Environmental science: atmospheres最新文献

Fairbanks-North Star Borough, Alaska (FNSB) regularly experiences some of the worst wintertime air quality in the United States. Exceedances of the EPA's 24 h fine particulate matter (PM_2.5) rule are common, and can last for weeks-long periods. Here we present sub-hourly measurements of chemically-speciated aerosol measurements over a 25 month span from an Aerosol Chemical Speciation Monitor (ACSM). This dataset includes measurements from all four seasons and over three separate winters (2020, 2021, 2022). It spans a long enough duration to provide an overview of typical seasonal and diurnal variations in aerosol concentrations, composition, and sources in Fairbanks. We observe consistent high PM_2.5 concentrations in wintertime, which is dominated by organic aerosol (OA) and, to a lesser extent, sulfate (SO₄). We perform factor analysis of the OA using Positive Matrix Factorization (PMF), which reveals three factors, two of which are attributable to primary sources. These primary OA factors are highest in concentration and fractional contribution during wintertime. We show that high concentration periods are correlated with cold temperatures, and enriched in those organic aerosol components related to primary emissions. High concentration periods are also enriched in SO₄, though we show that some of the “SO₄” measured by the ACSM is very likely organosulfur compounds, which are more prevalent at high concentrations. We also show that within winter, there are significantly different diurnal patterns in PM components depending on meteorological parameters. This analysis is important for understanding air quality patterns in Fairbanks, and as context for the 2022 ALPACA measurement campaign.

Polycyclic aromatic compounds (PACs) encompass a range of organic pollutants, including polycyclic aromatic hydrocarbons (PAHs), alkyl-substituted PAHs (AlkPAHs), and others. PAHs have been extensively studied due to their environmental and health implications. AlkPAHs, however, have received relatively less attention, despite recent evidence suggesting their greater abundances in ambient air. Given their prevalence and potential risks, investigating the atmospheric transformation of AlkPAHs is crucial. This work focuses on the heterogeneous oxidation of AlkPAHs, specifically addressing the influence of alkyl groups on reaction kinetics. Oxidation by gas phase ozone was conducted on quartz filters, which serve as models for silica surfaces on which PACs can deposit with minimal chemical interactions. The results reveal that AlkPAHs react faster with ozone than PAHs do, with reaction rates increasing with higher alkyl group substitutions. Furthermore, oxygenated polycyclic aromatic hydrocarbons (OPAHs) were formed during the oxidation of 1-methylpyrene, with greater diversity than those from pyrene. These products are more polar and potentially more toxic than parent compounds. In conclusion, this research advances our understanding of PAC oxidation, focusing on AlkPAHs' heterogeneous oxidation, the influence of alkyl groups, and the formation of OPAHs. These insights have significant implications for air quality, health risk assessments, and the fate of PACs in the environment.

The development of catastrophic mesoscale convective systems in the atmosphere, such as thunderstorms, is caused by several factors, the most important of which is moisture in the lower troposphere and then the instability and lifting of air parcels. In pre-monsoon, northeast and adjoining eastern India are susceptible to thunderstorms. Herein, we analyse the spatial and temporal changes in thunderstorm activities in terms of convective available potential energy (CAPE) and other parameters during the pre-monsoon period (March, April and May) in northeast (NE) and adjoining eastern India using ground-based and reanalysis data. It is observed that atmospheric instability is relatively higher in southern West Bengal and Tripura compared to the other regions in NE and adjoining eastern India, with a CAPE value of about 1500–3000 J kg⁻¹ during pre-monsoon and 2000–3500 J kg⁻¹ in May, indicating that these regions are more vulnerable to thunderstorms. Other thunderstorm indicators such as convective inhibition (CIN), K-index (KI) and total totals index (TTI) also exhibit relatively higher values in these regions during pre-monsoon. Causal discovery and correlation analysis reveal a positive association of thunderstorm days with CAPE and TTI, but a negative link with CIN. A significant negative trend is estimated in CAPE and other parameters in NE and eastern India during May, which is more dominant in southern West Bengal and Tripura (about −8 to −12 J per kg per year). Stability indices such as KI and TTI also show significant negative trends in NE India. There is a negative trend in thunderstorm days at Mohanbari, Barapani, Jorhat, Pasighat and Silchar, while positive trends at Dhubri, Imphal, Tezpur and Lengpui in the recent decade (2011–2020), which is consistent with the changes in thunderstorm indicators at these stations. This study provides an important insight into thunderstorm activity in areas susceptible to extreme weather events in the context of recent climate change and global warming.

