This paper synthesizes data on aerosol (particulate matter, PM) physical and chemical characteristics, which were obtained over the past decade in aerosol research and monitoring activities at more ...than 60 natural background, rural, near-city, urban, and kerbside sites across Europe. The data include simultaneously measured PM
10 and/or PM
2.5 mass on the one hand, and aerosol particle number concentrations or PM chemistry on the other hand. The aerosol data presented in our previous works (
Van Dingenen et al., 2004; Putaud et al., 2004) were updated and merged to those collected in the framework of the EU supported European Cooperation in the field of Scientific and Technical action COST633 (
Particulate matter:
Properties related to health effects). A number of conclusions from our previous studies were confirmed. There is no single ratio between PM
2.5 and PM
10 mass concentrations valid for all sites, although fairly constant ratios ranging from 0.5 to 0.9 are observed at most individual sites. There is no general correlation between PM mass and particle number concentrations, although particle number concentrations increase with PM
2.5 levels at most sites. The main constituents of both PM
10 and PM
2.5 are generally organic matter, sulfate and nitrate. Mineral dust can also be a major constituent of PM
10 at kerbside sites and in Southern Europe. There is a clear decreasing gradient in SO
4
2− and NO
3
− contribution to PM
10 when moving from rural to urban to kerbside sites. In contrast, the total carbon/PM
10 ratio increases from rural to kerbside sites. Some new conclusions were also drawn from this work: the ratio between ultrafine particle and total particle number concentration decreases with PM
2.5 concentration at all sites but one, and significant gradients in PM chemistry are observed when moving from Northwestern, to Southern to Central Europe. Compiling an even larger number of data sets would have further increased the significance of our conclusions, but collecting all the aerosol data sets obtained also through research projects remains a tedious task.
Size‐segregated marine aerosols were collected at Mace Head Atmospheric Research Station (Ireland) during spring and autumn 2002 corresponding with the phytoplankton bloom periods in the North ...Atlantic. Strict control of the sampling, air mass back trajectory analysis, and analysis of pollutant tracers allowed the selection of a set of samples representative of clean marine conditions. A comprehensive chemical characterization of both (1) water‐soluble and water‐insoluble organic fraction and (2) water‐soluble inorganic ions was performed. The selected samples illustrated a consistent picture in terms of chemical composition. The supermicron mode predominantly comprises sea‐salt aerosol with a mass concentration of 10.16 ± 0.80 μg m−3, the remainder being non‐sea‐salt (nss) sulphate, 0.03 ± 0.01 μg m−3, and nitrate, 0.13 ± 0.04 μg m−3. By comparison, the mass of sea salt, nss sulphate, and nitrate in the submicron mode is found to be 0.39 ± 0.08 μg m−3, 0.26 ± 0.04 μg m−3, and 0.02 ± 0.01 μg m−3, respectively. Water‐soluble organic carbon (WSOC) is observed in the submicron mode with a mass concentration of 0.25 ± 0.04 μg m−3, comparable to that of nss sulphate, and in the supermicron mode with a mass concentration of 0.17 ± 0.04 μg m−3. The WSOC to total carbon (TC) ratio is found to be 0.20 ± 0.12 for the submicron fraction and 0.29 ± 0.08 for the supermicron fraction, while the black carbon (BC) to TC ratio is, on average, 0.032 ± 0.001 for both aerosol modes. The remaining carbon, water‐insoluble organic carbon, contributes 0.66 ± 0.11 μg m−3 and 0.26 ± 0.06 μg m−3 to the submicron and supermicron modes, respectively and, thus, represents the dominant submicron aerosol species. Furthermore, the WSOC chemical composition comprises mainly aliphatic and only partially oxidized species and humic‐like substances, resulting in appreciable surface‐active properties. The observed organic matter chemical features (size‐dependent concentration, hydrophobic nature of a substantial fraction of the organic matter, and low oxidized and surface‐active WSOC species) are consistent with the hypothesis of a primary marine source; bubble‐bursting processes, occurring at the surface of the North Atlantic Ocean during phytoplankton blooms, effectively transfer organic matter into marine aerosol particles, particularly enriching the fine‐aerosol fraction.
