Source Of Particles Research Articles

Assessment of the applicability of a model for aviation-related ultrafine particle concentrations for use in epidemiological studies

Background and objectivesIn recent years it has been shown that aircraft emissions are a dominant source of ultrafine particles in the surroundings of airports. However, health effects of long-term (monthly to yearly) exposure to these particles are unknown. As part of an integrated research program into the health risks of ultrafine particles around Schiphol Airport, the applicability of the dispersion model STACKS+ to assess long-term exposure to ultrafine particles from aviation was assessed. MethodologyA detailed comparison between modelled and measured particle number concentrations (PNC) due to aircraft emissions was carried out at ten locations in the surroundings of Schiphol Airport during two six-month periods in 2017 and 2018. In order to deduce the contribution of aviation to measured PNC, we applied a fitting method of the sum of the modelled contributions from aviation, the modelled contributions from traffic on main roads and the contributions from outside the study area estimated from the measurements, to the measured total PNC. The analysis yielded scaling factors and uncertainty estimates for each of the main contributions. We then subtracted the estimated background and modelled contributions of road traffic from the total measured PNC and took the remainder as an approximation of the measured contribution from aviation to PNC. We compared it to the modelled contribution from aviation, based on the averaged values for the six-month periods. ResultsBoth six-month averaged modelled and measured PNC due to aircraft emissions (i.e., adjusted for background) showed a large range at the monitoring locations representative for population exposure (from close to zero to 10 000 particles/cm3). Spearman and Pearson correlation coefficients between model and measurement results were high (>0.83). ConclusionsThe applied approach enabled us to obtain a robust estimate of the contribution of aviation to the measured PNC. The dispersion model is able to determine the spatially varying average concentrations due to aircraft emissions in residential areas over periods of 6 months, allowing for application in epidemiological studies into long-term exposure.

Tomato brown rugose fruit virus in aqueous environments - survival and significance of water-mediated transmission.

Tomato brown rugose fruit virus (ToBRFV) has recently emerged as a major disease of tomatoes and peppers. ToBRFV is a seed- and contact-transmitted virus. In Slovenia, ToBRFV RNA was detected in samples of wastewater, river, and water used to irrigate plants. Even though the source of detected RNA could not be clearly established, this raised the question of the significance of the detection of ToBRFV in water samples and experimental studies were performed to address this question. The data presented here confirm that the release of virus particles from the roots of infected plants is a source of infectious ToBRFV particles in water and that the virus can remain infective up to four weeks in water stored at room temperature, while its RNA can be detected for much longer. These data also indicate that irrigation with ToBRFV-contaminated water can lead to plant infection. In addition, it has been shown that ToBRFV circulated in drain water in commercial tomato greenhouses from other European countries and that an outbreak of ToBRFV can be detected by regular monitoring of drain water. A simple method for concentrating ToBRFV from water samples and a comparison of the sensitivity of different methods, including the determination of the highest ToBRFV dilution still capable of infecting test plants, were also investigated. The results of our studies fill the knowledge gaps in the epidemiology and diagnosis of ToBRFV, by studying the role of water-mediated transmission, and provide a reliable risk assessment to identify critical points for monitoring and control.

Molybdenum in basalt-hosted seafloor hydrothermal systems: Experimental, theoretical, and field sampling approaches

