Coupled redox cycling of arsenic and sulfur regulates thioarsenate enrichment in groundwater.

High­arsenic groundwater is influenced by a combination of processes: reductive dissolution of iron minerals and formation of secondary minerals, metal complexation and redox reactions of organic matter (OM), and formation of more migratory thioarsenate, which together can lead to significant increases in arsenic concentration in groundwater. This study was conducted in a typical sulfur- and arsenic-rich groundwater site within the Datong Basin to explore the conditions of thioarsenate formation and its influence on arsenic enrichment in groundwater using HPLC-ICPMS, hydrogeochemical modeling, and fluorescence spectroscopy. The shallow aquifer exhibited a highly reducing environment, marked by elevated sulfide levels, low concentrations of Fe(II), and the highest proportion of thioarsenate. In the middle aquifer, an optimal ∑S/∑As led to the presence of significant quantities of thioarsenate. In contrast, the deep aquifer exhibited low sulfide and high Fe(II) concentration, with arsenic primarily originating from dissolved iron minerals. Redox fluctuations in the sediment driven by sulfur­iron minerals generated reduced sulfur, thereby facilitating thioarsenate formation. OM played a crucial role as an electron donor for microbial activities, promoting iron and sulfate reduction processes and creating conditions conducive to thioarsenate formation in reduced and high­sulfur environments. Understanding the process of thioarsenate formation and the influencing factors is of paramount importance for comprehending the migration and redistribution of arsenic in groundwater systems.

Influence of Air Volume and Temperature in the Air Inlet Tunnel on the Characteristics of Dust Movement.

In order to clarify the movement characteristics of dust particles in the intake tunnel and improve the underground intake tunnel environment, the main intake tunnel of Wulihou Coal Mine was taken as the engineering background, the COMSOL simulation software was adopted to establish a model, the influence of air volume and temperature on dust movement characteristics was studied, and the critical air volume and particle size of dust at room temperature were determined. The results show that with the ventilation air volume being the same, when the dust reaches the exit of the tunnel, its falling height is positively correlated with the particle size. When the dust particle size is the same, the height of the dust falling is negatively correlated with the ventilation air volume. As the particle size of dust increases, the impact of changes in air volume on its movement decreases and the trajectory of dust movement gradually becomes consistent. The height of dust falling is negatively correlated with the air flow temperature. Therefore, when other factors remain unchanged, dust pollution in the tunnel is relatively severe during the day and the dust concentration in the tunnel is higher in summer. The critical air volume for dust emission in the intake tunnel of Wulihou Coal Mine is 75.84 m3/s, corresponding to a central wind speed of 5.29 m/s in the tunnel. The critical particle size for dust emission is 1.4 µm.

Arsenic transformation and redistribution in groundwater induced by the complex geochemical cycling of iron and sulfur.

Iron (hydr)oxides are effective sorbents of arsenic that undergo reductive dissolution when exposed to dissolved sulfide, which significantly impacts the movement and repartition of arsenic in groundwater. This study investigated the sulfidation of As-bearing ferrihydrite and its consequences on arsenic repartitioning as well as formation and transformation of secondary minerals induced by sulfide in batch experiments. The sulfidation of As(III) and As(V) adsorbed on ferrihydrite shows very different results. In the As(V) system, sulfidation resulted in the production of significant amounts of elemental sulfur (S0) and Fe2+, and Fe2+ and sulfide combine to form mackinawite. Subsequently, Fe2+ adsorbed and catalyzed the conversion of residual ferrihydrite to lepidocrocite. However, in the As(III) system, As(III) was protonated in the presence of sulfide to produce thioarsenate, which accounted for 87.9 % of the total aqueous arsenic concentration. The formation of thioarsenate also consumed the S0 produced by the sulfidation, resulting in no detectable S0 during solid phase characterization. The adsorption of thioarsenate on iron minerals notably affected the surface charge density of ferrihydrite, hindering the further formation of secondary minerals. Studies on the influence of thiolation on As-Fe-S system are of great significance for understanding the migration and redistribution of arsenic in groundwater systems under sulfur-rich conditions.

An amino-functionalized ordered mesoporous polymer as a fiber coating for solid phase microextraction of phenols prior to GC-MS analysis.

