Effects on aerosol size distribution of polycyclic aromatic hydrocarbons from the heavy-duty diesel generator fueled with feedstock palm-biodiesel blends

Effects on aerosol size distribution of polycyclic aromatic

hydrocarbons from the heavy-duty diesel generator

fueled with feedstock palm-biodiesel blends

Yuan-Chung Lin

a,b,*

_{, Cheng-Hsien Tsai}

c

_{, Chi-Ru Yang}

d

_{, C.H. Jim Wu}

e

_,

Tzi-Yi Wu

c

, Guo-Ping Chang-Chien

b

a_{Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwan} b_{Super Micro Mass Research and Technology Center, Cheng Shiu University, Kaohsiung County 833, Taiwan}

c_{Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan} d_{Department of Environmental Resource Management, Chia-Nan University of Pharmacy and Science, Tainan 717, Taiwan} e_{Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, IL 60801, USA}

a r t i c l e

i n f o

Article history:

Received 26 December 2007 Received in revised form 2 April 2008 Accepted 7 April 2008 Keywords: PAH Size distribution Biodiesel Engine Emission

a b s t r a c t

Biodiesels are promoted as alternatives to fossil fuels and their applications in diesel en-gine have been studied extensively. However, the size distribution of polycyclic aromatic hydrocarbons (PAHs) and generator particulate material (GPM) emitted from heavy-duty diesel generator fueled with biodiesel blends has seldom been addressed. Seven different biodiesel blends with volume fractions of biodiesel ranging from 0% to 30% were studied. Experimental results indicate that the mean reductions of sum of PAHi/GPM0.056–18 (gen-erator particulate material with aerodynamic diameter 0.056–18mm) and BaPeqi [¼(ben-zo[a]pyrene equivalent)i]/GPM0.056–18of B5, B10, B15, B20, B25 and B30 are (8.21%, 5.72%), (36.7%, 29.7%), (1.25%, 2.32%), (16.2%, 18.6%), (33.4%, 35.0%) and (40.5%, 42.4), respectively, compared with B0. Both PAHi/GPMi and BaPeqi/GPMi in stage 1 (0.056 – 0.166mm) and stage 2 (0.166 – 0.31mm) of all test fuels are higher than those in the other stages due to higher specific surface area of smaller particles. It is also observed that there are more highly toxic PAHs in stage 2. It should be noticed that the trend of par-ticle-phase PAH contents is different from the trend of parpar-ticle-phase PAH concentration and opposite to the trend of total GPM0.056–18emission. The differences are due to a higher number of particles with diameters between 0.056 and 0.31mm. The above results indicate that fuel blends with less than 15% biodiesel would increase PAH content at particle size between 0.056 and 0.31mm. Therefore, the blending fraction should be between 15% and 30%. Moreover, particle-size control is needed in future emission regulations which would necessitate further improvements in combustion quality. Besides, researches on health effects of biodiesel blends are needed as well.

Crown Copyright Ó 2008 Published by Elsevier Ltd. All rights reserved.

1. Introduction

Biodiesel has been promoted as a promising alternative to diesel fuels since it is renewable, compatible with cur-rent engine designs and fuel delivery/storage. On the other hand, lawmakers have been responding to the global concerns on environmental issues with more stringent *Corresponding author. Institute of Environmental Engineering,

National Sun Yat-Sen University, Kaohsiung 804, Taiwan. Tel.: þ886 7 5252000x4412; fax: þ886 7 5254449.

E-mail address:yclin@faculty.nsysu.edu.tw(Y.-C. Lin).

