Environmental science: atmospheres最新文献

Meteorology can alter bioaerosol properties, potentially enhancing their impact on public health and cloud microphysics. The BioAerosols and Convective Storms (BACS) study was conducted over May-June 2022 and 2023 in Northern Colorado and examines how convective storm processes such as precipitation and cold pools affect bioaerosol concentrations and properties, including pollen, fungal spores and bacterial endotoxin. The two seasons were vastly different climatologically, with drought-like conditions and greater endotoxin concentrations during 2022 and near record rainfall with higher fungal spore concentrations during 2023. Online (fluorescence) and offline (chemical tracer) measurements were used to characterize bioaerosols, alongside collocated measurements of ice-nucleating particles (INPs). Precipitation events generally increased supermicron fluorescent particle concentrations which consisted primarily of fungal spores, as determined from fungal spore counts, chemical tracers, and fluorescent particle types. Storm-generated cold pools had more varied impacts on bioaerosols, sometimes causing depletion and other times enrichment, with peak fluorescent particle concentrations correlating significantly with cold pool strength (r _s = 0.79, p < 0.05, n = 12), indicating that stronger cold pools produce greater increases in local bioaerosol concentrations. Biological INP concentrations in air active at warmer than -15 °C from 1-10 µm in size were enhanced by roughly one order of magnitude in samples collected during convective storms compared to pre-rain samples. Contributions of fungal spores to the enhanced INPs were supported by a significant correlation between large (2.5-10 µm) heat-labile INP concentrations active at -15 °C with mannitol, a fungal spore tracer (r = 0.91, n = 8, p < 0.01). This study found convective storms can greatly increase boundary-layer concentrations of fungal spores and warm-temperature biological INPs, leading to high exposure risks for sensitized populations and the potential for bioaerosols to influence cloud processes.

Biogenic volatile organic compounds are emitted into the atmosphere where they can oxidize forming compounds with lower volatilities. These low-volatility compounds can participate in the formation of secondary organic aerosols (SOAs) that affect human health and the climate in various ways. We studied the oxidation pathways initiated by the acetyl peroxy radical (APR) of less frequently studied oxygenated monoterpenes (monoterpenoids) using computational methods. The studied reactions included APR-addition, ring-opening reactions and C-C bond scissions. Ring-rearrangement after APR-addition was shown to be significant (43% yield) for one bicyclic monoterpenoid, sabinol. All other studied monoterpenoids will mostly react only with O₂ forming a peroxy radical which will go on to form an alkoxy radical. Alkoxy radical β-scissions lead to different kinds of products depending on the reacting monoterpenoid. Verbenol and α-terpineol will mostly form closed-shell species through alkoxy radical C-C bond scissions leading to low SOA yields. The fate of carveol depends strongly on the stereoisomer. The S-isomer will form a closed-shell species with a 50% yield, whereas the R-isomer will form an alkyl radical with a 100% yield capable of further oxidation. Therefore, a significant SOA yield could be expected for carveol depending on the stereoisomer. For sabinol, umbellulone and carvone, high SOA yields are expected as the majority of them will form an alkyl radical that reacts with O₂ forming a new peroxy radical. In the case of umbellulone and carvone, the formed peroxy radical is an acyl peroxy radical which can undergo rapid unimolecular reactions initiating fast autoxidation. Compared to the monoterpene counterparts of the studied monoterpenoids, significant differences were observed in reaction pathways and SOA yields. While APR-initiated oxidation serves as a minor pathway in the atmosphere, the studied reactions could have an impact on the production of low-volatility compounds.

Modern office infrastructure, furnishings, and traditional cooking practices contribute to air pollution, posing significant health risks, including respiratory issues, cancer, and immune system suppression, especially for vulnerable groups. This review examines recent progress in adsorption, catalytic oxidation, and phytoremediation for reducing volatile organic compounds and fine particulate matter, major air pollutants. Adsorption technologies employ conventional materials like activated carbon and advanced options like metal–organic frameworks and biochars, offering high adsorption capacities due to tunable structures and large surface areas. Catalytic oxidation, including photocatalytic and thermocatalytic methods, effectively degrades pollutants, with composites like nano-ZnO/coke enhancing removal efficiencies. Phytoremediation using household plants like Epipremnum aureum and green walls effectively removes pollutants through enzymatic degradation, stomatal absorption, and microbial synergy. This review assesses integrated strategies' scalability, efficiency, and practicality for comprehensive air quality management, highlighting their potential to enhance public health.

