Environmental science: atmospheres最新文献

Entrainment-mixing processes of fog with the surrounding ambient air are extremely intricate and impose significant effects on the microphysical and radiative properties of fog. However, it is difficult to utilize the default Thompson scheme of the atmospheric chemistry model GRAPES_Meso5.1/CUACE to examine the effects of different entrainment-mixing mechanisms on the microphysical and radiative properties of fog. To address this issue, this scheme is modified to include homogeneous mixing degree to investigate the effects of various entrainment-mixing processes on typical regional fog simultaneously occurring in the Northeast China and Yangtze River Delta regions from December 31, 2016, to January 2, 2017, and from January 6 to 8, 2017. It is revealed that inhomogeneous entrainment-mixing processes can result in smaller fog droplet number concentration and lower liquid water path, and larger fog droplet size. These phenomena, in turn, can lead to a decreased fog optical thickness and increased visibility. Furthermore, the effects of inhomogeneous entrainment-mixing processes depend on fog thickness, i.e., the effects in thin fog in the Northeast China region are more significant than those in thick fog in the Yangtze River Delta region. This primarily occurs because the proportion of evaporated grids in thin fog is higher than that in thick fog by 16% and 6%, respectively. These findings enhance the theoretical understanding of entrainment-mixing processes and lay the foundation for improving model parameterization.

Carbon monoxide has long been known as an indoor air pollutant, but has rarely been in the focus of scientific interest. This circumstance is certainly disadvantageous for the health-related assessment of indoor air quality, because exposure to carbon monoxide is often associated with serious or fatal poisoning. From an analytical perspective, the problem is that increased carbon monoxide concentrations often occur unexpectedly and within a short period of time, usually in connection with incomplete combustion processes. Therefore, the exposure of the general population to carbon monoxide cannot be determined using environmental surveys. In recent years, however, carbon monoxide has again received significantly greater attention. A number of studies have been carried out on carbon monoxide exposure under certain conditions, for example when using candles, gas stoves or in waterpipe cafés. In addition, the World Health Organization has derived guideline values for different exposure times. Due to its molecular properties, carbon monoxide is very suitable for selective and sensitive measurement with high time resolution using infrared techniques. In addition, sensor technology has made significant progress, so that robust devices are now available for online monitoring. Carbon monoxide can definitely be considered a priority pollutant for indoor air. Actually, increased concentrations are always associated with health risk. It is therefore recommended to use carbon monoxide as an indicator of indoor air quality. This can be realized in a variety of ways and preferably in combination with other parameters.

The composition of air-exposed surfaces can have a strong impact on air quality and chemical exposure in the indoor environment. Third hand smoke (THS), which includes surface-deposited cigarette smoke residue along with the collection of gases evolved from such residues, is becoming increasingly recognized as an important source of long-term tobacco smoke exposure. While studies have described gas/surface partitioning behaviour and some multiphase reaction systems involving THS, the possibility of time-dependent changes in chemical composition due to chemical reactivity that is endogenous to the deposited film has yet to be investigated. In this study, sidestream cigarette smoke was allowed to deposit on glass surfaces that were either clean or pre-coated with chemicals that may be oxidized by reactive oxygen species found in the smoke. Surface films included a low volatility antioxidant, tris(2-carboxyethyl)phosphine (TCEP), and two compounds relevant to surface films found within buildings, oleic acid (OA) and squalene (SQ). Upon deposition, oxidation products of nicotine, TCEP, OA, and SQ were formed over time periods of hours to weeks. The inherent oxidative potential of cigarette smoke deposited as a THS film can therefore initiate and sustain oxidation chemistry, transforming the chemical composition of surface films over long periods of time after initial smoke deposition. An interpretation of the THS oxidation results is provided in the context of other types of deposited particulate air pollutants with known oxidative potential that may be introduced to indoor environments. Continued study of THS and deposited surface films found indoors should consider the concept that chemical reservoirs found on surfaces may be reactive, that the chemical composition of indoor surface films may be time-dependent, and that the deposition of aerosol particles can act as a mechanism to initiate oxidation in surface films.

Increased throughput and container ship backlogs at the ports of Los Angeles and Long Beach due to supply chain disruptions related to the COVID-19 pandemic caused a significant increase in the number of ships near the California coast, leading to concerns about increased air pollution exposure of nearby communities. We use a combination of satellite-based observations from TROPOMI and ground-based observations from routine surface monitoring sites with chemical transport model results to analyze the changes in NO₂ and PM_2.5 in the Los Angeles Basin during a period in 2021 when the number of ships was at its peak. Using simulations to account for meteorological effects, changes are apportioned to emissions and meteorology. The largest emission-related changes in column NO₂ occurred immediately east of the ports where emission-related NO₂ increased by 28% compared to the baseline (2018–2019 average). In Central Los Angeles, emission reductions led to a 10% decrease in NO₂ during the same period. Emission-related PM_2.5 increased by 0.7 μg m⁻³ on average with a maximum increase of 4.5 μg m⁻³ in the eastern part of Basin. The emission/meteorology attribution method presented here provides a novel approach to quantify emission-influenced changes in air quality that are consistent with observations and suggests that both NO₂ and PM_2.5 were elevated in parts of the Los Angeles area during a period of increased port activity.

