Environ Sci Pollut Res DOI 10.1007/s11356-015-4394-x
RESEARCH ARTICLE
Elements and polycyclic aromatic hydrocarbons in exhaust particles emitted by light-duty vehicles Célia A. Alves 1 & Cátia Barbosa 1 & Sónia Rocha 1 & Ana Calvo 2 & Teresa Nunes 1 & Mário Cerqueira 1 & Casimiro Pio 1 & Angeliki Karanasiou 3 & Xavier Querol 3
Received: 29 October 2014 / Accepted: 17 March 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract The main purpose of this work was to evaluate the chemical composition of particulate matter (PM) emitted by eight different light-duty vehicles. Exhaust samples from petrol and diesel cars (Euro 3 to Euro 5) were collected in a chassis dynamometer facility. To simulate the real-world driving conditions, three ARTEMIS cycles were followed: road, to simulate a fluid traffic flow and urban with hot and cold starts, to simulate driving conditions in cities. Samples were analysed for the water-soluble ions, for the elemental composition and for polycyclic aromatic hydrocarbons (PAHs), respectively, by ion chromatography, inductively coupled plasma atomic emission spectroscopy (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and gas chromatography-mass spectrometry (GC-MS). Nitrate and phosphate were the major water-soluble ions in the exhaust particles emitted from diesel and petrol vehicles, respectively. The amount of material emitted is affected by the vehicle age. For vehicles ≥Euro 4, most elements were below the detection limits. Sodium, with emission factors in the ranges 23.5–62.4 and 78.2–227μg km−1, for petrol and diesel Euro 3 vehicles,
respectively, was the major element. The emission factors of metallic elements indicated that diesel vehicles release three to five times more than petrol automobiles. Element emissions under urban cycles are higher than those found for on-road driving, being three or four times higher, for petrol vehicles, and two or three times, for diesel vehicles. The difference between cycles is mainly due to the high emissions for the urban cycle with hot start-up. As registered for elements, most of the PAH emissions for vehicles ≥Euro 4 were also below the detection limits. Regardless of the vehicle models or driving cycles, the two- to four-ring PAHs were always dominant. Naphthalene, with emission factors up to 925 μg km−1, was always the most abundant PAH. The relative cancer risk associated with naphthalene was estimated to be up to several orders of magnitude higher than any of the chemical species found in the PM phase. The highest PAH emission factors were registered for diesel-powered vehicles. The condition of the vehicle can exert a decisive influence on both element and PAH emissions.
Keywords Exhaust particles . Dynamometer . Driving Responsible editor: Constantini Samara
cycles . Euro 3–5 vehicles . Elements . PAHs
Electronic supplementary material The online version of this article (doi:10.1007/s11356-015-4394-x) contains supplementary material, which is available to authorized users.
