Search Results (264)

This study describes a quite special and interesting atmospheric event characterized by the simultaneous presence of fresh and aged smoke layers. These peculiar conditions occurred on 16 July 2024 at the CNR-IMAA atmospheric observatory (CIAO) in Potenza (Italy), and represent an ideal case for the evaluation of the impact of aging and transport mechanisms on both the optical and microphysical properties of biomass burning aerosol. The fresh smoke was originated by a local wildfire about 2 km from the measurement site and observed about one hour after its ignition. The other smoke layer was due to a wide wildfire occurring in Canada that, according to backward trajectory analysis, traveled for about 5–6 days before reaching the observatory. Synergetic use of lidar, ceilometer, radar, and microwave radiometer measurements revealed that particles from the local wildfire, located at about 3 km a.s.l., acted as condensation nuclei for cloud formation as a result of high humidity concentrations at this altitude range. Optical characterization of the fresh smoke layer based on Raman lidar measurements provided lidar ratio (LR) values of 46 ± 4 sr and 34 ± 3 sr, at 355 and 532 nm, respectively. The particle linear depolarization ratio (PLDR) at 532 nm was 0.067 ± 0.002, while backscatter-related Ångström exponent (AEβ) values were 1.21 ± 0.03, 1.23 ± 0.03, and 1.22 ± 0.04 in the spectral ranges of 355–532 nm, 355–1064 nm and 532–1064 nm, respectively. Microphysical inversion caused by these intensive optical parameters indicates a low contribution of black carbon (BC) and, despite their small size, particles remained outside the ultrafine range. Moreover, a combined use of CIAO remote sensing and in situ instrumentation shows that the particle properties are affected by humidity variations, thus suggesting a marked particle hygroscopic behavior. In contrast, the smoke plume from the Canadian wildfire traveled at altitudes between 6 and 8 km a.s.l., remaining unaffected by local humidity. Absorption in this case was higher, and, as observed in other aged wildfires, the LR at 532 nm was larger than that at 355 nm. Specifically, the LR at 355 nm was 55 ± 2 sr, while at 532 nm it was 82 ± 3 sr. The AEβ values were 1.77 ± 0.13 and 1.41 ± 0.07 at 355–532 nm and 532–1064 nm, respectively and the PLDR at 532 nm was 0.040 ± 0.003. Microphysical analysis suggests the presence of larger, yet much more absorbent particles. This analysis indicates that both optical and microphysical properties of smoke can vary significantly depending on its origin, persistence, and transport in the atmosphere. These factors that must be carefully incorporated into future climate models, especially considering the frequent occurrences of fire events worldwide. Full article

Biomass burning processes affect many semi-rural areas in the Mediterranean, but there is a lack of long-term datasets focusing on their classification, obtained by monitoring carbonaceous particle concentrations and optical properties variations. To address this issue, a campaign to measure equivalent black carbon (eBC) and particle number size distributions (0.3–10 μm) was carried out from August 2019 to November 2020 at a coastal semi-rural site in the Basilicata region of Southern Italy. Long-term datasets were useful for aerosol characterization, helping to clearly identify traffic as a constant eBC source. For a shorter period, PM_2.5 mass concentrations were also measured, allowing the estimation of elemental and organic carbon (EC and OC), and chemical and SEM (scanning electron microscope) analysis of aerosols collected on filters. This multi-instrumental approach enabled the discrimination among different biomass burning (BB) processes, and the analysis of three case studies related to domestic heating, regional smoke plume transport, and a local smoldering process. The AAE (Ångström absorption exponent) daily pattern was characterized as having a peak late in the morning and mean hourly values that were always higher than 1.3. Full article