Monitoring and control of indoor air hygiene has gained much interest since the COVID-19 pandemic because the airborne route is the main pathway for the spread of SARS-CoV-2 and other pathogens, making it necessary to develop strategies to mitigate airborne transmission of diseases. This work addresses indoor breathable air hygiene by proposing the “in situ” reduction of airborne microorganisms with the nebulization of low and safe concentrations of hydrogen peroxide (H₂O_2, 0.5 and 1 ppm), ozone (O_3, 0.06 and 0.2 ppm), triethylene glycol (TEG, 17.1, 52 and 171.2 ppm), and their combinations. The antimicrobial activity was evaluated in an office room by assessing the viability of commercial extremophile sporulated bacteria and naturally present bacteria and fungi in surfaces and air. All three chemicals individually dispersed reduced the viability of sporulated bacteria and naturally occurring microorganisms. Binary combinations were more effective than individual agents in the case of the H₂O₂ and O₃ mixture against sporulated bacteria, and the O₃ and TEG mixture against airborne and surface bacteria. The ternary mixture was the most effective against commercial sporulated bacteria and airborne microorganisms. These results illustrate that the application of low and safe concentrations of antimicrobial compounds in indoor air could be an interesting strategy to reduce infection risk.

Light absorbing organic molecules known as brown carbon (BrC) can be emitted during processes such as cooking and combustion in indoor environments. We hypothesized that indoor BrC-containing cooking organic aerosols, or BrCOA, can act as sensitizers to generate the first excited state of molecular oxygen, singlet oxygen (), under indoor lighting conditions. Here, we used an impinger to collect aerosols from a range of cooking dishes, including pancakes, pan-fried Brussels sprouts and vegetable stir-fries, and irradiated these samples in a photoreactor with UVA and fluorescent lights and on a sunlit windowsill. Using furfuryl alcohol as a probe for , we determined steady-state concentrations of using liquid chromatography and calculated apparent quantum yields for each BrCOA sample. Our results show that under all indoor lighting conditions tested, BrCOA can indeed sensitize . Specifically, in solutions of BrCOA from pancakes, pan-fried Brussels sprouts, and vegetable stir-fries under UVA light, the concentrations were 2.56 ± 1.24 × 10⁻¹³ M, 2.24 ± 1.51 × 10⁻¹³ M, and 3.12 ± 0.86 × 10⁻¹³ M, respectively. These results suggest that production is not dish-dependent, but rather produced across a range of BrCOA samples. We then normalized the concentrations to the rate of absorbance to obtain apparent quantum yields up to 6.1%. Both the quality and the quantity of the chromophoric BrCOA were important for predicting the apparent quantum yield. Moreover, the indoor sunlit experiments led to the highest concentrations observed, with important implications on the formation of oxidants in sunlit kitchens. These results demonstrate the ability of BrCOA to produce in indoor environments, and thus for to be a competitive indoor oxidant.

Understanding the impact of rubber-derived particles on indoor environmental quality is crucial for effective environmental management. Emissions from both roads and textiles are recognized contributors to pollution across diverse environments, including indoor spaces. Benzothiazoles and their derivatives serve as valuable tracers for identifying pollutant sources. In this study, a total of eight benzothiazoles were determined in indoor size-segregated aerosol samples collected from 6th November to 11th December 2023 in Mestre-Venice. The selected offices host both university personnel and students. The results indicate that SO₃H-BTH, SH-BTH and OH-BTH were the most concentrated benzothiazoles in aerosol samples. The inhaled daily intake remained low if compared with previous studies, but higher values were found in fine particles (<0.56 μm). Despite the presence of an advanced filtration system, BTHs have been detected across various dimensional fractions, indicating an internal source. Considering that most of the benzothiazoles were distributed in the finest fraction, the findings raise concerns about their capability to reach alveoli and causing health issues.