Seafloor hydrothermal vents represent potential sources of Mo and other biologically relevant transition metals to the global ocean, complementing continental runoff. Here, we use a combination of experimental, theoretical, and field-sampling approaches to investigate the behavior of Mo in basalt-hosted seafloor hydrothermal systems to provide insight into the processes controlling Mo concentrations in hydrothermal fluids and to derive estimates of vent fluid Mo concentrations and fluxes. Results of this study demonstrate that reaction fluids generated from 350 °C, 500 bar hydrothermal basalt alteration experiments contain 775–801 nmol/kg Mo and are thus comparable to a recently collected time series of natural seafloor vent fluids that contained 200–220 nmol/kg Mo at 302 °C and 29–30 nmol/kg at 281–282 °C (Evans et al., 2023). Synchrotron-based analyses of experimentally altered basalt produced in this study and additional natural samples of altered oceanic crust originally collected from Pito Deep Rift reveal the presence of Mo-rich particles consistent with trace molybdenite. Comparisons of Mo:Cu ratios in natural vent fluids and near-vent sediment trap samples from Main Endeavour Field indicate that vent fluid Mo is readily incorporated into buoyant plume particles and advected out of the near-vent field, analogous to previous mass balance studies of Cu in this region.Thermodynamic calculations of molybdenite solubility in the context of mineral-buffered hydrothermal fluids and comparisons with natural and experimental hydrothermal fluids suggest that high-temperature vent fluids contain 30–1500 nmol/kg Mo. While a minor component of the modern Mo budget, hydrothermal Mo fluxes are estimated to have constituted 0.3–200× the contemporaneous continental weathering fluxes prior to the ∼2.4 Ga ago “Great Oxidation Event” and widespread oxidative continental weathering. Overall, identification of hydrothermal vents as a source of Mo-rich plume particles with potential for dispersal into the wider marine environment has significant implications for hypotheses regarding the co-evolution of Life and Earth’s environments, specifically the form and availability of Mo in anoxic Archean-Eon oceans, where Mo-dependent enzymatic pathways are thought to have emerged and subsequently evolved.

Interpretation of Flat Energy Spectra Upstream of Fast Interplanetary Shocks

Interplanetary shocks are large-scale heliospheric structures often caused by eruptive phenomena at the Sun, and represent one of the main sources of energetic particles. Several interplanetary (IP) shock crossings by spacecraft at 1 au have revealed enhanced energetic-ion fluxes that extend far upstream of the shock. Surprisingly, in some shock events ion fluxes with energies between 100 keV and about 2 MeV acquire similar values (which we refer to as “overlapped” fluxes), corresponding to flat energy spectra in that range. In contrast, closer to the shock the fluxes are observed to depend on energy. In this work, we analyze three IP-shock-related energetic particle events observed by the Advanced Composition Explorer spacecraft where flat ion energy spectra were observed upstream of the shock. We interpret these observations via a velocity-filter mechanism for particles in a given energy range. In particular, ions with velocity parallel to the local magnetic field larger than the speed of the upstream plasma, in the reference frame of the shock, can easily propagate back upstream, while lower-energy ions tend to be confined to the shock front, thus reducing their fluxes far upstream and giving rise to flat energy spectra. The velocity-filter mechanism has been corroborated from observations of particle flux anisotropy by the Solid-State Telescope of Wind/3DP.

On the role of interplanetary shocks in accelerating MeV electrons

Context. One of the sources of solar energetic particle (SEP) events is shocks that are driven by fast coronal mass ejections (CMEs). They can accelerate SEPs up to relativistic energies and are attributed to the largest SEP events. New studies suggest that CME-driven shocks can potentially accelerate electrons to MeV energies in the vicinity of the Sun. Aims. We focus on relativistic electrons associated with strong interplanetary shocks between 2007 and 2019 to determine whether the shocks can keep accelerating such electrons up to a distance of 1 AU. Methods. We analyze observations by the High Energy Telescope (HET) aboard the STEREO spacecraft of potential electron energetic storm particle (ESP) events characterized by intensity time series that peak at the time of, or close to, the associated CME-driven shock crossing. We present a new filtering method to assess the statistical significance of particle intensity increases and apply it to MeV electron observations in the vicinity of IP shocks. We employ a STEREO in situ shock list, which contains a total of 587 shocks occurring at the two STEREO spacecraft. From this list, we identify 27 candidate events through visual inspection. Results. Our method identifies nine clear cases where a significant increase of MeV electrons was found in association with a shock. Typically, the highest statistical significance was observed in the highest of the three HET energy channels (2.8–4.0 MeV). All nine cases are associated with shocks driven by IP CMEs that showed large transit speeds in excess of 900 km s−1. In several cases, multiple shocks were observed within one day of the shock related to the electron increase. Conclusions. Although electron ESP events at MeV energies are found to be rare at 1 AU, our filtering method is not designed to identify a potential IP shock contribution from distances closer to the Sun. Observations from the Parker Solar Probe or Solar Orbiter taken during closer approaches to the Sun would likely provide clarity on the IP shock acceleration of electrons.

