Aerosol Generation Research Articles

Study on Characterization of SrO Aerosols Generated by Optimized Thermal Plasma Torch Aerosol Generator

AbstractPlasma Torch Aerosol Generation System (PTAGS) has been employed to generate nano aerosols with desirable characteristics. The operational parameters of PTAGS installed in the aerosol test facility have been optimized, and aerosols are generated using non-radioactive SrO2 powder. The current-voltage characteristics, electro-thermal efficiency and torch power are studied as a function of the flow rate of the plasma-generating gas (mixture of argon and nitrogen) and the arc current of the plasma torch. The relation of arc characteristics is determined using the Nottingham formulation. Based on this, torch parameters evolved and optimized as 20 kW power, 70% electro-thermal efficiency, 25 L min− 1 flow rate of plasma forming gas, 5 mg min− 1 powder feed rate and for 4–5 min torch operation towards the generation of SrO nano aerosols to achieve 1012 m− 3 and ~ 25 mg m− 3 for the count and mass concentration of aerosol respectively. The initial size distribution of the aerosols is in the few tens of nanometre range (10–40 nm) with a mean diameter of 26 nm (σg = 1.45). Scanning Electron Microscope and Energy dispersive X-ray analysis revealed that the morphology of nano aerosols was nearly spherical and the formation of SrO nanoparticles. A set of PTAGS operational parameters has been standardized to perform further experiments related to reactor safety analysis. PTAGS shall be tuned for aerosol generation in a large facility to achieve the characteristics equivalent to reactor accidental conditions.

The role of refractive indices in measuring mineral dust with high-spectral-resolution infrared satellite sounders: application to the Gobi Desert

Abstract. Mineral dust significantly influences the Earth's climate system by affecting the radiative balance through the emission, absorption and scattering of solar and terrestrial radiation. Estimating the dust radiative effect remains challenging due to the lack of detailed information on the physical and chemical properties of dust. High-spectral-resolution instruments in the infrared (IR) spectrum, such as the Infrared Atmospheric Sounding Instrument (IASI), have demonstrated the ability to quantify these aerosol properties. A crucial parameter for characterizing mineral dust from space is the complex refractive index (CRI), as it links the dust's physical and chemical properties to its optical properties. This paper examines the impact of six prior laboratory CRI datasets to improve the characterization of dust microphysical properties using IASI. The CRIs include older measurements obtained through the classical pellet method, commonly employed in mineral dust applications, as well as newer datasets that incorporate the latest advancements in laboratory measurement techniques for aerosol generation. These datasets are tested on IASI measurements during a dust storm event over the Gobi Desert in May 2017. We evaluate the sensitivity of IASI to different CRI datasets using the Atmospheric Radiation Algorithm for High-Spectral Resolution Measurements from Infrared Spectrometer (ARAHMIS) radiative transfer algorithm and explore the datasets' impact on retrieving size distribution parameters by mapping their spatial distributions. The results indicate that the laboratory CRI datasets decrease the total error in the covariance matrix by 30 %. In addition, we assess the ability to accurately reconstruct IASI detections and the extent to which we can retrieve the microphysical properties of dust particles. The choice of CRI significantly impacts the accuracy of dust detection and characterization from satellite observations. Notably, datasets that incorporate recent aerosol generation techniques with higher spectral resolution and samples from the case study region show improved compatibility with IASI observations. The outcomes of this research emphasize two key points: the crucial link between chemical composition of dust and its optical properties and the importance of considering the specific composition of the CRI dataset for improved retrieval of the microphysical parameters. Furthermore, this study highlights the critical role of ongoing enhancements in CRI measurement approaches, as well as the potential of high-spectral-resolution infrared sounders for aerosol atmospheric investigation and for understanding the radiative impacts of sounders.

Analyzing Morphology and Composition of Coarse Aerosol Particles in Bangkok, Thailand: Implications to Sources and Impacts of Aged Aerosols on Ecosystem Health and Climate Dynamics

AbstractDuring dry seasons, elevated aerosol levels across Thailand pose nationwide problems. Understanding and addressing this issue is challenging due to the dynamic nature of aerosol modification and generation during transport. This study investigates the morphology and elemental compositions of coarse aerosol particles in Bangkok, Thailand, during the dry seasons of 2020/21. Through scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDS), the study reveals a complex mixture of anthropogenic, mineral, biogenic, and marine aerosols. Anthropogenic sources, including biomass burning, vehicular emissions, and industrial activities, contribute to carbonaceous particles like soot aggregates and tar balls. Mineral dust particles, predominantly calcium-rich and aluminosilicate, originate from various sources including construction, industry, and natural processes. Aging processes alter the composition and properties of both carbonaceous and mineral particles, influencing nutrient deposition, carbon sequestration, cloud condensation nuclei formation, and light scattering. These processes have multifaceted impacts on ecosystem health and climate dynamics, highlighting the need for further research and mitigation strategies to address the environmental consequences of aged aerosol particles in urban environments like Bangkok.

