环境科学与技术最新文献

Herein, we propose preferential dissolution paired with Cu-doping as an effective method for synergistically modulating the A- and B-sites of LaMnO₃ perovskite. Through Cu-doping into the B-sites of LaMnO₃, specifically modifying the B-sites, the double perovskite La₂CuMnO₆ was created. Subsequently, partial La from the A-sites of La₂CuMnO₆ was etched using HNO₃, forming novel La₂CuMnO₆/MnO₂ (LCMO/MnO₂) catalysts. The optimized catalyst, featuring an ideal Mn:Cu ratio of 4.5:1 (LCMO/MnO₂-4.5), exhibited exceptional catalytic ozonation performance. It achieved approximately 90% toluene degradation with 56% selectivity toward CO₂, even under ambient temperature (35 °C) and a relatively humid environment (45%). Modulation of A-sites induced the elongation of Mn-O bonds and decrease in the coordination number of Mn-O (from 6 to 4.3) in LCMO/MnO₂-4.5, resulting in the creation of abundant multivalent Mn and oxygen vacancies. Doping Cu into B-sites led to the preferential chemisorption of toluene on multivalent Cu (Cu(I)/Cu(II)), consistent with theoretical predictions. Effective electronic supplementary interactions enabled the cycling of multiple oxidation states of Mn for ozone decomposition, facilitating the production of reactive oxygen species and the regeneration of oxygen vacancies. This study establishes high-performance perovskites for the synergistic regulation of O₃ and toluene, contributing to cleaner and safer industrial activities.

Ozone and its oxidation products result in negative health effects when inhaled. Despite painted surfaces being the most abundant surface in indoor spaces, surface loss remains one of the largest uncertainties in the indoor ozone budget. Here, ozone uptake coefficients (γ_O3) on painted surfaces were measured in a flow-through reactor where 79% of the inner surfaces were removable painted glass sheets. Flat white paint initially had a high uptake coefficient (8.3 × 10^-6) at 20% RH which plateaued to 1.1 × 10^-6 as the paint aged in an indoor office over weeks. Increasing the RH from 0 to 75% increased γ_O3 by a factor of 3.0, and exposure to 134 ppb of α-terpineol for 1 h increased γ_O3 by a factor of 1.6 at 20% RH. RH also increases α-terpineol partitioning to paint, further increasing ozone loss, but the type of paint (flat, eggshell, satin, semigloss) had no significant effect. A kinetic multilayer model captures the dependence of γ_O3 on RH and the presence of α-terpineol, indicating the reacto-diffusive depth for O₃ is 1 to 2 μm. Given the similarity of the kinetics on aged surfaces across many paint types and the sustained reactivity during aging, these results suggest a mechanism for catalytic loss.

Germicidal ultraviolet light (GUV) systems are designed to control airborne pathogen transmission in buildings. However, it is important to acknowledge that certain conditions and system configurations may lead GUV systems to produce air contaminants including oxidants and secondary organic aerosols (SOA). In this study, we modeled the formation and dispersion of oxidants and secondary contaminants generated by the operation of GUV systems employing ultraviolet C 254 and 222 nm. Using a three-dimensional computational fluid dynamics model, we examined the breathing zone concentrations of chemical species in an occupied classroom. Our findings indicate that operating GUV 222 leads to an approximate increase of 10 ppb in O₃ concentration and 5.2 μg·m^-3 in SOA concentration compared to a condition without GUV operation, while GUV 254 increases the SOA concentration by about 1.2 μg·m^-3, with a minimal impact on the O₃ concentration. Furthermore, increasing the UV fluence rate of GUV 222 from 1 to 5 μW·cm^-2 results in up to 80% increase in the oxidants and SOA concentrations. For GUV 254, elevating the UV fluence rate from 30 to 50 μW·cm^-2 or doubling the radiating volume results in up to 50% increase in the SOA concentration. Note that indoor airflow patterns, particularly buoyancy-driven airflow (or displacement ventilation), lead to 15-45% lower SOA concentrations in the breathing zone compared to well-mixed airflow. The results also reveal that when the ventilation rate is below 2 h^-1, operating GUV 254 has a smaller impact on human exposure to secondary contaminants than GUV 222. However, GUV 254 may generate more contaminants than GUV 222 when operating at high indoor O₃ levels (>15 ppb). These results suggest that the design of GUV systems should consider indoor O₃ levels and room ventilation conditions.

