samples and their behavior was studied through temperature and strain variations. The Courville limestone appeared more sensitive to the thermo-hydric variations of the typical days, particularly by the presence of water in the porous network than the Savonnières. Water generated high stress in the wet layer due to hydric expansion and at the wet/dry interface due to strain difference. Furthermore, the ice formation in the wet layer could induce high stress. On the contrary, the Savonnières limestone did not appear sensitive and little to no stress was generated during the typical days. The realistic setup allowed a simulation of the temperature and water repartitions in the samples close to on-site conditions. It provided relevant information in this specific environment and could help anticipate stone weathering on the monument.

Source identification and weathering processes of tar ball deposited Qinhuangdao coast along the Bohai Sea, China.

Deposition of tar balls on the Qinhuangdao beaches along the coasts of the Bohai Sea (China) could affect people's leisure activities and tourism, and even affect the marine ecosystem. In 2020, representative tar balls collected from Qinhuangdao beaches, fingerprint analysis based on diagnostic ratios suggested that these tar balls were all very similar and may belong to the same source. Source identification by cross plot and principal component analysis (PCA), showed that the tar balls were likely from Penglai 19-3 crude oil. The weathering characterizations based on polycyclic aromatic hydrocarbons (PAHs), alkanes parameters and unresolved complex mixture (UCM), indicated that the tar balls had been significantly influenced by natural weathering processes such as evaporation, biodegradation and photooxidation. The study of this leakage provides a powerful support for determining the leakage source, evaluating the potential weathering mechanism and determining the accident liability. This is the first time to use fingerprint technology to identify the source of tar balls in Qinhuangdao coastal zone in the Bohai Sea.

Winter weathering of fractured sedimentary rocks in a temperate climate: observation of freeze–thaw and thermal processes on the Niagara Escarpment, Hamilton, Ontario

AbstractThe Niagara Escarpment is a fractured Palaeozoic sedimentary cuesta, subject to year-round weathering in a temperate climate. We examined the temperature of the rock surface and fractures at threein situsites with varying aspect and lithology, as well as the surface and interior of three control blocks maintained in outdoor conditions between December 2020 and March 2021. The objectives were to examine the interplay between freeze–thaw and thermal weathering in the winter months and to identify potential factors influencing these processes. Both diurnal-scale and prolonged freeze–thaw cycles differing in spatial and temporal extent were identified, coincident with periods of high moisture. We frequently observed rapid temperature changes (>1 °C min−1) at sites with strong insolation, which implies that the temperature regime is suitable for thermal shock and fatigue to occur. Site-specific factors, such as the aspect of the escarpment face and lithology, impact the mechanism and extent of weathering. Southeast-facing sites with high insolation are dominated by diurnal-scale freeze–thaw; west- and east-facing sites with lower insolation experience a more prominent prolonged freeze–thaw cycle. Across all sites there is a gradient between surface and fracture temperature that follows diurnal trends in air temperature and insolation. Variability in the surface-fracture gradient may enhance weathering processes by shifting the orientation and magnitude of stress, and by changing the spatial distribution of freezing and thawing. Our research indicates that site-specific factors and pre-existing fractures moderate the influence of air temperature and insolation on thermal gradients, and ultimately the weathering regime.

A unified multivariate statistical approach for the assessment of deep groundwater quality of rapidly growing city of Maharashtra Province, India, with potential health risk.

The main aim of this research is to assess the consequences of natural and anthropogenic processes on the groundwater quality of 65 deep aquifers of Nagpur city, Maharashtra Province, India, using a unified multivariate statistical approach. The dominant groundwater type recognized is Ca-HCO3 (recharge waters) in 43.1 and 38.5% of groundwater samples of pre- and post-monsoon seasons, followed by mixed water types. The seasonal distribution of physicochemical parameters shows increase in the concentration of EC, TDS, TH, Mg2+, SO42-, and NO3- signifying the high mineralization and anthropogenic loading from pre- and post-monsoon season respectively. The entropy-weight water quality index categorizes the 84.6% and 75.4% of total samples from pre- and post-monsoon seasons into moderate quality. The multiple linear regression and PCA analysis reveal the masking of rock weathering mechanism by anthropogenic activities. The % of PCA Variance varies from 79 to 83.7% from pre- to post-monsoon season. The high contributions of EC (0.76, 0.72), TDS (0.79, 0.73), TH (0.97, 0.962), Ca2+ (0.84, 0.78), Mg2+ (0.79, 0.83), Cl- (0.73, 0.75), and NO3- (0.78, 0.68) in PC1 components expose high salinity and hardness in urban groundwater that signifies the consequences of urbanization on the groundwater regime. About 55.4 and 70.8% of children population as compared to the adult female (53.8%, 69.2%) and male (32.3%, 46.1%) population in PRM and POM respectively were at high non-carcinogenic health threat of NO3--enriched groundwater. The study is beneficial for understanding the variation in groundwater composition due to unplanned urbanization and is very useful for protecting groundwater resources in urban areas.

