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Characterizing priority polycyclic aromatic hydrocarbons (PAH) in particulate matter from diesel and palm oil-based biodiesel B15 combustion
Atmospheric Environment 45 (2011) 6158e6162
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Characterizing priority polycyclic aromatic hydrocarbons (PAH) in particulate matter from diesel and palm oil-based biodiesel B15 combustion Nestor Y. Rojas a, *, Harvey Andrés Milquez a, Hugo Sarmiento b a b
Universidad Nacional de Colombia, Department of Chemical and Environmental Engineering, Carrera 30 45 e 03 Bogotá, Colombia Universidad de la Salle, Department of Environmental and Sanitary Engineering, Cra.5 No. 59A-44 Bogotá, Colombia
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 April 2011 Received in revised form 6 August 2011 Accepted 8 August 2011
A set of 16 priority polycyclic aromatic hydrocarbons (PAH) associated with particulate matter (PM), emitted by a diesel engine fueled with petroleum diesel and a 15%-vol. palm oil methyl ester blend with diesel (B15), were determined. PM was filtered from a sample of the exhaust gas with the engine running at a steady speed and under no load. PAH were extracted from the filters using the Soxhlet technique, with dichloromethane as solvent. The extracts were then analyzed by gas chromatography using a flame ionization detector (FID). No significant difference was found between PM mass collected when fueled with diesel and B15. Ten of the 16 PAH concentrations were not reduced by adding biodiesel: Benz(a) anthracene, benzo(a)pyrene, benzo(b)fluoranthene, chrysene, dibenz(a,h)anthracene, fluoranthene, fluorene, indeno(1,2,3-c,d)pyrene, naphthalene and phenanthrene. The acenaphthene, acenaphthylene and anthracene concentrations were 45%e80% higher when using diesel, whereas those for benzo(k)fluoranthene, benzo(g,h,i)perylene and pyrene were 30%e72% higher when using the B15 blend. Even though the 16 priority-PAH cumulative concentration increased when using the B15 blend, the total toxic equivalent (TEQ) concentration was not different for both fuels. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: Polycyclic aromatic hydrocarbons Biodiesel Particulate matter Toxicity equivalent factor
1. Introduction Adding biodiesel to petroleum diesel has been suggested as being an effective way of reducing impacts associated with emissions from fossil fuel combustion, i.e. their toxicity and potential for causing damage to DNA. Given that the Colombian Government has created incentives for promoting palm oil-based biodiesel use in a 10% blend with diesel (CONPES, 2008) and intends to explore blends up to 20%, clear evidence is needed to establish what kind of effects on emissions are to be expected from such addition. This study investigated the effect of a 15% biodiesel blend on the emissions of 16 priority polycyclic aromatic hydrocarbons (PAH) included by the USEPA in the National Air Toxic Assessment (USEPA, 1999), given the concerns regarding their toxicity and mutagenicity. A significant percentage of child mortality and morbidity is attributable to air pollutants (Buka et al., 2006), which are also associated with problems during pregnancy and fetal development, including premature birth, low birth weight, intrauterine growth restriction (Liu et al., 2003), abnormal head size and circumference
* Corresponding author. Tel.: þ57 1 3165000x14304. E-mail address: [email protected] (N.Y. Rojas). 1352-2310/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2011.08.016
at birth (Jedrychowski et al., 2004). Laboratory mice prenatally exposed to diesel exhaust particles have shown reduced locomotion, decreased levels of dopamine and increased frequency of asthma episodes, owing to oxidative stress in cells (Li et al., 2003). Although compression-ignition (diesel) engines are energetically more efficient and emit less CO and unburnt hydrocarbons than spark-ignition engines, they emit more particulate matter containing PAH and other toxic, mutagenic and carcinogenic compounds (Correa and Arbilla, 2008; Fenger, 2009; IPCS, 1996). PM and PAH concentrations emitted depend on engine technology and maintenance, fuel quality and composition, combustion air/ fuel ratio and driving characteristics (IPCS, 1996; Nelson et al., 2008; Jones et al., 2004; de Abrantes et al., 2009; Maricq, 2007). PAH emissions using biodiesel depend on the oil (palm, soy, sunflower, rapeseed) and alcohol (methanol, ethanol) used in transesterification (Ballesteros et al., 2010). Baldassarri et al. (2004) have studied the chemical characteristics and mutagenicity of PM emitted by a Euro-II turbocharged diesel engine running on diesel and a 20% blend of rapeseed-oil biodiesel. They found no statistically significant differences in the levels of CO, total hydrocarbons (THC), nitrogen oxides (NOx), PM and the soluble organic fraction of PM. Furthermore, they found no statistically significant differences in PM mutagenicity for several biodiesel blends.