Five-year PM
10 concentrations (2000–05) at Heraklion (urban), Crete, and concurrent measurements of TSP and PM
10 (2001–02 and 2004–05, respectively) at Finokalia (background) have been used to ...discriminate between the various sources of PM over the area and investigate the factors that control their levels. PM
10 concentrations at Heraklion (51±33
μg
m
−3) and Finokalia (28±30
μg
m
−3) lie within the range found for urban and background-rural sites in the Eastern Mediterranean, respectively. Special focus has been given to the influence of transported dust from N. Africa, which is found to be more frequent during spring and fall. The additional effect from local sources has been also calculated at Heraklion (about 20
μg
m
−3). The EU limit of 50
μg
m
−3 is exceeded at Heraklion, one in 4 days, during winter and spring (50% due to transported dust) and half of the days during summer and fall (pollution). At Finokalia exceedances are observed in winter and spring during one in 5 days, 80–100% of which are associated with dust events. The mass balance estimation for periods with no influence from dust shows that ions dominate the PM
10 mass (40–60%) with dust and particulate carbonaceous matter (PCM) comprising the rest. During the identified dust outbreaks, the contribution of dust rises to 60–65%, while the contribution of ions declines to 30% and only 10% is PCM.
•For moderate reductions, emission and PM concentration changes are linearly linked.•Reducing SO2 emissions where abundant is always efficient.•Reducing NH3 emissions is more efficient where it is ...less abundant.•Reducing NOx emissions where NOx are abundant can be counter-productive.•Both NOx and NH3 regimes occur in some regions, calling for combined reductions
Given the remaining air quality issues in many European regions, smart air quality strategies are necessary to reduce the burden of poor air quality. While designing effective strategies for non-reactive primary pollutants is straightforward, this is not the case for secondary pollutants for which the relationship between emission changes and the resulting concentration changes can be nonlinear. Under such conditions, strategies targeting the largest emitting sources might not be the most effective. In this work, we provide elements to better understand the role of the main emission precursors (SO2, NOx, NH3) on the formation of secondary inorganic aerosols. By quantifying the PM2.5 sensitivity to emission reductions for each of these three precursors, we define and quantify the intensity of PM2.5 formation chemical regimes across Europe. We find that for emission reductions limited to 25%, the relation between emission and PM concentration changes remain mostly linear, with the exception of the Po Valley where non-linearities reach more than 30% in winter. When emission reductions increase to 50%, non-linearity reaches more than 60% in the Po Valley but stay below 30% in the rest of Europe. In terms of implications on abatement strategies, our findings can be summarized in the following key messages: (1) reducing SO2 emissions where abundant is always efficient (e.g. eastern Europe and Balkans); (2) reducing NH3 emissions is more efficient where it is less abundant (e.g. the Po basin) than where it is abundant, given the limiting role of NH3 in the PM formation; (3) reducing NOx emissions where NOx are abundant can be counter-productive with potential increases of PM due to the increased oxidant capacity of the atmosphere (e.g. Po valley); (4) because regions with both NH3 and NOx sensitive chemical regimes are mixed within countries, both need to be reduced together, as pollution reduction policies need at least to be defined at a country level; (6) while for NH3 the focus is clearly on wintertime, it is the whole year for NOx. The simulations proposed in this work could be used as benchmark for other models as they constitute the type of scenarios required to support air quality strategies. In addition, the straight and systematic emission reductions imposed for the scenarios in this work are well suited for a better understanding of the behavior of the model, in terms of responses to emission reductions.
A reliable assessment of the optical properties of atmospheric black carbon is of crucial importance for an accurate estimation of radiative forcing. In this study we investigated the spatio-temporal ...variability of the mass absorption cross-section (MAC) of atmospheric black carbon, defined as light absorption coefficient (σap) divided by elemental carbon mass concentration (mEC). σap and mEC have been monitored at supersites of the ACTRIS network for a minimum period of one year. The 9 rural background sites considered in this study cover southern Scandinavia, central Europe and the Mediterranean. σap was determined using filter based absorption photometers and mEC using a thermal-optical technique. Homogeneity of the data-set was ensured by harmonization of all involved methods and instruments during extensive intercomparison exercises at the European Center for Aerosol Calibration (ECAC). Annual mean values of σap at a wavelength of 637 nm vary between 0.66 and 1.3 Mm−1 in southern Scandinavia, 3.7–11 Mm−1 in Central Europe and the British Isles, and 2.3–2.8 Mm−1 in the Mediterranean. Annual mean values of mEC vary between 0.084 and 0.23 μg m−3 in southern Scandinavia, 0.28–1.1 in Central Europe and the British Isles, and 0.22–0.26 in the Mediterranean. Both σap and mEC in southern Scandinavia and Central Europe have a distinct seasonality with maxima during the cold season and minima during summer, whereas at the Mediterranean sites an opposite trend was observed. Annual mean MAC values were quite similar across all sites and the seasonal variability was small at most sites. Consequently, a MAC value of 10.0 m2 g−1 (geometric standard deviation = 1.33) at a wavelength of 637 nm can be considered to be representative of the mixed boundary layer at European background sites, where BC is expected to be internally mixed to a large extent. The observed spatial variability is rather small compared to the variability of values in previous literature, indicating that the harmonization efforts resulted in substantially increased precision of the reported MAC. However, absolute uncertainties of the reported MAC values remain as high as ± 30–70% due to the lack of appropriate reference methods and calibration materials.
