Journal of Atmospheric Chemistry最新文献

Brominated and iodinated methanes impact atmospheric chemistry, particularly through ozone depletion, but the environmental factors controlling their production by marine phytoplankton are not fully understood. This study examined how different light intensities (30, 60, 90, and 120 µmol photons m^− 2 s^− 1) affect the growth and halomethane production by the marine diatom Achnanthes subconstricta. Cultures were incubated under full-spectrum light, and concentrations of CHBr₃, CHBr₂Cl, CHBrCl₂, CH₂I₂, CH₂ClI, and CH₂BrI were measured using purge-and-trap gas chromatography–mass spectrometry. Phytoplankton growth, assessed by chlorophyll a concentration, increased with light intensity. Among brominated methanes, CHBr₃ and CHBr₂Cl were generally more abundant, and CHBrCl₂ was least abundant. Similarly, CH₂I₂ was generally the dominant iodinated methane, followed by CH₂ClI and CH₂BrI. The production rate ratios of CHBr₃ : CHBr₂Cl : CHBrCl₂ and CH₂I₂ : CH₂ClI : CH₂BrI were 1.8 : 1.7 : 1 and 5.2 : 2.0 : 1, respectively, at 120 µmol photons m^− 2 s^− 1 during the exponential phase. CHBr₃ production rates normalized to chlorophyll a were 2.13, 3.12, 9.49, and 7.24 nmol (g chlorophyll a)⁻¹ d^− 1 at 30, 60, 90, and 120 µmol photons m^− 2 s^− 1, respectively. Similarly, CH₂I₂ production rates normalized to chlorophyll a were 5.47, 2.53, 10.5, and 29.8 nmol (g chlorophyll a)⁻¹ d^− 1 at the same light intensities. These results demonstrate that halomethane production in A. subconstricta is markedly affected by light intensity, with distinct patterns observed for different compounds. The findings suggest that A. subconstricta may play a significant role in marine halocarbon emissions, with production that varies depending on light conditions and growth phase. 

Environmental pollution due to fine particulate matter (particulate matter ≤ 2.5 μm; PM_2.5) is a major health concern worldwide, especially in India. In the post-monsoon and winter seasons, meteorological conditions favor the confinement of aerosols, leading to higher concentrations of PM_2.5 in the Indo-Gangetic Plain (IGP). Scientific research has associated PM_2.5 exposure with various causes of premature mortality, including ischemic heart disease (IHD), chronic obstructive pulmonary disease (COPD), and lung cancer (LC). This study investigates spatial and temporal variability and transport of particulate matter (utilizing the airmass back trajectory analysis) over six states in the IGP to gain insights into their origin and transport, during the most polluted (post-monsoon and winter) seasons. Among all monitored locations, Delhi reported the greatest PM_2.5 loading during the winter and post-monsoon seasons (170.47 ± 84.80 µg m⁻³), followed by Patna, Bihar (130.47 ± 61.97 µg m⁻³). Using the Integrated Exposure–Response (IER) model, our analysis indicates that annual exposure to PM_2.5 could lead to more than 3,000 premature deaths per million people in each city, based on the WHO guideline limits. This study presents a comparative assessment of PM concentrations and the associated mortality risks across six states of the Indo-Gangetic Plain (IGP), with two monitoring sites in each state. The findings provide valuable insights to support policymakers in developing effective air quality management and mitigation strategies.

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Atmospheric simulation chambers (ASCs) are one of the most advanced tools for the experimental investigation of the oxidation of volatile organic compounds (VOCs) and the subsequent secondary organic aerosol (SOA) formation. Toluene is one of the most prevalent anthropogenic VOCs. Its photo-oxidation yields a wide range of products in the gas phase and a significant amount of SOA. Some of the remaining uncertainties about toluene atmospheric chemistry are possibly linked with chamber artifacts. In this study, several atmospheric simulation chambers, characterized by a great diversity (size, shape, material of walls, light source, instrumentation, measurement techniques, etc.), performed several toluene photo-oxidation experiments under different pre-set conditions (levels of toluene, NO_x, and relative humidity, presence, or lack of seeds). A model based on the Master Chemical Mechanism (MCM) and a SOA production module were used to facilitate the synthesis of the results. The results of the multiple-chamber toluene experiments suggest that a combination of facilities can provide a better picture of the overall behavior and that significant gaps remain in our understanding of the system, especially in the later oxidation stages. For cresol, a first-generation product, the observed gas-phase yields, ranging from 3% to 8% under low-NO_x conditions, were consistent with model predictions. In contrast, the measured gas-phase yields of benzaldehyde (8–16%%) were higher than the predicted (3–5%) yields, highlighting uncertainties in the H-abstraction pathway of the toluene reaction with hydroxyl radicals (OH). Glyoxal and methylglyoxal yields varied between facilities, with the model often failing to capture their temporal profiles. Additionally, the MCM-based model struggled to reproduce concentrations of oxygenated products (e.g., C₇H₈O₂ and C₇H₈O₃), suggesting shortcomings in simulating later oxidation stages. Most notably, the model consistently underpredicted SOA mass across experiments, pointing to critical gaps in the representation of SOA-forming pathways in the currently used version of the MCM.

