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Atmospheric aerosol particles, being composed of various types of chemical mixtures, affect significantly on human health and climate. During the last decade, many studies were focused on characterization of chemical and physical properties as well as source apportionment of atmospheric aerosols, which have made substantial implications for aerosol-induced air pollution and climate mitigation. Instrumental measurement techniques provide one of the most direct and effective ways to determine aerosol physicochemical characterization and thereby to constrain aerosol modeling. The Aerodyne soot particle aerosol mass spectrometer (SP-AMS), a state-of-the-art instrument, combines the advantages of both high-resolution time-of-flight AMS (HR-ToF-AMS) and single particle soot photometer (SP2). It can measure high-resolution chemical composition, size distribution, and mixing state of both non-refractory and refractory aerosol particles. Specially, chemical-resolved coating materials of refractory black carbon-containing particles can be quantified by SP-AMS. Moreover, same as HR-ToF-AMS, highly time-resolved organic mass spectral data can be applied for further identification and quantification of organic aerosol sources with receptor models, such as positive matrix factorization (PMF). This review summarizes results and findings obtained by recent SP-AMS measurements in field observations and laboratory studies. These SP-AMS measurements mainly cover the topics of soot cluster ions, trace metals, chemical composition and sources of non-refractory bulk aerosols, mixing state, and light absorption properties of black carbon-containing particles. Finally, we propose some potential prospects for future studies by using the SP-AMS.

Cooking organic aerosol (COA) constitutes a considerable fraction of organic aerosol (OA) in urban environments, yet it is often challenging to resolve COA in summer through positive matrix factorization of unit mass resolution spectra of OA from aerosol mass spectrometer measurements. Here we developed a black carbon‐tracer method for estimating COA in summer. The estimated COA agreed reasonably well with those from other methods. This method can also be applied to other seasons and megacities without substantial emissions from biomass burning and coal combustion. Globally, much higher COA concentrations in China and India than those in North America and Europe were observed, while the COA contributions were comparable (15.5–20%), highlighting the importance of COA in urban areas. Considering the rapidly increased aerosol mass spectrometer measurements worldwide, this method has significant implications for a better source apportionment of OA and also benefits the health studies associated with cooking exposure.

Since early 2020, the COVID-19 pandemic has led to lockdowns at national scales. These lockdowns resulted in large cuts of atmospheric pollutant emissions, notably related to the vehicular traffic source where daily commuting of light-duty vehicles was almost completely stopped in numerous urban areas worldwide, especially during Spring 2020. As a result, air quality changed in manners that are still currently under investigation. Long-term in-situ monitoring of atmospheric composition provides, to this perspective, essential information. However, a robust quantitative assessment of the impact of lockdown measures on ambient concentrations is hindered by weather variability. Basic comparisons with previous years may thus be flawed, especially regarding secondary pollutants, whose concentrations strongly depends on meteorological conditions. In order to circumvent this difficulty, an innovative methodology has been developed. The Analog Application for Air Quality (A3Q) method is based on the comparison of each day of lockdown to a group of analog days having similar meteorological conditions. The A3Q method has been successfully evaluated and applied to a comprehensive in-situ dataset of primary and secondary pollutants obtained at the SIRTA observatory, a suburban background site of the Paris megacity (France). The overall slight decrease of PM1 concentrations (−14 %) compared to business-as-usual conditions conceals contrasting behaviours. Primary traffic tracers (NOx and traffic-related carbonaceous aerosols) dropped by 42–66 % during the lockdown period. Further, the A3Q method enabled us to characterize of changes triggered by NOx decreases. Particulate nitrate and secondary organic aerosols (SOA), two of the main springtime aerosol components in North-Western Europe, decreased by −45 % and −25 %, respectively. A NOx-relationship emphasizes the interest of NOx mitigation policies at the regional (i.e. city) scale, although long-range pollution advection sporadically overcompensated regional decreases. Variations of the oxidation state of SOA suggests discrepancies in SOA formation processes. At the same time, the expected ozone increase (+20 %) underlines the negative feedback of NO titration. These results provide a quasi-comprehensive observation-based insight on mitigation policies regarding air quality in future low-carbon urban areas.

