Search Results (75)

Litter decomposition regulates the quantity and quality of plant-derived carbon (C) and nitrogen (N) inputs to soil and is closely associated with microbial community structure. However, how elevated ozone (O₃) and nitrogen (N) addition interactively affect residual litter inputs and their associations with soil microbial communities remains poorly understood, especially in agroforestry systems. Here, we conducted a 12-month in situ litter decomposition experiment using two poplar clones (107 and 546) under ambient or elevated O₃ with or without N addition (60 kg N ha⁻¹ yr⁻¹) at an O₃-FACE platform in northern China. Litter mass and chemical traits were measured during decomposition, and endpoint soil microbial community structure was characterized using phospholipid fatty acid (PLFA) profiling. Treatment effects and litter–microbe associations were evaluated using linear mixed-effects models, correlation analysis, and redundancy analysis (RDA). Endpoint litter mass remaining was significantly affected by O₃, clone identity, and their interactions with N addition, while endpoint litter chemical traits showed trait-specific responses. PLFA-derived microbial community indices also showed treatment- and clone-dependent responses, particularly in bacterial groups, AM fungi, and the fungal-to-bacterial ratio. Endpoint litter mass remaining showed the strongest statistical association with PLFA-derived microbial community structure, whereas individual nutrient concentrations showed weaker independent effects. These findings suggest that O₃- and N-induced changes in residual litter quantity and quality are associated with shifts in PLFA-derived microbial community structure. Because PLFA characterizes microbial community structure rather than process rates, these findings should be interpreted as evidence of structural microbial reorganization associated with altered residual litter inputs, rather than direct evidence of changes in C or N cycling rates. Full article

Ground-level ozone (GLO₃) poses a critical threat to public health and the success of the Saudi Green Initiative, yet its long-term spatiotemporal evolution across the Arabian Peninsula remains poorly constrained. Utilizing CAMS-derived mixing ratios (1000–850 hPa) from 2003 to 2024, this study identifies a major systemic regime shift occurring in 2016–2017, marking a transition toward a more O₃-enriched atmospheric state across Saudi Arabia. While the early study period was characterized by pronounced spatial heterogeneity, post-2017 diagnostics reveal a synchronized intensification of GLO₃, particularly within the urban industrial belts of the Eastern and Western Provinces. Statistical trend metrics, including Mann–Kendall and regime-shift detection, show a persistent upward trend in GLO₃ concentrations, most significantly during winter and over the southwestern highlands. These trends are robustly coupled with increasing boundary-layer height, temperature, and UV-B radiation, alongside shifting precursor stoichiometry (CO, VOCs, NO_x) that separates titration-dominated from production-dominated regimes. Our results suggest that this mid-decade intensification reflects a convergence of anthropogenic forcing under Saudi Vision 2030 and shifting regional climatic drivers. By uncovering the transition from localized variability to kingdom-wide synchronization, this research provides a process-based foundation for targeted air quality management and the safeguarding of regional sustainability frameworks. Full article

Twenty years of MODIS satellite data (2002–2022), TROPOMI glyoxal observations (2018–2022), and ground-based isoprene measurements were used to examine vegetation greenness (NDVI) and atmospheric glyoxal over Houston, Texas. Biogenically produced glyoxal grew by 51% between 2018 and 2022, despite a 2% per decade decrease in summer vegetation greenness and continued urbanization. Ambient mixing ratios of isoprene, the main biogenic glyoxal precursor, paradoxically dropped by 14% within the same time frame. Temperature (+0.68 °C/year), ozone (+28%), and photochemical oxidants all significantly increased over this time, according to analysis of concurrent environmental data. The results indicate that higher temperature-driven isoprene emissions (+35%) and accelerated photochemical oxidation (+10%) overcame the declining vegetation signal, resulting in net increases in atmospheric glyoxal. This suggests that Houston’s remaining flora is experiencing temperature-driven changes in biogenic volatile organic compound (VOC) emissions per unit area, even while its greenness has reduced. Full article

