Atmospheric Environment: X最新文献

Open storage yards at industrial sites represent a significant fugitive dust emission source. Granular material subjected to wind erosion may emit significant dust into the atmosphere. Several windbreaks and fences with different shapes have been proposed to control and reduce those emissions. Solid fences are commonly erected around the open yard (i.e., open bays) to prevent and reduce those emissions, even though they have some limitations. The present study aims to enhance the effectiveness of solid fences by coupling them with dynamic wind deflectors. Computational fluid dynamics was employed to simulate the flow and shear stresses on storage pile surfaces using the numerical Reynolds-averaged Navier–Stokes equations and the k-ω SST turbulence model. At the same time, dust emission was estimated using an Environmental Protection Agency (EPA) method, which estimates the emission potential of a material based on the wind friction velocity and the material's threshold friction velocity. The numerical model was validated against experimental data from an EPA study. In addition, this study investigated the efficiency of various dynamic wind deflectors with different heights and inclination angles. The results showed that most of the investigated dynamic fence-deflector models reduced the velocity magnitude, vortices, and turbulence intensity, lessening the impact of shear stresses compared to single solid fences and consequently reducing the emission of dust from the exposed surfaces (i.e., a primary measure of impact reduction). More specifically, the deflector of width (Y_def) 2 m with an inclination of (∅_def) 65° was the most effective, where the shear stress on the pile surface and the emission factor were reduced by 29.16% and 21.79%, respectively, compared to the single fence of the same height. Finally, adding dynamic wind deflectors enhances the performance of solid fences, and it is a more effective and less expensive solution than replacing single fences with other windbreak models.

The rise of fine particulate matter (PM_2.5) levels in urban areas, driven by traffic, construction, and combustion emissions, has prompted urgent air quality concerns. Understanding source-specific PM_2.5 chemical characteristics and developing associated source markers is essential for knowing their accurate contribution to atmospheric PM_2.5. This study focuses on developing PM_2.5 chemical source profiles from nine different emissions, primarily categorized under traffic and combustion sources. The chemical characterization included the carbonaceous thermal fractions, inorganic ions, and elemental composition. Heterogeneity in chemical composition across emission sources was examined using the coefficient of divergence and diagnostic ratio, and finally, source-specific chemical fingerprints were developed using the ratio normalization approach. The finding revealed significant inter and intra-variation in the chemical composition among traffic and combustion emission sources. Organic matter is observed significantly higher in combustion sources (84%–92%) than in traffic sources (22%–45%). Both OC/EC and char-EC/soot-EC values showed much higher values for combustion sources than traffic emissions, with cow dung cake burning emissions displaying the largest values. Also, char-EC/soot-EC values showed a similar trend with OC/EC values and thus can be used as an additional marker for deciphering emission sources. The ion-balance ratio revealed particle emissions from coal, cow dung, and garbage burning to be highly acidic, while traffic and construction sources were alkaline. Source marker results provide new insights into differences in the chemical fingerprint of specific emission sources. A new set of source markers was seen for garbage burning while coal-burning emissions showed varying chemical fingerprints and were found to be dependent on coal processing. Among elements, bromine and chlorine are found to be the unique markers for cow dung cake-burning emissions. Receptor models can use the database developed from the current work to demarcate the emission sources accurately and benefit the regulatory bodies in developing efficient control measures.

Early control of atmospheric methane is essential to achieving a 1.5 °C warming pathway. This paper considers a range of academic and gray literature reviews of methane control techniques, as a starting point for a more comprehensive, integrative review. Novel approaches are considered across anthropogenic and natural sources; where these are lacking, existing approaches are discussed. Four principal sectors meriting action and research are identified: mining and oil & gas emissions, agriculture (including near-term minor interventions and future synthetic food production), effective waste management, and interventions in natural methane sources (e.g., permafrost, methane clathrates, and wetlands). Where abatement is impractical, this review discusses speculative geoengineering technologies (e.g., enhancing the •OH and •Cl sinks, photocatalysis, and adsorbent air capture). Atmospheric methane removal proposals merit research, but may remain impractical due to methane concentrations and lifetime.