Influencing Factors Analysis of Infectious SARS-CoV-2 Aerosols Sampling

Assessing the potential infectivity of airborne viruses is critical for evaluating the risk of their transmission through air. This study investigated the factors influencing the collection of infectious SARS-CoV-2 aerosols using three common aerosol samplers: the impactor sampler AGI-30, the SKC Biosampler, and a cyclone sampler WA-400III. It was found that the sampling process over time significantly impacted the infectivity of SARS-CoV-2 captured in the sampler, and the infectivity loss of different SARS-CoV-2 variants in the process varied. Additionally, adding newborn calf serum in the collection suspension could effectively preserve viral infectivity in the sampler. Further tests conducted under various ventilation occasions indicated that ventilation can reduce the virus concentration in the environment and rapidly clear viral particles after aerosol generation. Although the flow rate of WA-400III is higher, it only could collect higher concentrations of viral RNA instead of live viruses than AGI-30 or SKC Biosampler when aerosol was generated constantly in the environment. After aerosol generation stopped, the WA-400III collected more infectious viruses and viral RNA. This study highlights the impact of the sampling process on captured virus should be assessed and protective agent is needed to preserve viral viability. And it is crucial to select appropriate sampler based on environmental characteristics and research objectives for obtaining optimal results. The AGI-30 and SKC Biosampler are preferable for collecting infectious viruses in environments with high aerosol concentrations, while the cyclone sampler WA-400III is more effective for collecting viral nucleic acids and enriching virus samples in confined spaces with lower viral loads.

ОБОСНОВАНИЕ ПАРАМЕТРОВ ТЕХНИЧЕСКОГО СРЕДСТВА ДЛЯ КРАЕВОЙ ОБРАБОТКИ ПОЛЯ ОТ СОРНЯКОВ И ВРЕДИТЕЛЕЙ ПОЛЕВЫХ КУЛЬТУР

The main method of spraying for plant protection in the fight against weeds and pests in the marginal area of the field with forest plantations is currently implemented by various technical means. The following shortcomings have been identified: when using the main chemical method of spraying weeds and pests by technical means, universal requirements for droplet dispersion are not met; when spraying the forest belt with fans - instability of aerosol jets in the external environment; when creating a cold aerosol with fans - uncontrollability for achieving the required dispersion, and when creating a cold aerosol with generators, the initial conditions of its formation are insufficient to justify the spread of dispersion as intended; when using aerosol generators with a thermo-mechanical principle of operation - non-compliance with modern environmental requirements. The recommendations for the use of air means given in literary sources are not relevant. The technical means including an axial fan with a diameter of 0.61 m and an air capacity of 22,000 m3 /h were studied. The conical nozzle was equipped with nozzles with spray tips on its generatrix. The working process of the axial fan with a hydraulic motor was provided by the tractor hydraulic system, and the supply of working fluid from the sprayer tank to the spray tips was carried out by a pump. Theoretical studies were conducted to justify the nozzle to the fan with the justification for creating an air-dispersed system and settling polydisperse droplets from it on the target objects. Experimental data on the dispersion of droplets were processed using software. The results of the studies represent the novelty of theoretical and practical solutions for the combined use of the process of spraying the edge area of the field with its further development in practical application for plant protection.

Improvement of aerosol spray scavenging efficiency by pre-injecting electrically charged water mist

Efficient aerosol scavenging is crucial for gas purification to reduce environmental pollution in various chemical industries. In nuclear reactor decommissioning, especially for damaged reactors after severe accidents like Fukushima Daiichi, controlling radioactive aerosol generation and dispersion is essential. Radioactive aerosols sizing from 0.1 to 1 μm are expected during containment cleaning and fuel debris retrieval processes. To ensure safe decommissioning and mitigate environmental radioactivity, a containment water spray system is used for aerosol scavenging. However, conventional water spray has low efficiency for these submicron aerosols. Our recent experiments at UTARTS demonstrated that pre-injection of water mist enhances scavenging efficacy by increasing aerosol size and hydrophilicity through aerosol-mist agglomeration prior to spraying. On this basis, in this study, we introduced an innovative method using electrically charged water mist, which significantly facilitates aerosol-mist agglomeration through additional electrostatic coagulation, further improving scavenging efficacy (maximum 35 % in current configurations). The present experimental results attained under various mist conditions and charging configurations provided insights into optimizing the mist charging system. Our developed technology is expected to be useful in radioactive aerosol control during damaged reactor decommissioning and has potential applications in other environmental chemical engineering processes.