Introduction
* Célia A. Alves [email protected] 1
Centre for Environmental and Marine Studies, Department of Environment, University of Aveiro, 3810-193 Aveiro, Portugal
2
Department of Physics, IMARENAB, University of León, 24071 León, Spain
3
Institute of Environmental Assessment and Water Research, Spanish Research Council, 08034 Barcelona, Spain
Motor vehicle emissions are the dominant sources of particulate matter (PM) in urban environments (e.g. Byčenkienė et al. 2014; Callén et al. 2013; Delhomme and Millet 2012; Đorđević et al. 2014; Grigoratos et al. 2014b; Lianou et al. 2011; Mirante et al. 2014; Samara et al. 2014; Tan et al. 2014). Numerous studies have linked vehicular exhaust particles to adverse health effects, including premature deaths (Hoek et al. 2002; Tsai et al. 2000), respiratory and cardiovascular problems (Gauderman et al. 2007;
Environ Sci Pollut Res
Harrod et al. 2005; McDonald et al. 2007; Pope and Dockery 2006; Seagrave et al. 2006) and neurodegenerative disorders (Peters et al. 2006). Primary PM emitted by vehicles contains a variety of chemical constituents, such as polycyclic aromatic hydrocarbons (PAHs) and trace elements that are usually of great environmental and health interest. Wang et al. (2003) tested, in a dynamometer system, the emissions of a non-catalyst turbo-charged diesel engine and assessed the characteristics and significance of the metal content. Hu et al. (2009) have studied the metals emitted from heavy-duty diesel vehicles equipped with advanced PM and NO x emission controls. Biswas et al. (2009) have characterised some inorganic ions in PM emissions from heavy-duty diesel vehicles equipped with particulate filter (DPF) and selective catalytic reduction (SCR) retrofits. The effects of fuel characteristics and engine operating conditions on elemental composition of emissions from 12 heavy-duty diesel buses have been investigated by Lim et al. (2007). Light-duty diesel exhaust PM and its constituents, including water-soluble ionic species, elements and PAHs, were measured by Chiang et al. (2012) in a dynamometer study following the driving pattern of the American federal test procedure-75 (FTP-75). Grigoratos et al. (2014a) have evaluated the impact of rapeseed methyl ester (RME) application on unregulated particulate emissions of modern diesel passenger vehicles and specifically on exhaust particles’ most important chemical constituents. Particle emissions were analysed for their soluble organic fraction (SOF) and its constituents (fuel-derived SOF and lube oil-derived SOF), as well as for major inorganic ions (nitrate, sulphate, ammonium). Many studies have investigated PAH emissions of biodiesel or biodiesel blends (Bakeas and Karavalakis 2013; Borrás et al. 2009; Cardone et al. 2002; Chien et al. 2009; Corrêa and Arbilla 2006; Durbin et al. 2000; How et al. 2012; Kalam et al. 2003; Karavalakis et al. 2010; Lin et al. 2006a, b; Ratcliff et al. 2010; Turrio-Baldassarri et al. 2004; Vojtisek-Lom et al. 2012; Yang et al. 2007). Lapuerta et al. (2008) collected and analysed the body of work written mainly in scientific journals about diesel engine emissions when using biodiesel fuels as opposed to conventional diesel fuels. However, although particulate emissions were presented, no bibliographic information was given on their chemical composition. Also, Giakoumis et al. (2012) conducted a literature review regarding the effects of diesel–biodiesel blends on the regulated exhaust emissions of diesel engines operating under transient conditions. The analysis focused on all regulated pollutants and included particle size distributions, but, once again, details on the chemical composition of the emitted PM were not provided. Liu et al. (2008) and Hu et al. (2013) evaluated the effects of DPF and SCR systems on the emission levels of PAHs found in the exhaust of heavy-duty diesel engines. In comparison, very few researches were undertaken
to characterise the PAH content of emissions from light-duty vehicles (Riddle et al. 2007a; Schauer et al. 2002). Among other factors, the composition of exhaust PM depends on driving conditions, vehicle age and category, fuel, lubricant, after-treatment technology, etc. The literature dealing with individual engine operating conditions for light-duty vehicles is very limited. Comprehensive studies describing the chemical composition of exhaust particles from light-duty diesel and gasoline vehicles representative of the Southern European fleet under typical driving cycles are, as far as we know, unavailable. Thus, an exhaustive description of lightduty exhaust emissions is a priority task, given the huge number of passenger cars. Most of the traffic emission profiles have been obtained in US studies. However, the European fleet is quite different from the US fleet, with lower engine power and much higher per cent of diesel vehicles in Europe (Plotkin 2007). Cars in the USA are about 8 % heavier and 5 % larger on average than in the EU. A better characterisation of the PAH and element exhaust emissions from several light-duty engine fleets in Southern Europe is needed for various reasons: (i) implement either source-oriented mitigation measures or health protection programmes, (ii) help reduce inaccuracies associated with the application of source apportionment models, such as the chemical mass balance (CMB), which has been very little applied in Europe due to poor knowledge of the composition of particles from specific sources and (iii) improve emission inventories. The present investigation illustrates the chemical composition of PM emissions from in-use gasoline and diesel passenger cars of the Southern European fleet under typical driving cycles, with a focus on water-soluble ions, elements and PAHs. Information related to gaseous regulated pollutants (CO, CO2, NOx and hydrocarbons), carbonaceous content of particulate matter and about 20 different volatile organic compounds (VOCs) in the C6–C11 range have been reported in a previous paper (Alves et al. 2015).
