OA is a major component of particulate matter (PM) that affects air quality and health, especially in highly polluted, low-income, densly populated cities. This study examines organic aerosol (OA) in São Paulo, Brazil, using water-based offline setup with soft and hard ionization mass spectrometry. This study provides a detailed chemical characterization and quantitative analysis using AMS-LToF and EESI-ToF, along with source apportionment of the primary and secondary OA drivers in Sao Paulo, Brazil’s most populous city.

Identifying aerosol sources is key to air quality policies. Traditional methods rely on chemical analysis but are labor-intensive and limit data coverage. This study proposes a novel approach using physical properties (size distribution and light absorption) from high-time-resolution optical instruments: a particle counter (Palas Fidas 200) and an aethalometer (AE33). PMF of hourly data identifies six PM10 sources, validated against traditional methods and active/passive remote sensing. Applications of real-time implementation include wildfire smoke and pollution transport tracking, and emergency surveillance. This cost-effective technique enhances spatial and temporal resolution, supporting the new EU Air Quality directive by improving emission pattern analysis.

Multi-year observations at three Irish coastal sites—Mace Head, Valentia, and Carnsore Point—reveal dynamic interactions between marine and continental aerosols in the northeastern Atlantic. Using an HR-ToF-AMS, ACSMs, and gas analysers, we monitored organic aerosols (OAs), black carbon, and trace gases for a decade. Positive matrix factorization identified primary and secondary OA sources, including marine biogenic emissions, peat burning, and continental pollution. Long-range transport events were studied with backtrajectories, while decadal trends were analysed with advanced statistics to assess impacts of climate change, anthropogenic pollution, and air quality regulation. This study lays the groundwork for integrating observations with climate models effectively.

Ultrafine particles, defined as aerosols with diameter smaller than 100 nm, represent a growing concern due to their significant impact on human health and the environment. Despite their importance, our knowledge of UFP size distribution and the processes determining their atmospheric dynamics and air-surface fluxes remains limited.

To address these gaps, a comprehensive experimental campaign was conducted from October 2024 to March 2025 at the “Comando Generale dei Carabinieri” in downtown Rome adjacent to Villa Ada, a large urban park. This location offers a unique opportunity to explore the interactions between urban emissions and vegetation in a composed environment.

Aerosol particles in the atmosphere over the Qinghai-Tibet Plateau (QTP) are important but less understood due to paucity of measurements. We presented the key findings from an intensive field observation of atmospheric aerosols in the central QTP region in summer 2022 mainly using SP-AMS, SMPS, and AE33. During the measurement period, coincided with the monsoon season, the average mass concentration of submicron aerosol was 0.98 ± 0.60 μg/m³, dominated by organic aerosol (OA). Five sources or processes were identified for OA using Positive Matrix Factorization (PMF). Two special events were selected as the “high-sulfate” and the “high-nitrate” periods and discussed.

Mobile measurements of particles containing metals and trace elements are needed to understand the emissions and spatial distributions of these pollutants, which are strongly implicated in adverse aerosol health effects. The recently developed Microwave-Induced Plasma Time-of-Flight Mass Spectrometer (mipTOF) is the first instrument providing the requisite combination of time resolution, sensitivity, and quantitative capability to enable such studies. We present the first mobile field deployment of the mipTOF, conducted during Jan.-Feb. 2025 in central Switzerland. The mipTOF successfully characterizes diverse sources, including train and tram emissions, vehicular brake wear, a quarry, and particulate lead.

We showcase a novel MS, the Thermal Desorption Multi-scheme IONization inlet Orbitrap (TD-MION-Orbitrap), for analyzing filters from a boreal forest site. The filters captured condensing vapors, such as sulfuric, iodic, methanesulfonic, and malonic acids, and highly oxygenated organic molecules (HOMs). The timeseries were compared to online measurements from a MION-APi-TOF at the same location, both boasting a nitrate (NO3-) source for chemical ionization. The filter-desorbed compounds matched the online observations by 51% and the signal intensities acquired were comparable in both methodologies. These results provide support for the use of filters in the study of condensing vapors in various environments.

We report on the development and characterization of a new trace-element mass spectrometer for the direct and real-time quantitative analysis of metals in air. The microwave-induced plasma time-of-flight mass spectrometer (mipTOF) features a nitrogen-sustained MICAP high-power plasma source that can be used to directly vaporize, atomize, and ionize nano-to-micron-sized particles from the ambient air. The mipTOF is a fieldable instrument that delivers detection limits from 0.1-5 ng/m³ for almost all elements per 10-second analysis. We will discuss instrument design, performance, calibration strategies, and both stationary and mobile applications of the mipTOF instrument.