Contents lists available atScienceDirect

Atmospheric Environment

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / a t m o s e n v

1352-2310/$ – see front matter Crown Copyright Ó 2008 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2008.04.018

regulations such as tighter controls on engine emissions. To meet these tightened regulations, oxides of nitrogen (NOx)

and particulate matter must be reduced. Biodiesel is virtu-ally free of sulfur and polycyclic aromatic hydrocarbon (PAH) contents. Moreover, biodiesel is also nontoxic and biodegradable. Biodiesel can be used as an alternative fuel in diesel engines to improve combustion efficiency, reduce hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), and PAH emissions,

but slightly increase the brake specific fuel consumption (BSFC) and NOx emission (Wang et al., 2000; Monyem

and Van Gerpen, 2001; Cardone et al., 2002; Antolin et al., 2002; Durbin and Norbeck, 2002; Beer et al., 2002; Kalam et al., 2003; Dorado et al., 2003; Kalligeros et al., 2003; Lin et al., 2006a; Lin et al., 2006b). Besides, biodiesel contributes less to global warming than fossil fuels due to its closed carbon cycle. On a lifecycle basis, biodiesel can reduce CO2by 78% (Central Coast Vineyard Team, 2005).

However, few studies were done on the particle-size distribution from diesel generators fueled with biodiesel blends due to no regulations. Small particles have higher specific surface area and they are more toxic than coarse particles. Moreover, small particles are more likely to be in-haled and deposited in both respiratory tract and alveolar region and cause symptoms in the respiratory systems (Pope et al., 1995; McAughey, 1997; Health Effects Institute, 2002). Furthermore, the efficiency of particle deposition in the respiratory tract is a function of the particle size and the relationship between fine particles and health effect is log-ical (Pope et al., 1995; McAughey, 1997).Turrio-Baldassrri et al. (2004) noted that most of the particles emitted from the bus engine fueled with rapeseed-biodiesel are in the range 0.06–0.3

m

m.Krahl et al. (2001)concluded that pure rapeseed-biodiesel leads to higher particle numbers and particulate matter emission than diesel fuel. The concentration of particles with aerodynamic diameter less than 0.019

m

m is significantly higher for rapeseed-biodie-sel, when compared with ultra low sulfur diesel fuel (Tsolakis, 2006).Krahl et al. (2007)found that the three-component blend (60% diesel fuel, 20% Shell middle distillate with additive and 20% rapeseed-biodiesel) caused higher mutagenicity than each of its components but it is not clear which type of synergistic effects may be responsi-ble for this phenomenon (Krahl et al., 2007). However, it may be because more fine specific particles in the three-component. Therefore, it could be seen that it is important to understand the effect on aerosol size distribution of either particulate matter or PAHs from the exhaust of diesel engines fueled with biodiesel blends.

Today, generators have been applied for emergent elec-tric power in mansions. Furthermore, industries have expanded rapidly in some countries, but electric cables have not been installed popularly in some area leading to the widespread use of diesel generators. Although much work has been devoted to the application of biodiesel in diesel engines, few studies have focused on the size distri-bution of both GPM and PAH emitted from a heavy-duty diesel generator fueled with palm-biodiesel. Furthermore, palm-biodiesel is cheaper than both soybean-biodiesel and corn-biodiesel (Kalam and Masjuki, 2002). The physi-cochemical properties of palm-biodiesel meets the

requirement of diesel engine combustion, and are compa-rable with those of other biodiesels such as soybean and rapeseed oils (Wibulswas et al., 1999; Kalam and Masjuki, 2002). It could be seen that palm-biodiesel has a higher po-tential for commercial application than other biodiesels. Hence, palm-biodiesel was selected in this study. Therefore, this study investigates PAH and GPM0.056–18emissions from

heavy-duty diesel generator. Additionally, the cumulative mass fractions and mass median diameter are compared and discussed. Finally, emission factors of both PAHs and GPM0.056–18 and brake specific fuel consumption are

obtained from experiments and analyzed for an assessment on the effects of palm-biodiesel blends in the environment. 2. Methods and materials