Oxygen–ozone (O₂–O₃) therapy is widely used for treating lumbar disc herniation. However, controversy remains regarding the safest and most effective route of administration. While intradiscal injection is purported to show clinical efficacy, it has also been associated with serious complications. In contrast, the intramuscular route can exhibit a more favourable safety profile and comparable pain outcomes, suggesting its potential as a safer alternative in selected patient populations. This mixed-method study combined computed tomography (CT) imaging, biophysical diffusion modelling, and a meta-analysis of clinical trials to evaluate whether intramuscular O₂–O₃ therapy can achieve disc penetration and therapeutic efficacy comparable to intradiscal nucleolysis, while minimizing procedural risk. Literature searches across PubMed, Scopus, and Cochrane databases identified seven eligible studies (four randomized controlled trials and three cohort studies), encompassing a total of 120 patients. Statistical analyses included Hedges’ g, odds ratios, and number needed to harm (NNH). CT imaging demonstrated gas migration into the intervertebral disc within minutes after intramuscular injection, confirming the plausibility of diffusion through annular micro-fissures. The meta-analysis revealed substantial pain reduction with intramuscular therapy (Hedges’ g = −1.55) and very high efficacy with intradiscal treatment (g = 2.87), though the latter was associated with significantly greater heterogeneity and higher complication rates. The relative risk of severe adverse events was 6.57 times higher for intradiscal procedures (NNH ≈ 1180). O₂–O₃ therapy offers a biologically plausible, safer, and effective alternative to intradiscal injection, supporting its adoption as a first-line, minimally invasive strategy for managing lumbar disc herniation. Full article

Investigating atmospheric volatile organic compounds (VOCs) is critical for understanding their sources, chemical reactivity, and impacts on air quality, climate, and human health, especially in remote regions like the Tibetan Plateau where baseline data remains scarce. In this study, ambient VOCs species were simultaneously measured at four remote background sites on the Tibetan Plateau (Nyingchi, Namtso, Ngari, and Mount Everest) from 2012 to 2014 to investigate their concentration, composition, sources, and chemical reactivity. Weekly integrated samples were collected and analyzed using a Gas Chromatograph-Mass Spectrometer/Flame Ionization Detector (GC-MS/FID) system. The total VOC mixing ratios exhibited site-dependent variability, with the highest levels observed in Nyingchi, followed by Mount Everest, Ngari and Namtso. The VOC composition in those remote sites was dominated by alkanes (25.7–48.5%) and aromatics (11.4–34.7%), followed by halocarbons (19.1–28.1%) and alkenes (11.5–18.5%). A distinct seasonal trend was observed, with higher VOC concentrations in summer and lower levels in spring and autumn. Source analysis based on correlations between specific VOC species suggests that combustion emissions (e.g., biomass burning or residential heating) were a major contributor during winter and spring, while traffic-related emissions influenced summer VOC levels. In addition, long-range transport of pollutants from South Asia also significantly impacted VOC concentrations across the plateau. Furthermore, reactivity assessments indicated that alkenes were the dominant contributors to OH radical loss rates, whereas aromatics were the largest drivers of ozone formation potential (OFP). These findings highlight the complex interplay of local emissions and regional transport in shaping VOC chemistry in this high-altitude background environment, with implications for atmospheric oxidation capacity and secondary pollutant formation. Full article