Experimental Description of the chassis dynamometer The exhaust emission tests were carried out using a chassis dynamometer belonging to the French Institute of Science and Technology for Transport, Spatial Planning, Development and Networks (IFSTTAR). The chassis dynamometer platform consists of a large roller placed underneath the vehicle’s tyres. When a chassis dynamometer test is run, the vehicle to be tested is driven onto the dynamometer platform according to a defined driving cycle. The dynamometer platform simulates road resistance. During a test, the chassis dynamometer gives an accurate reading of the engine’s power, speed, torque,
Environ Sci Pollut Res
exhaust temperature, etc. The exhausts of tested vehicles are diluted with filtered ambient air through a constant volume sampler (CVS) composed of two dilution tunnels, one dedicated to diesel vehicles and the other one to petrol vehicles. Measurements and samplings are made from the dilution tunnel. The sampling units and the chassis dynamometer are servo-controlled in order to relate the measurements to the activity of the vehicle so that the emission factors may be computed. A schematic representation of the dynamometer facility is given in Fig. 1.
Sampling of vehicle exhausts was performed using two real-world driving cycles determined within the European ARTEMIS project. The ARTEMIS Road (ArtRoad) and ARTEMIS Urban (ArtUrb) cycles are representative of real driving behaviour on roads and in an urban environment, respectively (André 2004; André et al. 2006). In addition, the New European Driving Cycle (NEDC) was only performed for the measurements of regulated gases in order to relate the vehicle to a Euro emission class and to possibly exclude highemission vehicles.
Fig. 1 Schematic representation of the chassis dynamometer emission test facility
Environ Sci Pollut Res
Particulate matter sampling and analytical determinations Collection of PM exhaust emissions was performed using two sampling lines operating at flow rates up to 50 L min−1 onto pre-combusted (500 °C, 6 h) 47-mm-quartz fibre filters. Samples were refrigerated immediately after the chassis dynamometer experiments. Conditions of sampling, including dilutions and the repetition of driving cycles, were defined for each vehicle, depending on its emission levels, which were previously checked using the NEDC test. Each driving cycle was repeated three to five times. A minimum of one blank per day was performed. Blanks correspond to the sampling of dilution air in the same conditions as the exhaust samples (including sampling time, transfer in the CVS, etc.). The following driving cycles were tested: – – –
Urban driving cycle with cold start, Urban driving cycle with hot start and Road driving cycle (always hot start).
Both hot and cold start tests were completed in order to simulate real-world conditions. Based on national statistics, eight representative vehicles of the Portuguese fleet, according to motorisation, European emission class and engine capacity, were selected for the chassis dynamometer tests (Table 1). It should be noted that the tested vehicles were borrowed from private individuals, since rental vehicles may not be representative of national fleets. Due to very low particle emissions, especially for Euro 5 and DPF Euro 4 vehicles, which would definitely lead to non-detectable values for most pollutants, punches of the several filters of each driving cycle were extracted or digested together to obtain Bmean^ values. All the results were tunnel blank corrected before converting to mass per distance travelled. For the determination of soluble inorganic ions, small parts of the filters were extracted with ultra-pure Milli-Q water.
