Fossil versus contemporary sources of fine elemental and organic carbonaceous particulate matter during the DAURE campaign in Northeast Spain

Abstract

We present results from the international field campaign DAURE (Determination of the sources of atmospheric Aerosols in Urban and Rural Environments in the Western Mediterranean), with the objective of apportioning the sources of fine carbonaceous aerosols. Submicron fine particulate matter (PM<sub>1</sub>) samples were collected during February–March 2009 and July 2009 at an urban background site in Barcelona (BCN) and at a forested regional background site in Montseny (MSY). We present radiocarbon (<sup>14</sup>C) analysis for elemental and organic carbon (EC and OC) and source apportionment for these data. We combine the results with those from component analysis of aerosol mass spectrometer (AMS) measurements, and compare to levoglucosan-based estimates of biomass burning OC, source apportionment of filter data with inorganic composition + EC + OC, submicron bulk potassium (K) concentrations, and gaseous acetonitrile concentrations. <br></br> At BCN, 87 % and 91 % of the EC on average, in winter and summer, respectively, had a fossil origin, whereas at MSY these fractions were 66 % and 79 %. The contribution of fossil sources to organic carbon (OC) at BCN was 40 % and 48 %, in winter and summer, respectively, and 31 % and 25 % at MSY. The combination of results obtained using the <sup>14</sup>C technique, AMS data, and the correlations between fossil OC and fossil EC imply that the fossil OC at Barcelona is ∼47 % primary whereas at MSY the fossil OC is mainly secondary (∼85 %). Day-to-day variation in total carbonaceous aerosol loading and the relative contributions of different sources predominantly depended on the meteorological transport conditions. The estimated biogenic secondary OC at MSY only increased by ∼40 % compared to the order-of-magnitude increase observed for biogenic volatile organic compounds (VOCs) between winter and summer, which highlights the uncertainties in the estimation of that component. Biomass burning contributions estimated using the <sup>14</sup>C technique ranged from similar to slightly higher than when estimated using other techniques, and the different estimations were highly or moderately correlated. Differences can be explained by the contribution of secondary organic matter (not included in the primary biomass burning source estimates), and/or by an overestimation of the biomass burning OC contribution by the <sup>14</sup>C technique if the estimated biomass burning EC/OC ratio used for the calculations is too high for this region. Acetonitrile concentrations correlate well with the biomass burning EC determined by <sup>14</sup>C. K is a noisy tracer for biomass burning

The Multi-Wavelength Absorption Analyzer (MWAA) Model as a Tool for Source and Component Apportionment Based on Aerosol Absorption Properties: Application to Samples Collected in Different Environments

“…From optical apportionment (Equation (6)), EC resulted mainly of fossil origin in most cases (range 62-87%, except three cases in the range 42-44%), consistent with 14 C studies in the Milan area [40] and in other cities in Europe during wintertime [62,64]. As already found between b abs BrC and levoglucosan, very good correlation was found also between b abs,WB BC and levoglucosan (R 2 = 0.92).…”

Fossil and Non-Fossil Sources of Different Carbonaceous Fractions in Fine and Coarse Particles by Radiocarbon Measurement

“…In summer, the PM 1 EC f accounted for 90 ± 2% of the total EC at Bern and Moleno, indicating EC is predominantly stemming from road traffic. The high contribution of vehicular emissions to EC was also found in summer in Barcelona (Minguillon et al 2011). EC f and EC bb in the fine size fraction contributed on average 80 ± 5% and 73 ± 14% to the total EC (in PM 10 ) for all sites, respectively.…”

Source apportionment of fine PM and sub-micron particle number concentrations at a regional background site in the western Mediterranean: a 2.5 year study

“…In the same study, it was found that the fraction of OC attributed to fossil fuel consumption (mainly traffic emissions) was 34 ± 4 % and 31 ± 4 % for winter and summer respectively. Considering the clear seasonality of this source with elevated concentrations in summer, the low contribution of biomass burning to OC concentrations reported by Minguillón et al (2011), the absence of EC in this source and the prohibition of open burning of agricultural biomass during summer (Spanish Decreto 64/1995), it can be reasonably assumed that this source is SOA with negligible input from biomass burning. As observed for the secondary sulphate source, some typical crustal elements such as La, Rb, Ti, Ca, Al, Mg, Fe and Sr are present, for the same reasons already described.…”

“…(2) The observed increasing summer trend can be attributed to increased biogenic emissions from local vegetation, and enhanced photochemical reactions (Seco et al, 2012). A study performed by Minguillón et al (2011) reported that the fraction of OC attributed to biomass burning at MSY in winter was 17-21 % and only 12 % in summer. In the same study, it was found that the fraction of OC attributed to fossil fuel consumption (mainly traffic emissions) was 34 ± 4 % and 31 ± 4 % for winter and summer respectively.…”

“…This source explains 78 % of the variance in EC. Minguillón et al (2011) reported that 66-79 % of EC measured at MSY had a fossil origin, with the remainder attributed to biomass burning. The influence of biomass burning is highlighted by the presence of K, a known biomass burning tracer (Pio et al, 2008).…”