Abstract
PM10 and black smoke were monitored at a suburban sampling station located in the northern Spanish city of Gijón. Thirty-two metals and total carbon (TC) (i.e., organic carbon (OC) and elemental carbon (EC)) were analyzed over a year. The study of air-mass origin based on 5-day back trajectories was carried out to assess its influence on the recovery data. Different strategies were implemented to infer the influence of traffic in the area. On average, TC accounted for 29 % of the PM10 fraction, with OC forming 77 % of this TC. The influence of traffic was clearly reduced during intense Atlantic advection episodes, when OC and EC decreased up to 0.39 and 0.22 μg C/m3, respectively. In contrast, the highest values were reported during regional episodes, exceeding 10 μg C/m3 of OC and 2 μg C/m3 of EC. The correlation between EC and OC was found to notably improve when considering the days with high traffic flow (from R2 = 0.46 to R2 = 0.74). This pattern was also reproduced by black smoke and EC (from R2 = 0.49 to R2 = 0.59). Cu and Sn were found to be reliable traffic tracers given their high dependence on EC (R2 = 0.82 and R2 = 0.79, respectively). Nevertheless, Sn, Ba, and Sb showed a better correlation with Cu than EC, suggesting a common origin. In the case of Sn, R2 improved from 0.79 to 0.91. The Cu/Sb ratio had a mean value of 6.6 which agrees with diagnostic criterions for brake wear particles. The relationships and ratios between EC, Cu, Sb, Sn, Ba, and Bi pointed out to non-exhaust emissions, playing a significant role in the chemical composition of PM10. Brake wear was presented as the most likely origin for Cu, Sb, and Sn.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-015-5955-8) contains supplementary material, which is available to authorized users.
Highlights
Different sources contribute to airborne particulate matter (PM)
December 2013 and March 2014 were characterized by great variation between the mean PM10 levels recorded under the predominant air-mass origins: ANW and RE (Fig. 3)
The organic carbon (OC)/elemental carbon (EC) ratio varies daily from 1.30–9.22 (Table 1), with an average of 3.79 ± 1.58. This mean value was similar to the results reported by other authors in urban locations or sites influenced by road traffic in Spain (OC/EC = 2.3), Helsinki (OC/EC = 3.23), Coimbra (OC/EC = 2.75), and Delhi (OC/EC = 4.38) (Harrison et al 1997; Viidanoja et al 2002; Sánchez de la Campa et al 2009; Sharma et al 2014)
Summary
Different sources contribute to airborne particulate matter (PM). Certain chemical species have been scientifically proposed as tracers for road traffic, the presence of which in PM may differ depending on the type of vehicle engine and road surface abrasion (Sternbeck et al 2002; Amato et al 2009).PM emissions involve carbon in different chemical and physical forms. Different sources contribute to airborne particulate matter (PM). Certain chemical species have been scientifically proposed as tracers for road traffic, the presence of which in PM may differ depending on the type of vehicle engine and road surface abrasion (Sternbeck et al 2002; Amato et al 2009). PM emissions involve carbon in different chemical and physical forms. Total carbon (TC) comprises of organic carbon (OC) and elemental carbon (EC). The latter is called black carbon (BC), depending on the method employed in its determination. EC is a suitable indicator to assess the impact of traffic on PM (Minguillón et al 2014). According to Environ Sci Pollut Res (2016) 23:8669–8678
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