N.Y. Rojas et al. / Atmospheric Environment 45 (2011) 6158e6162
Correa and Arbilla (2006) investigated the effect of adding castor-oil biodiesel on monocyclic aromatic hydrocarbons (MAHs) and PAH emissions. Tests were run using a heavy-duty six-cylinder engine at a steady 1500 rpm speed. Ten PAH and eight MAHs were identified. MAH emissions became reduced by 4.2% for the B2 blend (2% vol.), 8.2% for B5 and 21.2% for B20. Average PAH reduction was 2.7% for B2, 6.3% for B5 and 17.2% for B20. Based on these results, Correa and Arbilla concluded that biodiesel impact on MAH and PAH emissions was beneficial for human health. Yang et al. (2007) examined emissions in an 80,000-km study using two diesel engines fueled with diesel and a 20% biodiesel blend from used cooking oil, CO, HC, NOx, PM and PAH emissions were measured every 20,000 km simulating driving conditions with USEPA’s transient driving cycle (FTP 75). The results showed that using B20 could reduce PAH emissions and, therefore, their toxic and carcinogenic potential. Lin et al. (2008) compared 21 PAH emissions from the combustion of several palm oil-based biodiesel blends and the effect on the emitted particle size using a Mitsubishi 6D14 engine. The test was run at a steady state at 75% of maximum load using B0, B10, B15, B20, B25 and B30 blends. PAH emissions gradually decreased with the increase of the biodiesel fraction in the blend. Considering the increasing use of palm oil biodiesel blends and the importance of PAH effects on human health, the aim of this study was to quantify 16 PAH from USEPA’s 1999 National Air Toxic Assessment in the particulate matter emitted by a palm oil B20 fueled engine (in contrast to a diesel-fueled engine) and examine the B20 toxicity reduction potential. This is the first study of this kind conducted using Colombian palm oil. Results shown here correspond to the first stage of a more comprehensive study, and were obtained at limited conditions of constant speed and no load. We expect, however, that they contribute to discussions on defining future blends and regulating emissions from biodiesel combustion. 2. Methods 2.1. Engine and running conditions A Cummins C83 direct-injection engine was used, having nominal 170 HP at 1800 rpm power without emission control devices. This engine has more than 20 years of service, and can be representative of the Colombian fleet (Ibáñez, 2005). Tests were run without load, at a steady 2000 rpm engine speed, which is a limitation of this study, when compared to more realistic test conditions. Conventional petroleum diesel fuel with 1000 ppm sulfur content and commercial palm oil methyl ester was used to prepare a 15%-vol. biodiesel blend. The fuels used in this study met the requirements of the Colombian Technical Standard 1438. Tests were run with diesel and the B15 blend. Diesel and B15 properties are show in Table 1. 2.2. Sampling and chemical analysis PM samples were filtered from a partial-flow sample of exhaust gas using 55 mm glass fiber filters of 0.6 mm pore size (Whatman QM-A series PM10), which had been previously baked at 400 C for 4 h to burn off organic impurities. No heated line was used during sample collection, but the line was short and was connected to a heated filter holder. Sample flow was kept at 25 L min1 for 5 min by means of a Barnant 401-1901 vacuum pump. No back filter was used. Filters were stored in a desiccator before and after sampling at constant humidity and temperature for 24 h and then weighed 3 times using a Sartorius BP 201d balance. No XAD cartridges were used to collect gas-phase PAH for this study, since the PAH toxicity
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Table 1 Fuel properties. Property
Units Diesel
B15
Test method
Cetane index Cooper corrosion, 3 h to 50 C, max API gravity Viscosity to 40 C, minemax Distillation properties Start boiling point Temperature of 50% volume recovered, maximum Temperature of 90% volume recovered Final boiling point Water and sediment content, maximum Pour point, max Cloud point Flash point, min Ash content, max
e Class API SUS
45.90 1A 36.60 37.01
50.77 1A 37.96 37.96
ASTM D976 ASTM D130 N.A. ASTM D88
67.79 68.47 ASTM D86 249.96 260.19
C C
C C vol. % C C C wt %
318.87 334.22 0.05 <15 10.00 71.80 0.0015
319.55 323.30 0.10 <15 8.00 71.40 0.0016
ASTM ASTM ASTM ASTM ASTM
D1796 D97 D2500 D93 D482
increases with size, and the heaviest PAH are in the particulate phase, rather than the gas-phase. Thirty PM samples were obtained for each fuel; each one was submitted to Soxhlet extraction using 250 mL of dichloromethane HPLC grade (Merck) for 18 h, concentrated to 4-mL by the use of a rotary evaporator. Samples were not filtered prior to analysis. PAH concentration was determined by GC/FID (Thermo Scientific Finnigan, Trace GC Ultra), using a capillary column with 5% phenyl methyl silicone (DB-5 30 m 0.32 mm I.D 1 mm film thickness) and 4 mL sample splitless injection at 250 C. Although injection temperatures higher than 300 C are commonly used in this kind of analysis, recovery tests using 250 C were successful. We wished to have worked with the GC/MS technique, but it was not yet available at our laboratory. However, according to Weber and Cataluña (2008), Angulo and Navarro (2007), Correa and Arbilla (2006) and Chao et al. (2009), GC/FID produce similar results to GC/MS, so we relied on GC/FID for this study. Hydrogen was used as carrier gas and 8 C min1 from 80 C to 150 C temperature ramp, followed by subsequent ramps as follows: 3 C min1 to 180 C, 1.5 C min1 to 230 C, 1 C min1 to 260 C and 10 C min1 to 310 C, with a flow of 16.3 cm s1. These conditions were defined in previous work made by Angulo and Navarro (2007). PAH identification and quantification was based on the calibration of the GC/FID with a standard PAH mix (RESTEK 610) in 25e200 ng mL1. Five-point curves constructed for the calibration had a correlation coefficient higher than 0.980. The same column and analytical conditions were used for calibration and sample analysis. The reliability of the quantification was ensured by performing periodical field blank and recovery analysis. No significant contamination was found when using field blanks and the PAH recovery was higher than 90%, with different efficiencies for different PAH, as determined by adding a diluted solution of the standard to a blank filter. The recovery standard used was 610 HAPs Mix Restek, with 2000 mg mL1 of each of the 16 PAH evaluated in this study. 