To reduce emissions and thereby decrease the effect of black carbon (BC) on human health and the climate, the knowledge of BC concentrations and quantification of its contributions from different sources are necessary for establishing strategies for policymakers. The lockdown due to the COVID-19 pandemic has provided a unique scenario to analyze the impact of anthropogenic activities on BC concentration and their sources. In this study, the variation in BC mass concentration (eBC), its source apportionment, absorption angstrom exponent and their inter-annual variations, and the impact of COVID-19 lockdown on BC are analyzed using a six-year observation of eBC (from the year 2016–2021) over a semi-urban location (Vijayawada (16.44°N, 80.62°E), 30m a.m.s.l) in India. BC mass concentration peaks during the morning (around 06:00–08:00 LT) and evening (after 18:00 LT) hours and is low during the daytime. High eBC is observed during the winter season whereas low eBC during the monsoon season. The source apportionment of BC is carried out using the aethalometer model and it shows that the major source of BC over the site is fossil fuel combustion (>60%) along with a non-negligible contribution from biomass burning (<40%). This result is supported by the absorption angstrom exponent values of less than 1.6 during all seasons. A significant decrease (30%) in the total eBC over the site is observed during the COVID-19 lockdown days. It clearly shows the impact of the reduction in the contribution from anthropogenic activities mainly vehicular and industrial emissions (fossil fuel combustion) on the BC concentration. Interestingly, even after significant reduction of fossil fuel source emission during the lockdown, 53% of BC over the observational site is still contributed by fossil fuel combustion. This obviously shows the dominance of long-range transported BC due to fossil fuel combustion over the observational site.

The air quality and climate of the Himalaya is found to be impacted profoundly by strong anthropogenic emissions and photochemical processes in the valley region. Considering rapid urbanization and population growth, we performed surface ozone (O₃) measurements over Doon valley of the Indian Himalaya during April 2018–June 2023, in conjunction with the analysis of satellite observations and modeling. Noontime O₃ levels are observed to be the highest during pre-monsoon (63.8 ± 15.3 ppbv in May) and lower (22.1–56.7 ppbv) during winter and monsoon seasons. Notably, the daily maximum 8-h average (MDA8) O₃ exceeds the 50 ppbv threshold for ∼60% of the days during April–June, which suggests substantial health impacts in the region. Impact of O₃ exposure on vegetation is also significant during this period of year, as reflected from high Accumulated Ozone above Threshold 40 ppbv (AOT40) and Mean of daytime 7 hours (M7) indices. The Copernicus Atmosphere Monitoring Service (CAMS) reanalysis successfully reproduced the observed variability in the noontime O₃ (r² = 0.79–0.91). Analysis of a tracer in the CAMS model shows that the mean stratospheric contributions to surface O₃ were typically smaller (up to 8%). This suggests that O₃ pollution is governed primarily by the photochemical production favored by regional emissions and meteorological conditions. Analysis combining in-situ O₃ measurements with satellite retrievals (HCHO and NO₂) revealed that the photochemical O₃ production is in the transition or VOC-limited regime, and therefore emission of both NO_x and volatile organic compounds (VOCs) are to be reduced to mitigate O₃ pollution. Finally, a statistical model considering the non-linearities was successfully applied to simulate observed O₃ variability from available satellite observations and meteorological reanalysis data (r² = 0.75, RMSE = 7 ppbv). Our study highlights the need to mitigate O₃ pollution in the Doon valley of the Indian Himalaya and also provides invaluable inputs for designing science-informed policies.

Volatile organic compounds (VOCs) emitted from fugitive sources are crucial for environmental and health risk assessments. However, monitoring these emissions at ground level, according to traditional technical specifications, has made it challenging to identify polluted air masses and collect purposeful samples. In this study, we focused on utilizing an unmanned aerial vehicle system to obtain air samples around a petrochemical industrial park. We conducted a quantitative analysis of 108 VOC species and compared the results between aerial and ground-level samples. The findings indicated a higher presence of reactive compounds in the aerial samples. The sample pairs exhibited relatively homogeneous compositions of hydrocarbons with fewer than eight carbon atoms, suggesting a well-mixed condition for light compounds. Conversely, the aerial samples exclusively exhibited high mixing ratios of C8–C15 compounds, including branched paraffins and aldehydes. Based on the quantified VOCs, we evaluated the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAP). The results highlighted aldehydes, alkenes, and aromatics, particularly propanal, 2-butene, m/p-xylene, and benzaldehyde, as priority control compounds. Additionally, the semiquantitative concentrations of these non-quantitative C8–C15 species ranged from 1 to 15 ppbv, with a total content exceeding 150 ppbv, it indicated the significant contribution to ambient secondary pollution. These results provide valuable insights into the identification of potential emission sources and the assessment of environmental repercussions attributed to these intermediate-volatile organic compounds from fugitive emissions around petrochemical plant.