The mass ratio between elemental carbon and non-light-absorbing matter was used as a proxy for the thickness of coatings around the BC cores, in order to assess the influence of the mixing state on the MAC of BC. Indeed, the MAC was found to increase with increasing values of the coating thickness proxy. This provides evidence that coatings do increase the MAC of atmospheric BC to some extent, which is commonly referred to as lensing effect.
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•The mass absorption cross-section of black carbon is homogeneous over Europe.•Mass absorption cross-section of European black carbon is quantified in 10 m2 g−1.•Presence of non-absorbing matter induces an enhancement of black carbon absorption.
The chemical composition of the plumes of seagoing ships was measured during a two week long measurement campaign in the port of Rotterdam, Hoek van Holland The Netherlands, in September 2009. ...Altogether, 497 ships were monitored and a statistical evaluation of emission factors (g kg−1 fuel) was provided. The concerned main atmospheric components were SO2, NO2, NOx and the aerosol particle number. In addition, the elemental and water-soluble ionic composition of the emitted particulate matter was determined. Emission factors were expressed as a function of ship type, power and crankshaft rotational speed. The average SO2 emission factor was found to be roughly half of what is allowed in sulphur emission control areas (16 vs. 30 g kg−1 fuel), and exceedances of this limit were rarely registered. A significant linear relationship was observed between the SO2 and particle number emission factors. The intercept of the regression line, 4.8 × 1015 (kg fuel)−1, gives the average number of particles formed during the burning of 1 kg zero sulphur content fuel, while the slope, 2 × 1018, provides the average number of particles formed with 1 kg sulphur burnt with the fuel. Water-soluble ionic composition analysis of the aerosol samples from the plumes showed that ~144 g of particulate sulphate was emitted from 1 kg sulphur burnt with the fuel. The mass median diameter of sulphate particles estimated from the measurements was ~42 nm.
This paper synthesizes data on aerosol (or particulate matter, PM) chemical characteristics, which were obtained in European aerosol research activities at natural, rural, near-city, urban, and ...kerbside sites over the past decade. It includes only two (nearby) sites in the semi-arid Mediterranean area, and lacks data from Eastern Europe. PM chemical compositions are compared with the PM mass concentrations in PM10, PM2.5, and further size resolved PM fractions (chemical mass closure). Such data sets are more comprehensive than those currently provided by air quality monitoring networks (e.g. EMEP, EUROAIRNET). Data available from 24 sites in Europe were reviewed. They were processed and plotted to allow comparisons in spite of differences in the sampling and analytical techniques used in various studies. A number of conclusions are drawn among which are the following.
Organic matter appears to be the major component of PM10 and PM2.5, except at natural and rural background sites, where sulphate contribution may be larger. Mineral dust shows up as a major component of PM10 at kerbside sites. Black carbon contributes 5–10% to PM2.5 and somewhat less to PM10 at all sites, including the natural background sites. Its contribution seems higher (15–20%) at some of the kerbside sites, but these data may be affected by analytical artefacts. On days when PM10 >50
μg
m
−3, nitrate concentrations can overtake organic matter concentrations in PM10 and PM2.5. High PM concentration episodes are often observed in cold periods, when the pollutant dispersion is least. Measurements indicate that the condensation in the particle phase of semi-volatile species like nitrate and (unspecified) organics is also favoured by cold temperatures. In particles with a diameter <150
nm (i.e., most atmospheric particles), organic matter and black carbon are by far the major components.
More data are known to be available within the scientific community, which could enrich the present data set and strengthen the conclusions made above. Most of them are not made available yet. The investment in new approaches, which would bridge the technological gap between scientific measurements and regulatory monitoring networks, is strongly needed.
Aerosol properties and vertical velocities relevant to cloud droplet concentrations in marine stratocumulus clouds are presented. Data were collected at a coastal surface site, and on an aircraft ...that flew north (upwind) of the surface site during the CLOUDYCOLUMN portion of the second Aerosol Characterization Experiment (ACE‐2). In a closure study we compare observations, from five study days, and predictions based on Köhler and parcel theory. Measured and predicted cloud condensation nuclei (CCN) do agree after accounting for differences between the mobility equivalent (Dme) and sphere equivalent (Dse) diameters, but only when considering results from two study days unaffected by continental pollution. After applying the Dme − Dse correction, cloud droplet concentration closure was also achieved, or nearly achieved, on three study days. Discrepancies between predicted and measured CCN, or between predicted and measured droplet concentration, were always in the direction of predicted values being larger than that measured. Although theoretical studies do specify scenarios where droplet concentration and CCN overestimation can occur, the observed disparities may also be due to multiple and poorly characterized experimental biases.
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