2.3. Toxicity analysis A mixture of substances’ toxicity and hazard is often evaluated by relating them to a common mechanism of action. This is the underlying principle of the toxicity equivalent factor (TEF) adopted by the USEPA (Schoeny and Poirier, 1993), which quantifies the toxicity of any substance related to a reference compound, this being benzo(a)pyrene in the case of PAH (also expressed as BaPeq). The TEF has been widely used in studies by the California Air
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Resources Board (CARB), Lin et al. (2006), Baldassarri et al. (2004), Angulo and Navarro (2007) and de Abrantes et al. (2009). The toxicity equivalent concentration (TEC) of the PAH mixture is estimated as being the weighed addition of the toxicity equivalent factor of every PAH, according to their mass fractions, as follows:
TECmixture ¼
n X ðxi ÞðTEFi Þ i
where xi is the mass fraction of the i-th PAH in the emitted PM with respect to total PAH. TEF values for every PAH were taken from Nisbet and Lagoy (1992). 3. Results and discussion 3.1. Gravimetric analysis Gravimetric measurements sets for diesel and B15 are well represented by a normal distribution at 95% confidence level. Based on the results from the t-test applied to the sets of particulate mass collected on the filters using diesel and B15, it can be said that the mean concentration of particulate matter emitted when using both fuels was the same at 95% confidence level (Fig. 1). Adding 15%-vol. biodiesel did not affect particulate matter emissions in the conditions used for this experiment. 3.2. Chemical composition The concentrations and standard deviations for the 16 priority particulate matter-associated PAH are shown in Table 2. Total PAH concentration was around 46% higher when B15 was used as fuel. ttest results for the concentration datasets for each 16 PAH collected when running on diesel and B15 fuels (95% confidence level) showed that there were no statistically significant changes for 10 out of 16 PAH when using both fuels: Benz(a)anthracene (B(A)A), benzo(a)pyrene (B(A)P), benzo(b)fluoranthene (B(B)F), chrysene (CHR), dibenz(a,h)anthracene D(a,h)A, fluoranthene (FLA), fluorine (FLU), indene(1,2,3-c,d)pyrene (IND), naphthalene (NAP) and phenanthrene (PHE). Among the remaining 6 PAH, acenaphthene (ACE), acenaphthylene (ACY) and anthracene (ANT) were present at higher concentrations when using diesel as fuel. By contrast, benzo(k)fluoranthene (B(K)F), benzo(g,h,i)perylene (B(g,h,i)P) and pyrene (PYR) had higher concentrations when using B15 as fuel (Fig. 2). These results are discussed in the following section.
Fig. 1. Boxplot for the t-test applied to the particulate mass collected using D and B15 as fuels. No statistical difference of particulate mass emitted by the combustion of B15 and diesel was found at steady speed and under no load.
Table 2 Concentration and standard deviation of the 16 priority PAHs in the exhaust from the combustion of D and B15 fuels (pg std m3). PAH
Abbreviation
mD
sD
mB15
sB15
Naphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene Fluoranthene Pyrene Benz(a)anthracene Chrysene Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(a)pyrene Indeno(1,2,3-c,d)pyrene Dibenz(a,h)anthracene Benzo(g,h,i)perylene Total
NAP ACY ACE FLU PHE ANT FLA PYR B(A)A CRI B(B)F B(K)F B(A)P IND D(A)A B(GHI)P
6.41 2.14 2.88 0.85 1.38 3.11 1.31 9.82 2.23 1.49 2.43 1.53 2.13 4.09 5.03 3.19 50.01
7.47 2.55 2.36 0.55 1.12 2.33 0.62 9.01 1.29 0.63 1.76 0.53 1.03 2.54 3.51 2.14
4.14 0.52 1.78 0.68 1.11 1.36 1.85 34.8 1.75 1.65 2.71 2.47 1.75 5.18 6.7 4.7 73.16
1.93 0.29 1.39 0.38 0.79 1.05 1.5 21.9 1.05 1.09 2.04 1.29 1.05 3.11 4.21 2.38
Pyrene, naphthalene and dibenz(a,h)anthracene were the three PAH making the highest individual contributions to total PAH in PM, accounting for 43% and 62% of total PAH when using diesel and biodiesel (B15), respectively. These PAH are characteristic of particulate matter in diesel exhaust, as stated by the WHO and the International Programme for Chemical Safety (IPCS, 1996). 3.3. Toxicity analysis Table 3 shows the benzo(a)pyrene-based toxicity equivalent factor TEF for PAH mixtures using diesel and B15. Although total PAH mass was higher when using diesel than using B15, there was virtually no difference between diesel toxicity equivalent concentration (TECD) and B15 toxicity equivalent concentration (TECB15). This was due to higher pyrene contribution to total PAH mass when using biodiesel, since it has a 0.01 TEF. Results from this study confirm those of Baldassarri et al. (2004), since no statistically significant change was found in total PM emissions when adding biodiesel. They appear to contradict, however, Correa and Arbilla (2006), Yang et al. (2007) and other authors’ findings regarding the reduction of PM and PAH emissions induced by the addition of biodiesel. This may be explained by the differences in engine conditions among studies. According to the results found by Karavalaskis et al. (2011), PAH concentration may
Fig. 2. Percent change in concentration of the 16 PAH emitted using B15 compared to D. Whilst average PAH reduction was statistically significant for acenaphthene, acenaphthylene and anthracene, average increase occurred for benzo(k)fluoranthene, benzo(g,h,i)perylene and pyrene.
