Extreme oxidant amounts produced by lightning in storm clouds

Pollen and sub-pollen particles: External interactions shaping the allergic potential of pollen

Pollen allergies, such as allergic rhinitis, are triggered by exposure to airborne pollen. They are a considerable global health burden, with their numbers expected to rise in the coming decades due to the advent of climate change and air pollution. The relationships that exist between pollens, meteorological, and environmental conditions are complex due to a lack of clarity on the nature and conditions associated with these interactions; therefore, it is challenging to describe their direct impacts on allergenic potential clearly. This article attempts to review evidence pertaining to the possible influence of meteorological factors and air pollutants on the allergic potential of pollen by studying the interactions that pollen undergoes, from its inception to atmospheric traversal to human exposure. This study classifies the evidence based on the nature of these interactions as physical, chemical, source, and biological, thereby simplifying the complexities in describing these interactions. Physical conditions facilitating pollen rupturing for tree, grass, and weed pollen, along with their mechanisms, are studied. The effects of pollen exposure to air pollutants and their impact on pollen allergenic potential are presented along with the possible outcomes following these interactions, such as pollen fragmentation (SPP generation), deposition of particulate matter on pollen exine, and modification of protein levels in-situ of pollen. This study also delves into evidence on plant-based (source and biological) interactions, which could indirectly influence the allergic potential of pollen. The current state of knowledge, open questions, and a brief overview of future research directions are outlined and discussed. We suggest that future studies should utilise a multi-disciplinary approach to better understand this complex system of pollen interactions that occur in nature.

Ionic Route to Atmospheric Relevant HO2 and Protonated Formaldehyde from Methanol Cation and O2

Gas-phase ion chemistry influences atmospheric processes, particularly in the formation of cloud condensation nuclei by producing ionic and neutral species in the upper troposphere-stratosphere region impacted by cosmic rays. This work investigates an exothermic ionic route to the formation of hydroperoxyl radical (HO2) and protonated formaldehyde from methanol radical cation and molecular oxygen. Methanol, a key atmospheric component, contributes to global emissions and participates in various chemical reactions affecting atmospheric composition. The two reactant species are of fundamental interest due to their role in atmospheric photochemical reactions, and HO2 is also notable for its production during lightning events. Our experimental investigations using synchrotron radiation reveal a fast hydrogen transfer from the methyl group of methanol to oxygen, leading to the formation of CH2OH+ and HO2. Computational analysis corroborates the experimental findings, elucidating the reaction dynamics and hydrogen transfer pathway. The rate coefficients are obtained from experimental data and shows that this reaction is fast and governed by capture theory. Our study contributes to a deeper understanding of atmospheric processes and highlights the role of ion-driven reactions in atmospheric chemistry.

Spatiotemporal Characteristics Determining the Multifaceted Nature of Reactive Oxygen, Nitrogen, and Sulfur Species in Relation to Proton Homeostasis

Significance: Reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) act as signaling molecules, regulating gene expression, enzyme activity, and physiological responses. However, excessive amounts of these molecular species can lead to deleterious effects, causing cellular damage and death. This dual nature of ROS, RNS, and RSS presents an intriguing conundrum that calls for a new paradigm. Recent Advances: Recent advancements in the study of photosynthesis have offered significant insights at the molecular level and with high temporal resolution into how the photosystem II oxygen-evolving complex manages to prevent harmful ROS production during the water-splitting process. These findings suggest that a dynamic spatiotemporal arrangement of redox reactions, coupled with strict regulation of proton transfer, is crucial for minimizing unnecessary ROS formation. Critical Issues: To better understand the multifaceted nature of these reactive molecular species in biology, it is worth considering a more holistic view that combines ecological and evolutionary perspectives on ROS, RNS, and RSS. By integrating spatiotemporal perspectives into global, cellular, and biochemical events, we discuss local pH or proton availability as a critical determinant associated with the generation and action of ROS, RNS, and RSS in biological systems. Future Directions: The concept of localized proton availability will not only help explain the multifaceted nature of these ubiquitous simple molecules in diverse systems but also provide a basis for new therapeutic strategies to manage and manipulate these reactive species in neural disorders, pathogenic diseases, and antiaging efforts.