We present results on limonene oxidation using the new Bipolar FUSION PTR-TOF for detection of volatile oxidation products and formed SOA constituents that we produced in a novel laminar flow oxidation reactor. The Bipolar FUSION PTR-TOF provides multiple selective reagent ions, the positive (H3O+, NH4+, NO+, O2+) and the new negative (CO3-) ion modes for detection of organic and inorganic compounds. We will show data of chamber and ambient measurements using H3O+, NH4+, NO+, and CO3- primary reagent ion modes and discuss the benefits and limitations of complementary ionization modes of the Bipolar FUSION PTR-TOF.

In this work, we present the development and comprehensive characterization of a novel chemical ionization source designed for real-time detection of trace gases and aerosol-related compounds. This source is compatible with proton-transfer-reaction (PTR) and other chemical ionization schemes, enabling the generation of both positive and negative analyte ions. Key innovations include fast reagent ion switching on the timescale of seconds, and the ability to operate across a broad range of ion-molecule reactor (IMR) pressures (1 - 10 mbar) and sample flow rates, enhancing flexibility for diverse measurement conditions.

Oxidative potential was measured with chemical composition in mulitiple cities in western and Eastern Europe, China, and India. The main drivers of oxidative potential in the different regions and seasons will be discussed taking into account measurements of DTT and ascorbic acid in conjuncition with organic aerosol characterization, elemental composition anaylysis and source apportionment.

The oxidative potential of PM [capacity of PM to oxidize the lungs] is attracting growing interest in research into PM health impacts. OP appears to be a relevant indicator, as it allows to provide information about the intrinsic reactivity of particles and their possible risk for health. In this work, a large database of homogeneous OP measurements throughout Europe has been used to assess its spatial variability and to distinguish several types of environments according to their oxidative burden. These observations then fuel the discussion on the integration of OP into European regulations, using various OP exposure scenarios.

In this work, mineral dust was aerosolized into an atmospheric simulation chamber and oxidized with HONO, SO₂ and O₃, then the OP of mineral dust was estimated with different assays (DTT, AA and H₂O_2eq) for the total and soluble fraction. Experiments were also run for bulk samples for controlled pH changed.

We used quasi-Poisson regression models to estimate the effects of PM2.5 and PM10 oxidative potential (OP) exposure on mortality from four European cities: Barcelona, Grenoble, Paris, and Zurich. The associations obtained were combined using random effect meta-analysis. Two OP assays were evaluated, ascorbic acid (AA) and dithiothreitol (DTT), and the results were normalized by mass and volume.

OP was associated with both increased and decreased mortality risks, depending on assay type, PM fraction, and normalization unit. More epidemiological studies are needed to elucidate the effects of OP exposure on health.

This work investigates spatial and seasonal variabilities of PM_2.5 and PM₁₀ concentrations, composition, and oxidative potential (OP^DTT_V, obtained with DTT-assay), simultaneously at 22 sites in a central Mediterranean area in south Italy. Source apportionment using PMF5 allowed to evaluate the contributions of eight sources: traffic, biomass burning (BB), nitrate, sulphate-rich, marine, crustal, carbonates/construction, and industrial (only for PM_2.5). OP^DTT_V had relevant spatial variability only during the cold season. The use of soluble and insoluble fractions of OC and Ca in PMF5 allowed a better separation between traffic and BB sources and allowed to determined the role of local construction works.

Although water-soluble OC (WSOC) and ON (WSON) constitute a substantial fraction of aerosols, particularly in urban areas affected by agricultural, biogenic, and biomass burning emissions, there remains a paucity of information regarding the size-segregated levels, sources, and seasonality of these parameters. The primary objective of this study is to determine the levels, seasonality, and sources of WSOC and WSON in size-segregated aerosol samples collected at a ground-based station (40.73° N, 31.60º E, 743 m asl) in Bolu (Türkiye) between April 2021 and April 2022.

This study examines the chemical composition and sources of aerosols during severe winter pollution episodes in Ioannina, Greece. Using data from an ACSM, a PTR-MS and an aethalometer, biomass burning was identified as the dominant pollution source, significantly contributing to organic aerosols (OA) and brown carbon absorption. Combined aerosol acidity and liquid water content lead to enhanced secondary aerosol formation through aqueous phase processing. Concurrently, PMF showed that 58% of OA originates from biomass burning. Not least, Ioannina’s basin location and temperature inversions lead to pollutant accumulation, highlighting the urgent need for targeted air quality policies in southeastern European cities.

