The velocity of near-surface materials is one of the most important for Ground-Penetrating Radar (GPR). In the study, we evaluate the options for determining the GPR velocity to measure the accuracy of velocity approximations from the acquired GPR data at an experimental site in Hangzhou, China. A vertical profile of interval velocities can be estimated from each common mid-point (CMP) gather using velocity spectrum analysis. Firstly, GPR data are acquired and analyzed using the popular method of hyperbola fitting which generated surprisingly high subsurface signal velocity estimates while, for the same profile, the Amplitude variation with offset (AVO) analysis of the GPR data (using the same hyperbola fitting method) generate a more reasonable subsurface signal velocity estimate. Several necessary processing steps are applied both for CMP and AVO analysis. Furthermore, experimental analysis is conducted on the same test site to get velocities of samples based on dielectric constant measurement during the drilling process. Synthetic velocities generated by AVO analysis are validated by the experimental velocities which confirmed the suitability of velocity interpretations.

This study introduces a series of Fe/Mn-GOCS composites using high-temperature impregnation with graphene oxide and chitosan as substrates, modified by diverse manganese salts, including MnCl₂∙4H₂O, KMnO₄, and MnSO₄. Among these, FeCl₂/MnSO₄-GOCS demonstrated the highest adsorption capacity for Sb(III), peaking at 57.69 mg/g. The adsorption performance was extensively evaluated under various conditions, such as different initial concentrations, pH levels, solid–liquid ratios, and adsorption durations. It was observed that when the Fe/Mn molar ratio exceeded 4:1, there was a notable decrease in both the adsorption capacity and removal rate. Kinetic analyses using the pseudo-second-order model revealed a better fit (R² > 0.99) compared to the pseudo-first-order model, indicating that chemisorption dominated the adsorption process. Additionally, isothermal modeling highlighted the efficiency of Fe/Mn-GOCS, particularly in high-concentration environments, with the Sips model demonstrating the best fit, integrating characteristics of both Langmuir and Freundlich models. These results not only offer a robust theoretical and practical basis for efficient Sb(III) removal but also underscore the potential of multi-metal-modified adsorbents as sustainable solutions for environmental remediation.

Antimony (Sb) is one of the most concerning toxic metals globally, making the study of methods for efficiently removing Sb(III) from water increasingly urgent. This study uses graphene oxide and chitosan as the matrix (GOCS), modifying them with FeCl₂ and four MnO_x to form iron–manganese oxide (FM/GC) at a Fe/Mn molar ratio of 4:1. FM/GC quaternary composite microspheres are prepared, showing that FM/GC obtained from different MnO_x exhibits significant differences in the ability to remove Sb(III) from neutral solutions. The order of Sb(III) removal effectiveness is MnSO₄ > KMnO₄ > MnCl₂ > MnO₂. The composite microspheres obtained by modifying GOCS with FeCl₂ and MnSO₄ are selected for further batch experiments and characterization tests to analyze the factors and mechanisms influencing Sb(III) removal. The results show that the adsorption capacity of Sb(III) decreases with increasing pH and solid–liquid ratio, and gradually increases with the initial concentration and reaction time. The Langmuir model fitting indicates that the maximum adsorption capacity of Sb(III) is 178.89 mg/g. The adsorption mechanism involves the oxidation of the Mn-O group, which converts Sb(III) in water into Sb(V). This is followed by ligand exchange and complex formation with O-H in FeO(OH) groups, and further interactions with C-OH, C-O, O-H, and other functional groups in GOCS.

Monothioarsenate (MTAs^V) is one of the major arsenic species in sulfur- or iron-rich groundwater, and the sediment adsorption of MTAs^V plays an important role in arsenic cycling in the subsurface environment. In this study, batch experiments and characterization are conducted to investigate the sorption characteristic and mechanism of MTAs^V on natural sediments and the influences of arsenite and arsenate. Results show that MTAs^V adsorption on natural sediments is similar to arsenate and arsenite, manifested by a rapid early increasing stage, a slowly increasing stage at an intermediate time until 8 h, before finally approaching an asymptote. The sediment sorption for MTAs^V mainly occurs on localized sites with high contents of Fe and Al, where MTAs^V forms a monolayer on the surface of natural sediments via a chemisorption mechanism and meanwhile the adsorbed MTAs^V mainly transforms into other As species, such as AlAs, Al-As-O, and Fe-As-O compounds. At low concentration, MTAs^V sorption isotherm by natural sediments becomes the Freundlich isotherm model, while at high concentration of MTAs^V, its sorption isotherm becomes the Langmuir isotherm model. The best-fitted maximum adsorption capacity for MTAs^V adsorption is about 362.22 μg/g. Furthermore, there is a competitive effect between MTAs^V and arsenate adsorption, and MTAs^V and arsenite adsorption on natural sediments. More specifically, the presence of arsenite greatly decreases MTAs^V sorption, while the presence of MTAs^V causes a certain degree of reduction of arsenite adsorption on the sediments before 4 h, and this effect becomes weaker when approaching the equilibrium state. The presence of arsenate greatly decreases MTAs^V sorption and the presence of MTAs^V also greatly decreases arsenate sorption. These competitive effects may greatly affect MTAs^V transport in groundwater systems and need more attention in the future.

Mineral extraction can significantly affect the groundwater flow and hydrochemical environment. However, for hilly areas, significant ground elevation changes and complex geological conditions make it difficult to accurately analyze and predict the impact of mineral mining. This study takes the Nuodong rare earth mining area as an example. Based on field investigations and experiments, GOCAD software (version 2022) was used to establish a geological model in combination with GMS numerical simulation software, which was used to build a groundwater flow model and a solute transport model. The flow model in the hilly area indicated that the absolute error between the simulated and measured water levels of each observation well is 0.554 m. The solute-transport model showed that the maximum pollutant concentration of ammonia-nitrogen (NH₃-N) in the liquid injection area, stream area, and village area monitoring wells reaches 139.15, 27.9, and <0.5 mg/L, respectively. During the mining period, streams in the area are affected by NH₃-N, which threatens the safety of the water for mine area residents. To control pollutant transport, two stages of pumping were adopted to reduce NH₃-N concentrations in groundwater. After adopting the first stage, the peak concentration of the stream area monitoring wells decreased significantly, with the maximum peak concentration decreasing from 27.9 mg/L to 5.51 mg/L. Based on the results of the first stage of the pump-out treatment, a second stage was adopted. The model results showed that the peak concentration of NH₃-N pollutants discharged into the stream is less than 0.5 mg/L. The results provide a theoretical basis and reference for groundwater monitoring and pollution control after mining in this area.

Environmental air pollution has become an important threat to human health. As one of the major air pollutants, atmospheric particulates have received attention widely. In which, ultrafine particulate matters (UPM) with diameter below 0.1μm have become the main components of ambient air particulates, posing a serious threat to the health of the organism. Therefore, this paper investigated and summarized the research on ultrafine particles at home and abroad, systematically analysed the sources of UPM in ambient air, investigated its toxicological effects of ultrafine particles on the respiratory system, cardiovascular system, and central nervous system of organisms. This study will provide a theoretical reference for environmental air protection and pollution control in China.