The 17 April 2021 widespread solar energetic particle event

Context.A complex and long-lasting solar eruption on 17 April 2021 produced a widespread solar energetic particle (SEP) event that was observed by five longitudinally well-separated observers in the inner heliosphere that covered distances to the Sun from 0.42 to 1 au: BepiColombo, Parker Solar Probe, Solar Orbiter, STEREO A, and near-Earth spacecraft. The event was the second widespread SEP event detected in solar cycle 25, and it produced relativistic electrons and protons. It was associated with a long-lasting solar hard X-ray flare that showed multiple hard X-ray peaks over a duration of one hour. The event was further accompanied by a medium-fast coronal mass ejection (CME) with a speed of 880 km s−1that drove a shock, an extreme ultraviolet wave, and long-lasting and complex radio burst activity that showed four distinct type III burst groups over a period of 40 min.Aims.We aim to understand the reason for the wide spread of elevated SEP intensities in the inner heliosphere as well as identify the underlying source regions of the observed energetic electrons and protons.Methods.We applied a comprehensive multi-spacecraft analysis of remote-sensing observations and in situ measurements of the energetic particles and interplanetary context to attribute the SEP observations at the different locations to the various potential source regions at the Sun. We used an ENLIL simulation to characterize the complex interplanetary state and its role in the energetic particle transport. The magnetic connection between each spacecraft and the Sun was determined using ballistic backmapping in combination with potential field source surface extrapolations in the lower corona. Using also a reconstruction of the coronal shock front, we then determined the times when the shock establishes magnetic connections with the different observers. Radio observations were used to characterize the directivity of the four main injection episodes, which were then employed in a 2D SEP transport simulation to test the importance of these different injection episodes.Results.A comprehensive timing analysis of the inferred solar injection times of the SEPs observed at each spacecraft suggests different source processes being important for the electron and proton events. Comparison among the characteristics and timing of the potential particle sources, such as the CME-driven shock or the flare, suggests a stronger shock contribution for the proton event and a more likely flare-related source for the electron event.Conclusions.In contrast to earlier studies on widespread SEP events, we find that in this event an important ingredient for the wide SEP spread was the wide longitudinal range of about 110° covered by distinct SEP injections, which is also supported by our SEP transport modeling.

Design of a Thick Gas Electron Multiplier based photon pre-amplifier

In this paper we present the design of a photon pre-amplifier based on a photo-cathode coated Thick Gas Electron Multiplier (THGEM). Such device is crucial in application where a weak light signal produced in a radiation detector must be amplified so that it can be carried to a photo-detector by means of optical fibres. An example of a device where a light signal must be amplified is a gamma-ray Cherenkov detector for fusion power measurements in magnetic confinement devices. In such application the active part of the detector must be located very close the plasma, typically in a harsh radiation environment where standard photodetectors cannot operate. The photon pre-amplifier allows to increase the signal generated in the active part of the detector so that it can be easily detected by the photodetector located outside the harsh environment. We present the conceptual design of a THGEM based photon pre-amplifier supported by Garfield++ simulations. The device working principle is the following: primary photons impinge on the photo-cathode and extract electrons that are accelerated by the THGEM electric field. Upon collisions with the accelerated electrons, the gas molecules in the pre-amplifier are brought to excited states and de-excite emitting scintillation photons. Since each electron excites multiple gas molecules, the scintillation photons outnumber the primary photons, leading to the amplification. In addition, we present the first observation of measurements of Nitrogen gas scintillation in a THGEM device. We devised an experimental setup consisting of a vacuum chamber containing a THGEM and an alpha particle source. The vacuum chamber is filled with pure nitrogen and is coupled to a photomultiplier tube via a view-port to detect the scintillation photons generated in the THGEM. For sake of simplicity the electrons that induce the scintillation are generated by the ionization track of an alpha particle rather than by the THGEM photo-cathode coating. A good qualitative agreement between simulations and experiment has been found, however no quantitative conclusions can be made due to the lack of N2 excitation cross sections in the Garfield++ code.