This study evaluated the effects of conventional cigarette smoke compared to aerosol from a heat-non-burn tobacco product on the color stability of two UDMA-based dental composite resins, namely a monochromatic (Omnichroma) and a polychromatic (Vittra APS) resin. Twenty disc-shaped specimens were prepared, divided into two groups of ten, and exposed to 105 cigarettes or 105 aerosol tobacco sticks via a custom-made smoking chamber. Puff duration was 2 s, with a 60 s interval between puffs in which smoke saturated the chamber for 30 s; then, clean air was introduced into the chamber for 30 s. Six puffs and six intervals were simulated. Color parameters were measured before and after exposure and following brushing of each specimen with 15 strokes. Color differences were determined based on the CIEDE2000 formula. Significant color change was found in all specimens exposed to cigarette and tobacco aerosol. The highest color-change mean value was obtained from composite resin exposed to cigarette smoke. Although both cigarette and thermal heating systems cause discoloration, the aerosol causes reduced composite resin discoloration, which compromises aesthetics and increases patient dissatisfaction, impacting the overall dental care. Color stability is the hallmark of success, as it is the main reason for replacing dental restorations. Full article

This study presents a global aerosol climatology derived from six years (October 2018–October 2024) of the Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) observations, using a U-Net Convolutional Neural Network (CNN) machine learning algorithm for Cloud–Aerosol Discrimination (CAD). Despite ICESat-2’s design primarily as an altimetry mission with a single-wavelength, low-power, high-repetition-rate laser, ICESat-2 effectively captures global aerosol distribution patterns and can provide valuable insights to bridge the observational gap between the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) missions to support future spaceborne lidar mission design. The machine learning approach outperforms traditional thresholding methods, particularly in complex conditions of cloud embedded in aerosol, owing to a finer spatiotemporal resolution. Our results show that annually, between 60°S and 60°N, 78.4%, 17.0%, and 4.5% of aerosols are located within the 0–2 km, 2–4 km, and 4–6 km altitude ranges, respectively. Regional analyses cover the Arabian Sea (ARS), Arabian Peninsula (ARP), South Asia (SAS), East Asia (EAS), Southeast Asia (SEA), the Americas, and tropical oceans. Vertical aerosol structures reveal strong trans-Atlantic dust transport from the Sahara in summer and biomass burning smoke transport from the Savanna during dry seasons. Marine aerosol belts are most prominent in the tropics, contrasting with earlier reports of the Southern Ocean maxima. This work highlights the importance of vertical aerosol distributions needed for more accurate quantification of the aerosol–cloud interaction influence on radiative forcing for improving global climate models. Full article

Tobacco control policies have aimed to reduce the global prevalence of smoking. Unfortunately, the recent survey data shows that about 24% of Europeans still smoke. Although combustible cigarettes remain the most used tobacco product, the tendency made evident in the prevalence of smoking-alternative nicotine-containing products increases. Studies that can objectively assess the long-term health effects of the latter products are lacking, so assessing toxic substances associated with smoking-alternative products and comparing them to substances from combustible cigarettes could inform future public health efforts. The manufacturers of these alternative products claim that the use of alternatives to combustible cigarettes reduces exposure to toxic compounds, but the reality is unclear. This study compares the concentrations of toxic substances in generated aerosols and performs calculations based on mainstream cigarette smoke and aerosols from smoking-alternative products. It summarizes the amounts of harmful and potentially harmful constituents per single puff. Alternative smoking products are undoubtedly harmful to non-smokers. Still, based on the analysis of the latest independent studies’ empirical data, the concentrations of inhaled HPHCs using heated tobacco products or e-cigarettes are reduced up to 91–98%, respectively; therefore, for those who cannot quit, these could provide a less harmful alternative. However, more well-designed studies of alternative product emissions are needed, including an analysis of the compounds that are not present in conventional tobacco products (e.g., thermal degradation products of propylene glycol, glycerol, or flavorings) to evaluate possible future health effects objectively. Full article