Table 1 Vehicles selected for the tests
Dionex AS14 and CS12 chromatographic columns with Dionex AG14 and CG12 guard columns coupled to Dionex AMMS II and Dionex CMMS III suppressors, respectively, for anions and cations, were used. Filter punches were submitted to acidic digestion in closed Teflon 60 mL reactors by using a HF/HNO 3/ HClO4 mixture, with subsequent HF evaporation, and final re-dissolution with HNO3 (Querol et al. 2001), after which they were analysed for a total of about 60 elements. Levels of trace elements in completely dissolved samples were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and/or inductively coupled plasma mass spectroscopy (ICP-MS). Other punches of the same PM filters were extracted by refluxing 300 mL of dichloromethane for 24 h. The filter portions were then extracted three times with methanol (75 mL for 10 min, each extraction) in an ultrasonic bath. After filtration, all the extracts were combined, vacuum concentrated and dried under a gentle nitrogen stream. The total organic extracts were separated into different organic fractions by flash chromatography with silica gel (230–400 mesh, 60 Å Merck Grade 9385) and various solvents of increasing polarity. PAHs were eluted with a binary mixture composed of toluene and n-hexane. After elution, the extract was vacuum concentrated (25–30 °C under reduced pressure), evaporated by a gentle ultra-pure nitrogen stream and analysed by gas chromatography-mass spectrometry (GC-MS). A Shimadzu QP5050A equipped with an automatic injector and a TRB-5MS column (30 m × 0.25 mm × 0.25 μm) was used. Samples were coinjected with a mixture of deuterated internal standards: 1,4-dichlorobenzene-D4, naphthalene-D8, acenaphtheneD10, phenanthrene-D10, chrysene-D12 and peryleneD12 (Sigma-Aldrich). The EPA 525 mix (Supelco) was used to calibrate the equipment in the selected ion monitoring (SIM) mode. Additional details on the extraction procedure and chromatographic conditions can be found elsewhere (Alves et al. 2011).
No.
Vehicle class
Model (year)
Engine (L)
Mileage (km)
DPF
1 2 3 4 5 6 7 8
Euro 3 petrol (
RESEARCH ARTICLE
Elements and polycyclic aromatic hydrocarbons in exhaust particles emitted by light-duty vehicles Célia A. Alves 1 & Cátia Barbosa 1 & Sónia Rocha 1 & Ana Calvo 2 & Teresa Nunes 1 & Mário Cerqueira 1 & Casimiro Pio 1 & Angeliki Karanasiou 3 & Xavier Querol 3
Received: 29 October 2014 / Accepted: 17 March 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract The main purpose of this work was to evaluate the chemical composition of particulate matter (PM) emitted by eight different light-duty vehicles. Exhaust samples from petrol and diesel cars (Euro 3 to Euro 5) were collected in a chassis dynamometer facility. To simulate the real-world driving conditions, three ARTEMIS cycles were followed: road, to simulate a fluid traffic flow and urban with hot and cold starts, to simulate driving conditions in cities. Samples were analysed for the water-soluble ions, for the elemental composition and for polycyclic aromatic hydrocarbons (PAHs), respectively, by ion chromatography, inductively coupled plasma atomic emission spectroscopy (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and gas chromatography-mass spectrometry (GC-MS). Nitrate and phosphate were the major water-soluble ions in the exhaust particles emitted from diesel and petrol vehicles, respectively. The amount of material emitted is affected by the vehicle age. For vehicles ≥Euro 4, most elements were below the detection limits. Sodium, with emission factors in the ranges 23.5–62.4 and 78.2–227μg km−1, for petrol and diesel Euro 3 vehicles,
respectively, was the major element. The emission factors of metallic elements indicated that diesel vehicles release three to five times more than petrol automobiles. Element emissions under urban cycles are higher than those found for on-road driving, being three or four times higher, for petrol vehicles, and two or three times, for diesel vehicles. The difference between cycles is mainly due to the high emissions for the urban cycle with hot start-up. As registered for elements, most of the PAH emissions for vehicles ≥Euro 4 were also below the detection limits. Regardless of the vehicle models or driving cycles, the two- to four-ring PAHs were always dominant. Naphthalene, with emission factors up to 925 μg km−1, was always the most abundant PAH. The relative cancer risk associated with naphthalene was estimated to be up to several orders of magnitude higher than any of the chemical species found in the PM phase. The highest PAH emission factors were registered for diesel-powered vehicles. The condition of the vehicle can exert a decisive influence on both element and PAH emissions.