The CARA program has been developed since 2008 by the French reference laboratory for air quality monitoring (LCSQA) and the regional monitoring networks to gain a better knowledge at the national level on the particulate matter (PM) chemistry and its diverse origins in urban environments. It results of strong collaborations with international-level academic partners, allowing to bring state-of-the-art, straightforward and robust results and methodologies within operational air quality stakeholders (and subsequently, decision makers). Here, we illustrate some of the main outputs obtained over the last decade thanks to this program, regarding methodological aspects (both in terms of measurement techniques and data treatment procedures) as well as acquired knowledge on the predominant PM sources. Offline and online methods are used following well-suited quality assurance and quality control procedures, notably including inter-laboratory comparison exercises. Source apportionment studies are conducted using various receptor modeling approaches. Overall, the results presented herewith underline the major influences of residential wood burning (during the cold period) and road transport emissions (exhaust and non-exhaust ones, all along the year), as well as substantial contributions of mineral dust and primary biogenic particles (mostly during the warm period). Long-range transport phenomena, e.g., advection of secondary inorganic aerosols from the European continental sector and of Saharan dust into the French West Indies, are also discussed in this paper. Finally, we briefly address the use of stable isotope measurements (δ15N) and of various organic molecular markers for a better understanding of the origins of ammonium and of the different organic aerosol fractions, respectively.

China's severe air pollution was widely concerned in the past decade. A rigorous emission control has been implemented by the Chinese government since 2013. It is essential to evaluate changes of air pollutants to understand effectiveness of present air-pollution control on improving air quality. Here, we investigate temporal trends of air pollutants, including PM2.5, SO2, NO2 and O3, observed at 12 sites over the Kunshan area in the Yangtze River Delta region during 2012–2018 using Mann-Kendall statistical test. Overall, significant reduction trends of monthly PM2.5 (−7.4% yr−1) were observed, together with reduction in the PM2.5 to CO ratio (−5.8% yr−1), an indicator of secondary aerosol production. Secondary aerosol precursors, SO2 (−10.3% yr−1) and NO2 (−4.4% yr−1) also presented statistically significant reduction trends. These results reflect the consequence of emission control that leads to substantial reduction in the bulk PM2.5 concentration, as well as secondary aerosols likely formed from SO2 and NO2. However, O3 had statistically significant increase trend (+3.4% yr−1) during 2014–2018. Limited formation of O3 under high PM2.5 and NO2 concentrations condition was found at daytime in summer, which might reflect one of the reasons causing the increase trend of O3 under the current reduction scenario of PM2.5 and NO2. Potential source contribution function analysis demonstrated that the transport from the regions located to northwest of Kunshan could contribute to high concentrations of PM2.5 in all seasons, while the south and southeast could be the high potential as source areas for O3.

International audience; A single particle soot photometer (SP2) was deployed in urban Nanjing, located in the Yangtze River Delta (China), to investigate the mixing state and sources of ambient refractory black carbon (rBC) from 26 January to 25 February 2014, along with an in-situ measurement of submicron aerosol chemical species by an aerodyne aerosol chemical speciation monitor (ACSM). The results showed that anthropogenic activities associated with firework emissions can be a significant source for rBC-containing particles during the period of the Chinese New Year, resulting from the evident peaks of rBC at midnight. During the residual periods, namely regular day (RD), the diurnal cycles of rBC presented two typical peaks that can be attributed to a synergistic influence of local traffic emissions and boundary layer changes throughout a day. Three coating factors, including organics, sulfate, and nitrate (-rich), were resolved using a positive matrix factorization (PMF) approach to explain the potential contribution of non-rBC coatings (i.e., organics, sulfate, and nitrate) to the coating thickness of rBC-containing particles. As the results show, organic aerosols (OAs) might be a major contributor to the coating thickness of rBC-coating particles during the whole period. The relative coating thickness (a ratio between coated particle size to BC core) exhibited a positive relationship with sulfate, indicative of the favorable coating factor during the episode caused by firework emissions. Source apportionment of rBC was performed via a multiple linear regression between the total rBC mass and each ACSM-PMF factor (rBC-ACSM-PMF). On average, biomass burning emissions accounted for 43%, being the largest contributor during the RD period, whereas local traffic emissions played a major role during the new year time.

