In Europe, a large proportion of the population lives in industrial and urban coastal areas, due to their role as hubs of population migration and economic activity. Despite regulatory efforts, these areas frequently experience PM10 and PM2.5 pollution episodes due to the high density of emission sources combined with complex atmospheric dynamics. In this context, we investigate pollution days (PDs) over a 4-year period (2018-2021) on the Great Dunkirk Area, a coastal region significantly affected by diverse pollution sources. We show that PM2.5 pollution plumes predominantly exhibit regional extension, while PM10 plumes are more often local, with clear seasonal patterns. Using SEM-EDX analysis of over 23,000 individual particles collected during the 2021 MIX-TAPE campaign, we reveal a highly heterogeneous aerosol composition, dominated by sea salt and carbonaceous particles, with fine particles enriched in sulfur secondary species and coarse particles in calcium. The mixing state index (chi) ranges from 0.5 to 0.9, indicating a continuum from external to internal mixtures, strongly influenced by atmospheric ageing, recirculation, and turbulent mixing. Our results highlight that neither local wind direction nor plume extension alone can explain the observed chemical variability. Instead, the evolution of particle composition and mixing state depends on fine-scale meteorological dynamics including sea breezes and recirculation periods affecting pollutant dispersion and ageing. This work underlines the need to incorporate high-resolution particle chemistry and urban-scale atmospheric dynamics in air quality assessments and dem-onstrates the added value of single-particle analysis in complex, multisource coastal environments.

Coastal industrial and urban regions in Europe host a substantial fraction of the population and economic activity, yet they remain highly vulnerable to particulate matter (PM) pollution episodes. Despite the implementation of air quality regulations, exceedances of PM10 and PM2.5 concentration thresholds persist, driven by the coexistence of dense emission sources and complex coastal atmospheric dynamics. In this study, pollution days (PDs) were analyzed over a four-year period (2018–2021) in the Greater Dunkirk Area, a coastal region influenced by multiple anthropogenic and marine sources. Spatial analyses indicate that PM2.5 pollution episodes are predominantly associated with regionally extended plumes, whereas PM10 episodes are more frequently linked to locally confined plumes, exhibiting marked seasonal variability. Detailed aerosol chemical characterization was conducted using SEM–EDX analysis on more than 23,000 individual particles collected during a one-year field campaign in 2021. The results reveal a highly heterogeneous particle population, largely dominated by sea-salt and carbonaceous aerosols, with fine particles enriched in secondary sulfur-containing species and coarse particles characterized by calcium-rich components. The particle mixing state index (χ) spans a wide range (0.5–0.9), reflecting a continuum between externally and internally mixed aerosols, strongly modulated by atmospheric ageing processes, pollutant recirculation, and turbulent mixing. Our findings demonstrate that neither local wind direction nor plume spatial extent alone adequately explains the observed chemical variability. Instead, the evolution of aerosol composition and mixing state is governed by fine-scale meteorological processes, including sea-breeze circulations and recirculation events, which critically influence pollutant dispersion and ageing. These results underscore the importance of integrating high-resolution single-particle chemistry with urban-scale meteorological dynamics in air quality assessments, particularly in complex coastal environments subject to multiple emission sources.

More than a thousand Doppler lidars are already deployed in the world for wind energy or airport safety applications. Although such instruments are optimized for wind measurements, if they could also be qualified for aerosol observations, they would provide a cheap and immediately accessible large database, which would also open perspectives for pollutant dispersion studies. A scanning Doppler lidar was deployed for 8 months in Dunkerque, a 200,000 inhabitants harbor city in northern France. The lidar performed horizontal scans to acquire collocated observations with ground-level in-situ concentrations of PM10 and PM2.5 (beta-absorption monitor) and particle size distributions (optical particle counter, OPC). The signal from a commercial Doppler lidar cannot be inverted into aerosol optical properties, so the lidar signal intensity was directly compared with the concentrations. There was no overall correlation between the lidar signal and the mass concentrations (r2 = 0.041 with PM10 and 0.182 with PM2.5), but better results were obtained with the number concentration in the 0.7 mu m diameter channel of the OPC (r2 = 0.519) and the cumulated volume concentration over all channels below a 2 mu m cutoff diameter (r2 = 0.433). The correlation coefficient between the number concentration and lidar signal exceeded 0.8 during several periods lasting up to 5-6 days, even with varying meteorological conditions. However, coupling the lidar with a network of sensors appears to be more promising, as it was not possible to determine a global conversion factor to turn the lidar signal into particle mass or number concentration.Copyright (c) 2024 American Association for Aerosol Research