This work focuses on wildfire events, in the climate sensitive area of the Eastern Mediterranean and especially in Greece. The analysis focuses on three intense wildfire events that occurred in the proximity of Athens during the first half of August 2021 (August 3–10: Varympompi and Euboea forest fires; August 17–19: Vilia forest fire), following a prolonged and intense heatwave. The study assesses the impact of transported smoke from forest fires on urban air quality and aerosol optical, physical and chemical properties.

This work combines chamber experiments and field measurements to determine the contribution of different secondary organic aerosol precursors into the organic carbon observed at urban and forested areas of Paris. Organic carbon measurements and molecular scale analyses using HRMS, LC-MS and GC-MS highlight the contribution of anthropogenic sources into the aerosol composition, which predominates for both environments.

Domestic wood burning is a major source of particulate matter (PM) emissions in the UK, exceeding road traffic emissions. Despite mitigation efforts like 'EcoDesign' stoves, emissions have risen over two decades. UK estimates rely on lab tests that may not reflect real-world conditions, especially during transient phases like ignition and reloading. A new test facility at the University of Manchester used real-time analysers, including EESI mass spectrometry, to monitor emissions under varied conditions. Findings reveal significant chemical variations across burn phases, with oxidised gases peaking early and nitrogen-containing aerosols increasing during smouldering, highlighting the impact of combustion conditions

Free and combined amino acids and nucleobases were measured in extracts from Antarctic marine aerosol and water samples. Transfer processes were studied, revealing a gap for atmospheric biotic and abiotic processing of the analytes. Samples were also investigated for mass, back trajectories, Ion concentrations and OC/EC or WSOC.

The SIDDARTA project aims to investigate present-day sources and transport processes supplying mineral dust to the Antarctic plateau. The project includes the study of the composition of mineral dust at Dome C (Concordia Station), both in the form of atmospheric particulate matter (PM₁₀), surface snow and snow-pit samples (to achieve a multi-annual record of dust deposition), as well as the resuspension and analysis of soil samples previously collected in Potential Source Areas (PSA) in Australia and Southern South America. The analysis included measurements of elemental composition, major and trace metals, and isotopic composition of Pb and Sr.

Antarctica, the coldest and driest continent, is crucial for global climate regulation. Recent warming trends, especially in West Antarctica and the Antarctic Peninsula, have increased surface melting and altered precipitation patterns. Atmospheric Rivers (ARs), though infrequent, contribute significantly to precipitation, ice shelf destabilization, and microbial transport. To study microbial communities in precipitation over the northern Antarctic Peninsula, we conducted a culture-dependent analysis on samples from expeditons during 2022 and 2024. Using DNA sequencing and back-trajectory analysis, we identified viable microbial taxa and their sources. These findings provide insights into the role of ARs in microbial dispersal and ecosystem impacts.

Clouds enhance Antarctic Ice Sheet melting through thermal-infrared emissions but remain poorly understood and misrepresented in models. Inaccurate treatment of ice-nucleating particles and cloud condensation nuclei impacts cloud persistence and radiative effects. Surface aerosol observations represent local features, while satellite sensing struggles with low concentrations. To address this, two campaigns in 2024-2025 deployed a tethered balloon for vertical profiles at Neumayer III Station and a Twin Otter aircraft for a 15000 km transect. These platforms measured aerosols concentrations, providing insights into regional variability, with the aim of improving the representation of aerosol-cloud interactions in the Antarctic lower troposphere.

The Southern Ocean and Antarctica are remote from anthropogenic influence, making the region one of the most pristine in the world and a unique testbed for probing natural atmospheric processes. Understanding these “baseline” conditions is critical for reducing the uncertainty in our climate models. A recent effort, PICCAASO, was initiated to coordinate the over 20 international projects funded since 2020 aimed at investigating the complex natural interactions between ocean biogeochemistry, trace gas emissions, aerosols and clouds. In this presentation, early results from several Australian-based PICCAASO-themed campaigns (MISO, CAPE-k, COAST-k and Denman Marine Voyage) in the region are presented.

This study compares ELPI’s electrical measurements (2 units equipped with different impaction plates) with well-established aerosol spectrometers, including MPSS, APSS, and CPC, using a set of well-defined aerosols of varying composition, size, and morphology.

