Carbonaceous particles and aerosol mass closure in PM2.5 collected in a port city A. Genga a, ⁎, P. Ielpo b,c , T. Siciliano d , M. Siciliano a a Department of Biological and Environmental Science and technology, University of Salento, 73100 Lecce, Italy b Institute of Atmospheric Sciences and Climate, National Research Council, 73100 Lecce, Italy c Water Research Institute, National Research Council, 70132 Bari, Italy d Department of Cultural Heritage, University of Salento, 73100 Lecce, Italy abstract article info Article history: Received 21 October 2015 Received in revised form 13 July 2016 Accepted 30 August 2016 Available online 31 August 2016 Mass concentrations of PM2.5, mineral dust, organic carbon (OC) and elemental carbon (EC), water-soluble or- ganic carbon (WSOC), sea salts and anthropogenic metals have been studied in a city-port of south Italy (Brindi- si). This city is characterized by different emission sources (ship, vehicular traffic, biomass burning and industrial emissions) and it is an important port and industrial site of the Adriatic sea. Based on diagnostic ratios of carbo- naceous species we assess the presence of biomass burning emissions (BBE), fossil fuel emissions (FFE) and ship emission (SE). Our proposed conversion factors from OC to OM are higher than those reported in the literature for urban site: the reason of this could be due to the existence of aged combustion aerosols during the sampling cam- paign (WSOC/OC = 0.6 ± 0.3). © 2016 Elsevier B.V. All rights reserved. Keywords: PM2.5 Diagnostic ratios Aerosol organic mass Mass reconstruction 1. Introduction It is known that carbonaceous species constitute a major, sometimes dominant, fraction of atmospheric particulate matter (Querol et al., 2013; Srinivas and Sarin, 2014; Pio et al., 2011). Carbonaceous aerosol is commonly divided into an organic carbon (OC) and an elemental car- bon (EC) fraction. Both of these have important roles and effects on cli- mate and health because of their physical and chemical characteristics (Pio et al., 2011; Viidanoja et al., 2002). Due to its special surface prop- erties, EC provides a good adsorption site for many semi-volatile com- pounds such as the PAHs (Pio et al., 2011 and therein references). OC is an effective light scatterer and may contribute significantly to both visibility degradation and the direct aerosol climate forcing (Tegen et al., 1997; Malm and Day, 2000). A significant fraction of the particulate OC is water soluble, making it important to various aerosol–cloud inter- actions (Corrigan and Novakov, 1999; Decesari et al., 2000). Finally, car- bonaceous species have the potential to influence many heterogeneous reactions involving atmospheric aerosols and trace gases (Grgić et al., 1998). Despite the very large proportion of carbonaceous aerosols in partic- ulate matter PMx (PM10, PM2.5 and PM1) and the consequent rele- vance of this component for air quality, their origins are not fully understood and probably their contribution to PMx load vary largely across the different regions in Europe (Querol et al., 2013 and therein references). The major sources of these species are biomass, bio-fuel burning emission (BBE) (Gonçalves et al., 2011), and fossil-fuel combus- tion (FFC) (Hamad et al., 2015). The origin of OC, especially of SOA (sec- ondary organic aerosol), is a hot topic in atmospheric sciences and a recent WHO report (REVIHAAP report, WHO, 2013) indicates that fur- ther studies are needed to characterize the health effects of SOA. Anoth- er recent WHO report (WHO, 2012) also evidences clear health consequences from the increased concentrations of EC, although this is probably not only due to EC per se but to the OC compounds adsorbed on EC particles. During long-range atmospheric transport, oxidation of organic com- pounds is a prime interest in assessing the organic matter (OM) to OC ratio. OM/OC conversion factor (fOM/OC) is not site or time dependent and in the literature, in relationship with the extent of OM oxidation and secondary organic aerosol (SOA) formation, values for f OM/OC from 1.2 for fresh aerosol to 2.6 for aged aerosol have been suggested (Chow et al., 2015 and therein references). Different studies have estimated the conversion factor using different methods such as: (a) measuring the distribution of functional groups by FTIR spectroscopy to estimate com- posite organic carbon from the number of carbon bonds present and or- ganic mass from the molecular mass of each functional group (Russell, 2003; Gilardoni et al., 2007; Liu et al., 2009); (b) estimating aerosol or- ganic matter as the difference of total aerosol mass and the sum of the other major species, namely mass balance approach (Sciare et al., 2005; Bae et al., 2006); and (c) examining spectral data using Aerosol Mass Spectrometer (Aiken et al., 2008; Chan et al., 2010). In the present study, the reconstructed mass balance method for es- timating the OM/OC ratio is applied to data collected at the port city of Brindisi (Italy).The estimation of f OM/OC could give more information Atmospheric Research 183 (2017) 245–254 ⁎ Corresponding author. E-mail address: alessandra.genga@unisalento.it (A. Genga). http://dx.doi.org/10.1016/j.atmosres.2016.08.022 0169-8095/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Atmospheric Research journal homepage: www.elsevier.com/locate/atmosres