Effects of Variations in Injection Timing on Persistent Organic Pollutant

Transcription

1 1 2 Effects of Variations in Injection Timing on Persistent Organic Pollutant Emissions from a Diesel Engine Yixiu Zhao, Kangping Cui 1*, Jingning Zhu 1, Shida Chen 1, Lin-Chi Wang 2,3,4**, Justus Kavita Mutuku 5***, 1. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei , China 2. Department of Civil Engineering and Geomatics, Cheng Shiu University, Kaohsiung 83347, Taiwan 3. Center for Environmental Toxin and Emerging-Contaminant Research, Cheng Shiu University, Kaohsiung 83347, Taiwan 4. Super Micro Mass Research and Technology Center, Cheng Shiu University, Kaohsiung 83347, Taiwan 5. Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan Abstract The effect of changing the injection timing on emission composition was investigated. The results confirmed that when the injection timing of the diesel engine was changed from -8 to -6, the CO and PM concentrations in the exhaust gas increased, while that of NOx decreased. The concentration of POPs for both gaseous and particulate phases increased significantly except for gaseous phase PCDD/Fs. The ratio of the increase in the mass concentrations of various organic toxic pollutants was between 1.44 and 62.6, while the ratio of increase in the toxicity equivalence was between 2.04 and Unlike other persistent organic pollutants, the total mass concentrations and toxicity equivalences of PCDD/FS decreased when the injection time was changed from -8 to -6, but the decrease in the toxicity equivalent was not proportional to the drop in the total mass. There was a significant rise in the proportion of slightly chlorinated PCDD/FS, indicating the occurrence of de novo regeneration in the flue gas. Therefore, although changing the injection timing from -8 to -6 can reduce NOx emissions, it will also reduce the combustion efficiency, thus leading to an increase in the emission of organic toxic pollutants and hence making the formation of PCDD/Fs more likely to occur. 27 Keywords: Diesel engine; Injection timing; POPs; Emission; Organic toxic pollutants; 28 PCDD/Fs. 1

2 29 30 Corresponding author * Kangping Cui, cuikangping@163.com ** Lin-Chi Wang: lcwang@csu.edu.tw *** Justus Kavita Mutuku, justusmuttuku@gmail.com 2

3 Introduction The diesel internal combustion engine is considered a key source of power for application both in transportation and industry due to its high power output coupled with high fuel efficiency (Alriksson and Denbratt, 2006; Dober et al., 2008). Despite its great advantages, research has shown that emissions from diesel engines cause significant adverse effects on human health. Fine particulate matters discharged at the exhaust can easily bypass the respiratory system and penetrate deep into the alveoli of human lungs (Khaefi et al., 2017; Chen et al., 2018). Consequently, they can be transported to the epithelial stroma and lymph nodes through the circulatory system and finally accumulate in the organs (Kreyling et al., 2012). Exhaust gas from diesel engines contains toxic and carcinogenic persistent organic pollutants (POPs) including poly aromatic hydrocarbons (PAHs), dioxins or polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) (Lee et al., 1995). Several techniques have been proposed to reduce the emissions associated with the combustion process in a diesel engine including enhancing the structure of the engine and the engine operation parameters. However, technological improvements in the diesel powered engine have been occurring for more than one hundred years, and it is unlikely that any other possible advancement can be made on the engine s design (McCormick et al., 2001). Alternative approaches include changing the properties of diesel fuel by reducing the content of sulfur and using other additives such as water containing acetone, alcohols, and dimethyl ether (Chang et al., 2014; Tsai et al., 2017). There has been a great interest on the part of researchers in developing fuels to substitute fossil-based diesel, including the application of blends of biodiesel and diesel 57 (Chang et al., 2014a, b; Rakopoulos et al., 2015; Mwangi et al., 2015b, c). Biodiesel provides a 3