N.Y. Rojas et al. / Atmospheric Environment 45 (2011) 6158e6162 Table 3 Toxicity equivalent factors (TEF) and toxicity equivalent concentrations (TEC) of PAH in the exhaust emission from the combustion of D and B15 fuels. Component
TEFa
TECD 103 (ng m3)
TECB15 103 (ng m3)
ACE ACY ANT B(A)A B(A)P B(B)F B(K)F B(GHI)P CHR D(AH)A FLA FLU IND NAP PHE PYR Total TEC
0.001 0.001 0.01 0.1 1 0.1 0.1 0.01 0.01 0.1 0.001 0.001 0.1 0.001 0.001 0.001
0.0029 0.0021 0.0311 0.2230 2.1300 0.2430 0.1526 0.0319 0.0149 0.5030 0.0013 0.0008 0.4090 0.0064 0.0014 0.0098 3.763
0.0018 0.0005 0.0136 0.1750 1.7500 0.2710 0.2470 0.0470 0.0165 0.6700 0.0019 0.0007 0.5180 0.0041 0.0011 0.0348 3.753
a
Nisbet and Lagoy (1992).
increase when adding biodiesel to diesel if the quality of the process and the raw material used in producing biodiesel is low. Other factors affecting PAH emission include combustion temperature (McGrath et al., 2001; Mastral et al., 1996), combustion efficiency (Gulyurtlu et al., 2003), engine damage (Blumenstock et al., 2000) and an increase in the air/fuel ratio (Mastral et al., 1999). Without load, combustion temperatures are lower and air fuel ratios are higher than under medium or heavy load. This affects combustion efficiency for both diesel and B15, and may counteract the biodiesel emission reduction potential. This may also be true for gas-phase PAH, but no evidence for this was obtained in this study. A slight reduction in total TEC was found when using B15 regarding D, thereby agreeing with the results published by Lin et al. (2006), Angulo and Navarro (2007), de Abrantes et al. (2009) and Chen et al. (2010). However, the individual and total TEC found in this work were nearly three orders of magnitude lower than those found by Lin et al. (2006), Angulo and Navarro (2007) and de Abrantes et al. (2009). Such difference was attributable to the different test conditions, engines and fuels, engine load being the most significant factor affecting the TEC, according to Tsai et al. (2010). 4. Conclusions According to the evidence found in this study, the amount of particulate matter emitted by a diesel engine running at a steady speed and under no load had no statistically significant difference when using a 15%-vol. biodiesel blend compared to using diesel fuel. Regarding the 16 priority PAH concentrations, the biodiesel blend had no statistically significant effect on 10 of them. Whilst it reduced the concentration of acenaphthene, acenaphthylene and anthracene present in the particulate matter emitted, it also increased benzo(k)fluoranthene, benzo(g,h,i)perylene and pyrene emission. Adding biodiesel increased total PAH concentration. Pyrene was the PAH making the highest total PAH concentration contribution using both fuels; naphthalene and dibenz(a,h) anthracene made the second and third most significant contributions to total PAH concentrations when using petroleum diesel. As an overall result, adding biodiesel to petroleum diesel had no statistically significant effect on total toxicity equivalent concentration under the conditions of this study. These results are not representative of real running conditions, since no load and no transient behavior were applied to the engine. Therefore, as future research work, it is necessary to investigate
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dynamic conditions, variations in engine load and concentration of the biodiesel blend, improvement of the sampling methodology and modification of the extraction technique and identification of alkyl, nitro- and amino-PAH. Acknowledgments This work was sponsored by a graduate students’ research grant from the Universidad Nacional de Colombia. The authors wish to thank Merck Colombia for donating the solvents used for chemical analysis; the engine laboratory and Professor Helmer Acevedo at Universidad Nacional de Colombia for their support with the diesel engine used for this study; and the Environmental Engineering laboratory at the Universidad de La Salle for their support with the extraction and GC/FID analysis. References Angulo, J., Navarro, A., 2007. Analysis of the Concentration of Polycyclic Aromatic Hydrocarbons (PAH) in Ambient Air and Risk Assessment for Human Health Through Air Quality Monitoring in Puente Aranda Area. 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Néstor Y. Rojas R. Dr. Rojas is a Chemical Engineer (Universidad Nacional de Colombia, 1996) with a Ph.D. in Diesel Engines Emissions from the University of Leeds, United Kingdom. He held an Assistant Professor position at Universidad de Los Andes between 2002 and 2006 and he is currently an Associate Professor at the Department of Chemical and Environmental Engineering of Universidad Nacional de Colombia at Bogotá. Dr. Rojas’ research is focused on particulate matter air pollution in Bogota, including its effects on health, its chemical characterization and source contribution. Dr. Rojas is the editor/co-author of the book “Material particulado atmosférico y salud” (Ediciones Uniandes, Bogotá, 2005).
Harvey Andrés Milquez Sanabria. Chemical Engineer (Universidad Nacional de Colombia, 2006) with a MSc. in Chemical Engineering from the Universidad Nacional de Colombia. He is currently Professor at the Department of Chemical Engineering of Universidad de América at Bogotá.
Hugo Sarmiento Vela. B. S. in Chemistry (Universidad Nacional de Colombia, 1997) with an MSc in Environment and Development from the Universidad Nacional de Colombia. He is currently professor at the faculty of Environmental Engineering of the Universidad de la Salle at Bogotá.