Benchmarking magnetised three-wave coupling for laser backscattering: analytic solutions and kinetic simulations

Understanding magnetised laser–plasma interactions is important for controlling magneto-inertial fusion experiments and developing magnetically assisted radiation and particle sources. For nanosecond pulses at non-relativistic intensities, interactions are dominated by coherent three-wave interactions, whose nonlinear coupling coefficients became known only recently when waves propagate at oblique angles with the magnetic field. In this paper, backscattering coupling coefficients predicted by warm-fluid theory are benchmarked using particle-in-cell simulations in one spatial dimension, and excellent agreements are found for a wide range of plasma temperatures, magnetic field strengths and laser propagation angles, when the interactions are mediated by electron-dominant hybrid waves. Systematic comparisons between theory and simulations are made possible by a rigorous protocol. On the theory side, the initial boundary value problem of linearised three-wave equations is solved, and the transient-time solutions allow the effects of growth and damping to be distinguished. On the simulation side, parameters are carefully chosen and calibration runs are performed to ensure that comparisons are well controlled. Fitting simulation data to analytical solutions yields numerical growth rates that match theory predictions within error bars. Although warm-fluid theory is found to be valid for a wide parameter range, genuine kinetic effects have also been observed.

The impacts of building opening characteristics on dust particle deposition indoors

PurposeThe effects of dust exposure in buildings and its health and comfort consequences continue to concern occupants, particularly those who spend most of their time indoors. This study examines the influence of building opening characteristics on surface dust loading in indoor environments to determine the dust particles' impact on different opening configurations.Design/methodology/approachIndoor Harmattan dust surface loading data were collected from Maiduguri, Northeastern Nigeria, using model rooms with six different window configurations. A simple mathematical relationship was employed to assess surface dust loading characteristics in the model rooms. The study measured dust thrice between December and February for three days (72 h). The results were analyzed using descriptive statistics.FindingsThe results determined the highest average surface dust loading of 12.03 g/m2 in the room with awning windows at an indoor-to-outdoor (I/O) ratio of 0.7. In contrast, the experiment in the room with a closed window recorded the lowest average surface dust loading of 5.24 g/m2 at an I/O ratio of 0.30, which is infiltration. The outcomes further indicate that the average surface dust loading varies with the building opening type and position, as higher surface dust loadings were recorded in locations closer to the openings (doors and windows), reaffirming that the dominant source of the dust particles is outdoors. According to the study, dust incursion due to infiltration accounts for 30% of the outdoor surface loading.Originality/valueThus, Harmattan dust is a serious challenge to the health, productivity and hygiene of building occupants in the study area. The built-environment professionals must use the study's outcome to optimize building openings' designs (shape, size and form) for effective indoor dust control.

Changing particle content of the modern desert dust storm: a climate × health problem.