2.1. Test fuels and engine

In our previous research, high fraction of biodiesel blends would cause incomplete combustion (Lin et al., 2006a). Therefore, the fraction of biodiesel is limited to 30% in this study. Seven test fuels were used: premium die-sel fuel B0, B5 (5 vol% palm-biodiedie-sel þ 95 vol% B0), B10, B15, B20, B25 and B30. The palm-biodiesel was purchased from Gibson Chemical Corporation in Malaysia. Fuel speci-fications of palm-biodiesel used in this study are shown in Table 1. It could be seen that pure palm-biodiesel meets ASTM-D6751 standards. The heavy-duty diesel generator used in this study is Mitsubishi-6D14, direct injection,

bore and stroke with dimensions of 110 mm

(dia.)  115 mm, a total displacement of 6557 cc, a compres-sion ratio of 17.9:1 and a maximum power of 160 ps at 3000 rpm. The tests were performed under a steady state (75% of maximum power) for all test fuels in a diesel gen-erator company in southern Taiwan. Neither dilution

Table 1

Specifications of pure palm-biodiesel

Fuel parameter B100 Mean RSDa_(%) Density, g ml1_{at 15}_{C 0.873 0.175} Flash point,_{C 166 2.11} Kinematic viscosity, mm2_s1_{(cSt) at 40}_{C 4.40 0.455} Cetane index 49.3 0.310 Cetane number 64.0 0.393 Carbon residue, wt% NDb_{<0.01 NA}c Distillation, T90,_{C 333 0.347} Sulfated ash, wt% ND < 0.001 NA Sulfur content, ppmw 1.1 9.09

Water and sediment, vol% ND < 0.0005 NA Copper strip corrosion, 3 h at 50_{C 1A NA}

Acid number, mg KOH g1 _{0.121 2.19}

Methanol content, vol% ND < 0.01 NA

Cloud point,_{C 14 4.22}

Free Glycerin, wt% 0.009 6.66

Total Glycerin, wt% 0.141 1.47

Phosphorus content, ppm ND < 0.5 NA

Calcium and magnesium, ppmw 1.7 6.66

Sodium/potassium, ppm 2.0 5.00

Oxidation stability, h 7.1 3.56

a_{Relative standard deviation.} b_{Not detected.}

tunnel nor cooler was used. A Micro-Orifice Uniform De-posit Impactor (MOUDI; Model 110, MSP Corporation, USA) was installed downstream of the diesel generator ex-haust to collect the suspended particles and particle-phase PAHs. No gaseous specie was sampled. There are three tests for each test fuel. Statistical significance was examined by using the two-sided Student’s t-test. The t-test can be used to determine whether the means are distinct when two given data with each characterized by its mean, stan-dard deviation and number of data points. Differences between mean values at level of p-value (95% confidence level) were considered statistically significant.

2.2. Sample collection

A MOUDI equipped with aluminum filters (with diam-eters of 37 mm) was used to collect size-resolved samples. Particles with diameter less than 0.056

m

m were collected but gas phase PAHs may be adsorbed when the exhaust gas goes through the Teflon filter. Therefore, this research

is focused on particles with diameter between

0.056 w 18

m

m. Therefore, the sum of MOUDI mass is less than total GPM mass. These impactors effectively sepa-rated the particulate matters into 9 ranges with the fol-lowing equivalent cut-off diameters; 18–10

m

m (stage 9), 10–5.6

m

m (stage 8), 5.6–3.2

m

m (stage 7), 3.2–1.8

m

m (stage 6), 1.8–1.0

m

m (stage 5), 1.0–0.52

m

m (stage 4), 0.52–0.31

m

m (stage 3), 0.31–0.166

m

m (stage 2) and 0.166–0.056

m

m (stage 1). Silicon grease was applied to the surface of each filter installed in the MOUDI. Before sampling, the greased filter-strips were baked in a 60_C

oven for 90 min to stabilize the silicon grease. Thus, parti-cle bounce between the different stages of the MOUDI dur-ing the sampldur-ing could be minimized. Before and after each sampling, the filters were dried for 24 h in a desicca-tor at 25_{C with 40% relative humidity. They were then}

weighed again. The suspended GPM concentration is determined by dividing the mass by the volume of sam-pled air.