Arsenic release from arsenopyrite weathering in acid mine drainage: Kinetics, transformation, and effect of biochar

Arsenopyrite (FeAsS) oxidative dissolution provides an important source for the occurrence of high arsenic in acid mine drainage (AMD). Biochar is a potent material that can dramatically sequestrate an array of heavy metals in water. However, little is known about the role of biochar on the fate of As from arsenopyrite in AMD. This study investigates the effects of biochar concentrations, AMD acidities, and temperatures on the release of As from arsenopyrite in a simulated AMD over a range of environmentally relevant conditions. Results show that biochar inhibits As release and further acidification without changing the arsenopyrite weathering mechanism. Arsenopyrite is first oxidized to Fe(II), As(III) and S0 and ultimately oxidized to Fe(III), As(V) and SO42-, respectively. Higher concentration, temperature or higher acidity promotes the arsenic release rate. Electrochemical studies showed that biochar inhibited As release and acidification for reduced the charge transfer resistance at the double layer and film resistance at the passivation layer, which was mainly attributed to Fe(III) ions in AMD being adsorbed, oxidized, and As complexed to biochar-Fe-As(V). This study reveals the release mechanism of As from arsenopyrite weathering in AMD and suggests the applicability of biochar in mitigating arsenic pollution and further acidification in sulfide mineral mine drainage.

Quantitative assessment of weathering of cretaceous sandstone relics in Longdong Area from the surface to the interior

Numerous cretaceous sandstone grottoes in Longdong area have been suffering from serious weathering, and the weathering is proceeding at a considerable rate, resulting in severe challenges for conservation practice. However, relatively little is known about the weathering behavior and mechanism of cretaceous sandstone in Longdong Area. In this study, cretaceous sandstone in North Grotto Temple was selected as a typical case, and the weathering characteristics from the surface to the interior in real environment were studied by field investigation and laboratory analysis (particle and pore size distribution, soluble salt content, microstructure, mineral and chemical composition). Cretaceous sandstones are mainly litharenite and feldspathic litharenite at the North Grotto Temple (NGT). Efflorescence and subflorescence were confirmed as the main weathering forms for litharenite and feldspathic litharenite, respectively. Sodium sulfate and sodium chloride observed from the SEM images were the most active soluble salts tend to accumulate at the certain depth below the surface (1 cm for litharenite and 3 cm for feldspathic litharenite). The salts migration kinetics inside the cliff were concluded based on the distribution of salts. The K-feldspar increased from the surface to the interior with the kaolinite, illite decreasing, indicating the corresponding alteration of K-feldspar in the surface layer. The weathering indexes indicated that the weathering degree along the depth was nonlinear, whereas the weathering degree was firstly increased and then decreased from the surface to the interior. The experimental results in this study can provide a better understanding for the weathering mechanisms of cretaceous sandstone in Longdong Area.

Assessment of chemical weathering mechanism and CO2 drawdown in distinct hydromicroclimate glacierized catchments, Western Himalayas

Assessment of chemical weathering mechanism and CO2 drawdown in distinct hydromicroclimate glacierized catchments, Western Himalayas

Concentration mechanism of fluorine, arsenic, and uranium in groundwater of the Hailar Basin, China

Located in a semiarid region of the Hulun Buir League in China’s Inner Mongolia Autonomous Region, the Hailar Basin is a region with less precipitation, where groundwater is the most important water supply source. It is important to study groundwater characteristics and hydrogeochemical processes for the better management of groundwater resources. Fluorine (F), arsenic (As), and uranium (U) cocontamination currently exists in the groundwater of the Hailar Basin, China. To understand the concentration mechanism of F, As, and U in groundwater in the study area, groundwater samples were collected for detection and analysis. The results showed that the main hydrochemical types in the study area were Cl–Na, HCO3–Na, and HCO3–Ca. The median values of F, As, and U were 3.32 mg/L, 0.029 mg/L, and 0.066 mg/L, respectively, which all exceeded the World Health Organization (WHO) guidelines. Through a Gibbs diagram and endmember diagram, it can be seen that the groundwater in the study area is mainly affected by the hydrogeochemical effects of evaporative crystallization, rock weathering mechanisms, and the dissolution of silicate rock and evaporative salt rock minerals. Mineral dissolution, cation exchange, and weakly alkaline environments are important factors affecting F concentrations. Low NO3− and SO42− concentrations cause a reducing environment, and the competitive adsorption of HCO3− promotes As pollution. The concentrations of Ca2+, Mg2+, SO42−, and NO3− have a great influence on the concentration of U.