Nitrate (NO₃^–) levels in air pollution have shown a sustained increase across eastern China. However, the key drivers behind rising surface NO₃^– concentrations remain unclear, posing challenges for targeted pollution control strategies. PM_2.5 samples were collected from September 2015 to August 2016 at both urban and suburban sites in Nanjing, a megacity in the Yangtze River Delta (YRD), for compositional analysis and source apportionment. The measured annual mean PM_2.5 concentration was 96.8 ± 46.0 µg m^–3. The positive matrix factorization model identified four primary PM_2.5 sources in Nanjing: secondary nitrate (19.4%), secondary sulfate (36.8%), coal and biomass burning (40.6%), and industrial emissions (3.2%). Water-soluble secondary inorganic aerosols (NO₃^–, SO₄^2–, NH₄⁺) dominated PM_2.5 composition, accounting for 92.7% of ionic components and 37.0% of total mass. NO₃^– concentrations exhibited significant increases in both absolute and relative terms as PM_2.5 pollution levels rose, suggesting its important role in PM_2.5 pollution. The results indicate that NO₃^– formation is enhanced under ammonia-rich conditions with low temperatures, high humidity, and elevated acidity. Policy-driven reductions in SO₂ and NO_x, without simultaneous NH₃ control, may have contributed to ammonia-rich conditions that facilitated NO₃^– formation, leading to NO₃^–-dominated PM_2.5 pollution in the YRD. Therefore, our results indicate that coordinated control of both nitrogen oxides and ammonia emissions may be necessary to mitigate NO₃^–-driven PM_2.5pollution.

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This study investigates the concentration and variation of key air pollutants SO₂, NOx, PM₁₀, and PM₂.₅ from 2009 to 2022 in Thiruvananthapuram, a city relatively free from industrial activities. SO₂ levels consistently remained well below the National Ambient Air Quality Standards whereas, PM₁₀ levels rose significantly, and often exceeded permissible limits. ICP-MS analysis revealed that Na, Zn, and Ca constitute up to 60% of the PM₁₀ mass, with major sources including sea salt, vehicular emissions, and construction activities. SEM and EDS analyses indicated a significant presence of carbonaceous particles and trace elements like Ba and Zn, which are linked to vehicular emissions and pose severe health risks. The presence of black carbon (BC) and organic carbon further underscores the contribution of transportation to air pollution. These findings are found to be consistent with broader national and global air quality challenges. The rising PM₁₀ levels mirror trends observed in other Indian cities, where urbanization and vehicular emissions remain the primary pollution sources. On a global scale, the presence of hazardous pollutants such as BC and heavy metals in urban environments is a critical public health concern. This study underscores the urgent need for targeted local air quality management strategies that align with national and global efforts to mitigate air pollution and protect public health.

Ozone (O₃) and carbon dioxide (CO₂) critically influence climate change through complex interactions with terrestrial vegetation. Ground-level O₃ forms via NO_x and VOCs photochemistry, while CO₂ primarily comes from fossil fuel combustion. Their atmospheric concentrations interact through physicochemical processes: elevated CO₂ levels may accelerate photochemical reaction rates of O₃ precursors due to climate warming, while O₃, as a potent oxidant, alters atmospheric oxidation capacity and consequently affects the lifetime of other greenhouse gases. Plant stomata serve as the primary interface for gas exchange between terrestrial ecosystems and the atmosphere, playing a critical role in regulating O₃ uptake and CO₂ assimilation. Plants simultaneously uptake CO₂ for photosynthesis and absorb O₃ through stomata. Interestingly, rising CO₂ concentrations induce partial stomatal closure, thereby reducing O₃ uptake. Conversely, elevated O₃ concentrations entering stomata trigger oxidative stress responses in plants, leading to decreased stomatal conductance. While this defensive mechanism limits further O₃ absorption, it simultaneously restricts CO₂ uptake efficiency, ultimately impairing photosynthetic performance and carbon sequestration capacity. This review investigates the ecological effects of O₃ and CO₂ interactions, focusing on vegetation-mediated gas exchange and its feedback on atmospheric composition. This review examines flux monitoring technologies and modeling approaches, highlighting how O₃ pollution influences CO₂ assimilation and how plant responses contribute to atmospheric O₃ regulation. Key factors such as species traits, growth conditions, and environmental variables are analyzed to evaluate how they modulate these interactions. By synthesizing current understanding of vegetation-regulated O₃ and CO₂ interactions, this study provides important insights for pollution control and sustainable ecosystem management.