Oxidized organic molecules in the tropical free troposphere over Amazonia

New particle formation (NPF) in the tropical free troposphere (FT) is a globally important source of cloud condensation nuclei, affecting cloud properties and climate. Oxidized organic molecules (OOMs) produced from biogenic volatile organic compounds are believed to contribute to aerosol formation in the tropical FT, but without direct chemical observations. We performed in situ molecular-level OOMs measurements at the Bolivian station Chacaltaya at 5240 m above sea level, on the western edge of Amazonia. For the first time, we demonstrate the presence of OOMs, mainly with 4-5 carbon atoms, in both gas-phase and particle-phase (in terms of mass contribution) measurements in tropical FT air from Amazonia. These observations, combined with air mass history analyses, indicate that the observed OOMs are linked to isoprene emitted from the rainforests hundreds of kilometers away. Based on particle-phase measurements, we find that these compounds can contribute to NPF, at least the growth of newly formed nanoparticles, in the tropical FT on a continental scale. Thus, our study is a fundamental and significant step in understanding the aerosol formation process in the tropical FT.

Natural Selection and Scale Invariance

This review points out that three of the essential features of natural selection—competition for a finite resource, variation, and transmission of memory—occur in an extremely simple, thermalized molecular population, one of colliding “billiard balls” subject to an anisotropy, a directional flux of energetic molecules. The emergence of scaling behavior, scale invariance, in such systems is considered in the context of the emergence of complexity driven by Gibbs free energy, the origins of life, and known chemistries in planetary and astrophysical conditions. It is suggested that the thermodynamic formalism of statistical multifractality offers a parallel between the microscopic and macroscopic views of non-equilibrium systems and their evolution, different from, empirically determinable, and therefore complementing traditional definitions of entropy and its production in living systems. Further, the approach supports the existence of a bridge between microscopic and macroscopic scales, the missing mesoscopic scale. It is argued that natural selection consequently operates on all scales—whether or not life results will depend on both the initial and the evolving boundary conditions. That life alters the boundary conditions ensures nonlinearity and scale invariance. Evolution by natural selection will have taken place in Earth’s fluid envelope; both air and water display scale invariance and are far from chemical equilibrium, a complex condition driven by the Gibbs free energy arising from the entropy difference between the incoming solar beam and the outgoing infrared radiation to the cold sink of space acting on the initial conditions within evolving boundary conditions. Symmetry breaking’s role in the atmospheric state is discussed, particularly in regard to aerosol fission in the context of airborne bacteria and viruses in both current and prebiotic times. Over 4.4 billion years, the factors operating to support natural selection will have evolved along with the entire system from relative simplicity to the current complexity.

Spaceborne Observations of Lightning NO2 in the Arctic

The Arctic region is experiencing notable warming as well as more lightning. Lightning is the dominant source of upper tropospheric nitrogen oxides (NO_x), which are precursors for ozone and hydroxyl radicals. In this study, we combine the nitrogen dioxide (NO₂) observations from the TROPOspheric Monitoring Instrument (TROPOMI) with Vaisala Global Lightning Dataset 360 to evaluate lightning NO₂ (LNO₂) production in the Arctic. By analyzing consecutive TROPOMI NO₂ observations, we determine the lifetime and production efficiency of LNO₂ during the summers of 2019-2021. Our results show that the LNO₂ production efficiency over the ocean is ∼6 times higher than over continental regions. Additionally, we find that a higher LNO₂ production efficiency is often correlated with lower lightning rates. The summertime lightning NO_x emission in the Arctic (north of 70° N) is estimated to be 219 ± 116 Mg of N, which is equal to 5% of anthropogenic NO_x emissions. However, for the span of a few hours, the Arctic LNO₂ density can even be comparable to anthropogenic NO₂ emissions in the region. These new findings suggest that LNO₂ can play an important role in the upper-troposphere/lower-stratosphere atmospheric chemical processes in the Arctic, particularly during the summer.