Bioaerosols, which come from natural or industrial sources and consist of airborne organisms or their fragments, pose health risks to the public and industry. As a result, there is growing emphasis on developing reliable early detection methods for these pathogens. This project aims to create an affordable "first alert" system to detect airborne bacteria, fungi, and pollen in real time. The system alerts users to potential pathogens or allergens in the air, enabling timely protective actions. While it cannot identify specific types, it captures and stores particles in a liquid sample, which can then be analyzed in the laboratory

We have developed and applied a new measurement technique to determine the 3D shape factor of aerosol particles deposited on impactor trays using scanning electron microscopy (SEM). Besides the determination of two characteristic size of the particles from 2D SEM images, the Everhart-Thornley detector’s “shadow effect” was used to measure the height perpendicular to the Si substrate of the samples. From these informations a 3D shape factor was compiled, and used to determine the size-dependent 3D shape factors of particles emitted from three different dry powder inhalers and to study the shape factor’s effects on their lung deposition properties by numerical modelling.

In this work describe a high purity aerosolization, aerosol heating, and threshold condensation particle counting (CPC) system. We demonstrate the capability of this system using ultrapure water doped with varying concentrations of non-volatile and semi-volatile materials. When the aerosol is heated, the semi-volatile components may evaporate. This reduces the mean size of the aerosolized particle distribution and eventually, particle concentrations above the CPC size threshold fall below its detection limit. Materials tested include mixtures of sodium chloride, sucrose, and adipic and succinic acids. Aerosol temperatures range from 60-250°C.

The triboelectric charging of aerosol particles during particle-wall collisions can be used for basic investigations of the mechanical properties of nanoparticles, but also for the targeted charging of micrometer particles in a material-specific sorting process. In order to understand the charge transfer, the exit work of both contact partners must be known. Two methods for measuring the work function of aerosols and walls/powders at atmospheric pressure are presented here.

A one year-long campaign (03/2024–03/2025) in Athens used the new AE36s Aethalometer and Total Carbon Analyzer to analyze carbonaceous aerosols (CA) with high-time resolution. The study applied spectral clustering and the 2D BC tracer method to differentiate sources like traffic, wildfire plumes, and mineral dust. Results showed distinct absorption fingerprints and significant secondary organic carbon (SOC) contributions in summer. These findings enhance real-time source apportionment and targeted mitigation strategies to reduce PM2.5 pollution effectively.

Multiple sources of air pollution in Moscow, no using of biomass and coal, have complicated the identifying observed BrC light absorption.Four sources obtained using BrC PMF analysis: FF combustion; BB; secondary aerosols and city dust. The uniqueness of Moscow megacity for BB impact studies in Europe and Asia is highlighted by gas-fueled heating system,and) exposure by BB emissions transported from the region around at the level similar during HP and non-HP periods. BB impact increases during spring regional agriculture and summer wildfires. Moscow is mostly affected by BrC which contribution is higher from FF combustion than from BB

We present a ¹⁴C-based source apportionment study carried out at an urban background site in the Po Valley, a hotspot area in Europe. Fourteen PM₁ samples were collected in Jan-Mar 2021 in Bologna with 48-h resolution and were prepared using MISSMARPLE, a recently developed sample preparation line for ¹⁴C measurements on atmospheric aerosol carbon fractions. ¹⁴C-based source apportionment was performed separately for elemental carbon (EC) and organic carbon (OC), after suitable optimization of model parameters. Fossil fuel combustion remains the main source of EC in the investigated area (60%), while modern contributions generally dominate the OC fraction (66%)

Biomass burning (BB) aerosol impacts climate and atmospheric
chemistry. To quantify BB aerosol’s contributions to aerosol optical
depth (AOD) at a given location we developed a new framework that
integrats satellite fire data with aerosol transport, BB emissions, and
plume rise models. Applying it in Warsaw (2006–2022) revealed dominant
transatlantic influences, with Canada (33%) and the USA (33%) together
surpassing European sources. Accounting for
vertical plume dynamics is crucial; neglecting them leads to biases in
source estimates. This framework can be broadly applied, though future
work should refine aerosol characterization, including plume structure,
aging, and emission inventories.