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Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv
Characterizing priority polycyclic aromatic hydrocarbons (PAH) in particulate matter from diesel and palm oil-based biodiesel B15 combustion Nestor Y. Rojas a, *, Harvey Andrés Milquez a, Hugo Sarmiento b a b
Universidad Nacional de Colombia, Department of Chemical and Environmental Engineering, Carrera 30 45 e 03 Bogotá, Colombia Universidad de la Salle, Department of Environmental and Sanitary Engineering, Cra.5 No. 59A-44 Bogotá, Colombia
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 April 2011 Received in revised form 6 August 2011 Accepted 8 August 2011
A set of 16 priority polycyclic aromatic hydrocarbons (PAH) associated with particulate matter (PM), emitted by a diesel engine fueled with petroleum diesel and a 15%-vol. palm oil methyl ester blend with diesel (B15), were determined. PM was filtered from a sample of the exhaust gas with the engine running at a steady speed and under no load. PAH were extracted from the filters using the Soxhlet technique, with dichloromethane as solvent. The extracts were then analyzed by gas chromatography using a flame ionization detector (FID). No significant difference was found between PM mass collected when fueled with diesel and B15. Ten of the 16 PAH concentrations were not reduced by adding biodiesel: Benz(a) anthracene, benzo(a)pyrene, benzo(b)fluoranthene, chrysene, dibenz(a,h)anthracene, fluoranthene, fluorene, indeno(1,2,3-c,d)pyrene, naphthalene and phenanthrene. The acenaphthene, acenaphthylene and anthracene concentrations were 45%e80% higher when using diesel, whereas those for benzo(k)fluoranthene, benzo(g,h,i)perylene and pyrene were 30%e72% higher when using the B15 blend. Even though the 16 priority-PAH cumulative concentration increased when using the B15 blend, the total toxic equivalent (TEQ) concentration was not different for both fuels. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: Polycyclic aromatic hydrocarbons Biodiesel Particulate matter Toxicity equivalent factor
1. Introduction Adding biodiesel to petroleum diesel has been suggested as being an effective way of reducing impacts associated with emissions from fossil fuel combustion, i.e. their toxicity and potential for causing damage to DNA. Given that the Colombian Government has created incentives for promoting palm oil-based biodiesel use in a 10% blend with diesel (CONPES, 2008) and intends to explore blends up to 20%, clear evidence is needed to establish what kind of effects on emissions are to be expected from such addition. This study investigated the effect of a 15% biodiesel blend on the emissions of 16 priority polycyclic aromatic hydrocarbons (PAH) included by the USEPA in the National Air Toxic Assessment (USEPA, 1999), given the concerns regarding their toxicity and mutagenicity. A significant percentage of child mortality and morbidity is attributable to air pollutants (Buka et al., 2006), which are also associated with problems during pregnancy and fetal development, including premature birth, low birth weight, intrauterine growth restriction (Liu et al., 2003), abnormal head size and circumference
* Corresponding author. Tel.: þ57 1 3165000x14304. E-mail address: [email protected] (N.Y. Rojas). 1352-2310/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2011.08.016
at birth (Jedrychowski et al., 2004). Laboratory mice prenatally exposed to diesel exhaust particles have shown reduced locomotion, decreased levels of dopamine and increased frequency of asthma episodes, owing to oxidative stress in cells (Li et al., 2003). Although compression-ignition (diesel) engines are energetically more efficient and emit less CO and unburnt hydrocarbons than spark-ignition engines, they emit more particulate matter containing PAH and other toxic, mutagenic and carcinogenic compounds (Correa and Arbilla, 2008; Fenger, 2009; IPCS, 1996). PM and PAH concentrations emitted depend on engine technology and maintenance, fuel quality and composition, combustion air/ fuel ratio and driving characteristics (IPCS, 1996; Nelson et al., 2008; Jones et al., 2004; de Abrantes et al., 2009; Maricq, 2007). PAH emissions using biodiesel depend on the oil (palm, soy, sunflower, rapeseed) and alcohol (methanol, ethanol) used in transesterification (Ballesteros et al., 2010). Baldassarri et al. (2004) have studied the chemical characteristics and mutagenicity of PM emitted by a Euro-II turbocharged diesel engine running on diesel and a 20% blend of rapeseed-oil biodiesel. They found no statistically significant differences in the levels of CO, total hydrocarbons (THC), nitrogen oxides (NOx), PM and the soluble organic fraction of PM. Furthermore, they found no statistically significant differences in PM mutagenicity for several biodiesel blends.