As a highly reactive atmospheric oxidant, chlorine (Cl) atoms significantly contribute to the oxidation of volatile organic compounds (VOCs) and the formation of secondary organic aerosol (SOA) in coastal and industrial environments. To assess the environmental impacts of SOA generated from Cl-initiated oxidation, elucidating its chemical composition, formation mechanisms, and physicochemical properties under varying atmospheric conditions is of paramount importance. This review summarizes recent research advances on atmospheric chlorine chemistry. We first outline the sources and generation mechanisms of Cl atoms, followed by an analysis of the kinetic characteristics, oxidation mechanisms, and SOA formation potential of Cl-initiated VOC oxidation. Compared to hydroxyl (OH) radicals, Cl atoms exhibit faster reaction rates and reaction pathways that preferentially generate low-volatility products, significantly enhancing SOA formation and demonstrating higher SOA yields. Given the complexity of SOA formation and its strong dependence on environmental conditions, we further discuss the responses of gas-phase chemistry as well as SOA mass yields and composition to the [Cl₂/VOC]₀ ratios, Cl exposure, NO_x levels, and relative humidity. Finally, we outline key experimental challenges and future research priorities.

Diaterpenylic acid acetate (DTAA) (C₁₀H₁₆O₆) is a later-generation biogenic secondary organic aerosol (OA) component, formed during the oxidation of first-generation products of monoterpenes such as α-pinene, and β-pinene. Identified in aerosol in terrestrial and forested environments, DTAA is a product of the oxidation of both terpenylic acid and 1,8-cineole. Here, we present the first comprehensive chamber study investigating DTAA's volatility, gas–particle partitioning, and oxidative transformation under atmospherically relevant conditions through a combination of laboratory measurements, modeling, and chemical analysis. Its physicochemical properties were characterized by using two atmospheric simulation chambers, equipped with a range of particle and gas-phase instrumentation. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) identified DTAA aerosol characteristic peaks at mass-to-charge (m/z) 59, 67, 79, 91, 95, 101, 114 and 139. DTAA aerosol density was estimated to be 1.3 ± 0.2 g cm⁻³. DTAA was classified as a semi-volatile organic compound (SVOC), with a saturation concentration of 3.6–3.9 µg m⁻³. Upon hydroxyl (OH) radical exposure, DTAA underwent significant chemical aging, producing secondary organic aerosol (SOA) with distinct spectral features and a little higher oxygen-to-carbon ratio (O : C = 0.63). The AMS spectrum of the produced SOA was quite different from that of pure DTAA (R² = 0.48 or θ = 31°) and resembled to an extent (θ = 14–20°), the spectra of ambient biogenic SOA. A suite of oxidation products were identified via proton transfer reaction mass spectrometry (PTR-MS) and chemical ionization mass spectrometry (CIMS) ranging from small molecules (e.g. acetone) to multifunctional species. A kinetic model incorporating partitioning, wall loss, and oxidation accurately captured SOA production during the DTAA reaction with OH, assuming an effective fragmentation probability of 32%. These results highlight the atmospheric relevance of DTAA as a reactive SVOC and underline the importance of integrating later generation chemical processes in SOA studies.