A PM2.5-capable aerosol chemical speciation monitor (ACSM) was deployed in urban Nanjing, China for the first time to measure in-situ non-refractory fine particle (NR-PM2.5) composition from October 20 to November 19, 2015 along with parallel measurements of submicron aerosol (PM1) species by a standard ACSM. Our results show that the NR-PM2.5 species (organics, sulfate, nitrate, and ammonium) measured by the PM2.5-ACSM are highly correlated (r2 > 0.9) with those measured by a Sunset Lab OC/EC Analyzer and a Monitor for AeRosols and GAses (MARGA). The comparisons between the two ACSMs illustrated similar temporal variations in all NR species between PM1 and PM2.5, yet substantial mass fractions of aerosol species were observed in the size range of 1–2.5 μm. On average, NR-PM1–2.5 contributed 53 % of the total NR-PM2.5 with sulfate and secondary organic aerosols (SOA) being the two largest contributors (26 % and 27 %, respectively). Rapid formation and thereafter growth of secondary inorganic aerosols (SIA) were observed under fog processing in NH3-rich environments. Positive matrix factorization of organic aerosol showed similar temporal variations in both primary and secondary OA between PM1 and PM2.5 although the mass spectra were slightly different due to more thermal decomposition on the capture vaporizer of PM2.5-ACSM. We observed an enhancement of SOA under high relative humidity conditions, which is associated with simultaneous increases in particle surface area, gas-phase species (NO2, SO2, and NH3) concentrations and aerosol water content driven by anthropogenic SIA. These results likely indicate an enhanced reactive uptake of SOA precursors upon aqueous particles. Therefore, reducing anthropogenic NOx, SO2, and NH3 emissions might not only reduce SIA but also SOA burden during haze episodes in China.

Volcanic sulfate aerosols play a key role in air quality and climate. However, the rate of oxidation of sulfur dioxide (SO2) precursor gas to sulfate aerosols (SO42-) in volcanic plumes is poorly known, especially in the troposphere. Here we determine the chemical speciation as well as the intensity and temporal persistence of the impact on air quality of sulfate aerosols from the 2014–2015 Holuhraun flood lava eruption of Icelandic volcano Bárðarbunga. To do so, we jointly analyse a set of SO2 observations from satellite (OMPS and IASI) and ground-level measurements from air quality monitoring stations together with high temporal resolution mass spectrometry measurements of an Aerosol Chemical Speciation Monitor (ACSM) performed far from the volcanic source. We explore month/year long ACSM data in France from stations in contrasting environments, close and far from industrial sulfur-rich activities. We demonstrate that volcanic sulfate aerosols exhibit a distinct chemical signature in urban/rural conditions, with NO3:SO4 mass concentration ratios lower than for non-volcanic background aerosols. These results are supported by thermodynamic simulations of aerosol composition, using the ISORROPIA II model, which show that ammonium sulfate aerosols are preferentially formed at a high concentration of sulfate, leading to a decrease in the production of particulate ammonium nitrate. Such a chemical signature is however more difficult to identify at heavily polluted industrial sites due to a high level of background noise in sulfur. Nevertheless, aged volcanic sulfates can be distinguished from freshly emitted industrial sulfates according to their contrasting degree of anion neutralization. Combining AERONET (AErosol RObotic NETwork) sunphotometric data with ACSM observations, we also show a long persistence over weeks of pollution in volcanic sulfate aerosols, while SO2 pollution disappears in a few days at most. Finally, gathering 6-month long datasets from 27 sulfur monitoring stations of the EMEP (European Monitoring and Evaluation Programme) network allows us to demonstrate a much broader large-scale European pollution, in both SO2 and SO4, associated with the Holuhraun eruption, from Scandinavia to France. While widespread SO2 anomalies, with ground-level mass concentrations far exceeding background values, almost entirely result from the volcanic source, the origin of sulfate aerosols is more complex. Using a multi-site concentration-weighted trajectory analysis, emissions from the Holuhraun eruption are shown to be one of the main sources of SO4 at all EMEP sites across Europe and can be distinguished from anthropogenic emissions from eastern Europe but also from Great Britain. A wide variability in SO2:SO4 mass concentration ratios, ranging from 0.8 to 8.0, is shown at several stations geographically dispersed at thousands of kilometres from the eruption site. Despite this apparent spatial complexity, we demonstrate that these mass oxidation ratios can be explained by a simple linear dependency on the age of the plume, with a SO2-to-SO4 oxidation rate of 0.23 h−1. Most current studies generally focus on SO2, an unambiguous and more readily measured marker of the volcanic plume. However, the long persistence of the chemical fingerprint of volcanic sulfate aerosols at continental scale, as shown for the Holuhraun eruption here, casts light on the impact of tropospheric eruptions and passive degassing activities on air quality, health, atmospheric chemistry and climate., info:eu-repo/semantics/published