Climate and land use changes together are altering the particle content of desert dust storms on regional and local scales. These storms now carry a wide variety of pollutants and pathogens arising from urbanization, industrialization, mass transportation, warfare, or aerosolized waste in locations worldwide where deserts are intertwined with built infrastructure, transportation centers, and high-density human habitation. Accordingly, the modern desert dust storm has an anthropogenic particle load which presumably sets it apart from pre-industrial dust storms. Evidence for how particle content for modern dust storms is changing over the Arabian Peninsula holds relevance because dust storms are now more frequent and more severe. Furthermore, the Arabian Peninsula has asthma rates which are the highest worldwide. How the modern desert dust storm contributes to asthma and human health is a nascent issue. Meanwhile, public health decisions can benefit from a climate × health framework for dust storms, as proposed here. An imperative is testing each dust storm's particle content type, and for this, we propose the A-B-C-X model. Sampling a dust storm for its particle content data and then archiving samples for future analyses is advised. A storm's particle content data, once combined with its atmospheric data, allows a particle's source, transport, and deposition to be determined. In closing, the modern desert dust storm's changing particle content has far-reaching consequences for public health, transboundary issues, and international climate dialog. SIGNIFICANCE: Locally and regionally sourced particle pollution is a growing problem in deserts worldwide. Proposed here is a climate × health framework for studying how dust storm particles, entrained from both natural and engineered systems, may be contributing to declining human respiratory health.

The synergistic effect of organic and inorganic sulfonic acids promotes new particle formation

New particle formation (NPF) represents a significant source of aerosol particles in the atmosphere; however, the NPF mechanisms remain uncertain, hindering the understanding and assessment of its environmental effects. Hence, we investigated the nucleation mechanisms in multicomponent systems including two inorganic sulfonic acids (ISAs), two organic sulfonic acids (OSAs), and dimethylamine (DMA) by combining quantum chemical (QC) calculations and molecular dynamics (MD) simulations, and evaluated the comprehensive effect of ISAs and OSAs on DMA-driven NPF. The QC results showed that the (Acid)2(DMA)0–1 clusters were strongly stable, and the (ISA)2(DMA)1 clusters exhibited higher stability than the (OSA)2(DMA)1 clusters because ISAs (sulfuric and sulfamic acids) provided more H-bonds and stronger proton transfer than OSAs (methanesulfonic and ethanesulfonic acids). ISAs readily engaged in dimer formation, whereas the stability of trimer clusters was mainly regulated by the synergistic effects of ISAs and OSAs. OSAs participated in cluster growth earlier than ISAs. Our results revealed that ISAs promote cluster formation, whereas OSAs facilitate the growth of clusters. The synergistic effect of ISAs and OSAs should be further investigated in areas with high [OSAs]: [ISAs].

102 Application of Quantitative Mineralogy to Determine Sources of Airborne Particles at a European Copper Smelter

Abstract To ensure that regulatory compliance is maintained at mineral processing operations, worker exposure is regularly monitored. Determining the quantity and type of airborne particles permits the operation to identify the sources of dust, implement proper dust suppressant strategies, and ultimately, limit worker exposure. Conventional methods of analysis, such as chemical assay, are unable to rigorously differentiate between phases containing the same elements and may result in ambiguity related to identifying the source of airborne dust. A combination of Quantitative Evaluation of Materials by Scanning Electron Microscope (QEMSCAN) and chemical characterization has been used to evaluate personally taken size selective aerosol samples at key locations throughout a Cu smelter in Europe. Surface samples were also examined using higher resolution measurements. The Cu phases present in the workplace air samples are reflective of the activities performed at specific locations. Near the anode and electric furnace, the majority of Cu in the airborne dust is carried in metals and oxide phases (60-70%), and in the batch preparation area where Cu concentrate is received, significant amounts of Cu are carried in sulfide minerals (chalcocite, chalcopyrite/bornite, >40%). The results of the analysis will aid in the identification of the origin of emissions specific to location and activity, assist personnel in developing the appropriate mitigation strategies to limit workers exposure, and further understanding of the health risks associated with exposure. Additional metals of concern (e.g, Pb, As, and Cd) are also considered throughout this program. Speaker Biography Michelle Kelvin is a geoscientist and environmental mineralogist. She specializes in characterizing dust emissions that originate from industrial operations using modern geochemical methods and X-ray beam technologies.