Non-exhaust emissions are now recognized as a significant source of atmospheric particulate matter and the trend towards a reduction of conventionally fueled internal combustion engine vehicles on the road is increasing their contribution to air pollution due to lower exhaust emissions. These particles include brake wear particles (BWP) and tire-road contact particles (TRCP), which are composed of tire wear particles (TWP), road wear particles (RWP) and resuspended road dust (RRD). The goal of this study has therefore been to design an original experimental approach to provide insight into the chemical composition of particles emitted at the tire-road contact, focusing on the micron (PM10-1μm) and submicron (PM1-0.1μm) fractions. Through this characterization, an examination of the different TRCP generated by different materials (tire, road surface, brake system) was conducted. To achieve this, TRCP were collected at the rear of the wheel of an instrumented vehicle during road and track tests, and a SEM-EDX analysis was performed. Our experimental conditions have allowed us to demonstrate that, at the individual particle scale, TRCP are consistently associated with road dust materials and particles solely composed of tire or road materials are practically non-existent. The contribution of BWP to TRCP is marked by the emission of Fe-rich particles, including heavy metals like Ba, Mn and Cr. TWP, which result from rubber abrasion, consist of C-rich particles abundant in Si, Zn, and S. RWP, mainly composed of Al, Si, Fe, and Ca, can be either part of RRD or internally mixed with emitted TWP. The findings of this study highlight the substantial role of RRD to TRCP emissions under real driving conditions. Consequently, it underscores the importance of examining them simultaneously to achieve a more accurate estimation of on-road traffic emissions beyond the vehicle exhaust.

A new photoacoustic soot spectrometer (PASS) operating at 880 nm was developed, for the first time, for filter-free measurements of black carbon (BC). The performance of the developed PASS was characterized and evaluated using a reference aethalometer AE51 on incense smoke in the air. An excellent correlation on the measurement of incense smoke was found between the two instruments in comparison with a regression coefficient of 0.99. A 1 σ detection limit of 0.8 µg m−3 was achieved for BC measurement at a time resolution of 1 s. It can be further reduced to 0.1 µg m−3, using a longer integration time of 1 min.

To set up a sampling and analysis strategy for particulate matter (PM) based on the time periods used in international standards is often inadequate for assessing the impact of day/night cycles or episodic emissions on urban air quality. To obtain a detailed physico–chemical characterization of urban PM when concentrations exceed the regulatory thresholds, a new rotary cascade impactor named the Time-Resolved Atmospheric Particle Sampler (TRAPS) was designed and tested for coarse and fine particle sampling. The TRAPS implementation, coupled with Optical Particle Counter measurements, provides time-resolved samples that can be analyzed by a wide range of single-particle analysis techniques. The TRAPS theoretical design was verified experimentally. Experimental cut-off diameters of 1.32 and 0.13 µm, respectively, for coarse and fine stages, were found in good agreement with theoretical values. Additionally, good trace separation, preventing inter-sample contamination, was evidenced by Scanning Electron Microscopy (SEM). The homogeneous distribution of particles of different types over a trace was also verified. As a case study, automated SEM-EDX analysis of 2500 particles, collected during two pollution peaks of a transient PM2.5 pollution event, revealed that individual particles’ chemical composition was influenced by local sources during the first pollution peak, and mainly transported during the second peak.