Aerosols formed and grown by gas-to-particle processes are a major contributor to smog and haze in megacities, despite the competition between growth and loss rates. Rapid growth rates from ammonium nitrate formation have the potential to sustain particle number in typical urban polluted conditions. This process requires supersaturation of gas-phase ammonia and nitric acid with respect to ammonium nitrate saturation ratios. Urban environments are inhomogeneous. In the troposphere, vertical mixing is fast, and aerosols may experience rapidly changing temperatures. In areas close to sources of pollution, gas-phase concentrations can also be highly variable. In this work we present results from nucleation experiments at −10 °C and 5 °C in the CLOUD chamber at CERN. We verify, using a kinetic model, how long supersaturation is likely to be sustained under urban conditions with temperature and concentration inhomogeneities, and the impact it may have on the particle size distribution. We show that rapid and strong temperature changes of 1 °C min⁻¹ are needed to cause rapid growth of nanoparticles through ammonium nitrate formation. Furthermore, inhomogeneous emissions of ammonia in cities may also cause rapid growth of particles.

Ensuring environmental justice necessitates equitable access to air quality data, particularly for vulnerable communities. However, traditional air quality data from reference monitors can be costly and challenging to interpret without in-depth knowledge of local meteorology. Low-cost monitors present an opportunity to enhance data availability in developing countries and enable the establishment of local monitoring networks. While machine learning models have shown promise in atmospheric dispersion modelling, many existing approaches rely on complementary data sources that are inaccessible in low-income areas, such as smartphone tracking and real-time traffic monitoring. This study addresses these limitations by introducing deep learning-based models for particulate matter dispersion at the neighbourhood scale. The models utilize data from low-cost monitors and widely available free datasets, delivering root mean square errors (RMSE) below 2.9 μg m⁻³ for PM₁, PM_2.5, and PM₁₀. The sensitivity analysis shows that the most important inputs to the models were the nearby monitors' PM concentrations, boundary layer dissipation and height, and precipitation variables. The models presented different sensitivities to each road type, and an RMSE below the regional differences, evidencing the learning of the spatial dependencies. This breakthrough paves the way for applications in various vulnerable localities, significantly improving air pollution data accessibility and contributing to environmental justice. Moreover, this work sets the stage for future research endeavours in refining the models and expanding data accessibility using alternative sources.

Our estimates show that ‘proven reserves’ of fossil fuels in 2022, would generate an estimated 4777 Gt of CO₂ after allowing for non-fuel uses. This quantity already could ‘bust CO₂ budgets’ for IPCC RCP2.6, RCP4.5, and RCP6.0 and is approaching the range for RCP8.5. Notwithstanding these results, fossil fuel companies are still exploring and bringing new reserves onstream. We discuss the reasons behind this, and propose some policy options for governments as they address this situation.

Charging of the ice–vapor interface is a well-studied topic in ice physics and atmospheric electrification. However, these effects were not yet considered to examine chemical processes in snow in polar regions because electric potentials at ice surfaces have so far been considered insufficient to initiate chemical reactions and processes. In this review, we analyze literature data to estimate levels of electrification in snow and other frozen objects that can be caused by different processes occurring at the Earth's surface. This analysis demonstrates that threshold values of electric field strength can be exceeded for the appearance of corona discharges and even for the formation of Rayleigh jets due to combined effects of different meteorological and physical processes. The accumulation of electrical charges can lead to different chemical modifications such as electroosmotic phenomena or the accumulation of impurities from the atmosphere in growing ice crystals. Moreover, highly energetic states that occur and dissipate in microseconds as “hot spots” have the potential to initiate free radical processes and even the production of charged aerosols. The review also discusses in detail selected field observations to point out how processes driven by electrical charging may help to interpret these observations, which are at least partly inconsistent with our present understanding of snow and ice chemistry. Finally, some approaches are presented how these effects can be studied in field and laboratory experiments. A further development of this new field at the intersection of ice physics and snow chemistry seems very promising for a better understanding of relevant chemical processes related to the cryosphere.

Exposure to PM_2.5 emitted from traditional biomass cookstoves is a significant health risk for nearly one-third of the global population. Improved cookstoves aim to reduce pollutant emissions, but there is limited evidence of whether PM_2.5 toxicity is also reduced. Using the dithiothreitol (DTT) assay to measure the potential for PM_2.5 chemical components to induce oxidative stress through antioxidant depletion and/or oxidant generation, we characterized the mass- and volume-normalized DTT activity of PM_2.5 emitted from a traditional three-stone fire cookstove and three improved cookstoves burning wood or charcoal fuels. Although improved cookstoves typically yield lower PM_2.5 mass concentrations compared to traditional three-stone cookstove, exposure to DTT active PM_2.5 is not always reduced due to increases in mass-normalized DTT activity. A notable decrease in DTT active PM_2.5 exposure (by 67%) was only observed for a forced-draft improved cookstove burning wood, where low PM_2.5 mass concentration offsets the increased mass-normalized DTT activity. Additionally, elemental carbon and water-soluble organic matter were identified as key predictors of volume-normalized DTT activity. Compared to wood, the use of charcoal led to a 61–86% reduction in exposure to DTT active PM_2.5, owing to both lower PM_2.5 mass concentration and mass-normalized DTT activity. This further supports a proposed strategy whereby biomass fuel treatment can potentially reduce household exposure to toxic PM_2.5. Collectively, our findings emphasized the need to consider not only the mass concentration but also the toxic properties of PM_2.5 when evaluating the health impacts of cookstoves and fuels.

Correction for ‘Emerging investigator series: aqueous oxidation of isoprene-derived organic aerosol species as a source of atmospheric formic and acetic acids’ by Kelvin H. Bates et al., Environ. Sci.: Atmos., 2023, 3, 1651–1664, https://doi.org/10.1039/D3EA00076A.