Industrial organic wastewater, with its complex composition, high biological toxicity, and recalcitrance, has become a major challenge in water pollution control. This is especially true for antibiotic-containing wastewater, such as ofloxacin wastewater, for which there is an urgent need to develop effective treatment technologies. Conventional treatment processes are insufficiently efficient, while individual advanced oxidation processes (AOPs) have drawbacks such as poor oxidation selectivity and catalyst deactivation. To address these issues, researchers have explored the coupling of different AOPs and found that such combinations can enhance the oxidation performance, achieve complementary advantages, reduce the equipment costs, and offer great development potential. An experiment was conducted to evaluate the performance of an Ozone-Electro-Fenton coupled process in treating ofloxacin industrial wastewater. The results demonstrated that under the same conditions, after four hours of treatment, the coupled process achieved a 70% reduction in the UV absorption peak of the wastewater, compared to less than 20% for individual processes, indicating a significant synergistic effect. Further optimization of the ozone aeration structure revealed that with a hole size of 0.5 mm, single-layer aeration holes, and six holes, the COD removal rate reached 96% after six hours, the ozone utilization improved to 85%, and the gas holdup stabilized at 4.6%. Under these conditions, the mixture of ozone and air bubbles formed mixed bubbles. Influenced by the electric field and electrode plate wall effects, the bubble residence time was prolonged. The bubble size was approximately 2.8 mm, the gas flow horizontal velocity was about 18.5 m/s, and after a horizontal displacement of 0.17 mm in the wastewater, the lateral velocity became zero. The ratio of the distance between the bubble center and the wall to the equivalent bubble diameter was approximately 3.45. The bubbles were subject to a strong wall effect, which extended their residence time. This not only facilitated the removal of small bubbles from the electrode plates but also enhanced the ion diffusion near the plates, thereby boosting pollutant degradation. This study shows that the Ozone-Electro-Fenton coupled process is highly effective in degrading ofloxacin industrial wastewater, offering an innovative solution for treating other antibiotic-containing wastewater. Future research will focus on further optimizing the process, improving its adaptability to complex matrix wastewater, and validating it at the pilot scale to promote its engineering application. Full article

Global municipal solid waste (~2B tons/year) affects sustainability, as landfill and incineration face persistent leachate contamination, demanding effective management to advance water recycling and circular economies. Accelerated investigation of hybrid biocatalytic ozonation systems is imperative to enhance contaminant removal efficiency for stringent discharge compliance. This study investigates the catalytic ozonation effects of γ-Al₂O₃-based catalysts loaded with different metals (Cu, Mn, Zn, Y, Ce, Fe, Mg) on the biochemical effluent of landfill leachate. The catalysts were synthesized via a mixed method and subsequently characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Pseudo-second-order kinetics revealed active metal loading’s impact on adsorption capacity, with Cu/γ-Al₂O₃ and Mg/γ-Al₂O₃ achieving the highest Q_e (0.85). To elucidate differential degradation performance among the catalysts, the ozone/oxygen gas mixture was introduced at a controlled flow rate. Experimental results demonstrate that the Cu/γ-Al₂O₃ catalyst, exhibiting optimal comprehensive degradation performance, achieved COD and TOC removal efficiencies of 84.5% and 70.9%, respectively. UV–vis absorbance ratios revealed the following catalytic disparities: Mg/γ-Al₂O₃ achieved the highest aromatic compound removal efficiency; Ce/γ-Al₂O₃ excelled in macromolecular organics degradation. EEM-PARAFAC analysis revealed differential fluorophore removal: Cu/γ-Al₂O₃ exhibited broad efficacy across all five components, while Mg/γ-Al₂O₃ demonstrated optimal removal of C2 and C4, but showed limited efficacy toward C5. These findings provide important insights into selecting catalysts in practical engineering applications for landfill leachate treatment. This study aims to elucidate catalyst formulation-dependent degradation disparities, guiding water quality-specific catalyst selection to ultimately enhance catalytic ozonation efficiency. Full article