Particles will bounce off the filter if Quartz filters or Tef-lon filters are used. Aluminum filters with gel sprayed on its surface have been used to prevent particle bounce during the collection of size-segregated aerosol samples, which have been analyzed for trace-level airborne organic com-pounds, including PAHs. The use of the oiled impaction substrates, however, may introduce another sampling arti-fact – the absorption of semi-volatile species from the gas phase which could artificially increase the amount of PAHs attributed to the aerosol. According to the conclusion byAllen et al. (1999), the absorption artifact could be neg-ligible if the amount of PAHs collected by impactor was greater than the amount absorbed at equilibrium. The con-centration of particle-phase PAHs from diesel generator is higher than that in the atmosphere. Furthermore, each run was running for 200 min. Therefore, the amount of PAHs collected by each impactor is higher than that absorbed at equilibrium. Thus, the absorption artifact could be expected to be negligible in this study due to the conclu-sion byAllen et al. (1999)but the possibility of PAH desorp-tion should be avoided.

2.3. PAH analysis

Each collected sample was extracted in a Soxhlet extrac-tor with a mixed solvent (n-hexane and dichloromethane; vol/vol, 1:1; 500 ml each) for 24 h. The extract was then con-centrated, cleaned up and reconcentrated to exactly 0.2 mL. The PAH contents were determined by a Hewlett–Packard (HP) gas chromatograph (GC) (HP 5890A; Hewlett–Packard, Wilmington, DE, USA), a mass selective detector (MSD) (HP 5972), and a computer workstation (Aspire C500; Acer, Tai-pei, Taiwan). Detail information can be found in our previous studies (Lin et al., 2006a; Lin et al., 2006b). The twenty-one PAHs compounds were analyzed. They are naphthalene (Nap), acenaphthylene (AcPy), acenaphthene (Acp), fluorine (Flu), phenanthrene (PA), anthracene (Ant), fluoranthene (FL), pyrene (Pyr), benzo[a]anthracene (BaA), chrysene (CHR), cyclopenta[c,d]pyrene (CYC), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[e]pyrene (BeP), benzo[a]pyrene (BaP), perylene (PER), dibenzo[a,h]anthra-cene (DBA), benzo[b]chrydibenzo[a,h]anthra-cene (BbC), indeno[1,2,3,-cd]pyr-ene (IND), benzo[ghi]perylindeno[1,2,3,-cd]pyr-ene (Bghip) and coronindeno[1,2,3,-cd]pyr-ene (COR). The total PAH data for the diesel generator exhaust is given by the sum of the 21 individual PAHs. The GC/MSD was cali-brated with a diluted standard solution of 16 PAH com-pounds (PAH mixture-610 M; Supelco, Bellefonte, PA, USA) plus 5 additional individual PAHs obtained from Merck (Darmstadt, Germany). Analysis of serial dilutions of PAHs standards showed that the detection limit (DL) for GC/MSD was between 25 (pico-gram) and 306 pg for the 21 PAH com-pounds. Ten consecutive injections of a PAH standard yielded an average relative standard deviation of the GC/MSD inte-gration area of 7.18%, within a range of 4.51–9.38%. The rela-tive standard deviation of the GC/MSD integration data displays the stability of the GC/MSD. The above result indi-cates that GC/MSD is in excellent condition for PAH analysis. In this study, two internal standards (phenanthrene-d10

and perylene-d12) were used to check their response

fac-tors, the recovery efficiencies for PAH analysis and to deter-mine final concentrations. The recovery efficiencies of 21 individual PAHs and these two internal standards were determined by processing a solution containing known PAH concentrations through the same experimental proce-dure used for the samples. The experimental results showed that the recovery efficiencies for the 21 PAH com-pounds ranged from 0.836 to 0.975, with an average value of 0.912. The recovery efficiencies of two internal standards (phenanthrene-d10and perylene-d12) were between 89.7%

and 106% and were fairly constant. Analyses of field blanks showed that there were no significant contamination (GC/ MSD integrated area < detection limit). Twenty-seven (three blanks  nine stages) blanks were taken. The mass of GPM and PAH of samples background in each stage was not detected. The typical sample masses were higher than detection limits.

