Environmental science: atmospheres最新文献

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.

We combine machine learning (ML) and geospatial interpolations to create two-dimensional high-resolution ozone concentration fields over the South Coast Air Basin (SoCAB) for the entire year of 2020. The interpolated ozone concentration fields were constructed using 15 building sites whose daily trends were predicted by random forest regression. Spatially interpolated ozone concentrations were evaluated at 12 sites that were independent from the machine learning sites and historical data to find the most suitable prediction method for SoCAB. Ordinary kriging interpolation had the best performance overall for 2020. The model is best at interpolating ozone concentrations inside the sampling region (bounded by the building sites), with R² ranging from 0.56 to 0.85 for those sites. All interpolation methods poorly predicted and underestimated ozone concentrations for Crestline during summer, indicating that the site has a distribution of ozone concentrations that is independent from all other sites. Therefore, historical data from coastal and inland sites should not be used to predict ozone in Crestline using data-driven spatial interpolation approaches. The study demonstrates the utility of ML and geospatial techniques for evaluating air pollution levels during anomalous periods. Both ML and the Community Multiscale Air Quality model do not fully capture the irregularities caused by emission reductions during the COVID-19 lockdown period (March–May) in the SoCAB. Including 2020 training data in the ML model training improves the model's performance and its potential to predict future abnormalities in air quality.

Iodine oxoacids are recognised for their significant contribution to the formation of new particles in marine and polar atmospheres. Nevertheless, to incorporate the iodine oxoacid nucleation mechanism into global simulations, it is essential to comprehend how this mechanism varies under various atmospheric conditions. In this study, we combined measurements from the CLOUD (Cosmic Leaving OUtdoor Droplets) chamber at CERN and simulations with a kinetic model to investigate the impact of temperature, ionisation, and humidity on iodine oxoacid nucleation. Our findings reveal that ion-induced particle formation rates remain largely unaffected by changes in temperature. However, neutral particle formation rates experience a significant increase when the temperature drops from +10 °C to −10 °C. Running the kinetic model with varying ionisation rates demonstrates that the particle formation rate only increases with a higher ionisation rate when the iodic acid concentration exceeds 1.5 × 10⁷ cm⁻³, a concentration rarely reached in pristine marine atmospheres. Consequently, our simulations suggest that, despite higher ionisation rates, the charged cluster nucleation pathway of iodic acid is unlikely to be enhanced in the upper troposphere by higher ionisation rates. Instead, the neutral nucleation channel is likely to be the dominant channel in that region. Notably, the iodine oxoacid nucleation mechanism remains unaffected by changes in relative humidity from 2% to 80%. However, under unrealistically dry conditions (below 0.008% RH at +10 °C), iodine oxides (I₂O₄ and I₂O₅) significantly enhance formation rates. Therefore, we conclude that iodine oxoacid nucleation is the dominant nucleation mechanism for iodine nucleation in the marine and polar boundary layer atmosphere.

Particulate Matter (PM) Low-Cost Sensors (LCS) can be used to monitor air quality in regions with limited access to reference monitors. This study carried out within the framework of the Improving Air Quality in West Africa (IAQWA) project provides high temporal resolution of data on fine aerosol (PM_2.5) mass concentrations in Abidjan (Cote d'Ivoire) and Accra (Ghana) through the deployment of field calibrated Real-time Affordable Multi-pollutant (RAMP) monitors. From February 2020 to June 2021, RAMPs were deployed at five sites in Abidjan and four sites in Accra. Using a temporal resolution of 15 seconds, the datasets provided by RAMPs allowed a comparative analysis of diurnal, daily and seasonal variability of PM_2.5 concentrations for different urban sites with distinct pollution sources, over an extended period of time. Diurnal variations in PM_2.5 concentrations showed prominent morning peaks related to traffic rush hours reaching up to 50 μg m⁻³. Evening peaks were significant for sites in residential neighborhoods, and pointed to residential type pollution sources. Seasonal differences are analysed over a yearly cycle and maximum values are found during the so-called long dry season (Harmattan), between December and February. During a prominent pollution episode in January 2021 observed by the ground network, analysis of 3D satellite data, revealed Saharan dust transport as an additional source of (fine) aerosol pollution significantly increasing PM_2.5. The same episode also revealed a limitation of LCS – an inability to adequately capture dust-dominated pollution, which can be quantified by reference monitors. Annual average PM_2.5 concentrations vary between 17 and 26 μg m⁻³. PM_2.5 differences between sites within a city, especially between traffic impacted and urban background sites, are larger than the differences between the two cities. These annual averages exceed World Health Organization (WHO) annual pollution thresholds from the 2005 (10 μg m⁻³) and 2021 (5 μg m⁻³) guidelines.

Microplastic particles in the atmosphere are regularly detected in urban areas as well as in very remote locations. Yet the sources, chemical transformation, transport, and abundance of airborne microplastics still remain largely unexplained. Therefore, their impact on health, weather and climate related processes lacks comprehensive understanding. Single particle detection presents a substantial challenge due to its time-consuming process and is conducted solely offline. To get more information about the distribution, fluxes and sources of microplastics in the atmosphere, a reliable and fast online measurement technique is of utmost importance. Here we demonstrate the use of the autofluorescence of microplastic particles for their online detection with a high sensitivity towards different widely used polymers. We deploy online, single particle fluorescence spectroscopy with a Wideband Integrated Bioaerosol Sensor WIBS 5/NEO (Droplet Measurement Technologies, USA), which enables single particle fluorescence measurements at two excitation wavelengths (280 nm and 370 nm) and in two emission windows (310–400 nm and 420–650 nm). We investigated shredded (<100 μm) everyday plastic products (drinking bottles and yogurt cups) and pure powders of polyethylene terephthalate (PET), polyethylene and polypropylene. For the broad range of typical plastic products analyzed, we detected fluorescence on a single particle level using the WIBS. The online detection can identify particles smaller than 2 μm. In the case of microplastic particles from a PET bottle, 1.2 μm sized particles can be detected with 95% efficiency. Comparison with biological aerosols reveals that microplastics can be distinguished from two abundant pollen species and investigation of the complete fluorescence excitation emission maps of all samples shows that online identification of microplastics might be possible with fluorescence techniques if multiple channels are available.