We compare enhancements of mesospheric volume mixing ratios of hydroperoxyl radical ${\mathrm{HO}}_2$ and nitric acid ${\mathrm{HNO}}_3$, as well as ozone depletion in the Northern Hemisphere (NH) polar night regions during energetic particle precipitation (EPP) in January of 2005 and 2012. We utilize mesospheric observations of ${\mathrm{HO}}_2$, ${\mathrm{HNO}}_3$, and ozone from the Microwave Limb Sounder (MLS/Aura). During the second half of January 2005 and 2012, the GOES satellite identified strong solar proton events with virtually the same proton flux parameters. Geomagnetic disturbances in January of 2005 were stronger, with Dst decreasing up to 100 nT compared to January 2012 while the Dst drop did not exceed 70 nT. Comparison of observations made with the MLS/Aura shows the highest change of ${\mathrm{HO}}_2$ and ${\mathrm{HNO}}_3$ concentrations and also the deepest ozone destruction at the latitudinal range from ${60}^{\circ }$ NH to ${80}^{\circ }$ NH inside the north polar vortex right after the spike in energetic particle flux registered by GOES satellites. MLS/Aura observations show ${\mathrm{HNO}}_3$ maximum enhancements of about 1.90 ppb and 1.66 ppb around 0.5 hPa (about 55 km) in January 2005 and January 2012, respectively. The ${\mathrm{HO}}_x$ increases lead to short-term ozone destruction in the mesosphere, which is seen in MLS/Aura ozone data. The maximum ${\mathrm{HO}}_2$ enhancement is about 1.05 ppb and 1.62 ppb around 0.046 hPa (about 70 km) after the onset of EPP in the second half of January 2005 and January 2012, respectively. Ozone maximum depletion is observed around 0.02 hPa (about 75 km). Ozone recovery after EPP was much faster in January 2005 than in January 2012. Full article

Understanding baseline O₃ is important as it defines the fraction of O₃ coming from global sources and not subject to local control. We report the occurrence and sources of high baseline ozone days, defined as a day where the daily maximum 8 h average (MDA8) exceeds 70 ppb, as observed at the Mount Bachelor Observatory (MBO, 2.8 km asl) in Central Oregon from 2004 to 2022. We used various indicators and enhancement ratios to categorize each high-O₃ day: carbon monoxide (CO), aerosol scattering, the water vapor mixing ratio (WV), the aerosol scattering-to-CO ratio, backward trajectories, and the NOAA Hazard Mapping System Fire and Smoke maps. Using these, we identified four causes of high-O₃ days at the MBO: Upper Troposphere/Lower Stratosphere intrusions (UTLS), Asian long-range transport (ALRT), a mixed UTLS/ALRT category, and events enhanced by wildfire emissions. Wildfire sources were further divided into two categories: smoke transported in the boundary layer to the MBO and smoke transported in the free troposphere from more distant fires. Over the 19-year period, 167 high-ozone days were identified, with an increasing fraction due to contributions from wildfire emissions and a decreasing fraction of ALRT events. We further evaluated trends in the O₃ and CO data distributions by season. For O₃, we found an overall increase in the mean and median values of 2.2 and 1.5 ppb, respectively, from the earliest part of the record (2004–2013) compared to the later part (2014–2022), but no significant linear trends in any season. For CO, we found a significant positive trend in the summer 95th percentiles, associated with increasing fires in the Western U.S., and a strong negative trend in the springtime values at all percentiles (1.6% yr⁻¹ for 50th percentile). This decline was likely associated with decreasing emissions from East Asia. Overall, our findings are consistent with the positive trend in wildfires in the Western United States and the efforts in Asia to decrease emissions. This work demonstrates the changing influence of these two source categories on global background O₃ and CO. Full article

In this paper, we use ozone mixing ratio data from the MERRA-2, ERA-5 and JRA-55 reanalyses from 500 hPa to 1 hPa in the period 1980–2020 with the aim of assessing their suitability for trend analysis. We found that these data are not suitable for trend studies due to huge differences in trend values and large differences in the variance of the ozone mixing ratio between reanalyses, and due to strong discrepancies between the ozone mixing ratio from reanalyses and that from the reliable ozonesonde at Hohenpeissenberg. These large differences can be caused by satellite replacement or by the assimilation of imperfect homogeneous data. Full article