N.Y. Rojas et al. / Atmospheric Environment 45 (2011) 6158e6162
Correa and Arbilla (2006) investigated the effect of adding castor-oil biodiesel on monocyclic aromatic hydrocarbons (MAHs) and PAH emissions. Tests were run using a heavy-duty six-cylinder engine at a steady 1500 rpm speed. Ten PAH and eight MAHs were identified. MAH emissions became reduced by 4.2% for the B2 blend (2% vol.), 8.2% for B5 and 21.2% for B20. Average PAH reduction was 2.7% for B2, 6.3% for B5 and 17.2% for B20. Based on these results, Correa and Arbilla concluded that biodiesel impact on MAH and PAH emissions was beneficial for human health. Yang et al. (2007) examined emissions in an 80,000-km study using two diesel engines fueled with diesel and a 20% biodiesel blend from used cooking oil, CO, HC, NOx, PM and PAH emissions were measured every 20,000 km simulating driving conditions with USEPA’s transient driving cycle (FTP 75). The results showed that using B20 could reduce PAH emissions and, therefore, their toxic and carcinogenic potential. Lin et al. (2008) compared 21 PAH emissions from the combustion of several palm oil-based biodiesel blends and the effect on the emitted particle size using a Mitsubishi 6D14 engine. The test was run at a steady state at 75% of maximum load using B0, B10, B15, B20, B25 and B30 blends. PAH emissions gradually decreased with the increase of the biodiesel fraction in the blend. Considering the increasing use of palm oil biodiesel blends and the importance of PAH effects on human health, the aim of this study was to quantify 16 PAH from USEPA’s 1999 National Air Toxic Assessment in the particulate matter emitted by a palm oil B20 fueled engine (in contrast to a diesel-fueled engine) and examine the B20 toxicity reduction potential. This is the first study of this kind conducted using Colombian palm oil. Results shown here correspond to the first stage of a more comprehensive study, and were obtained at limited conditions of constant speed and no load. We expect, however, that they contribute to discussions on defining future blends and regulating emissions from biodiesel combustion. 2. Methods 2.1. Engine and running conditions A Cummins C83 direct-injection engine was used, having nominal 170 HP at 1800 rpm power without emission control devices. This engine has more than 20 years of service, and can be representative of the Colombian fleet (Ibáñez, 2005). Tests were run without load, at a steady 2000 rpm engine speed, which is a limitation of this study, when compared to more realistic test conditions. Conventional petroleum diesel fuel with 1000 ppm sulfur content and commercial palm oil methyl ester was used to prepare a 15%-vol. biodiesel blend. The fuels used in this study met the requirements of the Colombian Technical Standard 1438. Tests were run with diesel and the B15 blend. Diesel and B15 properties are show in Table 1. 2.2. Sampling and chemical analysis PM samples were filtered from a partial-flow sample of exhaust gas using 55 mm glass fiber filters of 0.6 mm pore size (Whatman QM-A series PM10), which had been previously baked at 400 C for 4 h to burn off organic impurities. No heated line was used during sample collection, but the line was short and was connected to a heated filter holder. Sample flow was kept at 25 L min1 for 5 min by means of a Barnant 401-1901 vacuum pump. No back filter was used. Filters were stored in a desiccator before and after sampling at constant humidity and temperature for 24 h and then weighed 3 times using a Sartorius BP 201d balance. No XAD cartridges were used to collect gas-phase PAH for this study, since the PAH toxicity
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Table 1 Fuel properties. Property
Units Diesel
B15
Test method
Cetane index Cooper corrosion, 3 h to 50 C, max API gravity Viscosity to 40 C, minemax Distillation properties Start boiling point Temperature of 50% volume recovered, maximum Temperature of 90% volume recovered Final boiling point Water and sediment content, maximum Pour point, max Cloud point Flash point, min Ash content, max
e Class API SUS
45.90 1A 36.60 37.01
50.77 1A 37.96 37.96
ASTM D976 ASTM D130 N.A. ASTM D88
67.79 68.47 ASTM D86 249.96 260.19
C C
C C vol. % C C C wt %
318.87 334.22 0.05 <15 10.00 71.80 0.0015
319.55 323.30 0.10 <15 8.00 71.40 0.0016
ASTM ASTM ASTM ASTM ASTM
D1796 D97 D2500 D93 D482
increases with size, and the heaviest PAH are in the particulate phase, rather than the gas-phase. Thirty PM samples were obtained for each fuel; each one was submitted to Soxhlet extraction using 250 mL of dichloromethane HPLC grade (Merck) for 18 h, concentrated to 4-mL by the use of a rotary evaporator. Samples were not filtered prior to analysis. PAH concentration was determined by GC/FID (Thermo Scientific Finnigan, Trace GC Ultra), using a capillary column with 5% phenyl methyl silicone (DB-5 30 m 0.32 mm I.D 1 mm film thickness) and 4 mL sample splitless injection at 250 C. Although injection temperatures higher than 300 C are commonly used in this kind of analysis, recovery tests using 250 C were successful. We wished to have worked with the GC/MS technique, but it was not yet available at our laboratory. However, according to Weber and Cataluña (2008), Angulo and Navarro (2007), Correa and Arbilla (2006) and Chao et al. (2009), GC/FID produce similar results to GC/MS, so we relied on GC/FID for this study. Hydrogen was used as carrier gas and 8 C min1 from 80 C to 150 C temperature ramp, followed by subsequent ramps as follows: 3 C min1 to 180 C, 1.5 C min1 to 230 C, 1 C min1 to 260 C and 10 C min1 to 310 C, with a flow of 16.3 cm s1. These conditions were defined in previous work made by Angulo and Navarro (2007). PAH identification and quantification was based on the calibration of the GC/FID with a standard PAH mix (RESTEK 610) in 25e200 ng mL1. Five-point curves constructed for the calibration had a correlation coefficient higher than 0.980. The same column and analytical conditions were used for calibration and sample analysis. The reliability of the quantification was ensured by performing periodical field blank and recovery analysis. No significant contamination was found when using field blanks and the PAH recovery was higher than 90%, with different efficiencies for different PAH, as determined by adding a diluted solution of the standard to a blank filter. The recovery standard used was 610 HAPs Mix Restek, with 2000 mg mL1 of each of the 16 PAH evaluated in this study. 