2.4. Data analysis

The mass median diameter (MMD; MMDo for overall particles; MMDf for fine particles meaning particle diame-ter 0.056–2.5

m

m; MMDc for coarse particles meaning par-ticle diameter 2.5–10

m

m) can be determined by the curves

4. Conclusion

According to the experimental results, the mean GPM0.056–2.5 (0.056

m

m < aerodynamic diameters < 2.5

m

m)

and GPM0.056–10 (0.056

m

m < aerodynamic

diame-ters < 10

m

m) reduction of B5 (5 vol% palm-biodie-sel þ 95 vol% pure diepalm-biodie-sel), B10, B15, B20, B25 and B30 are (11.8%, 14.9%), (31.9%, 37.2%), (15.9%, 19.5%), (9.07%, 12.1%), (2.96%, 3.83%) and (1.02%, 0.497%), respectively, compared with B0 (117 and 131 mg m3). The mean reductions of total particle-phase PAH and BaPeq concentrations of B5, B10,

B15, B20, B25 and B30 are (10.1%, 12.2%), (16.7%, 20.9%), (20.9%, 23.7%), (28.0%, 30.1%), (37.6%, 39.0%) and (41.2%, 43.1%), respectively. Both PAHi/GPMi and BaPeqi/GPMi in

stages 1 and 2 of all test fuels are higher than those in the other stages because the higher specific surface area of fine particles is higher than that of coarse particles. It is also ob-served that the ratio of stage 2 to stage 1 in BaPeqi/GPMi is

larger than that of PAHi/GPMi. Therefore, it can be concluded that there are more highly toxic PAHs in stage 2. Besides, both the sum of PAHi/GPM0.056–18and BaPeqi/GPM0.056–18contents

increase with increased fraction of palm-biodiesel from 0% to 10% but decrease with increased fraction of palm-biodiesel from 10% to 30%. The mean reductions of sum of PAHi/ GPM0.056–18in B5, B10, B15, B20, B25 and B30 are 8.21%,

36.7%, 1.25%, 16.2%, 33.4% and 40.5%, respectively, com-pared with B0. The mean reduction of sum of BaPeqi/

GPM0.05618in B5, B10, B15, B20, B25 and B30 were 5.72%,

29.7%, 2.32%,18.6%, 35.0% and 42.4%, respectively, compared with B0. It should be noticed that the trend of particle-phase PAH contents is different from the trend of particle-phase PAH concentration and opposite to the trend of total GPM0.056–18

emission. The differences are due to a higher number of par-ticles with diameters between 0.056 and 0.31

m

m. The above results indicate that fuel blends with less than 15% biodiesel would increase PAH content at particle size between 0.056 and 0.31

m

m. Therefore, the blending fraction should be be-tween 15% and 30%. Moreover, it could be visualized that par-ticle-size control should be needed in future emission regulations which would necessitate further improvements in combustion quality. Besides, researches on health effects of biodiesel blends are needed as well.

Acknowledgements

The authors gratefully acknowledge the contributions of Mr. Hsiao-Chung Hou, Department of Environmental

Engineering, National Cheng Kung University and Mr. Jiun-Ming Chen, Graduate Institute of Environment and Ecology, National University of Tainan, for sampling and PAH analysis. References

Akasaka, Y., Suzuki, T., Sakaural, Y., 1997. Exhaust Emissions of a Diesel Engine Fueled with Blends of Biodiesel and Low Sulfur Diesel Fuel. SAE Technical Paper No. 972998. Society of Automotive Engineers, Warrendale, PA.