Prospective Study of Contamination Spread Produced During Open Surgical vs Conventional Percutaneous vs Novel Percutaneous Tracheostomy During COVID-19 Era in a Pig Model.

Because of concerns about provider contamination during tracheostomy procedures in a pandemic such as COVID-19, it is essential to objectively evaluate aerosol generation in all tracheostomy approaches, including newly developed tracheostomy procedures. We performed open surgical tracheostomy (OST), conventional percutaneous tracheostomy (CPT), and novel percutaneous tracheostomy (NPT), a modification of CPT designed to reduce contamination spread, in pig models and then compared the degree of contamination to providers using Glo Germ (Glo Germ, Moab, UT, USA). Six Yorkshire pigs were used for data collection. Either OST, CPT or NPT was performed on the pigs by the same team including a surgeon, anesthesiologist, and respiratory therapist. A mixture of Glo Germ and water was administered via atomizer into the oral cavity to the tracheal bifurcation before each procedure, and additionally dispersed via an aersolizer in the trachea and lungs through the endotracheal tube before and throughout the procedure. Before and immediately after each procedure, pre-specified body parts of the providers were photographed and two independent examiners blindly evaluated the photographs to determine degree of Glo Germ contamination using a 3-point Likert scale. Total contamination among provider team average score (min. 0, max. 2), was significantly lower for OST than CPT (0.29 ± 0.59 vs 0.63 ± 0.65; P<0.01) or NPT (0.29 ± 0.59 vs 0.59 ± 0.66; p <0.01). No significant difference was seen in overall contamination of any provider between CPT and NPT (0.63 ± 0.65 vs 0.59 ± 0.66; p =0.92). Our results suggest that OST causes significantly less aerosol contamination to providers than either CPT or NPT.

Dependence of aerosol-borne influenza A virus infectivity on relative humidity and aerosol composition.

We describe a novel biosafety aerosol chamber equipped with state-of-the-art instrumentation for bubble-bursting aerosol generation, size distribution measurement, and condensation-growth collection to minimize sampling artifacts when measuring virus infectivity in aerosol particles. Using this facility, we investigated the effect of relative humidity (RH) in very clean air without trace gases (except ∼400 ppm CO2) on the preservation of influenza A virus (IAV) infectivity in saline aerosol particles. We characterized infectivity in terms of 99%-inactivation time, t 99, a metric we consider most relevant to airborne virus transmission. The viruses remained infectious for a long time, namely t 99 > 5 h, if RH < 30% and the particles effloresced. Under intermediate conditions of humidity (40% < RH < 70%), the loss of infectivity was the most rapid (t 99 ≈ 15-20 min, and up to t 99 ≈ 35 min at 95% RH). This is more than an order of magnitude faster than suggested by many previous studies of aerosol-borne IAV, possibly due to the use of matrices containing organic molecules, such as proteins, with protective effects for the virus. We tested this hypothesis by adding sucrose to our aerosolization medium and, indeed, observed protection of IAV at intermediate RH (55%). Interestingly, the t 99 of our measurements are also systematically lower than those in 1-μL droplet measurements of organic-free saline solutions, which cannot be explained by particle size effects alone.

The efficiency of portable air cleaners in reducing cross-exposure through respiratory aerosols: Effects of flowrate, location, and unit type

This study evaluates the efficacy of portable air cleaners (PACs) in a controlled climate chamber that simulates an office environment, assessing their impact on respiratory particle transmission between two thermal manikins (representing an infected and an exposed individual) as well as on the noise level in the chamber. The study explores three types of PAC, namely floor-type (PAC1), table (PAC2) and personalized (PAC3) in various locations and operation modes. The particles were generated using an aerosol generator and introduced into the infected manikin's exhalation; the particle concentration at the exposed manikin's breathing zone (BZ) was measured using an aerodynamic particle sizer. The results showed that the PAC2, operating at a flow rate of 97 m³/h, significantly reduced the intake fraction (IF) by over 90 % within the first hour, proving to be the most effective in minimizing cross-exposure risks while maintaining sound levels within the acceptable limits for office rooms. In contrast, PAC3, with a lower flow rate of 13 m³/h, reduced IF by only 21.6 % after 60 min. The result also showed that settings with higher flow rates (higher than 134 m3/h) resulted in noise levels above the maximum allowable for office spaces for all tested PACs. Additionally, prolonged operation did not further decrease IF significantly after reaching optimal reduction levels within 30–60 min, depending on the PAC type and settings. Further, the study showed that strategic placement away from direct alignment with occupants' BZ is recommended to optimize aerosol removal and noise management.