International audience; he present study proposes an advanced methodology to refine the source apportionment of organic aerosol (OA). This methodology is based on the combination of offline and online datasets in a single Positive Matrix Factorization (PMF) analysis using the multilinear engine (ME-2) algorithm and a customized time synchronization procedure. It has been applied to data from measurements conducted in the Paris region (France) during a PM pollution event in March 2015. Measurements included OA ACSM (Aerosol Chemical Speciation Monitor) mass spectra and specific primary and secondary organic molecular markers from PM10 filters on their original time resolution (30 min for ACSM and 4 h for PM10 filters). Comparison with the conventional PMF analysis of the ACSM OA dataset (PMF-ACSM) showed very good agreement for the discrimination between primary and secondary OA fractions with about 75% of the OA mass of secondary origin. Furthermore, the use of the combined datasets allowed the deconvolution of 3 primary OA (POA) factors and 7 secondary OA (SOA) factors. A clear identification of the source/origin of 54% of the total SOA mass could be achieved thanks to specific molecular markers. Specifically, 28% of that fraction was linked to combustion sources (biomass burning and traffic emissions). A clear identification of primary traffic OA was also obtained using the PMF-combined analysis while PMF-ACSM only gave a proxy for this OA source in the form of total hydrocarbon-like OA (HOA) mass concentrations. In addition, the primary biomass burning-related OA source was explained by two OA factors, BBOA and OPOA-like BBOA. This new approach has showed undeniable advantages over the conventional approaches by providing valuable insights into the processes involved in SOA formation and their sources. However, the origins of highly oxidized SOA could not be fully identified due to the lack of specific molecular markers for such aged SOA.

Atmospheric black carbon (BC) has a strong positive, but still controversial, effect on global warming. In particular, BC absorption enhancement (Eabs) due to internal mixing with other chemical species—so-called lensing effect—is poorly assessed. This bottleneck partly relies on the lack of long-term in situ measurements of both the optical and chemical properties of BC-containing particles. Here, we present experimental and computational results showing a significant Eabs increase with the aerosol photochemical aging. This was associated with the production of highly oxidized secondary organic aerosols (SOA), especially at summertime. The 3-year-long continuous aerosol chemical and optical measurements used for the present study was obtained in the Paris region, France, which might be representative of near-future air quality within developing countries. These findings suggest that SOA could represent one of the most critical chemical species to be considered within climate models. Tiny remnants of combustion, known as black carbon, absorb solar radiation and warm the atmosphere—an effect that can be doubled by “lensing” from secondary organic aerosols. A multi-institution team led by Olivier Favez at the Institut National de l’Environnement Industriel et des Risques conducted a three-year observational and modeling study near Paris. The researchers tested a range of atmospheric constituents and found that secondary organic aerosols—adhered to black carbon particles—are the most important determinant of the enhanced warming. The aerosols are produced by photochemical reactions with a wide variety of natural and human-produced volatile organic compounds, and act to focus solar radiation to the core of the black carbon particle, especially during the particle aging process during summer. The findings—although specific to Paris—provide insights into the specific compounds leading to enhanced warming, and reveal the most effective targets for remediating their effect.

To quantify regional sources contributing to submicron particulate matter (PM1) pollution in haze episodes, on-line measurements combining two modeling methods, namely, positive matrix factorization (PMF) and backward Lagrangian particle dispersion modeling (LPDM), were conducted for the period of one month in urban Nanjing, a city located in the western part of Yangtze River Delta (YRD) region of China. Several multi-day haze episodes were observed in December 2013. Long-range transport of biomass burning from the southwestern YRD region largely contributed to PM1 pollution with more than 25% of total organics mass in a lasting heavy haze. The LPDM analysis indicates that regional transport is a main source contributing to secondary low-volatility production. The high-potential source regions of secondary low-volatility production are mainly located in areas to the northeast of the city. High aerosol pollution was mainly contributed by regional transport associated with northeastern air masses. Such regional transport on average accounts for 46% of total NR-PM1 with sulfate and aged low-volatility organics being the largest fractions (>65%).

To investigate the composition, sources and evolution processes of submicron aerosol during wintertime, a field experiment was conducted during December 1–31, 2013 in urban Nanjing, a megacity in Yangtze River Delta of China. Non-refractory submicron aerosol (NR-PM1) species were measured with an Aerodyne Aerosol Chemical Speciation Monitor. NR-PM1 is dominated by secondary inorganic aerosol (55%) and organic aerosol (OA, 42%) during haze periods. Six OA components were identified by positive matrix factorization of the OA mass spectra. The hydrocarbon-like OA and cooking-related OA represent the local traffic and cooking sources, respectively. A highly oxidized factor related to biomass burning OA accounted for 15% of the total OA mass during haze periods. Three types of oxygenated OA (OOA), i.e., a less-oxidized OOA (LO-OOA), a more-oxidized OOA (MO-OOA), and a low-volatility OOA (LV-OOA), were identified. LO-OOA is likely associated with fresh urban secondary OA. MO-OOA likely represents photochemical products showing a similar diurnal cycle to nitrate with a pronounced noon peak. LV-OOA appears to be a more oxidized factor with a pronounced noon peak. The OA composition is dominated by secondary species, especially during haze events. LO-OOA, MO-OOA and LV-OOA on average account for 11%, (18%), 24% (21%) and 23% (18%) of the total OA mass for the haze (clean) periods respectively. Analysis of meteorological influence suggested that regional transport from the northern and southeastern areas of the city is responsible for large secondary and low-volatility aerosol formation.

