<p>Atmospheric particulate matter with an aerodynamic diameter < 2.5 µm (PM<sub>2.5</sub>) is associated with adverse effects on the climate system, the human health, vegetation and the ecosystems. The World Health Organization (WHO) lowered the guideline limit for PM<sub>2.5</sub> in autumn 2021 and this is exceeded in many regions including rural and remote areas in mainland Europe. Measurements of the chemical composition of PM<sub>2.5</sub> is essential to assess the sources which contribute to PM<sub>2.5</sub> mass concentrations and to further design meaningful policies to tackle sources at their origin.</p> <p>Here we report 6 years (2014- 2020) of PM<sub>2.5</sub> mass and chemical speciation at five remote sites across France belonging to the EMEP network (European Monitoring and Evaluation Programme). The seasonal and spatial variability of aerosol composition and source contributions based on the proximity of sources and long-range transport are discussed. Trends in PM<sub>2.5</sub> and the main components at the five locations were evaluated by means of random-forest modelling coupled with a de-weathering algorithm. This approach is advantageous as resulting trends are driven by changes in emission or atmospheric processes and not by changes in weather conditions and/or long-range transport patterns. Random-forest regression modelling was built using meteorological data, backtrajectory information and temporal variables at each site and quantified the most important factors that explain PM<sub>2.5</sub> concentrations at remote rural areas in France.</p> <p>All sites observed statistically significant downward trends in PM<sub>2.5</sub> at a rate of -4 to -9% year<sup>-1</sup> for the period 2014 – 2020. The decrease in PM<sub>2.5</sub> concentrations was mostly explained by changes in the secondary inorganic species (sulphate, nitrate and ammonium) and not by changes in primary PM<sub>2.5</sub> emissions. The variability in trends in PM<sub>2.5</sub> and components observed across the sites is discussed with their implications for policy makers.</p>

An original time series of about 300 atmospheric measurements of a wide range of volatile organic compounds (VOCs) was obtained at a remote Mediterranean station on the northern tip of Corsica (Ersa, France) over 25 months from June 2012 to June 2014. This study presents the seasonal variabilities of 35 selected VOCs and their various associated sources. The VOC abundance was largely dominated by oxygenated VOCs (OVOCs) along with primary anthropogenic VOCs with a long lifetime in the atmosphere. VOC temporal variations were then examined. Primarily of local origin, biogenic VOCs exhibited notable seasonal and interannual variations, related to temperature and solar radiation. Anthropogenic compounds showed increased concentrations in winter (JFM months) followed by a decrease in spring/summer (AMJ/JAS months) and higher winter concentration levels in 2013 than in 2014 by up to 0.3 µg m−3 in the cases of propane, acetylene and benzene. OVOC concentrations were generally high in summertime, mainly due to secondary anthropogenic/biogenic and primary biogenic sources, whereas their lower concentrations during autumn and winter were potentially more influenced by primary/secondary anthropogenic sources. Moreover, an apportionment factorial analysis was applied to a database comprising a selection of 14 individual or grouped VOCs by means of the positive matrix factorization (PMF) technique. A PMF five-factor solution was taken on. It includes an anthropogenic factor (which contributed 39 % to the total concentration of the VOCs selected in the PMF analysis) connected to the regional background pollution, three other anthropogenic factors (namely short-lived anthropogenic sources, evaporative sources, and long-lived combustion sources, which together accounted for 57 %) originating from either nearby or more distant emission areas (such as Italy and south of France), and a local biogenic source (4 %). Variations in these main sources impacting VOC concentrations observed at the Ersa station were also investigated at seasonal and interannual scales. In spring and summer, VOC concentrations observed at Ersa were the lowest in the 2-year period, despite higher biogenic source contributions. During these seasons, anthropogenic sources advected to Ersa were largely influenced by chemical transformations and vertical dispersion phenomena and were mainly of regional origins. During autumn and winter, anthropogenic sources showed higher contributions when European air masses were advected to Ersa and could be associated with potential emission areas located in Italy and possibly more distant ones in central Europe. Higher VOC winter concentrations in 2013 than in 2014 could be related to contribution variations in anthropogenic sources probably governed by their emission strength with external parameters, i.e. weaker dispersion phenomena and the pollutant depletion. High-frequency observations collected during several intensive field campaigns conducted at Ersa during the three summers 2012–2014 confirmed findings drawn from bi-weekly samples of the 2-year period in terms of summer concentration levels and source apportionment. However, they also suggested that higher sampling frequency and temporal resolution, in particular to observe VOC concentration variations during the daily cycle, would have been necessary to confirm the deconvolution of the different anthropogenic sources identified following the PMF approach. Finally, comparisons of the 25 months of Ersa observations with VOC measurements conducted at 17 other European monitoring stations highlighted the representativeness of the Ersa station for monitoring seasonal variations in VOC regional pollution impacting continental Europe. Nevertheless, VOC winter concentration levels can significantly vary between sites, pointing out spatial variations in anthropogenic source contributions. As a result, Ersa concentration variations in winter were more representative of VOC regional pollution impacting central Europe. Moreover, interannual and spatial variations in VOC winter concentration levels were significantly impacted by synoptic phenomena influencing meteorological conditions observed in continental Europe, suggesting that short observation periods may reflect the variability of the identified parameters under the specific meteorological conditions of the study period.