An amino-functionalized ordered mesoporous polymer (OMP-NH2) was synthesized and applied as a fiber coating for solid phase microextraction of polar phenols from environmental samples. The fiber coating was prepared by loading the OMP-NH2 powder onto a stainless steel wire through silicone gel. Combined with GC-MS, the fibers were employed to quantify trace of phenols in water through headspace-SPME. The characterization showed the OMP-NH2 to have a large specific surface area (420 m2 g-1) and good thermal stability (>400 °C). Due to its mesoporous structure and favorable interactions via hydrogen bonding and π stacking interactions with phenols, the sorbent represents a promising candidate for the separation and enrichment of polar phenols. Extraction conditions, such as temperature, extraction time, salt concentration, pH value and desorption time, were fully optimized. Under the optimized conditions, the coating exhibits an enrichment effect that is ~2-10 times better than that of a commercial polyacrylate coating. Figures of merit include (a) low limits of detection (0.05-0.16 ng L-1), (b) wide linear ranges (0.2-10,000 ng L-1), and (c) high enrichment factors (510-2272). The relative standard deviations for one fiber and fiber-to-fiber were in the range of 4.0-6.1% and 4.6-7.4%, respectively. The method was applied to the determination of phenols in water samples and gave satisfactory recoveries between 85.4 and 112.2%. Graphical abstract An amino-functionalized ordered mesoporous polymer (OMP-NH2) was synthesized by a solventless method and applied as headspace solid phase microextraction (HS-SPME) fiber coating for the extraction of polar phenols from the environmental samples.

In situ self-transformation metal into metal-organic framework membrane for solid-phase microextraction of polycyclic aromatic hydrocarbons.

In this work, a metal-organic framework (MOF) membrane coated copper wire (CW) was prepared as solid-phase microextraction (SPME) materials for extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples. The MOF based SPME fiber was fabricated by a facile and environment-friendly strategy, where the CW acted as both substrate and the copper ion source for MOF membrane growth. Characterization results confirmed that a uniform and dense HKUST-1 membrane was grown on the smooth surface of pristine CW. The effect of extraction parameters (i.e. extraction temperature, extraction time, desorption temperature, desorption time, and salt concentration) were fully optimized. Due to its large surface areas, the MOF membrane coated CW fiber showed good performance with great repeatability (2.6-14%, n = 5), low limits of detection (LODs, 0.12-9.9 ng L-1) and wide linear range (0.01-10 µg L-1). Moreover, the proposed method was proven to be highly effective for the determination of trace PAHs levels in real environmental water samples where the recoveries of PAHs were in the range of 80.8-114.1%, demonstrating that the as-prepared HKUST-1 membrane coated CW had great potential application in environmental water analysis.

Suspect screening and target quantification of human pharmaceutical residues in the surface water of Wuhan, China, using UHPLC-Q-Orbitrap HRMS.

In this study we developed a systematic method for suspect screening and target quantification of the human pharmaceutical residues in water, via solid phase extraction (SPE) followed by liquid chromatography-high resolution mass spectrometry (LC-HRMS). We then proceeded to study the occurrences and distribution of the pharmaceuticals in the surface waters of Wuhan, China, by analyzing water samples from lakes, rivers and municipal sewage. Initially, 33 human pharmaceuticals were identified from East Lake without using purchasing standards. Of these, 29 were later confirmed by using standards, and quantified using the aforementioned SPE pretreatment method and LC-HRMS analysis in full MS scan mode. The 29 compounds included 8 antibiotics, 9 metabolites, and 12 miscellaneous pharmaceuticals. The highest proportions of pharmaceutical residues were detected downstream of the Yangtze River and in the lakes close to the central city. Metformin, cotinine, and trans-3-hydroxy cotinine, were frequently encountered in all the surface water samples. High concentrations (>120 ng/l) of caffeine, metformin, theobromine, and valsartan were detected in the surface water samples; the removal rates of these compounds in the municipal sewage treatment plant were also high. In contrast, although the concentrations of 4-AAA and metoprolol acid in the surface water were high, the removal rates of these residues in the sewage treatment plant were low.