Source apportionment of submicron organic aerosol at an urban background and a road site in Barcelona (Spain) during SAPUSS

Abstract

Abstract. This study investigates the contribution of potential sources to the submicron (PM 1 ) organic aerosol (OA) simultaneously detected at an urban background (UB) and a road site (RS) in Barcelona during the 30 days of the intensive field campaign of SAPUSS (Solving Aerosol Problems by Using Synergistic Strategies, September-October 2010). A total of 103 filters at 12 h sampling time resolution were collected at both sites. Thirty-six neutral and polar organic compounds of known emission sources and photo-chemical transformation processes were analyzed by gas chromatography-mass spectrometry (GC-MS). The concentrations of the trace chemical compounds analyzed are herein presented and discussed.Additionally, OA source apportionment was performed by multivariate curve resolution-alternating least squares (MCR-ALS) and six OA components were identified at both sites: two were of primary anthropogenic OA origin and three of secondary OA origin, while a sixth one was not clearly defined. Primary organics from emissions of local anthropogenic activities (urban primary organic aerosol, or POA Urban), mainly traffic emissions but also cigarette smoke, contributed 43 % (1.5 µg OC m −3 ) and 18 % (0.4 µg OC m −3 ) to OA at RS and UB, respectively. A secondary primary source -biomass burning (BBOA) -was found in all the samples (average values 7 % RS; 12 % UB; 0.3 µg OC m −3 ), but this component was substantially contributing to OA only when the sampling sites were under influence of regional air mass circulation (REG.). Three secondary organic aerosol (SOA) components (describing overall 60 % of the variance) were observed in the urban ambient PM 1 . Products of isoprene oxidation (SOA ISO) -i.e.2-methylglyceric acid, C 5 alkene triols and 2-methyltetrols -showed the highest abundance at both sites when the city was under influence of inland air masses. The overall concentrations of SOA ISO were similar at both sites (0.4 and 0.3 µg m −3 , or 16 % and 7 %, at UB and RS, respectively). By contrast, a SOA biogenic component attributed to α-pinene oxidation (SOA BIO PIN) presented average concentrations of 0.5 µg m −3 at UB (24 % of OA) and 0.2 µg m −3 at RS (7 %), respectively, suggesting that this SOA component did not impact the two monitoring sites at the same level. A clear anti-correlation was observed between SOA ISO and SOA PIN during nucleation days, surprisingly suggesting that some of the growth of urban freshly nucleating particles may be driven by biogenic α-pinene oxidation products but inhibited by isoprene organic compounds. A third SOA component was formed by a mixture of aged anthropogenic and biogenic secondary organic compounds (SOA Aged) that accumulated under stagnant atmospheric conditions, contributing for 12 % to OA at RS (0.4 µg OC m −3 ) and for 18 % at UB (0.4 µg OC m −3 ).A sixth component, formed by C 7 -C 9 dicarboxylic acids and detected especially during daytime, was called "urban oxygenated organic aerosol" (OOA Urban) due to its high abundance at urban RS (23 %; 0.8 µg OCm −3 ) vs. ...

Speciation of organic aerosols in the Saharan Air Layer and in the free troposphere westerlies

“…The MCR-ALS method decomposes the data matrix using an alternating least squares algorithm under a set of constraints such as non-negativity, unimodality, closure, trilinearity or selectivity (Tauler, 1995;Tauler et al, 1995). The MCR-ALS method had been applied successfully in a previous study on organic aerosol in urban and rural areas (Alier et al, 2013;. The variance explained by the different components is similar to a principal component analysis, but not orthogonal.…”

“…Dicarboxylic acids can be emitted in small quantities from several natural and anthropogenic primary sources such as vegetation, meat cooking and motor exhaust emissions (Kawamura and Kaplan, 1987;Narukawa et al, 1999), although atmospheric photochemical transformation of volatile and semi-volatile organic compounds is considered to be an important source for the presence of these aged compounds in the atmosphere (Alier et al, 2013;Jang eand Mcdow, 1997;Kleindienst et al, 2012; Paulot et al, 2011). This oxidative degradation of VOCs by tropospheric oxidants may be responsible for the similar mean dicarboxylic acid concentrations within the FT (SAL: 14.4 ng m −3 ; WES: 16.7 ng m −3 ) and the BL (SAL: 11.1 ng m −3 ; WES: 12.9 ng m −3 ) at Izaña.…”

“…4 -is a result of the method limitation, as the analysis of the samples by means of gas chromatography mass spectrometry (GC-MS) covers a very small fraction (often < 5 %; Alier et al, 2013) of the organic matter. The OM composition determined within the BL (PM 2.5 ; BL-FT: 9 % of the OM; BL-WES: 77 % of the OM; Fig.…”

“…Alternatively, gas chromatography coupled with mass spectrometry analysis of aerosol samples allows the speciation of the organic compounds and the quantification of many of those identified as tracers used to distinguish sources and processes contributing to the budget of OA (Bauer et al, 2008;Mazurek et al, 1989;Claeys et al, 2007;Hallquist et al, 2009;Howsam et al, 1998;Iinuma et al, 2007;Kawamura and Kaplan, 1987;Medeiros and Simoneit, 2007;Narukawa et al, 1999;Rogge et al, 1993;Schauer et al, 2002;Simoneit et al, 1991Simoneit et al, , 2004aSimoneit, 2002;Szmigielski et al, 2007). A number of studies have focused on OA speciation in urban areas (Alier et al, 2013;Kawamura and Kaplan, 1987;Puxbaum et al, 2007;Schauer et al, 1996;Simoneit et al, 1991; compared to remote environments. Studies in the free troposphere are less common (Simoneit et al, 2004a;Fu et al, 2008Fu et al, , 2014Wang et al, 2009;Van Drooge et al, 2010;Meng et al, 2014), in spite of the fact that they are of interest due to the long-range transport potential linked to the high wind speeds above the boundary layer.…”

A Novel Tandem of Thermal Desorption Carbon Analyzer and Off-Axis Integrated Cavity Output Spectroscopy for Aerosol Stable Carbon Isotope Ratio Measurement

“…(Ke et al, 2008;Heo et al, 2013). These approaches require detailed chemical composition of atmospheric aerosols, usually measured using numerous advanced analytical instruments such as Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), Gas ChromatographyMass Spectrometry (GC-MS), High Resolution-Time of Flight-Mass Spectrometer (HR-ToF-AMS) to quantify metal, PAHs, semi-VOCs concentrations and tracer compounds (Ke et al, 2008;Xu et al, 2009;Alier et al, 2013;Crippa et al, 2014). In addition, numerous samples are required for performing source apportionment as technique is often based on statistical approach.…”