Atmospheric deposition is a key mode of iron (Fe) input to ocean regions where low concentrations of this micronutrient limit marine primary production. Various natural particles (e.g., mineral dust, volcanic ash) and anthropogenic particles (e.g., from industrial processes, biomass burning) can deliver Fe to the ocean, and assessment of their relative importance in supplying Fe to seawater requires knowledge of both their deposition flux and their Fe solubility (a proxy for Fe bioavailability). Iron isotope (54Fe, 56Fe, 57Fe, 58Fe) analysis is a potential tool for tracing natural and anthropogenic Fe inputs to the ocean. However, it remains uncertain how the distinct Fe isotopic signatures (δ56Fe) of these particles may be modified by physicochemical processes (e.g., acidification, photochemistry, condensation-evaporation cycles) that are known to enhance Fe solubility during atmospheric transport. In this experimental study, we measure changes over time in both Fe solubility and δ56Fe of a Tunisian soil dust and an Fe-Mn alloy factory industrial ash exposed under irradiation to a pH 2 solution containing oxalic acid, the most widespread organic complexing agent in cloud- and rainwater. The Fe released per unit surface area of the ash (∼1460 μg Fe m-2) is ∼40 times higher than that released by the dust after 60 min in solution. Isotopic fractionation is also observed, to a greater extent in the dust than the ash, in parallel with dissolution of the solid particles and driven by preferential release of 54Fe into solution. After the initial release of 54Fe, the re-adsorption of A-type Fe-oxalate ternary complexes on the most stable surface sites of the solid particles seems to impair the release of the heavier Fe isotopes, maintaining a relative enrichment in the light Fe isotope in solution over time. These findings provide new insights on Fe mobilisation and isotopic fractionation in mineral dust and industrial ash during atmospheric processing, with potential implications for ultimately improving the tracing of natural versus anthropogenic contributions of soluble Fe to the ocean.

Wet atmospheric deposition can account for up to 50% of the total iron input to surface waters, so establishing the extent to which kinetic and equilibrium isotope effects can influence aerosol soluble delta Fe-56 values is imperative to trace and constrain aerosol sources using Fe isotopes and to understand the differences found between delta Fe-56 values for bulk and soluble phases of aerosols. In this context, changes in iron solubility and isotopic composition of dissolved Fe during simulated atmospheric processing of industrial ash was investigated. Kinetic and equilibrium experiments were performed under UV/VIS light using ash from a Fe-Mn alloy metallurgical plant and a synthetic solution that mimics cloud water chemistry. The nature of the Fe species of the industrial ash was investigated by Mossbauer Spectroscopy, whereas ash and dissolved delta Fe-56 values were measured by MC-ICP-MS. Mossbauer Spectroscopy revealed that alpha-hematite, magnetite, and poorly crystallized manganoferrite nanoparticles are the main Fe species. In the early-stage dissolution (until 60 min) a Fe isotope fractionation (Delta Fe-56(solution-bulk ash)) of -0.284 +/- 0.103 parts per thousand was found at the minimum contact time evaluated herein (i.e., 5 min) due to kinetic isotopic effects. In the late-stage dissolution (after 60 min) a Delta Fe-56(solution-ash) of 0.227 +/- 0.091 parts per thousand was found due to equilibrium isotopic effects. The kinetic isotope effect within one ash surface monolayer was modeled with an enrichment factor (epsilon) of -1 parts per thousand in Fe-56/Fe-54 ratio. Iron fractional dissolution undergone during different atmospheric processing time scales may release Fe with contrasted isotope compositions to solution, changing the original soluble Fe isotope signature (which is linked to its source). This might be especially important when the dissolution process goes from kinetic to near-equilibrium conditions, in which higher amounts of Fe are progressively released from ash surface.