Development of a two-stage virtual impactor for the generation of micrometer-scale monodisperse aerosols

Monodisperse particles are useful across a wide range of industrial applications, such as LCD displays, solar cells and rechargeable batteries, due to their uniformly small sizes. However, generating high volumes of monodisperse particles remains challenging. In this study, it was aimed to generate monodisperse aerosols by classifying micrometer-scale solid aerosol particles within a narrow size range. Accordingly, a new particle-size classification device with two virtual impactors connected in series and clean air cores was developed. The first-stage virtual impactor had a slightly larger cutoff size than the second-stage, and the major flow discharged from the first-stage was directed to the second-stage. The target particle size range was altered by changing the nozzle sizes in the first and second stages or by adjusting the flow rate. Subsequently, the classification performance of the two-stage virtual impactor was simulated and validated through an experiment using Arizona test dust. The implemented combinations of cutoff sizes for the first and second stages were 3.0 and 2.0 μm, 3.9 and 2.7 μm, or 6.7 and 4.8 μm. As a result, monodisperse aerosol particles were classified at a geometric standard deviation of 1.04–1.14 and a particle size range of 2–6.7 μm. The two-stage virtual impactor developed herein may be useful for various research and performance evaluations, as it can classify micrometer-scale solid particle aerosols that exhibit high monodispersity.

Summer daily dynamics of the vertical structure of atmospheric aerosol over Baikal coastal area from ground-based lidar measurements

ABSTRACT The spatial structure of atmospheric aerosol over Baikal in summer is studied on a regular basis with the use of ground-based LOSA-M2 lidar measurements at the Boyarsky scientific station of the Institute of Physical Material Science, Siberian Branch, Russian Academy of Sciences (51.83°N, 106.06°E, 456 m a.s.l.), Republic of Buryatia, Russia. The lake is located in a basin surrounded by mountain ranges on all side; its water volume is large. The lidar data are analysed along with the regional meteorological situation and meteorological parameters of the atmosphere. The daily dynamics of aerosol distribution over the atmospheric is examined for the period from 2015 to 2023 accounting the effect of different air masses in the region. Three main typical air circulation types are identified for the coastal zone of southern Baikal in summer, which determine the atmospheric aerosol generation and transport. The first and most common type relates to breeze circulation, where the main changes in the spatial structure of aerosol occur in the 2–3-km layer and are determined by changes in the transport direction within a breeze cell during the day. The main feature of this type is a decrease in the altitude of an air layer which contains most of aerosol in the lower atmosphere up to 1 km. The second type refers to southwestern transport under the presence of an anticyclone over the region. The maximal altitude of the aerosol layers attains 7 km in this case. The most complex and dynamic changes in the daily spatial structure of atmospheric aerosol occurred under transport of cyclones and associated atmospheric fronts over Lake Baikal. Under this third type, the altitude of the aerosol layers decreases throughout the day within the altitude range from the surface to 3–4 km.

Secondary emission behavior analysis and aerosol characteristics evaluation in laser cutting for safe nuclear decommissioning

We analyzed secondary emissions and aerosol characteristics generated during the cutting of 10-30mm thick austenitic 304L stainless-steel plates with a high-power fiber laser. This study comprehensively includes exhausted aerosols, sedimented dross, wall deposits, and attached slag. The amount of secondary emissions for each cutting process condition was determined by type. Over 98% of the secondary emissions consisted of attached slag and sedimented dross, with wall deposits accounting for 0.5-1.4% and exhausted aerosols for less than 0.1%. As cutting thickness increased, the total amount of secondary emissions increased. The ratios of attached slag and sedimented dross varied depending on cutting speed and laser power. The count median aerodynamic diameter of aerosols was ~0.12 μm when a 30mm thick plate was cut with a laser power of 3kW. Aerosol concentration decreased by nearly 30% with increasing cutting speed, depending on conditions, suggesting that optimizing speeds can effectively reduce aerosol generation. Chemical composition analysis provides insights into aerosol reactivity, toxicity, and environmental impacts, aiding in the design of filtration and ventilation systems. These results are expected to reduce environmental and health impacts in nuclear decommissioning processes.