Global Distribution of Key Features of Streamer Corona Discharges in Thunderclouds

We present nighttime worldwide distributions of key features of Blue LUminous Events (BLUEs) detected by the Modular Multispectral Imaging Array of the Atmosphere-Space Interaction Monitor. Around 10% of all detected BLUEs exhibit an impulsive single pulse shape. The rest of BLUEs are unclear (impulsive or not) single, multiple or with ambiguous pulse shapes. BLUEs exhibit two distinct populations with peak power density <25 µWm^-2 (common) and ≥25 µWm^-2 (rare) with different rise times and durations. The altitude (and depth below cloud tops) zonal distribution of impulsive single pulse BLUEs indicate that they are commonly present between cloud tops and a depth of ≤4 km in the tropics and ≤1 km in mid and higher latitudes. Impulsive single pulse BLUEs in the tropics are the longest (up to ∼4 km height) and have the largest number of streamers (up to ∼3 × 10⁹). Additionally, the analysis of BLUEs has turned out to be particularly complex due to the abundance of radiation belt particles (at high latitudes and in the South Atlantic Anomaly [SAA]) and cosmic rays all over the planet. True BLUEs can not be fully distinguished from radiation belt particles and cosmic rays unless other ground-based measurements associated with the optically detected BLUEs are available. Thus, the search algorithm of BLUEs presented in Soler et al. (2021), https://doi.org/10.1029/2021gl094657 is now completed with a new additional step that, if used, can considerably smooth the SAA shadow but can also underestimate the number of BLUEs worldwide.

Extreme hydroxyl amounts generated by thunderstorm-induced corona on grounded metal objects

Atmospheric electrical discharges are now known to generate unexpectedly large amounts of the atmosphere's primary oxidant, hydroxyl (OH), in thunderstorm anvils, where electrical discharges are caused by atmospheric charge separation. The question is "Do other electrical discharges also generate large amounts of oxidants?" In this paper, we demonstrate that corona formed on grounded metal objects under thunderstorms produce extreme amounts of OH, hydroperoxyl (HO₂), and ozone (O₃). Hundreds of parts per trillion to parts per billion of OH and HO₂ were measured during seven thunderstorms that passed over the rooftop site during an air quality study in Houston, TX in summer 2006. A combination of analysis of these field results and laboratory experiments shows that these extreme oxidant amounts were generated by corona on the inlet of the OH-measuring instrument and that corona are easier to generate on lightning rods than on the inlet. In the laboratory, increasing the electric field increased OH, HO₂, and O₃, with 14 times more O₃ generated than OH and HO₂, which were equal. Calculations show that corona on lightning rods can annually generate OH that is 10-100 times ambient amounts within centimeters of the lightning rod and on high-voltage electrical power lines can generate OH that is 500 times ambient a meter away from the corona. Contrary to current thinking, previously unrecognized corona-generated OH, not corona-generated UV radiation, mostly likely initiates premature degradation of high-voltage polymer insulators.

Reaction between a NO2 Dimer and Dissolved SO2: A New Mechanism for ONSO3- Formation and its Fate in Aerosol

Experimental observations indicate that sulfate formation in aerosol is sensitive to the concentrations of nitric oxide (NO₂). While it also widely exists as a dimer in the gas phase, previous studies focus on the monomer of NO₂. In this study, we employ quantum chemical calculations and ab initio molecular dynamics simulations to investigate the reaction between the NO₂ dimer (ONONO₂) and sulfite (HSO₃^-/SO₃^2-) in the gas phase and in an aerosol. Gas-phase reactions turn out to be barrierless. In an aerosol, the reaction between adsorbed ONONO₂ and HSO₃^- to form ONSO₃^- follows a stepwise mechanism with proton and electron transfer processes. The reaction between ONONO₂ and SO₃^2- is more straightforward. Nevertheless, both reactions occur at a picosecond time scale. Decomposition of ONSO₃^- can form an NO molecule and SO₃^-, which gives a complementary pathway for sulfate formation in an aerosol. Hydrolysis of ONSO₃^- to form HNO and HSO₄^- is highly impossible in an aerosol, which calls for a revisit of the atmospheric N₂O formation mechanism. The results presented in this study deepen our understanding of the interaction between NO₂ and SO₂ pollutants in the atmosphere.