4 58 59 viable fuel option with impressive characteristics due to its ability to reduce pollutants such as CO, HC, PM, and persistent organic pollutants. This is due to significantly higher O 2 content and the resulting occurrence of complete combustion (Lin et al., 2010; Tsai et al., 2017). Some of the drawbacks related to the application of biodiesel as a fuel include high production costs, greater viscosity, and inferior calorific value compared to conventional fossil-based diesel (Saxena and Maurya et al., 2016). The emissions from a cold start at ambient atmospheric temperature is a few orders higher as compared to those associated with a hot start (Alriksson and Denbratt, 2006). The use of an emission control device results in the exhaust being poor under start-up conditions due to the inability of the catalyst to reach the ignition point at ambient atmospheric temperature. Consequently, emissions as a result of a cold start up account for the largest proportion of such emissions during the total emissions cycle (Liu et al., 2017). Most of the research on automobile emissions and the oil industry on efforts to curb emissions of pollutants have been concentrated on the emissions during a cold start of an engine. Effective combustion of a fuel-air mixture by a diesel engine is dependent on the geometry of the engine, characteristics of the fuel, the compression-temperature of the mixture of air and fuel, the method of fuel injection, and the temperature of the outside atmosphere (Chen et al., 2017a; Ansari et al., 2018). The injection of fuel at a lower ambient temperature has a negative effect on fuel atomization, specifically by delaying the heating and vaporization of the fuel droplets. The overall consequence is difficulty in starting the engine. In the absence of a combustion process, most of the fuel injected during the cold start-up period adheres to the cold surface of the combustion chamber and has difficulty evaporating. According to Dardiotis et al., (2013) combustion instability increases with decreases 80 in the ambient temperature. In order to meet the strict emission standards for nitrogen oxides 4

5 81 82 (NOx) post-treatment devices for exhaust gases are necessary, examples of which are NOx traps or application of selective catalytic reduction (SCR) technology. At low ambient temperatures, recycling of exhaust gas in diesel engines is impractical because it will result in condensation of water, which is not desireable (Cordtz et al., 2018). In order to fully understand the emission of toxic halogenated organic pollutants, the method of analysis selected may concurrently determine the content of various pollutants from a single exhaust gas sample, including PAHs, PCDD/Fs, polychlorinated diphenyl ethers (PCDEs), PBDD/Fs, PBDEs, polybrominated biphenyls (PBBs), and PCBs. All the tests carried out for heavy diesel engine emissions with different injection timing have been conducted at a steady state. Studies have been done in order to characterize the toxic organic pollutants emitted by a diesel engine, but none to the author s knowledge have concentrated on the effects of changes in fuel injection timing on emissions. 2. Methods and materials 2.1. Diesel engine and test fuel This experiment was performed using a Hino W06E, which is a heavy-duty diesel engine with a direct fuel injection system. Details of the specifications for the diesel engine are given in Table 1, including the engine configuration, the fuel injection system, the compression ratio, and the injection timing and working boundary conditions. The torque and speed of the engine were monitored using the Schenck W230 engine dynamometer. Four out of the existing thirteen European steady state cycle (ESC) modes were applied when running the diesel engine tests. The various modes and their associated revolutions per minute as well as pressure are as follows: The speeds for the first node, second mode, seventh mode, and eleventh mode were 750, 1650, 1650, 103 and 1950 rpm, respectively, while their respective pressures were: 0, 360, 90, and 96.2 Nm. The 5