Investigation of four-year chemical composition and organic aerosol sources of submicron particles at the ATOLL site in northern France

This study presents the first long-term online measurements of submicron (PM1) particles at the ATOLL (ATmospheric Observations in liLLe) platform, in northern France. The ongoing measurements using an Aerosol Chemical Speciation Monitor (ACSM) started at the end of 2016 and the analysis presented here spans through December 2020. At this site, the mean PM1 concentration is 10.6 μg m−3, dominated by organic aerosols (OA, 42.3%) and followed by nitrate (28.9%), ammonium (12.3%), sulfate (8.6%), and black carbon (BC, 8.0%). Large seasonal variations of PM1 concentrations are observed, with high concentrations during cold seasons, associated with pollution episodes (e.g. over 100 μg m−3 in January 2017). To study OA origins over this multiannual dataset we performed source apportionment analysis using rolling positive matrix factorization (PMF), yielding two primary OA factors, a traffic-related hydrocarbon-like OA (HOA) and biomass-burning OA (BBOA), and two oxygenated OA (OOA) factors. HOA showed a homogeneous contribution to OA throughout the seasons (11.8%), while BBOA varied from 8.1% (summer) to 18.5% (winter), the latter associated with residential wood combustion. The OOA factors were distinguished between their less and more oxidized fractions (LO-OOA and MO-OOA, on average contributing 32% and 42%, respectively). During winter, LO-OOA is identified as aged biomass burning, so at least half of OA is associated with wood combustion during this season. Furthermore, ammonium nitrate is also a predominant aerosol component during cold-weather pollution episodes – associated with fertilizer usage and traffic emissions. This study provides a comprehensive analysis of submicron aerosol sources at the recently established ATOLL site in northern France from multiannual observations, depicting a complex interaction between anthropogenic and natural sources, leading to different mechanisms of air quality degradation in the region across different seasons.

Micro- and nanoplastics transfer from seawater to the atmosphere through aerosolization under controlled laboratory conditions

Sea spray has been suggested to enable the transfer of micro- and nanoplastics (MNPs) from the ocean to the atmosphere, but only a few studies support the role of sea spray aerosols (SSAs) as a source of airborne particles. We demonstrated that MNPs are aerosolized during wave action, via SSAs, under controlled laboratory conditions. We used a mini-Marine-Aerosol-Reference-Tank (miniMART), a device that mimics naturally occurring physical mechanisms producing SSAs, and assessed the aerosolization of fluorescent polystyrene beads (0.5-10 μm), in artificial seawater. The SSAs contained up to 18,809 particles/mL of aerosols for 0.5 μm beads, with an enrichment factor of 19-fold, and 1977 particles/mL of aerosols for 10 μm beads with a 2-fold enrichment factor. Our study demonstrates that the use of the miniMART is essential to assess MNPs aerosolization in a standardized way, supporting the hypothesis which states that MNPs in the surface of the ocean may be transferred to the atmosphere.

32 Changes in Exposure and Related Health Effects After Preventive Actions at Black Steel Welding Environments

Abstract Welding fume constitutes a source of particles and dust that effects a large number of individuals at occupational environments throughout the world. Besides being classified as a carcinogen, welding fume has potential inflammatory properties and has been linked to cardiovascular disease. To further increase the knowledge regarding potential health and inflammatory effects, workers at occupational environments with exposure to welding fume were investigated before but also after extensive preventive actions to investigate potential effects that may be pathways for cardiovascular disease. Exposure was assessed by collecting respirable dust through stationary and personal sampling at multiple occasions over the study. Dust was used for metal analysis by ICP-MS. Particle levels were assessed by using three handheld particle-counting instruments, Lighthouse 3016-IAQ (0.3-10 µm), DustTrak 8520 (0.1-10µm) and Philips Aerasense NanoTracer (10-300 nm). A total of approximately 100 individuals were screened at the beginning and end of a workweek at the beginning of the study and again after two years after the companies had introduced a wide range of preventive actions to reduce the exposure of the workforce. Participants had metals measured in both blood and urine, markers used in clinical practice for stress in different tissues were measured, lung function using spirometry was done and a set of 40 different acute inflammatory markers were measured using electrochemiluminiscence. The study adds to the growing knowledge of effects of welding fumes on human health and how preventive actions may affect this.