Sea breeze (SB) phenomena may strongly influence air quality and lead to important effects on human health. In order to study the impact of SB dynamics on the properties and toxicity of aerosols, an atmospheric mobile unit was deployed during a field campaign performed in an urbanized and industrialized coastal area in Northern France. This unit combines aerosol samplers, two scanning lidars (Doppler and elastic) and an air-liquid interface (ALI, Vitrocell®) in vitro cell exposure device. Our study highlights that after the passage of an SB front, the top of the atmospheric boundary layer collapses as the thermal internal boundary layer (TIBL) develops, which leads to high aerosol extinction coefficient values (>0.4 km−1) and an increase of PM2.5 and NOx concentrations in the SB current. The number-size distribution of particles indicates a high proportion of fine particles (with diameter below 500 nm), while the volume-size distribution shows a major mode of coarse particles centered on 2–3 µm. Individual particle analyses performed by cryo-transmission scanning electron microscopy (cryo-TSEM)-EDX highlights that submicronic particles contained a high fraction of secondary compounds, which may result from nucleation and/or condensation of condensable species (vapors or gaseous species after photo-oxidation). Secondary aerosol (SA) formation can be enhanced in some areas, by the interaction between the SB flow and the upper continental air mass, particularly due to the effect of both turbulence and temperature/humidity gradients between these two contrasting air masses. Potential areas of SA formation are located near the ground, during the SB front passage and in the vicinity of the SB current top. During the sea breeze event, an increase in the oxidative stress and inflammation processes in exposed lung cells, compared to the unexposed cells, can also be seen. In some instances, short singularity periods are observed during SB, corresponding to a double flow structure. It consists of two adjacent SB currents that induce an important increase of the TIBL top, improving the pollutants dispersion. This is associated with a substantial decrease of aerosol mass concentrations.

A compact isotope ratio sensor based on laser absorption spectroscopy at 2.7 μm was developed for high precision and simultaneous measurements of the D/H, 18O/16O and 17O/16O isotope ratios in glacier water. Measurements of the oxygen and hydrogen isotope ratios in glacier water demonstrate a 1σ precision of 0.3‰ for δ18O, 0.2‰ for δ17O, and 0.5‰ for δ2H, respectively. The δ values of the working standard glacier water obtained by the calibrated sensor system is basically identical to the IRMS measurement results with a very high calibration accuracy from 0.17‰ to 0.75‰. Preliminary results on the reproducibility measurements display a standard deviation of 0.13‰ for δ18O, 0.13‰ for δ17O, and 0.64‰ for δ2H, respectively.

Industrial metalworking facilities emit a variety of air toxics including volatile organic compounds, polycyclic aromatic hydrocarbons (PAHs) and heavy metals. In order to investigate these emissions, a 1-month multi-instrument field campaign was undertaken at an industrial site in Grande-Synthe, Dunkirk (France), in May and June 2012. One of the main objectives of the study was to provide new information on the chemical composition of particulate matter with aerodynamic diameters smaller than 2.5 μm (PM2.5) in the vicinity of metalworking facilities. An aerosol time-of-flight mass spectrometer (ATOFMS) was deployed to provide size-resolved chemical mixing state measurements of ambient single particles at high temporal resolution. This mixing state information was then used to apportion PM2.5 to local metalworking facilities influencing the receptor site. Periods when the site was influenced by metalworking sources were characterised by a pronounced increase in particles containing toxic metals (manganese, iron, lead) and polycyclic aromatic hydrocarbons (PAHs) with a variety of chemical mixing states. The association of specific particle classes with a nearby ferromanganese alloy manufacturing plant was confirmed through comparison with previous analysis of raw materials (ores) and chimney filter particle samples collected at the facility. Particles associated with emissions from a nearby steelworks were also identified. The contribution of local metalworking activities to PM2.5 at the receptor site for the period when the ATOFMS was deployed ranged from 1 to 65% with an average contribution of 17%, while the remaining mass was attributed to other local and regional sources. These findings demonstrate the impact of metalworking facilities on air quality downwind and provide useful single particle signatures for future source apportionment studies in communities impacted by metalworking emissions.