Satellite observations provide broad spatial coverage of complex coastal environments but may lack temporal resolution to capture rapid changes in these dynamic systems. This study explores the potential of the recently installed NASA Aerosol Robotic Network Ocean Color (AERONET-OC) in the Chesapeake Bay, USA, both for comparison with satellite remote sensing and to complement the satellite observations by filling temporal gaps at a fixed site. Using AERONET-OC’s effectiveness as a validation tool through comparisons with multi- and hyperspectral satellites, we find agreement between AERONET-OC and satellite remote sensing reflectance measurements in the Chesapeake Bay. We use AERONET-OC to estimate total suspended matter transport through the upper bay, revealing a 3-day lag of sediment plume transport from riverine discharge to the AERONET-OC site. During the 2023 Canadian wildfire smoke episode, AERONET-OC aerosol optical depth measurements in the Chesapeake Bay agree with satellite products while capturing diurnal variations that are not observable through daily satellite passes. This study demonstrates the potential of continuous in situ monitoring by AERONET-OC to complement satellite observations with higher frequency, important for capturing extreme events that may be missed by daily satellite overpass or are less frequent when cloudy. Full article

Very rarely, the atmosphere produces a natural experiment that, if captured, has the potential to lend insight into the fundamentals of atmospheric behavior. During the North American solar eclipse on 8 April 2024, a prescribed fire on the grounds of Fort Benning produced a smoky haze in Columbus, Georgia, USA. This haze covered the Columbus State University main campus and the nearby Columbus Airport (KCSG) leading up to and during the peak of the eclipse. Automated Surface Observing Station (ASOS) and Georgia Weather Network observations were examined for the event. At the time of temperature minimum, the temperature depression at KCSG was 0.5 °C greater than at nearby ASOS stations. An “eclipse wind” was observed at KCSG but not at the nearby ASOS stations. Based on observations of steady-state air and dewpoint temperatures, together with rapid fluctuations in visibility, we propose the Subcritical Aerosol-Moisture Feedback (SAMF) mechanism, in which subtle feedbacks among particle growth, relative humidity, and scattering of radiation by aerosol-laden air may maintain steady-state thermodynamic conditions. This case study offers a unique opportunity to examine aerosol behavior under transient radiative forcing, suggesting insights into how a smoky environment enhances thermal buffering and stabilizes the boundary-layer response under rare conditions. Full article

Electronic cigarettes (e-cigarettes) are devices designed to vaporize a liquid solution, offering an alternative to traditional tobacco consumption. The identification, detection, and analysis of the compounds present in these devices are crucial for understanding their impacts on health and the environment. Numerous studies have identified a diverse range of compounds emitted by e-cigarettes, including well-known substances such as nicotine, thermal degradation products, and other toxicants that may be harmful or carcinogenic. Although e-cigarettes are often considered an alternative to conventional smoking, they are not without risks. Recent research has increasingly focused on assessing the health impacts of e-cigarettes, integrating findings from various scientific disciplines. Two primary analytical approaches are used for the sample preparation, identification, and quantification of these compounds. The first approach focuses on aerosol analysis, utilizing techniques such as headspace static extraction and gas chromatography coupled with mass spectrometry (GC-MS). The second approach is directed towards liquid analysis, employing liquid–liquid extraction techniques and liquid chromatography (LC) systems. Given the constant publication of new research in this area, a comprehensive review that consolidates information on identified compounds, sample preparation methods, and extraction and analysis techniques is necessary to integrate current knowledge and address emerging findings. Full article