Particulate matter (PM) pollution from industrial activities is a growing environmental and public health concern, particularly in sub-Saharan Africa; where metal recycling factories (MRFs) are expanding due to increasing urbanization and metal waste generation. However, data on the chemical composition of PM and associated health risks in this region, especially in countries like Nigeria, remain limited. The present study investigates the chemical composition-including water-soluble inorganic ions, sugars, and potentially toxic elements (PTEs), and evaluates the health risks of PM_2.5 and PM₁₀ collected during wet and dry seasons from an industrial hub in Nigeria dominated by MRFs. The average concentrations of PM_2.5 (27 ± 8 μg m⁻³) and PM₁₀ (109 ± 38 μg m⁻³) in the dry season exceeded the WHO Air Quality Guidelines (15 μg m⁻³ for PM_2.5; 45 μg m⁻³ for PM₁₀), highlighting severe seasonal air quality issues. Major water-soluble ions included SO₄²⁻, Cl⁻, NO₃⁻, Na⁺, Ca²⁺, and K⁺, with NH₄⁺, C₂O₄²⁻, and Mg²⁺ present in smaller amounts. The elevated ion concentrations point to anthropogenic sources, primarily MRFs. Principal component analysis (PCA) identified crustal materials and anthropogenic emissions (from MRFs and cement factories) as major contributors to PM-bound elements. Trace metals such as Cr, Cu, Mo, Ni, Pb, and Zn showed high enrichment, with MRF activities being the dominant source. Health risk assessments using hazard quotient (HQ) and hazard index (HI) indicated non-carcinogenic risks were within acceptable limits (<1.0) for most metals in both children and adults. Carcinogenic risks were also below the permissible range (1 × 10⁻⁶ to 1 × 10⁻⁴). However, Pb posed a near-threshold risk in children, with HQ (0.81) and HI (0.84), suggesting the need for regulatory attention to prevent potential lead toxicity in this area. Stricter regulations and monitoring of MRF activities are crucial to mitigate PM pollution and associated health risks, ensuring a safer and healthier environment for communities in Nigeria.

Brown carbon (BrC), a class of light-absorbing organic compounds produced during biomass burning, plays an important role in atmospheric radiative transfer and air quality. However, accurate representation of BrC in atmospheric models remains limited by insufficient understanding of its complex molecular composition and variable optical properties. In this study, we present a comparative molecular-level characterization of BrC chromophores in laboratory-generated organic aerosol (OA) mixtures representing pyrolysis components of wood-burning (WBOA) and dung-burning (DBOA) emissions, corresponding to two commonly used categories of residential biomass fuels. Using a hyphenated high-performance liquid chromatography-photodiode array-high-resolution mass spectrometry (HPLC-PDA-HRMS) platform, we analyzed these mixtures alongside 100 BrC reference compounds and evaluated the composition, volatility, and light-absorbing properties of their constituent species. WBOA was found to be enriched in CHO-class chromophores primarily derived from lignin decomposition, while DBOA contained a higher abundance of CHON and CHN classes corresponding to reduced N-containing organic compounds (RNOCs). N-heterocyclic compound classes, such as pyrrole- and pyrazine-containing species, were plausibly detected in the DBOA mixture. Double bond equivalency analysis identified a substantial fraction of potential BrC chromophores in both mixtures, although their chemical classes, structural features, and optical properties differed significantly. Volatility basis set modeling revealed that WBOA components are less volatile and remain in the particle phase under a wider range of atmospheric conditions, while DBOA constituents partition more readily to the gas phase. These findings underscore the need for more detailed treatment of BrC variability in chemical transport models, especially in regions where dung is a dominant household fuel. This study advances molecular-level understanding of BrC and highlights the importance of fuel type in shaping its atmospheric behavior.