The vertical profiles of aerosol optical properties are vital to clarify their transboundary transport, climate forcing and environmental health influences. Based on synergistic measurements of multiple advanced detection techniques, this study investigated aerosol vertical structure and optical characteristics during two dust and haze events in Lanzhou of northwest China. Dust particles originated from remote deserts traveled eastward at different altitudes and reached Lanzhou on 10 April 2020. The trans-regional aloft (~4.0 km) dust particles were entrained into the ground, and significantly modified aerosol optical properties over Lanzhou. The maximum aerosol extinction coefficient (σ), volumetric depolarization ratio (VDR), optical depth at 500 nm (AOD₅₀₀), and surface PM₁₀ and PM_2.5 concentrations were 0.4~1.5 km⁻¹, 0.15~0.30, 0.5~3.0, 200~590 μg/m³ and 134 μg/m³, respectively, under the heavy dust event, which were 3 to 11 times greater than those at the background level. The corresponding Ångström exponent (AE_440–870), fine-mode fraction (FMF) and PM_2.5/PM₁₀ values consistently persisted within the ranges of 0.10 to 0.50, 0.20 to 0.50, and 0.20 to 0.50, respectively. These findings implied a prevailing dominance of coarse-mode and irregular non-spherical particles. A severe haze episode stemming from local emissions appeared at Lanzhou from 30 December 2020 to 2 January 2021. The low-altitude transboundary transport aerosols seriously deteriorated the air quality level in Lanzhou, and aerosol loading, surface air pollutants and fine-mode particles strikingly increased during the gradual strengthening of haze process. The maximum AOD₅₀₀, AE_440–870nm, FMF, PM_2.5 and PM₁₀ concentrations, and PM_2.5/PM₁₀ were 0.65, 1.50, 0.85, 110 μg/m³, 180 μg/m³ and 0.68 on 2 January 2021, respectively, while the corresponding σ and VDR at 0.20–0.80 km height were maintained at 0.68 km⁻¹ and 0.03~0.12, implying that fine-mode and spherical small particles were predominant. The profile of ozone concentration exhibited a prominent two-layer structure (0.60–1.40 km and 0.10–0.30 km), and both concentrations at two heights always remained at high levels (60~72 μg/m³) during the entire haze event. Conversely, surface ozone concentration showed a significant decrease during severe haze period, with the peak value of 20~30 μg/m³, which was much smaller than that before haze pollution (~80 μg/m³ on 30 December). Our results also highlighted that the vertical profile of aerosol extinction coefficient was a good proxy for evaluating mass concentrations of surface particulate matters under uniform mixing layers, which was of great scientific significance for retrieving surface air pollutants in remote desert or ocean regions. These statistics of the aerosol vertical profiles and optical properties under heavy dust and haze events in Lanzhou would contribute to investigate and validate the transboundary transport and radiative forcing of aloft aerosols in the application of climate models or satellite remote sensing. Full article

Gaseous polycyclic aromatic hydrocarbons were measured in northern Thailand. No previous studies have provided data on gaseous PAHs until now, so this study determined the gaseous PAHs during two sampling periods for comparison, and then they were used to assess the correlation with meteorological conditions, other pollutants, and their sources. The total concentrations of 8-PAHs (i.e., NAP, ACY, ACE, FLU, PHE, ANT, FLA, and PYR) were 125 ± 22 ng m⁻³ and 111 ± 21 ng m⁻³, with NAP being the most pronounced at 67 ± 18 ng m⁻³ and 56 ± 17 ng m⁻³, for morning and afternoon, respectively. High temperatures increase the concentrations of four-ring PAHs, whereas humidity and pressure increase the concentrations of two- and three-ring PAHs. Moreover, gaseous PAHs were estimated to contain more toxic derivatives such as nitro-PAH, which ranged from 0.02 ng m⁻³ (8-Nitrofluoranthene) to 10.46 ng m⁻³ (1-Nitronaphthalene). Therefore, they could be one of the causes of local people’s health problems that have not been reported previously. Strong correlations of gaseous PAHs with ozone indicated that photochemical oxidation influenced four-ring PAHs. According to the Pearson correlation, diagnostic ratios, and principal component analysis, mixed sources including coal combustion, biomass burning, and vehicle emissions were the main sources of these pollutants. Full article

