Variability of carbonaceous aerosols in remote, rural, urban and industrial environments in Spain: implications for air quality policy

Abstract

We interpret here the variability of levels of carbonaceous aerosols based on a 12 yr database from 78 monitoring stations across Spain specially compiled for this article. Data did not evidence any spatial trends of carbonaceous aerosols across the country. Conversely, results show marked differences in average concentrations from the cleanest, most remote sites (around 1 μgm−3 of non-mineral carbon (nmC), mostly made of organic carbon (OC) with very little elemental carbon (EC), around 0.1 μgm−3; OC/ EC = 12–15), to the highly polluted major cities (8–10 μgm−3 of nmC; 3– 4 μgm−3 of EC; 4–5 μgm−3 of OC; OC/ EC = 1–2). Thus, urban (and very specific industrial) pollution was found to markedly increase levels of carbonaceous aerosols in Spain, with much lower impact of biomass burning and of biogenic emissions. Correlations between yearly averaged OC/ EC and EC concentrations adjust very well to a potential equation (OC = 3.37 EC0.326, R2 = 0.8). A similar equation is obtained when including average concentrations obtained at other European sites (OC = 3.60EC0.491, R2 = 0.7). A clear seasonal variability in OC and EC concentrations was detected. Both OC and EC concentrations were higher during winter at the traffic and urban sites, but OC increased during the warmer months at the rural sites. Hourly equivalent black carbon (EBC) concentrations at urban sites accurately depict road traffic contributions, varying with distance from road, traffic volume and density, mixing-layer height and wind speed. Weekday urban rush-hour EBC peaks are mimicked by concentrations of primary gaseous emissions from road traffic, whereas a single midday peak is characteristic of remote and rural sites. Decreasing annual trends for carbonaceous aerosols were observed between 1999 and 2011 at a large number of stations, probably reflecting the impact of the EURO4 and EURO5 standards in reducing the diesel PM emissions. This has resulted in some cases in an increasing trend for NO2 / (OC + EC) ratios as these standards have been much less effective for the abatement of NOx exhaust emissions in passenger diesel cars. This study concludes that EC, EBC, and especially nmC and OC+ EC are very good candidates for new air quality standards since they cover both emission impact and health-related issue

Long-term characterization of organic and elemental carbon in the PM<sub>2.5</sub> fraction: the case of Athens, Greece

“…It should be noted that most of these studies refer to shorter time periods ( Total carbon is calculated as the sum of OC and EC (TC = OC + EC), with OC accounting for 79 ± 4 % of the total carbon and constituting the predominant carbon contributor, which is in accordance with findings in other European sites (e.g., Lonati et al, 2007;Sanchez de la Campa et al, 2009). However, the contribution of TC to PM in this study (14 ± 3 %) is lower than what is reported in the literature for other urban/urban background locations (e.g., 25-46 % in Viana et al (2006); 27-28 % in Lonati et al (2007); about 19 % in Sanchez de la Campa et al (2009); 29 % in Perrone et al (2011);Querol et al (2013)). …”

Inventory of African desert dust events in the north-central Iberian Peninsula in 2003–2014 based on sun-photometer–AERONET and particulate-mass–EMEP data

“…Thresholds have been established to identify those conditions which stand above the clean background over the study area. Hence, the choice of these thresholds is based on the aerosol climatology of the site from our investigations (Bennouna et al, 2014;Mateos et al, 2015) and previous results (see, e.g., Querol et al, 2009Querol et al, , 2014. The mean values for the long-term period 2003-2014 are 0.13 ± 0.09 for AOD 440 nm and 10 ± 9 µg m −3 for PM 10 .…”

Climatology of aerosol optical properties and black carbon mass absorption cross section at a remote high altitude site in the Western Mediterranean Basin

“…MACs between 7 and 20 m 2 g −1 have often been reported in the literature (e.g. Quinn and Bates, 2005; Reche et al, 2011;Pandolfi et al, 2011;Querol et al, 2013).…”