Delhi experiences exceptionally high PM₂.₅-bound chlorine concentrations, with pronounced seasonal and diel variations, peaking in colder months and mornings due to meteorological influences like RH, temperature, and PBLH. Biomass burning, coal combustion, and industry contribute, but their relative impacts remain unclear. This study integrates Punjab field data (2023) with IIT Delhi observations (2019–2022) to assess stubble burning’s role. Elevated Cl levels in Punjab correlated with biomass-burning tracers (BC, K, OA, CO), with PMF analysis attributing 80% of Cl to stubble burning. Diagnostic ratios indicate mixed Cl sources in Delhi, including waste burning and industrial emissions.

Measuring the oxidative potential (OP) of atmospheric particles is used to assess their toxicity. We present a chemical kinetics model of aerosol oxidative potential to quantify the effects of particles on the production of reactive oxygen species and the depletion of ascorbic acid and dithiothreitol. An inverse modelling framework was applied to laboratory OP data. We extrapolate the findings from the laboratory experiments to field data, and find good agreement between the model and data across three sites. We further extend the to a multiphase kinetic model of the respiratory tract to translate assay-based OP into biomarkers of oxidative stress.

Poor indoor air quality can have a significant impact on occupants’ health and well-being. Despite this evidence, there are still major gaps in our understanding of the most important harmful pollutant components and their mechanisms of toxicity. This project aimed to investigate the mechanisms by which two dominant indoor air pollution sources (cooking and cleaning activities) can cause pulmonary adverse effects. A combination online of air-liquid interface lung epithelial cell exposure and accellular oxidative potential were used to link the chemical composition of the aerosol with adverse acellular and cellular toxicity measurements.

This study tackles key challenges in using oxidative potential (OP) to estimate health effects induced by various particulate matter (PM) sources. We employed OP^DTT, OP^AA, and OP^DCFH on more than one thousand fully chemically characterized PM samples collected in three urban/industrial areas of Italy. Samples were collected in each area using multi-stage impactors, conventional one-site daily samplings, and innovative spatially-resolved, long-term samplings. Source apportionment of PM₁₀ and its OP was performed using PMF, principal component analysis (PCA), and focused PCA. Size distribution analyses and spatially-resolved data significantly enhanced OP source apportionment, allowing for a more thorough investigation of its complexity.

This study examines the oxidative potential (OP) of airborne particulate matter (PM) and settled dust from homes in Slovenia, Sweden, and the UK, as part of the INQUIRE project. Using simulated lung fluid and LC-MS, antioxidant depletion rates (ascorbic acid, glutathione, cysteine) and glutathione disulfide accumulation were measured. Preliminary results show a strong correlation between PM mass and the initial depletion rate of ascorbic acid, and the later depletion phase of glutathione. These patterns suggest distinct oxidative mechanisms involving organics and soluble metals. These findings emphasize the potential health risks of indoor PM, particularly through oxidative stress in respiratory pathways.

In the present work, for first time an electrochemical sensor was developed for monitoring oxidative potential with high sensitivity and easy operation using portable devices. The proposed approach is based on ascorbic acid assay where, after being oxidized by particulate matter, the remaining ascorbic acid is analyzed directly by flow injection analysis with chronoamperometric detection using a screen-printed carbon electrode modified with azure-A polymer and platinum nanoparticles.

Our study presents a novel methodology that integrates multiple high-dimensional imaging techniques to enhance the characterization of air pollution particles. By combining SEM-EDX and ToF-SIMS data with multiway analysis, we address the challenges posed by heterogeneous particle composition and evolving pollution sources. This approach enables more precise source apportionment and a deeper understanding of PM characteristics, particularly in the context of changing vehicle emissions and urban air quality. The results demonstrate the potential of multiway techniques to unlock new insights into air pollution dynamics, paving the way for improved regulatory strategies and pollution mitigation efforts

This study investigated the optical properties of soluble BrC and its impact on climate. Fluorescence analysis was used to obtain the structural characteristics of soluble BrC, contributing to a deeper insight into its composition in urban areas. The findings provide valuable information to support future atmospheric research utilizing fluorescence analysis. Furthermore, this study will employ the PMF model to apportion emission sources and assess their relationship with BrC optical properties. This approach aims to improve our understanding of the contributions of various urban emission sources to climate change.

Biological aerosol particles, or bioaerosols, represent a significant portion of atmospheric particulate matter (PM) and can profoundly affect the chemical and physical properties of atmospheric aerosols. Interest in atmospheric bioaerosols has increased recently because of the effects bioaerosols have on global climate and human health. In the present study, extracts of common bioaerosols were aged with an oxidation flow reactor (OFR) and with H₂O₂ under UV-Vis light. The chemical analysis of organic species in fresh and aged bioaerosol samples was performed using Liquid Chromatography Mass Spectrometry (LC-MS) and Nuclear Magnetic Resonance Spectroscopy (¹H-NMR).