2.3. Toxicity analysis A mixture of substances’ toxicity and hazard is often evaluated by relating them to a common mechanism of action. This is the underlying principle of the toxicity equivalent factor (TEF) adopted by the USEPA (Schoeny and Poirier, 1993), which quantifies the toxicity of any substance related to a reference compound, this being benzo(a)pyrene in the case of PAH (also expressed as BaPeq). The TEF has been widely used in studies by the California Air
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Resources Board (CARB), Lin et al. (2006), Baldassarri et al. (2004), Angulo and Navarro (2007) and de Abrantes et al. (2009). The toxicity equivalent concentration (TEC) of the PAH mixture is estimated as being the weighed addition of the toxicity equivalent factor of every PAH, according to their mass fractions, as follows:
TECmixture ¼
n X ðxi ÞðTEFi Þ i
where xi is the mass fraction of the i-th PAH in the emitted PM with respect to total PAH. TEF values for every PAH were taken from Nisbet and Lagoy (1992). 3. Results and discussion 3.1. Gravimetric analysis Gravimetric measurements sets for diesel and B15 are well represented by a normal distribution at 95% confidence level. Based on the results from the t-test applied to the sets of particulate mass collected on the filters using diesel and B15, it can be said that the mean concentration of particulate matter emitted when using both fuels was the same at 95% confidence level (Fig. 1). Adding 15%-vol. biodiesel did not affect particulate matter emissions in the conditions used for this experiment. 3.2. Chemical composition The concentrations and standard deviations for the 16 priority particulate matter-associated PAH are shown in Table 2. Total PAH concentration was around 46% higher when B15 was used as fuel. ttest results for the concentration datasets for each 16 PAH collected when running on diesel and B15 fuels (95% confidence level) showed that there were no statistically significant changes for 10 out of 16 PAH when using both fuels: Benz(a)anthracene (B(A)A), benzo(a)pyrene (B(A)P), benzo(b)fluoranthene (B(B)F), chrysene (CHR), dibenz(a,h)anthracene D(a,h)A, fluoranthene (FLA), fluorine (FLU), indene(1,2,3-c,d)pyrene (IND), naphthalene (NAP) and phenanthrene (PHE). Among the remaining 6 PAH, acenaphthene (ACE), acenaphthylene (ACY) and anthracene (ANT) were present at higher concentrations when using diesel as fuel. By contrast, benzo(k)fluoranthene (B(K)F), benzo(g,h,i)perylene (B(g,h,i)P) and pyrene (PYR) had higher concentrations when using B15 as fuel (Fig. 2). These results are discussed in the following section.
Fig. 1. Boxplot for the t-test applied to the particulate mass collected using D and B15 as fuels. No statistical difference of particulate mass emitted by the combustion of B15 and diesel was found at steady speed and under no load.
Table 2 Concentration and standard deviation of the 16 priority PAHs in the exhaust from the combustion of D and B15 fuels (pg std m3). PAH
Abbreviation
mD
sD
mB15
sB15
Naphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene Fluoranthene Pyrene Benz(a)anthracene Chrysene Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(a)pyrene Indeno(1,2,3-c,d)pyrene Dibenz(a,h)anthracene Benzo(g,h,i)perylene Total
NAP ACY ACE FLU PHE ANT FLA PYR B(A)A CRI B(B)F B(K)F B(A)P IND D(A)A B(GHI)P
6.41 2.14 2.88 0.85 1.38 3.11 1.31 9.82 2.23 1.49 2.43 1.53 2.13 4.09 5.03 3.19 50.01
7.47 2.55 2.36 0.55 1.12 2.33 0.62 9.01 1.29 0.63 1.76 0.53 1.03 2.54 3.51 2.14
4.14 0.52 1.78 0.68 1.11 1.36 1.85 34.8 1.75 1.65 2.71 2.47 1.75 5.18 6.7 4.7 73.16
1.93 0.29 1.39 0.38 0.79 1.05 1.5 21.9 1.05 1.09 2.04 1.29 1.05 3.11 4.21 2.38
Pyrene, naphthalene and dibenz(a,h)anthracene were the three PAH making the highest individual contributions to total PAH in PM, accounting for 43% and 62% of total PAH when using diesel and biodiesel (B15), respectively. These PAH are characteristic of particulate matter in diesel exhaust, as stated by the WHO and the International Programme for Chemical Safety (IPCS, 1996). 3.3. Toxicity analysis Table 3 shows the benzo(a)pyrene-based toxicity equivalent factor TEF for PAH mixtures using diesel and B15. Although total PAH mass was higher when using diesel than using B15, there was virtually no difference between diesel toxicity equivalent concentration (TECD) and B15 toxicity equivalent concentration (TECB15). This was due to higher pyrene contribution to total PAH mass when using biodiesel, since it has a 0.01 TEF. Results from this study confirm those of Baldassarri et al. (2004), since no statistically significant change was found in total PM emissions when adding biodiesel. They appear to contradict, however, Correa and Arbilla (2006), Yang et al. (2007) and other authors’ findings regarding the reduction of PM and PAH emissions induced by the addition of biodiesel. This may be explained by the differences in engine conditions among studies. According to the results found by Karavalaskis et al. (2011), PAH concentration may
Fig. 2. Percent change in concentration of the 16 PAH emitted using B15 compared to D. Whilst average PAH reduction was statistically significant for acenaphthene, acenaphthylene and anthracene, average increase occurred for benzo(k)fluoranthene, benzo(g,h,i)perylene and pyrene.