A Review of Accidental Aerosol Generation in Laboratories and Laboratory-associated Infections

A Review of Accidental Aerosol Generation in Laboratories and Laboratory-associated Infections

Direct Determination of Metallic Contamination on and in Wafers Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry

A new analytical technique was developed for determination of metallic impurities in wafers using LA-GED-MSAG-ICP-MS. Up to 300 mm wafer can be analyzed directly without using a small, enclosed chamber. Particles generated by a femto-second laser ablation were aspirated together with a particle free clean air by an ejector and introduced to the ICP-MS (Inductively Coupled Plasma Mass Spectrometry) via GED (Gas Exchange Device). The air was exchanged by Ar gas and the particles came out from GED in Ar gas stream. For quantitation of LA-ICP-MS, MSAG (Metal Standard Aerosol Generation) was used. MSAG could introduce nearly a 100% of aqueous multi-element standard solution to the plasma of ICP-MS, which allowed precise quantitation using the method of standard addition while ablating wafer samples. This paper describes how the new analytical technique works for ultra-trace level of metallic impurities in wafers.

Inhibition of influenza virus infection in mice by pulmonary administration of a spray dried antiviral drug

Increasing resistance to antiviral drugs approved for the treatment of influenza urges the development of novel compounds. Ideally, this should be complemented by a careful consideration of the administration route. 6′siallyllactosamine-functionalized β-cyclodextrin (CD-6′SLN) is a novel entry inhibitor that acts as a mimic of the primary attachment receptor of influenza, sialic acid. In this study, we aimed to develop a dry powder formulation of CD-6′SLN to assess its in vivo antiviral activity after administration via the pulmonary route. By means of spray drying the compound together with trileucine, a dispersion enhancer, we created a powder that retained the antiviral effect of the drug, remained stable under elevated temperature conditions and performed well in a dry powder inhaler. To test the efficacy of the dry powder drug against influenza infection in vivo, infected mice were treated with CD-6′SLN using an aerosol generator that allowed for the controlled administration of powder formulations to the lungs of mice. CD-6′SLN was effective in mitigating the course of the disease compared to the control groups, reflected by lower disease activity scores and by the prevention of virus-induced IL-6 production. Our data show that CD-6′SLN can be formulated as a stable dry powder that is suitable for use in a dry powder inhaler and is effective when administered via the pulmonary route to influenza-infected mice.

Aerosol generation of sweeteners solutions during a drinking process

In this study, we hypothesize that flavor compounds, volatile as well as non-volatile, can be transferred from the oral cavity to the nasal cavity in the form of aerosol particles. To test the potential of aerosol as the carrier of flavor compounds during a drinking process, the aerosol particles of sweetener solutions (sucrose or rebaudioside A) have been quantified at both the in situ and simulated conditions, with or without saliva mixing. As observed by an optical particle counter, shaking or splashing of test samples can generate huge numbers (1000–10000) of aerosol particles with most of them smaller than 1 μm. It was further observed that addition of sucrose, rebaudioside A, saliva, thickener (konjac glucomannan) and defoamer (simethicone emulsion) can significantly alter the generated aerosol particles of water both in situ and in vitro. As estimated by the intensity of fluorescence, the amount of transferred mass within the in vitro prepared aerosol can be 4.9 μg/min. The shear viscosities, surface tension, extensional break time and relaxation time were found to correlate with the aerosol generation of test sample. These results suggest that aerosol particles have the potential in carrying substantial amount of flavor compounds during oral processing, and their generation can be sensitively affected by the presence of food components and saliva.