Scenario trajectory optimization and control on STEP

In this paper we present optimized actuator trajectories, evolving in time and space, of non-inductive ramp-up scenarios for the Spherical Tokamak for Energy Production (STEP). These trajectories are computed by solving a non-linear, multi-objective, constrained, finite-time optimal control problem. A method unique to STEP ramp-up studies that provides an alternative to existing trajectory search strategies which rely on manually adjusting trajectories to reach a desired state. To navigate a non-linear parameter space which is densely populated with local minima, we demonstrate an iterative objective function construction process whereby costs and constraints are included successively and re-optimized after each inclusion to improve convergence and feasibility. This method is particularity useful when the initial trajectory is far from the desired operating space. We use the RApid Plasma Transport simulatOR (RAPTOR) code to self-consistently solve four coupled, 1-D state equations; poloidal flux, electron temperature, ion temperature and electron density. Our STEP actuator trajectories lasting 1500s, consist of 8 Gaussian electron cyclotron heating and current drive beams distributed across the minor radius, a Deuterium/Tritium particle source and plasma current. We also introduce a modified transport Bohm–gyroBohm model and a new actuator module to RAPTOR which were required to adequately simulate the STEP operating scenarios.

Mineralogy and phase transition mechanisms of atmospheric mineral particles: Migration paths, sources, and volatile organic compounds

Inorganic mineral particles play an important role in the formation of atmospheric aerosols in the Sichuan Basin. Atmospheric haze formation is accompanied by the phase transition of mineral particles under high humidity and stable climatic conditions. Backward trajectory analysis was used in this study to determine the migration trajectory of atmospheric mineral particles. Furthermore, Positive matrix factorization (PMF) was used to analyze the sources of atmospheric mineral particles. The phase transition mechanisms of atmospheric mineral particles were studied using ion chromatography, inductively coupled plasma emission spectrometry, total organic carbon analysis, X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy coupled with energy dispersive spectrometry, and grand canonical Monte Carlo methods. Three migration and phase transition paths were identified for the mineral particles. Sources of atmospheric mineral particles included combustion, vehicle emissions, industrial emissions, agricultural sources, and mineral dust. The main mineral phases in atmospheric particles, calcite and dolomite, were transformed into gypsum, and muscovite may be transformed into kaolinite. The phase transition of mineral particles seriously affects the formation of aerosols and worsens haze. Typically, along the Nanchong-Suining-Neijiang-Zigong-Yibin path, calcite is converted into gypsum under the influence of man-made inorganic pollution gases, which worsen the haze conditions and cause slight air pollution for 3–5 days. However, along the Guangyuan-Mianyang-Deyang-Chengdu-Meishan-Ya'an path, anthropogenic volatile organic compounds (VOCs) hindered gypsum formation from dolomite. Furthermore, dolomite and VOCs formed stable adsorption systems (system energies from −0.41 to −4.76 eV, long bonds from 0.20 to 0.24 nm). The adsorption system of dolomite and m/p-xylene, with low system energy (−1.46 eV/−1.33 eV) and significant correlation (r2 = 0.991, p < 0.01), was the main cause of haze formation. Consequently, calcite gypsification and dolomite–-VOC synergism exacerbated regional haze conditions. This study provides a theoretical reference for the mechanism of aerosol formation in basin climates.