Keywords Exhaust particles . Dynamometer . Driving Responsible editor: Constantini Samara
cycles . Euro 3–5 vehicles . Elements . PAHs
Electronic supplementary material The online version of this article (doi:10.1007/s11356-015-4394-x) contains supplementary material, which is available to authorized users.
Introduction
* Célia A. Alves [email protected] 1
Centre for Environmental and Marine Studies, Department of Environment, University of Aveiro, 3810-193 Aveiro, Portugal
2
Department of Physics, IMARENAB, University of León, 24071 León, Spain
3
Institute of Environmental Assessment and Water Research, Spanish Research Council, 08034 Barcelona, Spain
Motor vehicle emissions are the dominant sources of particulate matter (PM) in urban environments (e.g. Byčenkienė et al. 2014; Callén et al. 2013; Delhomme and Millet 2012; Đorđević et al. 2014; Grigoratos et al. 2014b; Lianou et al. 2011; Mirante et al. 2014; Samara et al. 2014; Tan et al. 2014). Numerous studies have linked vehicular exhaust particles to adverse health effects, including premature deaths (Hoek et al. 2002; Tsai et al. 2000), respiratory and cardiovascular problems (Gauderman et al. 2007;
Environ Sci Pollut Res
Harrod et al. 2005; McDonald et al. 2007; Pope and Dockery 2006; Seagrave et al. 2006) and neurodegenerative disorders (Peters et al. 2006). Primary PM emitted by vehicles contains a variety of chemical constituents, such as polycyclic aromatic hydrocarbons (PAHs) and trace elements that are usually of great environmental and health interest. Wang et al. (2003) tested, in a dynamometer system, the emissions of a non-catalyst turbo-charged diesel engine and assessed the characteristics and significance of the metal content. Hu et al. (2009) have studied the metals emitted from heavy-duty diesel vehicles equipped with advanced PM and NO x emission controls. Biswas et al. (2009) have characterised some inorganic ions in PM emissions from heavy-duty diesel vehicles equipped with particulate filter (DPF) and selective catalytic reduction (SCR) retrofits. The effects of fuel characteristics and engine operating conditions on elemental composition of emissions from 12 heavy-duty diesel buses have been investigated by Lim et al. (2007). Light-duty diesel exhaust PM and its constituents, including water-soluble ionic species, elements and PAHs, were measured by Chiang et al. (2012) in a dynamometer study following the driving pattern of the American federal test procedure-75 (FTP-75). Grigoratos et al. (2014a) have evaluated the impact of rapeseed methyl ester (RME) application on unregulated particulate emissions of modern diesel passenger vehicles and specifically on exhaust particles’ most important chemical constituents. Particle emissions were analysed for their soluble organic fraction (SOF) and its constituents (fuel-derived SOF and lube oil-derived SOF), as well as for major inorganic ions (nitrate, sulphate, ammonium). Many studies have investigated PAH emissions of biodiesel or biodiesel blends (Bakeas and Karavalakis 2013; Borrás et al. 2009; Cardone et al. 2002; Chien et al. 2009; Corrêa and Arbilla 2006; Durbin et al. 2000; How et al. 2012; Kalam et al. 2003; Karavalakis et al. 2010; Lin et al. 2006a, b; Ratcliff et al. 2010; Turrio-Baldassarri et al. 2004; Vojtisek-Lom et al. 2012; Yang et al. 2007). Lapuerta et al. (2008) collected and analysed the body of work written mainly in scientific journals about diesel engine emissions when using biodiesel fuels as opposed to conventional diesel fuels. However, although particulate emissions were presented, no bibliographic information was given on their chemical composition. Also, Giakoumis et al. (2012) conducted a literature review regarding the effects of diesel–biodiesel blends on the regulated exhaust emissions of diesel engines operating under transient conditions. The analysis focused on all regulated pollutants and included particle size distributions, but, once again, details on the chemical composition of the emitted PM were not provided. Liu et al. (2008) and Hu et al. (2013) evaluated the effects of DPF and SCR systems on the emission levels of PAHs found in the exhaust of heavy-duty diesel engines. In comparison, very few researches were undertaken
