Abstract
Similarities and differences in the submicron atmospheric aerosol chemical composition are analyzed from a unique set of measurements performed at 21 sites across Europe for at least one year. These sites are located between 35 and 62°N and 10° W – 26°E, and represent various types of settings (remote, coastal, rural, industrial, urban). Measurements were all carried out on-line with a 30-min time resolution using mass spectroscopy based instruments known as Aerosol Chemical Speciation Monitors (ACSM) and Aerosol Mass Spectrometers (AMS) and following common measurement guidelines. Data regarding organics, sulfate, nitrate and ammonium concentrations, as well as the sum of them called non-refractory submicron aerosol mass concentration ([NR-PM1]) are discussed. NR-PM1 concentrations generally increase from remote to urban sites. They are mostly larger in the mid-latitude band than in southern and northern Europe. On average, organics account for the major part (36–64%) of NR-PM1 followed by sulfate (12–44%) and nitrate (6–35%). The annual mean chemical composition of NR-PM1 at rural (or regional background) sites and urban background sites are very similar. Considering rural and regional background sites only, nitrate contribution is higher and sulfate contribution is lower in mid-latitude Europe compared to northern and southern Europe. Large seasonal variations in concentrations (μg/m³) of one or more components of NR-PM1 can be observed at all sites, as well as in the chemical composition of NR-PM1 (%) at most sites. Significant diel cycles in the contribution to [NR-PM1] of organics, sulfate, and nitrate can be observed at a majority of sites both in winter and summer. Early morning minima in organics in concomitance with maxima in nitrate are common features at regional and urban background sites. Daily variations are much smaller at a number of coastal and rural sites. Looking at NR-PM1 chemical composition as a function of NR-PM1 mass concentration reveals that although organics account for the major fraction of NR-PM1 at all concentration levels at most sites, nitrate contribution generally increases with NR-PM1 mass concentration and predominates when NR-PM1 mass concentrations exceed 40 μg/m³ at half of the sites.
Highlights
In the European Union (EU), Particulate Matter (PM) is regarded by the European Environment Agency as the air pollutant most harmful to human health (EEA, 2019)
Standardized and quality controlled measurements of non-refractory fraction of PM1 (NR-PM1) components performed with the same analytical technique at 21 Euro pean sites for periods long enough to be representative for a full year are reported here together for the first time
Comparable NR-PM1 levels have been reported in Northern America (1.4–19 μg/m3 across 12 sites) by Jimenez et al (2009), whereas the extreme concentrations measured in South Amer ica, e.g. 41 μg/m3 in Mexico City, Mexico (Salcedo et al, 2006) or in Asia, e.g. 63 μg/m3 in Beijing, China (Huang et al, 2010), and 87 μg/m3 in Delhi, India (Gani et al, 2019) were not observed at our set of sites in Europe (Fig. S3)
Summary
In the European Union (EU), Particulate Matter (PM) is regarded by the European Environment Agency as the air pollutant most harmful to human health (EEA, 2019). PM has respiratory and cardiovascular adverse effects (WHO, 2006, 2013) It has been classified as carcinogenic to humans by the International Agency for Research on Cancer since 2013 (Loomis et al, 2013). As a step towards WHO guidelines, various EU directives have attempted to reduce PM impacts on human health - and the environment - during the last decades by setting daily limit values for PM10, annual limit values for PM10 and PM2.5, long term exposure reduction targets for PM2.5, as well as emission ceilings for aerosol precursors (e.g. EU, 1996, 1999, 2008, 2016). A better understanding of PM chemical composition in Europe is necessary to identify its sources (e.g. Zhang et al, 2011), assess its toxicity (Kelly and Fussell, 2012), estimate its impacts on climate (Boucher et al, 2013), improve air quality models (Kukkonen et al, 2012) and support air quality related policies (Heal et al, 2012; EC, 2013)
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