Secondary organic aerosols (SOAs) originating from the oxidation of biogenic volatile organic compounds such as monoterpenes by atmospheric oxidants (e.g. OH, ozone, and NO₃), constitute a widespread source of organic aerosols in the atmosphere. Among monoterpenes, α-pinene has the highest emission rates and its ozonolysis is often used as a canonical SOA system. However, the molecular composition of SOAs obtained from monoterpene ozonolysis as a function of relative humidity (RH) remains unclear. Herein, we investigated the real-time molecular composition of SOAs obtained from the ozonolysis of α-pinene using extractive electrospray ionization coupled with long time-of-flight mass spectrometry (EESI-LTOF-MS). We investigated the dependence of the molecular composition on RH in the presence and absence of seed aerosols. We characterized a large number of organic compounds, including less oxygenated and highly oxygenated organic molecules (HOMs). In the presence of a ammonium sulfate (AS) seed aerosol, the fractions of both monomers and dimers in the SOAs from α-pinene ozonolysis remained largely unchanged as RH increased from 3% to 84%, which can be attributed to a similar extent of increase in the absolute abundance of both dimers and monomers with increasing RH. The increase of the absolute abundance of monomers is likely due to the enhanced partitioning of less oxygenated semi-volatile monomer products (such as C₁₀H₁₆O_x≤6) at higher RH. The increase in the absolute abundance of dimers may be attributed to acid-catalyzed reactions, which is corroborated by a marked change in the distribution pattern of dimers. The average O/C of the most abundant product families in the SOAs, such as C₁₀H₁₆O_x, decreased with increasing RH due to the decreasing fractions of more oxygenated products (C₁₀H₁₆O_x>6). However, the elemental composition (O/C and H/C) of the total SOA remained stable with increasing RH. In contrast, in the absence of the seed aerosol, an increase in the monomer fraction and a decrease in the dimer fraction were observed with increasing RH. These changes were attributed to a combination of different extents of condensation enhancement of monomer and dimer vapors by increasing RH and different vapor wall losses of monomers and dimers. Our results provide new insights into the RH-dependent molecular chemical composition of α-pinene SOAs. We also highlight the necessity to characterize the composition of SOAs at the molecular level.

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There is limited data on personal exposure to fine particulate matter (PM_2.5) for mothers in informal settlements in Africa. Identifying and characterizing the sources of exposure to PM_2.5 for this population is key to finding potential solutions for mitigating air pollution exposures. As part of the USAID-funded Kuboresha Afya Mitaani Urban Maternal, Newborn and Child Health project in Nairobi, Kenya, this study aimed to (1) characterize and map environments that contribute to fine particulate matter (PM_2.5) exposure for mothers and infants and (2) determine which factors drive exposure to PM_2.5. Mothers were enrolled and measured for 24 hours with PM_2.5 monitors and GPS loggers in two informal settlements in Nairobi (Dagoretti and Starehe), with complete data received from 73 participants. Two ambient PM_2.5 monitors were also installed in each of the respective communities. Time-activity surveys were administered following the monitoring period. Mean daily exposures were 39.9 and 45.5 µg m⁻³ in Dagoretti and Starehe, respectively, with 60% of samples exceeding the annual WHO Annual Interim-1 Target of 35 µg m⁻³. Normal daily activities such as sleeping, resting, running errands, and visiting with friends constituted over three-quarters of exposure sampling time. These activities were not associated with elevated PM_2.5 exposures, and generally tracked diurnal ambient patterns (morning and evening peaks). Personal exposures, however, did peak higher than ambient in the evenings when cooking was most common, and cooking with wood or charcoal was associated with higher PM_2.5 personal exposures (daily mean of 54.2 µg m⁻³ [n = 16], compared to 40.3 µg m⁻³ for those who used gas, liquid fuels or electricity [n = 57]). These results suggest that transitioning households to cleaner fuels, such as electricity, LPG, or ethanol, would be the most promising intervention that could rapidly reduce exposures of mothers in informal settlements where biomass use is common. At the same time, larger-scale sectoral efforts are needed to bring ambient PM_2.5 concentrations, and thus the overall population exposures, closer to WHO guidelines.

Accurate quantitative description of the atmospheric fine particulate matter (PM_2.5) burden requires an understanding of aerosol amounts and properties that transcends measurement platforms. For example, air quality studies often seek to describe ambient PM_2.5 with columnar aerosol optical depth (AOD), point measurements of mass, or some combination. PM_2.5 chemical constituents affect such measurements differently. We investigate the ratio of PM_2.5-to-AOD (η) from 2005 to 2016 at multiple surface locations across the contiguous U.S. using observations and models, and quantitatively account for PM_2.5 sampling bias of nitrate and aerosol liquid water (ALW). We find η peaks during winter and is lowest in summer at all locations, despite contrasting seasonality in PM_2.5 mass and AOD. Accounting for loss of nitrate and ALW from PM_2.5 monitors improves consistency among η calculations in space and time. Co-occurrence of extreme PM_2.5 mass concentrations and AOD events declined in the eastern U.S. but not in the west. On peak days, in all locations, ALW mass concentrations are higher and fractional contributions are larger relative to PM_2.5 chemical composition during average conditions. This suggests an increased fraction of ambient PM_2.5 is detectable via optical methods but not well described by surface mass networks on peak days. The Community Multiscale Air Quality (CMAQ) model reproduces similar spatial and temporal variability in η to surface observations in winter and summer simulations at the beginning and end of the analysis period. Accounting for sampling artifacts in surface monitors may improve agreement with model predictions and remote sensing of PM_2.5 mass concentrations. The poor understanding of organic compounds and their PM_2.5 sampling artifacts remains a critical open question.