Despite the critical importance of virus disinfection by chlorine, our fundamental understanding of the relative susceptibility of different viruses to chlorine and robust quantitative relationships between virus disinfection rate constants and environmental parameters remains limited. We conducted a systematic review of virus inactivation by free chlorine and used the resulting data set to develop a linear mixed model that estimates chlorine inactivation rate constants for viruses based on experimental conditions. 570 data points were collected in our systematic review, representing 82 viruses over a broad range of environmental conditions. The harmonized inactivation rate constants under reference conditions (pH = 7.53, T = 20 °C, [Cl^-] < 50 mM) spanned 4 orders of magnitude, ranging from 0.0196 to 1150 L mg^-1 min^-1, and uncovered important trends between viruses. Whereas common surrogate bacteriophage MS2 does not serve as a conservative chlorine disinfection surrogate for many human viruses, CVB5 was one of the most resistant viruses in the data set. The model quantifies the role of pH, temperature, and chloride levels across viruses, and an online tool allows users to estimate rate constants for viruses and conditions of interest. Results from the model identified potential shortcomings in current U.S. EPA drinking water disinfection requirements.

Health risks of microplastic exposure have drawn growing global concerns due to the widespread distribution of microplastics in the environment. However, more evidence is needed to understand the exposure characteristics of microplastics owing to the limitation of current spectrum technologies, especially the missing information on small-sized particles. In the present study, laser direct infrared spectroscopy and thermal desorption-gas chromatography-mass spectrometry combined pyrolysis using a tubular furnace (TD-GC/MS) were employed to comprehensively detect the presence of plastic particles down to 0.22 μm in human excreted samples. The results showed that polyethylene (PE), polyvinyl chloride, PE terephthalate (PET), and polypropylene dominated large-sized (>20 μm) and small-sized plastic plastics (0.22-20 μm) in feces and urine. Moreover, fragments accounted for 60.71 and 60.37% in feces and urine, respectively, representing the most pervasive shape in excretion. Surprisingly, the concentration of small-sized particles was significantly higher than that of large-sized microplastics, accounting for 56.54 and 50.07% in feces (345.58 μg/g) and urine (6.49 μg/mL). Significant positive correlations were observed between the level of plastic particles in feces and the use of plastic containers and the consumption of aquatic products (Spearman correlation analysis, p < 0.01), suggesting the potential sources for plastic particles in humans. Furthermore, it is estimated that feces was the primary excretory pathway, consisting of 94.0% of total excreted microplastics daily. This study provides novel evidence regarding small-sized plastic particles, which are predominant fractions in human excretion, increasing the knowledge of the potential hazards of omnipresent microplastics to human exposure.

International arsenic trade, physical and virtual, has resulted in considerable transfer of arsenic pollution across regions. However, no study has systematically captured, estimated, and compared physical and virtual arsenic trade and its relevant impacts. This study combines material flow analysis and embodied emission factors to estimate embedded (including direct and indirect trade) and embodied arsenic trade during 1990-2019, encompassing 18 arsenic-containing products among 244 countries. Global embedded arsenic trade increased considerably from 47 ± 7.3 to 450 ± 68 kilotonnes (kt) during this time and was dominated by indirect arsenic trade, contributing 94 and 90% to global arsenic trade in 1990 and 2019, respectively. Since the 1990s, global arsenic trade centers and the main flows have shifted from European and American markets to developing countries. The mass of arsenic involved in embodied trade increased from 87.5 ± 26 kt in 1990 to 800 ± 236 kt in 2019. Direct trade and indirect trade aggravate arsenic environmental emissions in major importing countries, like China, while embodied trade aggravates arsenic environmental emissions in major exporting countries, like Peru and Chile. The trade-related arsenic pollution transfer calls for a rational arsenic emission responsibility-sharing mechanism and corresponding policy recommendations for different trading countries.

This study presents an updated analysis spanning over two decades (1999-2023) of climate, water quality, and operational data from two drinking water facilities in Atlantic Canada that previously experienced gradual increases in the natural organic matter (NOM) concentration and brownification. The goal was to assess the impact of recent extreme weather events on acute NOM concentration increases and drinking water treatment processes. In 2023, a dry spring combined with a warm and wet summer caused NOM in the water supplies to increase by >67% (as measured by color). To mitigate increased NOM concentration, the alum dose nearly doubled in 2023 compared to that in 2022. Disinfection byproducts were elevated following the event but remained within the compliance levels. From 1999 to 2023, the two plants responded to gradual climate change impacts and brownification, with alum dose increases of between 4.1 and 8.3 times. Equivalent CO₂ emissions were estimated for alum usage, which increased by 3 to 7-fold in 2023 compared to when the plants were commissioned decades prior. The plants were not only adversely impacted by climate change but also contributed to the global CO₂ burden. Thus, a paradigm shift toward sustainable alternatives for NOM removal is required in the water sector, and climate change adaptation and mitigation principles are urgently needed.