N.Y. Rojas et al. / Atmospheric Environment 45 (2011) 6158e6162 Table 3 Toxicity equivalent factors (TEF) and toxicity equivalent concentrations (TEC) of PAH in the exhaust emission from the combustion of D and B15 fuels. Component
TEFa
TECD 103 (ng m3)
TECB15 103 (ng m3)
ACE ACY ANT B(A)A B(A)P B(B)F B(K)F B(GHI)P CHR D(AH)A FLA FLU IND NAP PHE PYR Total TEC
0.001 0.001 0.01 0.1 1 0.1 0.1 0.01 0.01 0.1 0.001 0.001 0.1 0.001 0.001 0.001
0.0029 0.0021 0.0311 0.2230 2.1300 0.2430 0.1526 0.0319 0.0149 0.5030 0.0013 0.0008 0.4090 0.0064 0.0014 0.0098 3.763
0.0018 0.0005 0.0136 0.1750 1.7500 0.2710 0.2470 0.0470 0.0165 0.6700 0.0019 0.0007 0.5180 0.0041 0.0011 0.0348 3.753
a
Nisbet and Lagoy (1992).
increase when adding biodiesel to diesel if the quality of the process and the raw material used in producing biodiesel is low. Other factors affecting PAH emission include combustion temperature (McGrath et al., 2001; Mastral et al., 1996), combustion efficiency (Gulyurtlu et al., 2003), engine damage (Blumenstock et al., 2000) and an increase in the air/fuel ratio (Mastral et al., 1999). Without load, combustion temperatures are lower and air fuel ratios are higher than under medium or heavy load. This affects combustion efficiency for both diesel and B15, and may counteract the biodiesel emission reduction potential. This may also be true for gas-phase PAH, but no evidence for this was obtained in this study. A slight reduction in total TEC was found when using B15 regarding D, thereby agreeing with the results published by Lin et al. (2006), Angulo and Navarro (2007), de Abrantes et al. (2009) and Chen et al. (2010). However, the individual and total TEC found in this work were nearly three orders of magnitude lower than those found by Lin et al. (2006), Angulo and Navarro (2007) and de Abrantes et al. (2009). Such difference was attributable to the different test conditions, engines and fuels, engine load being the most significant factor affecting the TEC, according to Tsai et al. (2010). 4. Conclusions According to the evidence found in this study, the amount of particulate matter emitted by a diesel engine running at a steady speed and under no load had no statistically significant difference when using a 15%-vol. biodiesel blend compared to using diesel fuel. Regarding the 16 priority PAH concentrations, the biodiesel blend had no statistically significant effect on 10 of them. Whilst it reduced the concentration of acenaphthene, acenaphthylene and anthracene present in the particulate matter emitted, it also increased benzo(k)fluoranthene, benzo(g,h,i)perylene and pyrene emission. Adding biodiesel increased total PAH concentration. Pyrene was the PAH making the highest total PAH concentration contribution using both fuels; naphthalene and dibenz(a,h) anthracene made the second and third most significant contributions to total PAH concentrations when using petroleum diesel. As an overall result, adding biodiesel to petroleum diesel had no statistically significant effect on total toxicity equivalent concentration under the conditions of this study. These results are not representative of real running conditions, since no load and no transient behavior were applied to the engine. Therefore, as future research work, it is necessary to investigate
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dynamic conditions, variations in engine load and concentration of the biodiesel blend, improvement of the sampling methodology and modification of the extraction technique and identification of alkyl, nitro- and amino-PAH. Acknowledgments This work was sponsored by a graduate students’ research grant from the Universidad Nacional de Colombia. The authors wish to thank Merck Colombia for donating the solvents used for chemical analysis; the engine laboratory and Professor Helmer Acevedo at Universidad Nacional de Colombia for their support with the diesel engine used for this study; and the Environmental Engineering laboratory at the Universidad de La Salle for their support with the extraction and GC/FID analysis. References Angulo, J., Navarro, A., 2007. Analysis of the Concentration of Polycyclic Aromatic Hydrocarbons (PAH) in Ambient Air and Risk Assessment for Human Health Through Air Quality Monitoring in Puente Aranda Area. 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Néstor Y. Rojas R. Dr. Rojas is a Chemical Engineer (Universidad Nacional de Colombia, 1996) with a Ph.D. in Diesel Engines Emissions from the University of Leeds, United Kingdom. He held an Assistant Professor position at Universidad de Los Andes between 2002 and 2006 and he is currently an Associate Professor at the Department of Chemical and Environmental Engineering of Universidad Nacional de Colombia at Bogotá. Dr. Rojas’ research is focused on particulate matter air pollution in Bogota, including its effects on health, its chemical characterization and source contribution. Dr. Rojas is the editor/co-author of the book “Material particulado atmosférico y salud” (Ediciones Uniandes, Bogotá, 2005).
Harvey Andrés Milquez Sanabria. Chemical Engineer (Universidad Nacional de Colombia, 2006) with a MSc. in Chemical Engineering from the Universidad Nacional de Colombia. He is currently Professor at the Department of Chemical Engineering of Universidad de América at Bogotá.
Hugo Sarmiento Vela. B. S. in Chemistry (Universidad Nacional de Colombia, 1997) with an MSc in Environment and Development from the Universidad Nacional de Colombia. He is currently professor at the faculty of Environmental Engineering of the Universidad de la Salle at Bogotá.