This study presents the first NMR-based seasonal analysis of organic aerosols in Mumbai, a tropical coastal megacity. PM₁₀, EC-OC, and NMR-derived functional groups were analyzed using high-resolution diurnal sampling. PM₁₀ peaked in winter afternoons due to meteorological factors, while summer recorded the lowest levels. EC-OC trends indicated biomass burning and secondary aerosol formation. NMR analysis revealed higher hydrocarbons in winter, with aliphatics dominating year-round. Oxygenated species peaked in winter, linked to stagnant conditions. Strong correlations between functional groups and EC-OC suggest seasonal variations in sources and processes. Advanced NMR analysis is ongoing for further insights

We characterize the chemical composition of particles from five wildfire plumes that reached the Jungfraujoch in 2023, using TOF-ACSM, AE33 and MAAP measurements. Organic aerosol (OA) dominated all biomass burning (BB) plumes, and the contribution to OA of m/z 60, a levoglucosan tracer, increases for these plumes. We also observe that the contribution of the m/z range 135-200 to OA increases during the BB plumes. A preliminary PMF source apportionment hints at a wildfire-specific BBOA factor in summer. Further work will focus on better separating the air masses and, consolidating the PMF and investigating more BB plumes.

Approximately 2% of the managed forest in Sweden is harvested annually. Our research captured a clearcutting event in 2022 at the Norunda station in Swedish boreal forest. During clearcutting, an increase in monoterpene concentration to over 60 ppb was observed. Sesquiterpene and diterpene showed diurnal patterns similar to that of monoterpene in pre-, during, and post-cutting periods. Isoprene did not show a significant increase. The cutting event altered the ratios of different BVOC, which further influenced the SOA formation. Higher signals of particulate organic compounds were observed during cutting. BVOC showed varying contributions to SOA compositions across different periods.

The Po Valley in Italy is a hotspot of pollution in Europe. In winter radiation fog occurs and affects the air composition, where gas-phase changes of organic aerosol are understudied. During in-situ observations in winter/spring 2021/2022 we analyzed the molecular-level chemical composition changes of organic aerosol in the gas and particle phase in the presence of fog, using mass spectrometry. Preliminary results show changes in the volatility distributions for both phases, suggesting scavenging by the droplets and phase partitioning. The study helps to establish a better assessment of aerosol-fog interactions on human health and climate in polluted regions.

This study investigates secondary organic aerosol (SOA) formation in São Paulo, a megacity influenced by both biogenic and anthropogenic emissions. Field measurements during the BIOMASP⁺ campaign (April-May 2023) were combined with chamber experiments to study VOC oxidation and SOA composition. Using CHARON-PTR-ToF-MS, the average SOA concentration was 4.5 µg m⁻³, with C_xH_yO₂, C_xH_yO₃, and C_xH_yO₄ compounds contributing most. High-NO_x isoprene markers, linked to polluted conditions, dominated, while low-NO_x epoxydiol products were scarce. This research enhances understanding of SOA formation mechanisms in biogenically influenced urban areas, supporting improved air quality management in complex urban environments like São Paulo.

The study investigates the seasonal transition of organic gases and particles in a polluted megcity, focusing on secondary organic aerosol (SOA) formation at molecular level. Using advanced mass spectrometry techniques, the research captures shifts from winter heating emissions to biogenic sources in spring. It highlights how volatile organic compounds (VOCs) and SOA compositions change with pollution levels and seasonal influences. Key findings include the transition from biomass burning SOA (BBOA) to biogenic SOA (BSOA) and the distinct role of fresh emissions. The study underscores the importance of co-located gas and particle-phase measurements in understanding complex atmospheric processes.

Biomass burning is a major source of PM₂.₅, significantly impacting air quality and SOA formation. This study investigates the molecular evolution of biomass burning OA (BBOA) through a field campaign in Punjab, integrating EESI-TOF and Orbitrap MS for high-resolution analysis. Fresh BBOA showed higher CHN compounds, while aged samples were enriched in unsaturated CHO species. Clustering analysis identified key molecular tracers increasing with aging. These findings support a molecular-tracer-based SOA estimation framework, enhancing assessments of smoke plume impacts on urban air pollution in South Asia.