to characterise the PAH content of emissions from light-duty vehicles (Riddle et al. 2007a; Schauer et al. 2002). Among other factors, the composition of exhaust PM depends on driving conditions, vehicle age and category, fuel, lubricant, after-treatment technology, etc. The literature dealing with individual engine operating conditions for light-duty vehicles is very limited. Comprehensive studies describing the chemical composition of exhaust particles from light-duty diesel and gasoline vehicles representative of the Southern European fleet under typical driving cycles are, as far as we know, unavailable. Thus, an exhaustive description of lightduty exhaust emissions is a priority task, given the huge number of passenger cars. Most of the traffic emission profiles have been obtained in US studies. However, the European fleet is quite different from the US fleet, with lower engine power and much higher per cent of diesel vehicles in Europe (Plotkin 2007). Cars in the USA are about 8 % heavier and 5 % larger on average than in the EU. A better characterisation of the PAH and element exhaust emissions from several light-duty engine fleets in Southern Europe is needed for various reasons: (i) implement either source-oriented mitigation measures or health protection programmes, (ii) help reduce inaccuracies associated with the application of source apportionment models, such as the chemical mass balance (CMB), which has been very little applied in Europe due to poor knowledge of the composition of particles from specific sources and (iii) improve emission inventories. The present investigation illustrates the chemical composition of PM emissions from in-use gasoline and diesel passenger cars of the Southern European fleet under typical driving cycles, with a focus on water-soluble ions, elements and PAHs. Information related to gaseous regulated pollutants (CO, CO2, NOx and hydrocarbons), carbonaceous content of particulate matter and about 20 different volatile organic compounds (VOCs) in the C6–C11 range have been reported in a previous paper (Alves et al. 2015).
Experimental Description of the chassis dynamometer The exhaust emission tests were carried out using a chassis dynamometer belonging to the French Institute of Science and Technology for Transport, Spatial Planning, Development and Networks (IFSTTAR). The chassis dynamometer platform consists of a large roller placed underneath the vehicle’s tyres. When a chassis dynamometer test is run, the vehicle to be tested is driven onto the dynamometer platform according to a defined driving cycle. The dynamometer platform simulates road resistance. During a test, the chassis dynamometer gives an accurate reading of the engine’s power, speed, torque,
Environ Sci Pollut Res
exhaust temperature, etc. The exhausts of tested vehicles are diluted with filtered ambient air through a constant volume sampler (CVS) composed of two dilution tunnels, one dedicated to diesel vehicles and the other one to petrol vehicles. Measurements and samplings are made from the dilution tunnel. The sampling units and the chassis dynamometer are servo-controlled in order to relate the measurements to the activity of the vehicle so that the emission factors may be computed. A schematic representation of the dynamometer facility is given in Fig. 1.
Sampling of vehicle exhausts was performed using two real-world driving cycles determined within the European ARTEMIS project. The ARTEMIS Road (ArtRoad) and ARTEMIS Urban (ArtUrb) cycles are representative of real driving behaviour on roads and in an urban environment, respectively (André 2004; André et al. 2006). In addition, the New European Driving Cycle (NEDC) was only performed for the measurements of regulated gases in order to relate the vehicle to a Euro emission class and to possibly exclude highemission vehicles.