Tropospheric aerosols play an important role in the notable warming phenomenon and climate change occurring in the Arctic. The accuracy of Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol optical depth (AOD) and the distribution of Arctic AOD based on the CALIOP Level 2 aerosol products and the Aerosol Robotic Network (AERONET) AOD data during 2006–2021 were analyzed. The distributions, trends, and three-dimensional (3D) structures of the frequency of occurrences (FoOs) of different aerosol subtypes during 2006–2021 are also discussed. We found that the CALIOP AOD exhibited a high level of agreement with AERONET AOD, with a correlation coefficient of approximately 0.67 and an RMSE of less than 0.1. However, CALIOP usually underestimated AOD over the Arctic, especially in wet conditions during the late spring and early summer. Moreover, the Arctic AOD was typically higher in winter than in autumn, summer, and spring. Specifically, polluted dust (PD), dust, and clean marine (CM) were the dominant aerosol types in spring, autumn, and winter, while in summer, ES (elevated smoke) from frequent wildfires reached the highest FoOs. There were increasing trends in the FoOs of CM and dust, with decreasing trends in the FoOs of PD, PC (polluted continental), and DM (dusty marine) due to Arctic amplification. In general, the vertical distribution patterns of different aerosol types showed little seasonal variation, but their horizontal distribution patterns at various altitudes varied by season. Furthermore, locally sourced aerosols such as dust in Greenland, PD in eastern Siberia, and ES in middle Siberia can spread to surrounding areas and accumulate further north, affecting a broader region in the Arctic. Full article

Tobacco smoking and electronic cigarette (EC) use are associated with elevated levels of particulate matter (PM) and nicotine in indoor environments. This study assessed filtration and nicotine capture efficiency of untreated and citric acid-treated high efficiency particulate air (HEPA) filters from two manufacturers, “on-brand” (original) and “off-brand” (replacement). When challenged with salt aerosol, the filtration efficiency (FE) (Mean ± RSD) of original HEPA filters (99.9% ± 0.1) was significantly higher than replacements (94.4% ± 1.7), but both were significantly below the HEPA designation of 99.97%. No significant differences in FE were observed between treated and untreated HEPA filters. All filters had lower FE for EC aerosol compared to salt aerosol, especially among replacement filters. Nicotine capture efficiency was significantly higher in citric acid-treated HEPA filters for originals (99.4% ± 0.22) and replacements (99.0% ± 1.07) compared to untreated originals (57.4% ± 2.33) and replacements (42.0% ± 14.20). This study demonstrated that our citric acid treatment of HEPA filters was effective and efficient at capturing airborne nicotine and did not affect the FE for PM. Use of citric acid-treated HEPA filters would be an effective exposure reduction strategy for both nicotine and PM in indoor settings. Full article

Electronic cigarettes (e-cigs) recently increased their popularity as “safer” alternatives to traditional tobacco smoking, including among pregnant women. However, the effect of e-cig exposure on fetal and neonatal developing lungs remains poorly investigated. In this review, we analysed the impact of e-cig aerosol components (e.g., nicotine, solvents, and flavouring agents) on respiratory system development. We particularly emphasized the role of e-cig-related oxidative stress and inflammation on lung impairment. Nicotine contained in e-cigs can impair lung development at anatomical and molecular levels. Solvents and flavours induce inflammation and oxidative stress and contribute to compromising neonatal lung function. Studies suggest that prenatal e-cig aerosol exposure may increase the risk of future development of respiratory diseases in offspring, such as asthma and chronic obstructive pulmonary disease (COPD). Preventive strategies, such as smoking cessation programs and antioxidant supplementation, may be essential for safeguarding respiratory health. There is an urgent need to explore the safety profile and potential risks of e-cigs, especially considering the limited studies in humans. This review highlights the necessity of regulating e-cig use during pregnancy and promoting awareness of its potential consequences on fetal and neonatal development. Full article

Black carbon (BC) aerosols emitted from biomass, fossil fuel, and waste combustion contribute to the radiation budget imbalance and are transported over extensive distances in the Earth’s atmosphere. These aerosols undergo physical and chemical modifications with co-existing aerosols (e.g., nitrate, sulfate, ammonium) through aging processes during long-range transport and are primarily removed from the troposphere by wet deposition. Using precipitation samples collected in North America between 26 October and 1 December 2020 by the National Atmospheric Deposition Program (NADP), we investigated the relationships between BC and both water-soluble ions and water-soluble organic carbon (WSOC) using Spearman’s rank coefficients. We then attempted to identify the sources of BC in the wet deposition using factor analysis (FA) and satellite data of fire smoke. BC showed a very strong correlation with nitrate (ρ = 0.83). Strong correlations were also found with WSOC, ammonium, calcium, and sulfate ions (ρ = 0.78, 0.74, 0.74, and 0.67, respectively). FA showed that BC was in the same factor as nitrate, ammonium, sulfate, and WSOC, indicating that BC could originate from secondary aerosol formation and biomass burning. Supported by satellite data of fire and smoke, BC and other correlated pollutants were believed to be associated with wildfire outbreaks in several states in the United States (US) during November 2020. Full article