The occurrence of benzene, toluene, ethylbenzene, and xylene (BTEX) in the environment has human health and ecological consequences; hence, it is essential to remediate the gas-phase industrial plume before its release. A laboratory-scale experimental apparatus was designed to investigate single-component gas-phase adsorption of BTEX compounds on commercially available granular activated carbon (CGAC) and laboratory-developed Mesquite-derived granular activated carbon (MDAC). The physical properties of CGAC and MDAC show that these adsorbents have a high N₂ BET surface area, with CGAC exhibiting microporosity features. The single-component adsorption of BTEX was modeled by considering the transport of BTEX by axial dispersion, convective transport, and accumulation in the adsorbent bed at isothermal conditions. A linear driving force model was used to examine the mass transfer process. The experimental breakthrough curves showed good agreement with the modeled breakthrough curves. The modeling parameters demonstrated the dominance of intraparticle diffusion with a negligible external diffusion of BTEX onto CGAC and MDAC. The analysis of experimental data validated the modeled dynamic behavior of BTEX adsorption onto CGAC and MDAC. Overall, BTEX compounds followed Langmuir isotherms for both adsorbents, with intra-particle diffusion as a dominant gas phase adsorption mechanism.

This paper discusses the impact of rapid economic development on air quality in the Emirate of Dubai, United Arab Emirates (UAE). Dubai is one of the fastest-growing cities in the world, with a population increase of approximately 80× over the last 60 years. The concentrations of five criteria air pollutants (CAPs) including carbon monoxide (CO), nitrogen dioxide (NO₂), particulate matter with diameter less than 10 μm (PM₁₀), ozone (O₃) and sulphur dioxide (SO₂) were studied from 2013 to 2021 at 14 regulatory monitoring stations. Results show that the biggest improvements in air pollution are for the primary air pollutants NO₂ and SO₂, with reductions of 54% and 93% respectively over the period studied. Gross domestic product (GDP), population growth and energy consumption are significantly and negatively correlated with NO₂ and SO₂ and strongly and positively correlated with PM₁₀. CO is positively correlated with the number of buildings completed, while the results for O₃ are inconclusive. Trends in NO₂ and SO₂ indicate that these two pollutants are decoupled from economic development, supporting, with caution, the Environmental Kuznets Curve hypothesis on the relationship between economic growth and environmental degradation. The improvement in the city's air quality is due to the effective implementation of local environmental policies, unaffected by large-scale development and urbanization. The monthly assessments of Dubai's air pollution for 2019 and 2020 show a 3–16% COVID-related improvement in the levels of the studied air pollutants, except for ozone, which increased by an average of 8%.

Among the ecosystem services provided by urban forests, the air quality amelioration is particularly relevant. The high level of air pollution in modern cities and the indirect involvement of particulate matter (PM) in the spread of COVID-19 have exacerbated the air quality issue worldwide. However, in the estimation of urban vegetation effectiveness in particle air pollution removal, there is a lack of a standard procedure. Different methods are used for this purpose, making the comparison across different studies difficult. Therefore, there is a need of an extensive review, aimed at: i) identifying the existing direct methods to quantify this ecosystem service, ii) assessing their pros and cons, accuracy and reliability, sustainability, and iii) laying the foundations to create a standard method, commonly and universally recognized. We identified and meticulously assessed five main direct metrics: the gravimetric method (G, 40%), aerosol monitor (AM, 20.5%), wind tunnels and deposition chambers (WT&CH, 19.5%), Scanning Electron Microscopy (SEM, 14%) and Saturation Isothermal Remanent Magnetization (SIRM, 6%). This work provides a crystal picture and a critical framework of the last thirty years literature on this topic and lays the foundations to create a common and shareable approach to quantify the air PM mitigation potential of the urban vegetation. This will be useful to guide researchers and urban planners in shaping greener, healthier, and more sustainable cities.

Positive matrix factorization (PMF) can be used to develop more targeted air quality mitigation strategies by identifying major sources of a pollutant in an area. This technique is dependent, however, on the ability of PMF to resolve factors that accurately represent all sources of that pollutant in an area. We investigated how the accuracy of PMF solutions might be influenced by monitoring data characteristics, such as temporal resolution, monitoring location, and species composition, to better inform the use of PMF in VOC mitigation strategies. We applied PMF to five VOC monitoring programs collected within a four-year period in Colorado and found generally consistent factors, which we identified as oil extraction, processing, and evaporation; natural gas; vehicle exhaust; and liquid gasoline/short-lived oil and gas. The main determinant influencing whether or not a dataset resolved each of these sources was whether the dataset had a comprehensive list of VOC species covering key species of each source. Pollution spikes were not well-modeled in any of the solutions. Hyperlocal and volatile chemical product factors expected to be resolved in the industrialized, urban location were also missing, highlighting three limitations of PMF analysis. Wind direction dependence and diurnal trends aided in source identification, suggesting that high-time resolution data is important for developing actionable PMF results. Based on these findings, we recommend that air monitoring for PMF-informed VOC mitigation efforts include high temporal resolution and a comprehensive array of VOC species.