Allen, J.O., Paschkewitz, J.S., Plummer, E.F., Lafleur, A.L., Sarofim, A.F., Smith, K.A., 1999. Absorption of semi-volatile compounds in oiled impaction substrates: measurement of pyrene absorption. Aerosol Science and Technology 30, 16–29.

Antolin, G., Tinaut, F.V., Briceno, Y., Castano, V., Perez, C., Ramı´rez, A.I., 2002. Optimisation of biodiesel production by sunflower oil transes-terification. Bioresource Technology 83, 111–114.

Beer, T., Grant, T., Williams, D., Watson, H., 2002. Fuel-cycle greenhouse gas emissions from alternative fuels in Australian heavy vehicles. Atmospheric Environment 36, 753–763.

Cardone, M., Prati, M.V., Rocco, V., Seggiani, M., Senature, A., Vitolo, S., 2002. Brassica carinata as an alternative oil crop for the production of biodie-sel in Italy: engine performance and regulated and unregulated exhaust emission. Environmental Science and Technology 36, 4656–4662. Chung, A., Lall, A.A., Paulson, S.E., 2008. Particulate emissions by a small

non-road diesel engine: biodiesel and diesel characterization and mass measurements using the extended idealized aggregates theory. Atmospheric Environment 42, 2129–2140.

Central Coast Vineyard Team, 2005. Update for Winegrape Growers, vol. 4, pp. 1–8.

Correˆa, S.M., Arbilla, G., 2006. Aromatic hydrocarbons emissions in diesel and biodiesel exhaust. Atmospheric Environment 40, 6821–6826. Dorado, M.P., Ballesteros, E., Arnal, J.M., Gomez, J., Lopez, F.J., 2003.

Exhaust emission from a diesel engine with transesterified waste ol-ive oil. Fuel 82, 1311–1315.

Durbin, T.D., Cocker III, D.R., Sawant, A.A., Johnson, K., Miller, J.W., Holden, B.B., Helgeson, N.L., Jack, J.A., 2007. Regulated emissions from biodiesel fuels from on/off-road applications. Atmospheric Envi-ronment 41, 5647–5658.

Durbin, T.D., Collins, J.R., 2000. Effects of biodiesel, biodiesel blends, and a synthetic diesel on emissions from light heavy-duty diesel vehicles. Environmental Science and Technology 34, 349–355.

Durbin, T.D., Norbeck, J.M., 2002. Effects of biodiesel blends and Arco EC-diesel on emissions from light heavy-duty diesel vehicles. Envi-ronmental Science and Technology 36, 1686–1691.

Haas, M.J., Scott, K.M., Alleman, T.L., Mccormick, R.L., 2001. Engine perfor-mance of biodiesel fuel prepared from soybean soapstock: a high quality renewable fuel produced from a waste feedstock. Energy and Fuels 15, 1207–1212.

Health Effects Institute., 2002. Research directions to improve estimates of human exposure and risk from diesel exhaust, Special Report. Kalligeros, S., Zannikos, F., Strournas, S., Lois, E., Anastopoulos, G., Teas, C.

H., Sakellarppoulos, F., 2003. An investigation of using biodiesel/mat-ine diesel blends on the performance of a stationary diesel engbiodiesel/mat-ine. Biomass and Bioenergy 24, 141–149.

Kalam, M.A., Husnawan, M., Masjuki, H.H., 2003. Exhaust emission and combustion evaluation of coconut oil-powered indirect diesel engine. Renewable Energy 28, 2405–2415.

Kalam, M.A., Masjuki, H.H., 2002. Biodiesel from palmoil – an analysis of its properties and potential. Biomass and Bioenergy 23, 471–479. Krahl, J., Baum, K., Uackbarth, U., Jeberien, H.E., Munack, A., Schutt, C.,

Schroder, O., Walter, N., Bunger, J., Muller, M.M., Weigel, A., 2001. Gas-eous compounds, ozone percursors, particle number and particle-size distributions, and mutagenic effects due to biodiesel. American Soci-ety of Agricultural Engineers 44, 179–191.