Secondary organic aerosol (SOA) derived from isoprene epoxydiols (IEPOX) has potential impacts on regional air quality and climate yet is poorly characterized under NOx-rich ambient environments. We report the first real-time characterization of IEPOX-derived SOA (IEPOX-SOA) in Eastern China in summer 2013 using comprehensive ambient measurements, along with model analysis. The ratio of IEPOX-SOA to isoprene high-NOx SOA precursors, e.g., methyl vinyl ketone and methacrolein, and the reactive uptake potential of IEPOX was lower than those generally observed in regions with prevailing biogenic emissions, low NOx levels, and high particle acidity, elucidating the suppression of IEPOX-SOA formation under NOx-rich environments. IEPOX-SOA showed high potential source regions to the south with large biogenic emissions, illustrating that the interactions between biogenic and anthropogenic emissions might have played an important role in affecting the formation of IEPOX-SOA in polluted environments in Eastern China.

A lasting haze pollution event occurred in the Central and East China in January 2013. In this study, Aerodyne Aerosol Chemical Speciation Monitor (ACSM), Photoacoustic Extinctiometer (PAX), and Aethalometer were deployed for real-time and lasting monitoring of non-refractory submicron aerosol (NR-PM1) components (i.e. organics, sulfate, nitrate, ammonium, and chloride), atmospheric aerosol extinction properties, and black carbon (BC) in Nanjing, respectively. During the measuring period, the contribution of PM1 (NR-PM1+BC) species, i.e., organics, nitrate, sulfate, ammonium, chloride, and BC were 32.3%, 26.0%, 17.9%, 13.2%, 2.8%, and 7.8%, respectively. Positive matrix factorization (PMF) analysis indicates that hydrocarbon-like (HOA), semi-volatile oxygenated organic aerosol (SV-OOA), low-volatile oxygenated organic aerosol (LV-OOA) were the major sources for PM1. HOA, SV-OOA, and LV-OOA on average accounted for 27.4%, 32.2%, and 40.4% of organic aerosol, respectively, which means that PM1 consisted mostly of the secondary species. Because of local cooking and traffic emissions, HOA loading dynamically increased at the nighttime, which resulted in a significant variation of organics. Generally, the mass concentrations, the mass fractions of secondary components (i.e. nitrate, sulfate, SV-OOA, and LV-OOA), as well as aerosol signal scattering albedo increased with increasing relative humidity (RH), respectively, implying that the increase in RH was beneficial to the continual formation of secondary aerosol. Furthermore, atmospheric visibility decreased with the increasing of RH and secondary species contents, indicating that there is a synergistic effect between the RH and the secondary species of PM1 on the atmospheric visibility during the haze period.

Real-time characterization of the aging of organic aerosol (OA) in the atmosphere is challenging in aerosol chemistry research. In this study, a continuous on-line monitoring instrument, the Aerosol Chemical Speciation Monitor (ACSM), was employed to measure non-refractory submicron aerosol (NR-PM1) characteristics during summertime in Nanjing. Ion fractions obtained from ACSM were used to evaluate the aging of atmospheric hydrocarbon-like OA (HOA) as a function of f 44 (the ratio of m/z 44 to total OA mass spectrometry signal) versus f 57 (the ratio of m/z 57 to total OA mass spectrometry signal) ( f 44 vs f 57). Results show that the mean mass concentration of NR-PM1 was 19.87 ± 8.46 μg m-3 for the entire study. OA constituted the largest component, on average accounting for 51.8% of the total NR-PM1. The oxygenated OA (OOA) on average accounted for the largest fraction (72% ± 0.14%) of OA. The diurnal trends of both the mass concentration of OOA and O x (O x = O3 + NO2) closely correlated with OOA/ΔCO ratios (ΔCO is the CO minus the background CO), indicating that OOA was largely effected by atmospheric photochemical activity. In the f 44 vs f 57 space, the OOA/ΔCO ratios and the mass concentration of O x increased with increasing f 44, while HOA/ΔCO and HOA/OA ratios decreased with increasing f 44, suggesting that HOA was gradually transformed to OOA by photochemical aging. Furthermore, the trend of f 57 implies that the aging time of HOA in the atmosphere was approximately 5-10 hours. This study not only provides a new method for long-lasting studies on the evolution of atmospheric organic aerosols, but also provides a new idea for the application of ACSM.