Atmospheric Environment: X最新文献

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.

Wildland fires, which includes both wild and prescribed fires, and agricultural fires in sum are one of the largest sources of fine particulate matter (PM_2.5) emissions to the atmosphere in the United States (US). Although wildland fire PM_2.5 emissions are primarily composed of carbonaceous material, many other elements including trace metals are emitted at very low levels. Lead (Pb) is a US Environmental Protection Agency (EPA) criteria pollutant that is ubiquitous in the environment at very low concentrations including in biomass that can burn and emit Pb into the atmosphere. Although fires may emit Pb at very low concentrations, they can be a source of sizeable Pb emissions to the atmosphere because of the large quantity of PM_2.5 emitted from fires. In this work, we measure Pb concentrations in unburned biomass, ash/residues, and particulate matter <2.5 μm (PM_2.5) emitted from wildland fires using in-field measurements near prescribed fires and in laboratory simulations. Emission factors were calculated for multiple biomass types, representative of different regions of the US including grasslands in Oregon and Kansas; forest litter from Oregon, Montana, Minnesota, and North Carolina; and peat cores from Minnesota. Most of the biomass Pb remains in the ash/residues. The small percentage (<10%) that is emitted in PM_2.5 is dependent on the biomass Pb concentration. The emissions factors measured here are several orders of magnitude lower than some reported in the literature, but the studies exhibited a wide range of values, which may be due to large uncertainties in the measurement method rather than differences in Pb emissions. Wildland fires are expected to increase in size and frequency in future years and these new emission factors can be used to improve the accuracy of Pb emissions estimates and better constrain our understanding of Pb emissions to the atmosphere.

Estimating the contribution of cities to regional and global methane (CH₄) budgets is challenging due to the complex infrastructures of cities. Mobile measurement devices are well suited to detect CH₄ sources via real-time ambient air measurements. Surveys involving mobile CH₄ measurements were conducted from May 2020 to July 2021 at the street level in two medium-sized cities in Germany. With coverage levels of 30% and 65% of the road networks in Heidelberg and Schwetzingen, respectively, Leak Indications (LIs) for CH₄ were observed with mole fractions of 100 to 9500 ppb above background. A minor portion of leaks (2 out of 70) was attributed to the sewer system, but most leaks originated from the gas distribution network with 0.48 LIs per km obtained in Heidelberg and 0.08 LIs per km determined in Schwetzingen. A method to assign an emission rate to all LIs developed by Weller et al. (2019) was assessed and adapted via controlled CH₄ release experiments in Heidelberg. The method was modified for cities with smaller street widths and smaller distances from the leak to the measurement device. The annual total street-level CH₄ emissions calculated for Heidelberg and Schwetzingen were 42 ± 17 and 1.5 ± 0.5 t CH₄ yr⁻¹ (1sigma), respectively, corresponding to 0.26 ± 0.11 and 0.03 ± 0.01 kg CH₄ yr⁻¹ per capita, respectively.

This study evaluated the concentrations of tropospheric nitrogen dioxide (NO₂), carbon monoxide (CO), ozone (O₃), and Aerosol Index (AI) as well as different meteorological parameters, including atmospheric temperature (AT), relative humidity (RH), and wind speed (WS) in nine Nigerian cities: Aba, Benin, Ibadan, Kaduna, Kano, Lagos, Onitsha, Port Harcourt, and Umuahia. The role of socioeconomic activities on air pollution was also investigated using nighttime light radiance as a surrogate measure. Welch's one-way ANOVA test was performed for the variance study to evaluate the concentration dynamics of the selected tropospheric air pollutants and their association with nighttime light radiance. The mean concentration of CO and AI was highest in Kano, while that of O₃ was the lowest. A similar pattern was also observed in the spatiotemporal transition of the selected pollutants and the nighttime light during the study period. Further, the correlation analysis revealed that AT is positively correlated with NO₂ except in Aba and Benin cities, while it is positively correlated with CO and AI for all cities. The principal component analysis (PCA) revealed that O₃ and RH have strong negative factor loadings, whereas CO, AI, and AT have strong positive factor loadings. This study will guide future researchers by associating the level of pollution with socioeconomic activities, especially during the absence of permanent air quality stations.

This study revealed the importance of two isoprene-derived pathways in the formation of sulfate aerosol (SO₄²⁻(p)), which are related to the gas-phase reactions of Criegee intermediates (CIs) and liquid-phase reactions of isoprene hydroxy hydroperoxide (ISOPOOH), in the atmosphere in the Asian region, using the community multiscale air quality (CMAQ) modeling system. The results showed that the incorporation of both isoprene-derived CIs and ISOPOOH chemistry increased the SO₄²⁻(p) concentration in specific domains of Asia, particularly isoprene hotspots, with up to 1% of the total SO₄²⁻(p) concentration compared to that obtained by the basic chemical transport model. The impact of ISOPOOH to SO₄²⁻(p) formation exhibited a more localized pattern compared to that of CIs, attributed to the tendency of ISOPOOH to condense in low-NO regions. SO₄²⁻(p) formation from CIs affected the compositions of nitrate (NO₃⁻), ammonium (NH₄⁺), and secondary organic aerosols (SOA) in the particle phase, and in most of the analyzed sites, those compositions increased from 0.5% to 2.5%. In contrast, SO₄²⁻(p) formation from ISOPOOH exhibits a negative impact on SOA, resulting in a potential reduction of up to 5% due to the loss of SOA precursor by incorporating the ISOPOOH uptake reaction. The sensitivity analysis results showed that most of the SO₄²⁻(p) was generated by the gas-phase reaction of SO₂ with OH; however, the CIs and ISOPOOH also affected the SO₄²⁻(p) formation more than the liquid-phase SO₄²⁻(p) formations by H₂O₂, O₃, O₂, etc.

Microplastics are emitted to the environment from many sources, and transported via water, soil and air. The airborne component is less well studied and measurements often focus on particles larger than 10 μm, while smaller particles are worse from a health perspective and likely more abundant. Measurement studies do often not include tyre wear, which is a large source of microplastics in urban areas. To improve the understanding of the microplastics concentration in urban areas, simulations of emissions and concentrations of atmospheric tyre wear particles (TWP) over Stockholm are performed. The results show that TWP are ubiquitous in urban areas, with highest concentrations along busy highways and in poorly ventilated street canyons. Yearly average roof level concentrations of TWP-PM₁₀ range from 0.2 μg m⁻³ in areas with moderate traffic to 1.2 μg m⁻³ close to busy highways. Average yearly concentrations at three selected street canyons range from 0.7 to 1.1 μg m⁻³. The modelled concentrations correspond to 4–6% of the total measured PM₁₀ concentration. TWP emissions are expected to increase with increasing traffic in future, and possibly also with the increase in vehicle weight with electric vehicles and SUV:s.