Fig. 1 Schematic representation of the chassis dynamometer emission test facility
Environ Sci Pollut Res
Particulate matter sampling and analytical determinations Collection of PM exhaust emissions was performed using two sampling lines operating at flow rates up to 50 L min−1 onto pre-combusted (500 °C, 6 h) 47-mm-quartz fibre filters. Samples were refrigerated immediately after the chassis dynamometer experiments. Conditions of sampling, including dilutions and the repetition of driving cycles, were defined for each vehicle, depending on its emission levels, which were previously checked using the NEDC test. Each driving cycle was repeated three to five times. A minimum of one blank per day was performed. Blanks correspond to the sampling of dilution air in the same conditions as the exhaust samples (including sampling time, transfer in the CVS, etc.). The following driving cycles were tested: – – –
Urban driving cycle with cold start, Urban driving cycle with hot start and Road driving cycle (always hot start).
Both hot and cold start tests were completed in order to simulate real-world conditions. Based on national statistics, eight representative vehicles of the Portuguese fleet, according to motorisation, European emission class and engine capacity, were selected for the chassis dynamometer tests (Table 1). It should be noted that the tested vehicles were borrowed from private individuals, since rental vehicles may not be representative of national fleets. Due to very low particle emissions, especially for Euro 5 and DPF Euro 4 vehicles, which would definitely lead to non-detectable values for most pollutants, punches of the several filters of each driving cycle were extracted or digested together to obtain Bmean^ values. All the results were tunnel blank corrected before converting to mass per distance travelled. For the determination of soluble inorganic ions, small parts of the filters were extracted with ultra-pure Milli-Q water.
Table 1 Vehicles selected for the tests
Dionex AS14 and CS12 chromatographic columns with Dionex AG14 and CG12 guard columns coupled to Dionex AMMS II and Dionex CMMS III suppressors, respectively, for anions and cations, were used. Filter punches were submitted to acidic digestion in closed Teflon 60 mL reactors by using a HF/HNO 3/ HClO4 mixture, with subsequent HF evaporation, and final re-dissolution with HNO3 (Querol et al. 2001), after which they were analysed for a total of about 60 elements. Levels of trace elements in completely dissolved samples were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and/or inductively coupled plasma mass spectroscopy (ICP-MS). Other punches of the same PM filters were extracted by refluxing 300 mL of dichloromethane for 24 h. The filter portions were then extracted three times with methanol (75 mL for 10 min, each extraction) in an ultrasonic bath. After filtration, all the extracts were combined, vacuum concentrated and dried under a gentle nitrogen stream. The total organic extracts were separated into different organic fractions by flash chromatography with silica gel (230–400 mesh, 60 Å Merck Grade 9385) and various solvents of increasing polarity. PAHs were eluted with a binary mixture composed of toluene and n-hexane. After elution, the extract was vacuum concentrated (25–30 °C under reduced pressure), evaporated by a gentle ultra-pure nitrogen stream and analysed by gas chromatography-mass spectrometry (GC-MS). A Shimadzu QP5050A equipped with an automatic injector and a TRB-5MS column (30 m × 0.25 mm × 0.25 μm) was used. Samples were coinjected with a mixture of deuterated internal standards: 1,4-dichlorobenzene-D4, naphthalene-D8, acenaphtheneD10, phenanthrene-D10, chrysene-D12 and peryleneD12 (Sigma-Aldrich). The EPA 525 mix (Supelco) was used to calibrate the equipment in the selected ion monitoring (SIM) mode. Additional details on the extraction procedure and chromatographic conditions can be found elsewhere (Alves et al. 2011).
No.
Vehicle class
Model (year)
Engine (L)
Mileage (km)
DPF
1 2 3 4 5 6 7 8
Euro 3 petrol (