Smoke particles from biomass burning events are typically assumed to be spherical despite previous observations of non-spherical smoke. As such, large uncertainties exist in some physical and optical parameters used in lidar aerosol retrievals, including depolarization and lidar ratio of non-spherical smoke aerosols. In this analysis, using NASA’s Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data during the biomass burning season over Africa from 2015 to 2017, we studied the frequency and distribution of non-spherical smoke particles to compare with findings of smoke particle non-sphericity from the Cloud-Aerosol Transport System (CATS) lidar. A supplemental smoke aerosol typing algorithm was developed to identify aerosol layers containing non-spherical smoke particles, which might otherwise be misclassified as desert dust, polluted dust, or dusty marine by the CALIOP standard aerosol typing algorithm. Then, the relationships between smoke particle sphericity, lidar ratio, and relative humidity are analyzed for CATS and CALIOP observations over Africa. Approximately 18% of smoke layers observed by CALIOP over Africa are non-spherical (depolarization ratio > 0.075) and agree with spatial distributions of non-spherical smoke found in CATS observations. A dependance of lidar ratio on relative humidity was found for layers of spherical smoke over Africa in both CATS and CALIOP data; however, no such dependance was evident for the depolarization ratio and layer relative humidity. While the supplemental smoke aerosol typing algorithm presented in this analysis was targeted only for specific biomass burning regions during biomass burning seasons and is not meant for global operational use, it presents one potential method for improved backscatter lidar aerosol typing. These results suggest that a dynamic lidar ratio, based on layer-relative humidity for spherical smoke, could be used to reduce uncertainties in smoke aerosol extinction retrievals for future backscatter lidars. Full article

Heated tobacco products (THPs) are increasingly promoted as potential harm reduction tools, offering an alternative to traditional cigarettes. Despite these claims, understanding of their toxicological impact on respiratory health and associated microbial communities is limited. Comprehensive investigations are needed to elucidate the biological mechanisms and potential health implications associated with their use. Methods: This study evaluated the toxicological effects of aerosols produced by THPs (IQOS 3 Duo with Heets “Sienna Selection”) in comparison to conventional cigarette smoke (1R6F). Antibacterial activity was evaluated using Streptococcus pneumoniae and Klebsiella pneumoniae as representative species of the respiratory microbiota through agar diffusion assays and MIC/MBC determinations. Cytotoxicity was assessed in human lung fibroblast cells (MRC5) through the neutral red uptake (NRU) assay, whereas mutagenicity was investigated using the Ames test. Results: THP aerosols demonstrated the ability to inhibit the growth of both S. pneumoniae and K. pneumoniae, exerting bacteriostatic effects at lower concentrations and bactericidal effects at higher concentrations. While these antibacterial effects might initially seem beneficial against pathogens such as K. pneumoniae, they raise concerns about the potential disruption of the respiratory microbial balance, particularly in relation to S. pneumoniae. Despite these microbiological effects, THP aerosols demonstrated minimal cytotoxicity on human lung fibroblasts and lacked detectable mutagenic activity, contrasting with the significant cytotoxicity and mutagenicity caused by cigarette smoke. Conclusions: THPs present a reduced short-term toxicological profile compared with conventional cigarettes; however, their effects on respiratory microorganisms deserve attention. The observed inhibition of commensal bacteria highlights the need to explore potential changes in the microbial ecosystem that could affect respiratory health. These findings highlight the need for additional studies to evaluate the long-term effect of THP use on respiratory microbiota and the stability of the overall microbial ecosystem. 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