The manuscript presents observations of VOCs at the Ersa site in Cape Corsica over a two-year period and provides a comprehensive description and analysis of their behaviour during this time. PMF analysis of the data is presented along with comparison to other station across Europe. The plots are clear and generally well presented. The length of the manuscript, however, is something of a problem with lots of repetition throughout. I am sure there is an interesting story here, but it is difficult to assess what that is from the current article. Careful consideration of each section, it’s findings and their relevance is required in order to make the manuscript worthy of publication. I

As a part of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx) and Cyprus Aerosols and Gas Precursors (ENVI-Med CyAr) programs, this study aims primarily to provide an improved understanding of the sources and the fate of volatile organic compounds (VOCs) in the eastern Mediterranean. More than 60 VOCs, including biogenic species (isoprene and eight monoterpenes) and oxygenated VOCs, were measured during a 1-month intensive field campaign performed in March 2015 at the Cyprus Atmospheric Observatory (CAO), a regional background site in Cyprus. VOC measurements were conducted using complementary online and offline techniques. Biogenic VOCs (BVOCs) were principally imputed to local sources and characterized by compound-specific daily cycles such as diurnal maximum for isoprene and nocturnal maximum for α- and β-pinenes, in connection with the variability of emission sources. The simultaneous study of pinene and isoprene temporal evolution and meteorological parameters has shown that BVOC emissions were mainly controlled by ambient temperature, precipitation and relative humidity. It was found that isoprene daytime emissions at CAO depended on temperature and solar radiation changes, whereas nocturnal BVOC concentrations (e.g., from oak and pine forests) were more prone to the relative humidity and temperature changes. Significant changes in monoterpene mixing ratios occurred during and after rainfall. The second part of the study focused on new particle formation (NPF) events at CAO. BVOCs are known to potentially play a role in the growth as well as in the early stages of formation of new atmospheric particles. Based on observations of the particle size distribution performed with a differential mobility particle sizer (DMPS) and the total number concentrations of particles larger than 1 nm diameter measured by particle size magnifier (PSM), NPF events were found on 14 out of 20 days of the field campaign. For all possible proxy parameters (meteorological parameters, calculated H2SO4 and measured gaseous compounds) having a role in NPF, we present daily variations of different classes during nucleation event and non-event days. NPF can occur at various condensational sink (CS) values and both under polluted and clean atmospheric conditions. High H2SO4 concentrations coupled with high BVOC concentrations seemed to be one of the most favorable conditions to observe NPF at CAO in March 2015. NPF event days were characterized by either (1) a predominant anthropogenic influence (high concentrations of anthropogenic source tracers observed), (2) a predominant biogenic influence (high BVOC concentrations coupled with low anthropogenic tracer concentrations), (3) a mixed influence (high BVOC concentrations coupled with high anthropogenic tracer concentrations) and (4) a marine influence (both low BVOC and anthropogenic tracer concentrations). More pronounced NPF events were identified during mixed anthropogenic–biogenic conditions compared to the pure anthropogenic or biogenic ones, for the same levels of precursors. Analysis of a specific NPF period of the mixed influence type highlighted that BVOC interactions with anthropogenic compounds enhanced nucleation formation and growth of newly formed particles. During this period, the nucleation-mode particles may be formed by the combination of high H2SO4 and isoprene amounts, under favorable meteorological conditions (high temperature and solar radiation and low relative humidity) along with low CS. During the daytime, growth of the newly formed particles, not only sulfate but also oxygen-like organic aerosol (OOA) mass contributions, increased in the particle phase. High BVOC concentrations were observed during the night following NPF events, accompanied by an increase in CS and in semi-volatile OOA contributions, suggesting further BVOC contribution to aerosol nighttime growth by condensing onto pre-existing aerosols.