An increase in the ozone content in the mesosphere over the Moscow region during the solar eclipses of 20 March 2015 and 25 October 2022 was observed by means of a ground-based microwave radiometer operated at frequencies of the ozone spectral line of 142.175 GHz. Changes in ozone mixing ratio (OMR) at altitudes of 90 km and 65 km were estimated and compared with diurnal ozone variations measured on the dates closest to the events. It was found that the observed increase in the OMR at 90 km during the 20 March 2015 eclipse was almost two times greater than during the 25 October 2022 eclipse, although the maximum Sun’s obscurations of these eclipses were close to each other (0.625 and 0.646). Most likely, this difference can be explained by the difference in concentration of atomic hydrogen, which plays an important role in ozone destruction at altitudes of around 90 km and above. Full article

A better understanding of background tropospheric ozone delivers multiple benefits. Robust estimates of regional background ozone are required to understand the limits of anthropogenic emissions controlling ozone reduction. Long-term estimates of background ozone assist in characterising changes in atmospheric composition and can help quantify the influence of human activity on the atmosphere. Background tropospheric ozone measurements representative of continental air masses are scarce in Australia. Here, we use k-means clustering to identify a cluster of measurements from the long-term air quality monitoring station at Oakdale, NSW, which are likely to be representative of background air. The cluster is associated with NO_x-limited air masses of continental origin. From this analysis, we estimate background ozone representative of Eastern Australia. We find recent (2017–2022) mean ozone mixing ratios of 28.5 ppb and identify a statistically significant (α = 0.05) trend in the mean of +1.8 (1.0–2.8) ppb/decade. Our methods demonstrate that some long-term monitoring stations within or near urban areas can provide suitable conditions and datasets for regional Global Atmosphere Watch monitoring. Full article

Changing urban emission landscapes and increasing population make it imperative to understand the driving forces for air quality in growing urban areas. Recent field studies in an industrial area in Houston and a semiurban area in San Antonio reveal unique emission signatures for these two growing Texas cities. A comparison of benzene, toluene, xylenes, isoprene, and methyl ethyl ketone (MEK) was conducted for these two Texas locations and previous studies in other megacities. It was found that San Antonio had similar emission ratios as these megacities for benzene, toluene, and xylenes (1.10, 4.57, and 3.60 pptv ppbv⁻¹ of CO, respectively), likely indicating a similar traffic emission source. Isoprene and MEK were of biogenic origin in San Antonio. However, analysis of emission ratios, diurnal trends, and comparison with emission inventories indicated that benzene, toluene, and MEK were likely associated with fugitive and stack emissions in the industrial corridor in Houston. Isoprene in Houston appeared to have mixed fugitive and biogenic sources in Houston, based on diurnal trends and emission ratio. The peak nighttime concentrations for benzene, toluene, xylene, isoprene, and MEK observed during the campaign were 66, 533, 21, 138, and 731 ppbv, respectively, in the Houston site. The emission ratio for xylenes (3.37 pptv ppbv⁻¹ of CO) for the Houston site was similar to Paris, London, and Mexico City, despite emission inventories indicating high fugitive and stack emissions. The conditional probability function (CPF) analysis closely matched the direction of the industrial sources with the highest recorded emission levels as listed in the emission inventory for the Houston site. The estimated ozone production efficiency (OPE) for the industrial area in Houston indicated volatile organic compound (VOC)–limited conditions in the morning, which transitioned to nitrogen oxide (NO_x)–limited conditions in the afternoon. Texas cities have complex emission scenarios, and future efforts to mitigate ozone and particulate matter may have to consider a variety of emission reduction strategies. Full article