Winter-autumn air pollution control plan in North China modified the PM2.5 compositions and sources in Central China

The additional impact of emission-reduction measures in North China (NC) during autumn and winter on the air quality of downwind regions is an interesting but less addressed topic. The mass concentrations of routine air pollutants, the chemical compositions, and sources of fine particles (PM2.5) for January 2018, 2019, and 2020 at a megacity of Central China were identified, and meteorology-isolated by a machine-learning technique. Their variations were classified according to air mass direction. An unexpectedly sharp increase in emission-related PM2.5 by 22.7% (18.0 μg m−3) and 25.7% (19.4 μg m−3) for air masses from local and NC in 2019 was observed compared to those of 2018. Organic materials exhibited the highest increase in PM2.5 compositions by 6.90 μg m−3 and 6.23 μg m−3 for the air masses from local and NC. PM2.5 source contributions related to emission showed an upsurge from 1.39 μg m−3 (biomass burning) to 24.9 μg m−3 (secondary inorganic aerosol) in 2019 except for industrial processes, while all reduced in 2020. From 2018 to 2020, the emission-related contribution of coal combustion to PM2.5 increased from 10.0% to 19.0% for air masses from the local area. To support the priority natural gas quotas in northern China, additional coal in cities of southern China was consumed, raising related emissions from transportation activities and road dust in urban regions, as well as additional biofuel consumption in suburban or rural regions. All these activities could explain the increased primary PM2.5 and related precursor NO2. This study gave substantial evidence of air pollution control measures impacting the downwind regions and promote the necessity of air pollution joint control across the administration.

Kinetic effects on geodesic acoustic modes and Stringer spin-up driven by a poloidally asymmetric particle source

The impact of the poloidally inhomogeneous particle source on the onset of Stringer spin-up (SSU) and geodesic acoustic mode (GAM) is investigated. Using a gyrofluid model with Hammet–Perkins closure, it was found that Landau damping stabilizes both waves and subsequently makes a threshold. To capture the full effects of Landau damping, a gyrokinetic model is adopted and results are compared with those from the gyrofluid model. Both models predicted the same value of the threshold for SSU, while for the case of GAM, the gyrofluid model overestimates the threshold value. Considering maximal throughput of the ITER pellet fueling system, the source intensity is calculated at a similar or slightly lower level compared to the source threshold for SSU.

Acceleration of suprathermal protons near an interplanetary shock

Context.Interplanetary collisionless shocks are known to be sources of energetic charged particles up to hundreds of MeV. However, the underlying acceleration mechanisms are still under debate.Aims.We determine the properties of suprathermal protons accelerated by the interplanetary shock on 2021 November 3 with the unprecedented high-resolution measurements by the SupraThermal Electron Proton sensor of the Energetic Particle Detector on board the Solar Orbiter spacecraft, in order to constrain the potential shock acceleration mechanisms.Methods.We first reconstructed the pitch-angle distributions (PADs) of suprathermal protons in the solar wind frame. Then, we studied the evolution of the PADs, the temporal flux profile, and the velocity distribution function of this proton population close to the shock and compared the observations to theoretical predictions.Results.We find that the suprathermal proton fluxes peak ∼12 to ∼24 s before the shock in the upstream region. The proton fluxes rapidly decrease by ∼50% in a thin layer (∼8000 km) adjacent to the shock in the downstream region and become constant farther downstream. Furthermore, the proton velocity distribution functions in the upstream (downstream) region fit a double power law,f(v)∼v−γ, at ∼1000 − 3600 km s−1, with aγof ∼3.4 ± 0.2 (∼4.3 ± 0.7) at velocities (v) below a break at ∼1800 ± 100 km s−1(∼1600 ± 200 km s−1) and aγof ∼5.8 ± 0.3 (∼5.8 ± 0.2) at velocities higher than this. These indices are all smaller than predicted by first-order Fermi acceleration. In addition, the proton PADs in the covered pitch-angle range show anisotropies in the direction away from the shock in the region close to the upstream region and become nearly isotropic farther upstream, while downstream of the shock, they show a tendency of anisotropies towards 90° PA.Conclusions.These results suggest that the acceleration of suprathermal protons at interplanetary shocks are dynamic on a timescale of ∼10 s, that is, few proton gyroperiods. Furthermore, shock-drift acceleration likely plays an important role in accelerating these suprathermal protons.