More than 7000 atmospheric measurements of over 60 C2 − C16 volatile organic compounds (VOCs) were conducted at a background site in Cyprus during a 1-month intensive field campaign held in March 2015. This exhaustive dataset consisted of primary anthropogenic and biogenic VOCs, including a wide range of source-specific tracers, and oxygenated VOCs (with various origins) that were measured online by flame ionization detection–gas chromatography and proton transfer mass spectrometry. Online submicron aerosol chemical composition was performed in parallel using an aerosol mass spectrometer. This study presents the high temporal variability in VOCs and their associated sources. A preliminary analysis of their time series was performed on the basis of independent tracers (NO, CO, black carbon), meteorological data and the clustering of air mass trajectories. Biogenic compounds were mainly attributed to a local origin and showed compound-specific diurnal cycles such as a daily maximum for isoprene and a nighttime maximum for monoterpenes. Anthropogenic VOCs as well as oxygenated VOCs displayed higher mixing ratios under the influence of continental air masses (i.e., western Asia), indicating that long-range transport significantly contributed to the VOC levels in the area. Source apportionment was then conducted on a database of 20 VOCs (or grouped VOCs) using a source receptor model. The positive matrix factorization and concentration field analyses were hence conducted to identify and characterize covariation factors of VOCs that were representative of primary emissions as well as chemical transformation processes. A six-factor PMF solution was selected, namely two primary biogenic factors (relative contribution of 43 % to the total mass of VOCs) for different types of emitting vegetation; three anthropogenic factors (short-lived combustion source, evaporative sources, industrial and evaporative sources; 21 % all together), identified as being either of local origin or from more distant emission zones (i.e., the south coast of Turkey); and a last factor (36 %) associated with regional background pollution (air masses transported both from the Western and Eastern Mediterranean regions). One of the two biogenic and the regional background factors were found to be the largest contributors to the VOC concentrations observed at our sampling site. Finally, a combined analysis of VOC PMF factors with source-apportioned organic aerosols (OAs) helped to better distinguish between anthropogenic and biogenic influences on the aerosol and gas phase compositions. The highest OA concentrations were observed when the site was influenced by air masses rich in semi-volatile OA (less oxidized aerosols) originating from the southwest of Asia, in contrast with OA factor contributions associated with the remaining source regions. A reinforcement of secondary OA formation also occurred due to the intense oxidation of biogenic precursors.

(1) SAGE, Institut Mines Telecom (IMT) Lille Douai, Douai, France, (2) Laboratoire des Sciences du Climat et de l’Environnement (LSCE), Unité Mixte CEA-CNRS-UVSQ, Gif sur Yvette, France, (3) Energy, Environment and Water Research Centre, the Cyprus Institute (CyI), Nicosia, Cyprus, (4) Department of Labour Inspection (DLI), Ministry of Labour, Welfare and Social Insurance, Nicosia, Cyprus, (5) now at: National Centre of Scientific Research (NCSR) “DEMOKRITOS”, Athens, Greece, (6) now at : Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), Créteil, France