Krahl, J., Munack, A., Grope, N., Ruschel, Y., Schr}oder, O., B}unger, J., 2007. Biodiesel, rapeseed oil, gas-to-liquid, and a premium diesel fuel in heavy duty diesel engines: endurance, emissions and health effects. Clean 35 (5), 417–426.

Lin, Y.C., Lee, C.F., Fang, T., 2008. Characterization of particle-size distribu-tion from diesel engines fueled with palm-biodiesel blends and paraffinic-fuel blends. Atmospheric Environment 42, 1133–1143. Lin, Y.C., Lee, W.J., Hou, H.C., 2006a. PAH emissions and energy efficiency

of palm-biodiesel blends fueled on diesel generator. Atmospheric En-vironment 40, 3930–3940.

Lin, Y.C., Lee, W.J., Wu, T.S., Wang, C.T., 2006b. Comparison of PAH and reg-ulated harmful matter emissions from biodiesel blends and paraffinic fuel blends on engine accumulated mileage test. Fuel 85, 2516–2523. Table 5

Mean reduction of GPM0.056–18and PAH in the exhaust of the diesel

generator B5 (n ¼ 3) B10 (n ¼ 3) B15 (n ¼ 3) B20 (n ¼ 3) B25 (n ¼ 3) B30 (n ¼ 3) In mg L1 GPM0.056–18 17.2 39.3 22.3 21.2 10.9 7.03 Total PAH 9.66 16.4 20.6 27.9 37.5 41.2 Total BaPeq 12.2 20.9 23.3 30.2 38.9 43.1 In mg kW h1 GPM0.056–18 16.9 38.9 21.6 20.2 8.78 4.37 Total PAH 10.0 16.9 21.3 28.8 38.9 42.8 Total BaPeq 12.5 21.4 24.1 31.1 40.3 44.7

McAughey, J.J., 1997. Regional Lung Deposition and Dose of Ambient Par-ticulate in Humans by Particle Mass and Number. Research Report. AEATechnology, Aerosol Science Centre, Oxfordshire, UK.

Monyem, A., Van Gerpen, J.H., 2001. The effect of biodiesel oxidation on engine performance and emission. Biomass and Bioenergy 20, 317–325.

Nisbet, C., LaGoy, P., 1992. Toxic equivalency factors (TEFs) for polycyclic aromatic hydrocarbons (PAHs). Regulatory Toxicology and Pharma-cology 16, 290–300.

Pope, C.A., Thun, M.J., Namboodriri, M.M., Dockery, D.W., Evans, J.S., Speizer, F.E., Heath, C.W., 1995. Particulate air pollution as a predictor of mortality in a prospective study of U.S. adults. American Journal of Respiratory and Critical Care Medicine 151, 669–674.

Tsolakis, A., 2006. Effects on particle-size distribution from the diesel en-gine operating on RME-biodiesel with EGR. Energy and Fuels 20, 1418–1424.

Turrio-Baldassrri, L., Battistlli, C.L., Conti, C., Crebelli, R., Berardis, B.D., Iamiceli, A.L., Gambino, M., Iannaccone, S., 2004. Emission compari-son of urban bus engine fueled with diesel oil and biodiesel blends. Science of the Total Environment 327, 147–162.

Wang, W.G., Lyons, D.W., Clark, N.N., Gautam, M., 2000. Emissions from nine heavy trucks fueled by diesel and biodiesel blend without engine modification. Environmental Science and Technology 34, 933–939. Wibulswas, P., Chirachakhrit, S., Keochung, U., Tlansuman, J., 1999.

Com-bustion of blends between plant oils and diesel oil. Renewable Energy 16, 1098–1101.