Non-exhaust particle (NEP) emissions from road traffic contribute significantly to Particulate Matter (PM) pollution in urban areas. The primary objective herein is to develop the knowledge required to move toward more sustainable mobility. NEP emissions are studied by means of complementary experiments on chassis dynamometers, on test tracks and at the roadside. Laboratory tests demonstrate that brake wear particles (BWP) emissions can change with braking force and frequency. A brake pad temperature threshold exists, above which the rate of ultrafine particle emissions is quite high. Below this threshold, the BWP emissions are dominant in the accumulation and coarse modes. Test track measurements have demonstrated that tire-road contact particle (TRCP) emissions considerably modify the atmospheric PM background especially for the supermicron fraction. Their number size distribution highlighted an ultrafine and accumulation modes centered at about 40 nm and 200 nm, respectively. The TRCP level increases with vehicle speed and during the acceleration and deceleration phases. Roadside measurements in the urban environment confirm the presence of NEP in significant proportions, in both the accumulation and coarse modes. The chemical composition of NEP differs depending on the size mode: BWP mainly stem from the degradation of brake pad lining materials, while TRCP are a mixture of tire tread wear and re-suspended dust. The presence of Fe-rich particles nevertheless serves as a good indicator of the NEP contribution to PM at the roadside. Lastly, in considering the parameters influencing NEP emissions, a series of recommendations are offered in order to achieve a more sustainable mobility.

Accurate measurement of atmospheric particulate matter (PM) absorption coefficient is highly required for study of earth climate change and for monitoring of air quality. In addition, multi-wavelength measurements of PM absorption can provide information on the PM chemical composition (black carbon or brown carbon). A multi-wavelengths photoacoustic (MW-PA) spectrophone operating at 444, 532 and 660 nm was developed and deployed for filter-free characterization of wavelength-dependent optical properties of PM mass absorption coefficient (MAC) and absorption Angstrom coefficient (AAC). It is worth noting that to date no any AAC of volcanic ashes determined by filter-free measurement have been reported. The developed MW-PA spectrophone was deployed to an intensive field campaign measurement of environmental PM in Grenoble (France). Side-by-side inter-comparison measurements of ambient PM showed a good correlation between the developed MW-PA spectrophone and a reference instrument aethalometer (Magee scientific, AE33).

In a context where a significant fraction of the population lives near industrial areas, the main objectives of this study are to provide (a) new data on PM2.5 chemical compositions, heavy-metal concentrations and trace gases released by metalworking activities and (b) new information on the near-field evolution (up to about a thousand meters) of such industrial plumes in terms of particle chemical composition and size distribution. For that purpose, a one-month field campaign was performed in an industrial area near the city of Dunkirk (Northern France), combining measurements of atmospheric dynamics and physico-chemical characterization of air masses. Comparisons between several elemental ratios (mainly Mn/Fe), particle size distributions and volatile organic compound (VOC) concentrations at the stacks and at a near-field site suggest that plumes of a ferromanganese alloy plant were quickly mixed with pollutants emitted by other sources (mainly other industries, possibly traffic and sea spray), in particular a neighboring steelworks, before reaching the sampling site. This led to the emergence of secondary particles related to condensation and/or aggregation phenomena inside the plumes. Metalworking emissions were also identified as a source of new particle formation, formed through the emission of gaseous precursors and their fast transformation and condensation, over a timescale of minutes before reaching the near-field site 800 m downwind. Ultrafine particles emitted at the stacks also quickly agglomerated to form larger particles before reaching the near-field site. These results show that, even over short distances, the chemical composition and size distribution of metalworking plumes may evolve rapidly and the characteristics of particles at the boundary of an industrial area (especially in contiguous urban areas) may differ from those emitted directly at the stacks.