Particulate-bound mercury (PBM) plays a critical role in atmospheric mercury (Hg) cycling, yet its complex spatiotemporal variability and potential driving factors remain insufficiently understood, particularly in the Southeast Asia (SEA) region. This study reported year-round (May 2022 to April 2023) data of PBM at an urban (Nguyen Van Cu: 59.81 ± 29.15 pg m⁻³) and a suburban site (Can Gio: 26.4 ± 9.59 pg m⁻³) in southern Vietnam. Distinct seasonal trends were observed at both sites, with elevated PBM concentrations in the dry season (November–February), likely driven by changes in the source origin and transport paths of air masses. Lower PBM concentrations in the wet season (July–September) may result from enhanced removal by wet deposition, whereas limited rainfall in the dry season reduces this effect, leading to higher concentrations. We employed Generalized Additive Models (GAMs), which effectively captured nonlinear relationships between PBM and meteorological-chemical covariates. GAMs explained 87.7% of PBM variance in the urban area and 41.6% in the suburban area, indicating better model performance in urban vs. suburban areas. In the urban area, metals (i.e. Cr, Sr, Pb, and V) were the dominant contributors (36.7%), suggesting influence from industrial and traffic-related sources. In contrast, PBM at the suburban site was mainly modulated by temperature (60.8%), Zn (21.3%), and planetary boundary layer height (17.9%), pointing to the significance of atmospheric processes over local emissions. Our findings highlight the utility of GAMs in resolving complex PBM-environment interactions and indicate their potential for advancing source attribution and informing targeted mercury mitigation strategies.

The increasing size, severity, and frequency of wildfires have led to dramatic increases in particulate matter concentrations in the troposphere. Severe wildfires can generate intense convective systems capable of transporting large quantities of biomass burning organic aerosols (BBOA) to the upper troposphere and lower stratosphere (UTLS). Chemically complex organic matter and light-absorbing carbonaceous material is introduced into stratospheric regions that were historically isolated from direct surface emissions. In this study, stratospheric particles were sampled over North America during the Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) campaign, an aircraft-based research project designed to characterize convective perturbation in the UTLS. Particle samples collected from six research flights during summer 2022 were analyzed using Computer-Controlled Scanning Electron Microscopy and Scanning Transmission X-ray Microscopy to investigate particle size distributions, morphology, chemical composition, and mixing state of stratospheric particles along transects across the continental United States and adjacent Pacific Ocean airspace. Analysis revealed that all sampled particles contained detectable levels of carbon, with most exhibiting organic volume fractions of 0.37 ± 0.20. Notably, about 5% of the particles also contained soot inclusions, which indicates the presence of refractory black carbon transported to stratospheric altitudes and provides direct evidence of wildfire-derived black carbon reaching the UTLS. Typical particle morphology exhibits organic shells over soot and inorganic cores and suggests secondary processing and aging of BBOA during transport to and within the UTLS. These findings provide compelling evidence that wildfire emissions play a critical role in affecting the long-term composition and radiative properties of stratospheric particles.

The formation of a peroxide accretion product (ROOR) has recently been shown to be a significant channel in self- and cross-reactions of peroxy radicals (RO₂) in the gas-phase. Here, we examine the formation of this accretion product in the self- and cross-reactions of RO₂ derived from the OH-initiated oxidation of propene, cis-2-butene, and methylpropene in the presence of ethene. We measure the formation rate coefficient of the various accretion products in each system relative to the formation rate coefficient of the ethene-derived ROOR, which was measured in our previous work. We find that the accretion product forms in all of the studied self- and cross-reactions. The measured ROOR formation rate coefficient for the self-reaction decreases by approximately an order of magnitude with increasing substitution, with average rate coefficients of 4.7 × 10⁻¹³ cm³ molec⁻¹ s⁻¹ for primary hydroxy peroxy radicals, 2.7 × 10⁻¹⁴ cm³ molec⁻¹ s⁻¹ for secondary hydroxy peroxy radicals, and 8.0 × 10⁻¹⁶ cm³ molec⁻¹ s⁻¹ for the tertiary hydroxy peroxy radical. The cross-reaction rate coefficients of secondary and tertiary peroxy radicals with primary peroxy radicals are both higher than the corresponsing self-reactions, and also decrease with increasing radical substitution. We estimate the branching fraction to the formation of the ROOR for these peroxy radical self- and cross-reactions and find that branching fractions range from 0.03–0.33, with self- and cross-reactions of primary peroxy radicals having the highest branching fractions. Finally, we compare the reaction and ROOR formation rate coefficients of self- and cross-reactions of small RO₂, and determine that the arithmetic mean of self-reaction rate coefficients provides a suitable method for estimating cross-reaction rate coefficients.