Oligomeric hydroperoxides, including stabilized Criegee intermediates generated during isoprene ozonolysis, play an important role in new particle formation (NPF). In this study, we experimentally determined the relative abundance (Φ^NPF) of new particles formed during isoprene ozonolysis, competing against the growth of preexisting particles. The number concentration of newly formed particles (N^NPF) during isoprene ozonolysis was derived by comparing the size distribution of secondary organic aerosols (SOAs) in the presence of seed particles with that under humid conditions (relative humidity (RH) > 20%) at the same reaction time. The number concentration of particles that took up semi-volatile organic compounds (N^uptake) was estimated from the difference in the size distribution between particle wall loss (PWL)-considered seed particles and SOAs with seed particles under humid conditions. The Φ^NPF was then calculated using the formula: N^NPF/(N^NPF + N^uptake) under different conditions. The methodology to determine the N^NPF was generally successful, whereas the determination of N^uptake was complicated due to the instability of PWL in the small Teflon bag experiments. The Φ^NPF can be represented as a product of the r^NPF(RH), the relative abundance of new particles formed during isoprene ozonolysis as a function of RH, and the ϕ^NPF(dry), the Φ^NPF value obtained under dry conditions. The obtained r^NPF(RH) values suggested that NPF can occur only under very limited RH conditions (RH < 10%) of isoprene ozonolysis in the atmosphere, but the products from the reaction of isoprene with O₃, probably Criegee intermediate oligomerization products, were found mainly to contribute to NPF.

The Hunga Tonga-Hunga Ha’apai volcanic eruption in January 2022 injected an extraordinary amount of water vapour into the tropical stratosphere (estimated at 150 Tg) along with a modest injection of sulphur dioxide (estimated at 0.4 Tg). Using a suite of ground-based remote-sensing trace gas measurements located at Arrival Heights, Antarctica (78 S, 167E), along with co-located satellite measurements of water vapour and stratospheric aerosol optical depth, we observed the evolution of the 2023 ozone hole. Arrival Heights was located beneath the polar vortex for extended periods during the austral spring (late August to early December) 2023. Within this period, satellite measurements of lower stratospheric water vapour above Arrival Heights fall within climatology norms (2004–2023) while elevated (70% increase in September mean sAOD), but highly variable, levels of stratospheric aerosol optical depth were observed. Ground-based measurements (total and partial columns) of ozone, ClO, HCl, ClONO₂, OClO, NO, NO₂ and HNO₃ throughout springtime show no measurable attributable impact of Hunga Tonga-Hunga Ha’apai water vapour on stratospheric chemical composition, and ozone depletion within the polar vortex. Prolonged denitrification and elevated levels of chlorine monoxide in the second half of September were caused by unseasonally low stratospheric temperatures. Contemporary TOMCAT 3-D chemical transport model simulations are in overall good agreement with observations. The model simulations indicate Hunga Tonga-Hunga Ha’apai water vapour caused an additional reduction in total column ozone of 5 -7 DU over Arrival Heights in spring and early summer within the polar vortex. Such small differences are not discernible using the current measurement dataset given atmospheric variability, measurement precision and observational gaps. The simulations indicate the largest additional reduction in total column ozone were in the polar vortex collar region, where increased water vapour loading caused additional ozone loss up to 13 DU over Arrival Heights.

In this study, the weekly total water-soluble inorganic ions (TWSII) concentrations of PM_2.5 in the coastal city of Algeria, Bou-Ismail, were determined from December 29th, 2013, to June 29th, 2014, under the ChArMEx project. This study aimed to identify the seasonal sources and chemical composition of PM2.5-bound water-soluble inorganic ions (WSIIs) in a coastal city of Algeria using principal component analysis (PCA). The findings indicated that the TWSII concentration was 14.06 ± 0.22 µg m⁻³ during the winter and 12.35 ± 0.42 µg m⁻³ during the spring. The Na⁺, NH₄⁺, NO₃⁻, and Cl⁻ ions were the main TWSII in winter, whilst Na⁺, NH₄⁺, oxalate, and NO₃⁻ ions were the main WSII in spring. PCA identified two sources for winter: PC1 is a mix of pollutants from secondary organic traces, marine sources, and stationary emissions from burning, while PC2 encompasses operations, construction materials, and secondary gas-particle transformations. For spring, four sources were identified: PC1, marine aerosol emissions; PC2, stationary emissions, agricultural practices, marine biogenic emissions, and biomass burning; PC3, photochemical response; and PC4, soil dust. The whole sample campaign had a 1.29 cationic-to-anionic regression slope. The [NO₃⁻]/[SO₄²⁻] mass ratio was greater than (1) The findings indicated the strong influence of pollutants from mobile sources over stationary sources. Pathway 1 includes all west and northwest air masses from the sample location. Large air masses traverse the Atlantic via Spain, Portugal, southern France, and western Algeria. An air mass from the south traversed the Algerian Desert and southern Libya in Pathway (2) In pathway 3, northwest Italy and Tunisia across the Mediterranean Sea were the most polluted.