Suppression of aerosol dispersion by highly viscoelastic poly(acrylic acid)- and poly(ethylene oxide)-based coolants during bone drilling

Bone drilling in neurosurgical, dental, and orthopedic procedures, combined with the use of coolants, generates a dispersion of bone particles, coolants, and blood aerosols in the air. This poses the threat of airborne transmission of infectious diseases between patients and medical practitioners. Highly viscoelastic polymeric poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO) solutions of various concentrations were used as coolants during bone drilling at different mass flow rates to suppress aerosol generation, thereby mitigating the threat of cross-infection. The results revealed that the PAA and PEO solutions provide less advection than water and a comparable cooling performance. However, excessive viscoelasticity of PEO causes the fluid to rise along the cutting burr (the Weissenberg effect), thereby reducing the cooling coverage area. In contrast, slightly lower viscoelasticity of PEO results in a high cooling coverage area. The cooling coverage area is smaller for the PAA at 20 ml/min because the corresponding PAA solution easily swirls or splashes away from the drilling location. However, at 80 ml/min, the supplied PAA solution sufficiently cools the drilling area, despite the loss through splashing. The numbers of atomized droplets of water and the PAA and PEO solutions were quantified and compared to investigate the degree of aerosol formation and dispersion. The solution with the strongest viscoelasticity most significantly suppressed aerosolization and produced the fewest dispersed aerosol droplets during bone drilling.

The role of puff volume in vaping emissions, inhalation risks, and metabolic perturbations: a pilot study

Secondhand vaping exposure is an emerging public health concern that remains understudied. In this study, saliva and exhaled emissions from ENDS users (secondhand) and non-ENDS users (baseline) were collected, firsthand emissions were generated using an automated ENDS aerosol generation system programmed to simulate puffing topography profiles collected from ENDS users. Particulate concentrations and sizes along with volatile organic compounds were characterized. We revealed puffing topography metrics as potential mediators of firsthand and secondhand particle and chemical exposures, as well as metabolic and respiratory health outcomes. Particle deposition modeling revealed that while secondhand emissions displayed smaller deposited mass, total and pulmonary particle deposition fractions were higher than firsthand deposition levels, possibly due to smaller secondhand emission particle diameters. Lastly, untargeted metabolomic profiling of salivary biomarkers of lung injury due to firsthand ENDS exposures revealed potential early indicators of respiratory distress that may also be relevant in bystanders exposed to secondhand vaping scenarios. By leveraging system toxicology, we identified 10 metabolites, including leukotriene D4, that could potentially serve as biomarkers for ENDS use, exposure estimation, and the prediction of vaping-related disease. This study highlights characterization of vaping behavior is an important exposure component in advancing our understanding of potential health effects in ENDS users and bystanders.

Continuous emission monitoring the trace Sr from simulant aerosol emission with LIPS

Continuous emission monitoring (CEM) of strontium in aerosols is of great significance for air pollution prevention and industrial facilities emission monitoring. Laser-induced plasma spectroscopy (LIPS, also LIBS) is a promising technology for direct and online monitoring aerosols because of the advantages of no sample preparation, rapid analysis, and online detection. An enhanced LIPS setup with high detection sensitivity and short detection cycles is integrated to meet the demand for continuous monitoring of trace element aerosols. The continuous monitoring of strontium in aerosols is introduced with an improved LIPS setup. The setup is calibrated and tested with different concentrations of strontium aerosols generated by aerosol generators. The enhanced LIPS setup can quantify 22 ng/m3 strontium in aerosol within 10 min. Based on experiments, a calibration curve for the strontium aerosol is established and the limit of detection (LOD) of the setup reaches 1.8 ng/m3, which meets the need for continuous monitoring of trace elements.

Effect of NO2 on SO2–SO42- conversion in atmosphere: Evidence from long-term precipitation

Sulfate aerosol (SO42−) is an important factor leading to acid rain and aggravating atmospheric particulate pollution. SO42− is mainly converted from gaseous SO2, in which the oxidant gas NO2 may play a key role. In real atmosphere with complexity and nonlinearity, the impact of NO2 on SO2–SO42- conversion exhibits scale dependence due to the combined effect of meteorology, atmospheric chemistry, and pollution emission. Here, based on the long-term atmospheric precipitation data from 2014 to 2021 of Nanchong City in the Sichuan Basin, the Extended Ensemble Empirical Mode Decomposition (EEMD) and Multifractal Detrended Cross-Correlation Analysis (MF-DCCA) methods have been employed to analyze the nonlinear correlations between gaseous SO2 and SO42− in rainwater at different time scales. A multifractal parameter Δh has been described as the scaling features of SO2–SO42- conversion efficiency in the real atmosphere. Then, the impact of NO2 on SO2–SO42- conversion in cold and warm seasons has been quantified, using sliding window analysis and Pearson correlation analysis. The results show that NO2 significantly promoted SO2–SO42- conversion in the cold season, but had little effect on it in the warm season. As direct evidence from atmospheric precipitation analysis, this finding has provided a new theoretical basis for evaluating the impact of NO2 on secondary aerosol generation.