6 first mode represents an engine at an idling state; the second mode represents an engine with a 100% load, and the remaining two modes both represent a 25% load (Schweizer and Stein, 2000) A blend of 98% fossil diesel and 2% biodiesel (B2) was used as the test fuel for this investigation Test methods and sampling procedures In order to carry out the tests on the exhaust gases, samples were collected at two different injection timings, the first of which was at -8, and the second one of which was at -6. Before each sampling, the engine was preheated for 30 minutes and for at least 3 minutes between the different test modes. During the entire testing cycle, samples of the exhaust gases from the diesel engine were collected directly at a constant velocity. The system used for sampling consisted of several components, including a filter made of glass-fiber, a flow-meter, a condenser, two stage glass cartridges, and a pump. A fiber glass filter was applied for the collection of particulate phase pollutants. A condenser positioned immediately before the two stage glass cartridges served two purposes, the first of which was to remove moisture from the exhaust gas, and the second of which was to lower the exhaust gas temperature to below 5 C. The toxic pollutants in their gaseous phase were collected through the two stage glass cartridges. Structurally, the cartridges were composed of 5.0 cm (about 20 g) of XAD-2 resin packed inside a tube and held in place by two 2.5 cm polyurethane foam plugs. Pre-concentrations involved the combination of four samples in order to achieve pollutant concentrations that exceeded the detection limit. It took about 20 minutes to collect each ESC mode sample, so the total sampling time was 80 minutes. The final step in the sample collection involved the normalization of the obtained sample to ambient temperature and pressure, which were 273 K and 760 mmhg, respectively Analytical procedures 6

7 To determine the mass of particulate matter in the respective samples, a Precisa XR 205SM- DR balance with a sensitivity of 0.01 mg was applied for weighing the filters. The concentration of NO X in the exhaust gas was determined using a Rosemount Model 951A NO/NO X analyzer (Chang et al., 2014b). The fiberglass filters as well as the two stage glass cartridges were analyzed to determine the concentrations of pollutants they contained. Extraction of the pollutants from the filters and cartridges was performed in a Soxhlet extractor, and the extraction solvent was a 250mL mixture of dichloromethane and n-hexane with a ratio of 1:1 by volume. The extraction time lasted for 24 hours. After being concentrated, the extract was gently purged with pure nitrogen and purified in a column filled with silica gel to obtain a 1 ml concentrate. Gas chromatography/mass spectrometry (GC/MS) was used to evaluate the concentrations of sixteen PAH homologues. Further details on PAH analysis procedures are available in similar investigations done in the past (Chen et al., 2017b; Dat et al., 2018). Following the GC/MS measurement were the analyses for seventeen PCDD/F congeners, twelve PBDD/Fs, fourteen PBDEs, twelve dioxin-like PCBs, six PCDEs, and five PBBs from the solution remaining in the vials. The first step in the analysis was treating the sample solution with concentrated sulfuric acid. The second step involved a number of sample purification and fractionation steps, including the use of an activated carbon column, a multi-layered silica- column, and lastly, an alumina-column. In the alumina-column, non-planar PBBs and PCBs were first eluted using 15 ml of hexane followed by 25 ml DCM/hexane at a ratio of 1:24 by volume. In the activated carbon column, 5 ml of toluene/methanol/ethyl acetate/hexane at a ratio of 1:1:2:16 by volume was applied as the eluent for PCDE, PBDEs, planar PCBBs, and PCBs. 149 Afterwards, 40 ml of toluene was used as the eluent for PBDD/Fs and PCDD/Fs. Prior to the 7

8 instrumental evaluations, the planar and non-planar PBBs/PCBs eluates were mixed to represent the PCB and PBB samples. More details on the procedures for analysis can be found in earlier investigations (Chang et al., 2014; Cheruiyot et al., 2017) Ying et al., 2014) Instrumental analysis The PAH concentration was determined using a GC/MS (Agilent 5890A and Agilent 5975), which had a capillary column (HP Ultra 2, 50 m 0.32 mm 0.17 m). The volume of the test sample injected into the GC/MS was 1 μl. A summary of the conditions during the test are as follows: A splitless injection at 300 C; the temperature of the ion source was 310 C. For 1 minute, the temperature of the furnace was kept at 45 C, and then steadily increased to 100 C over 5 minutes, and subsequently to 320 C at a rate of 8 C per minute and kept at 320 C for a duration of 15 minutes. The concentration of the PAH ions (both primary and secondary) was established through the scan mode for pure PAH standards. The selected ion monitoring mode (SIM) was subsequently applied to identify the individual PAHs. The remaining persistent organic pollutant analyses were performed with a high resolution gas-chromatograph (HRGC) and a high resolution mass-spectrometer (HRMS). The HRGC (Hewlett Packard 6970 Series gas) was fitted with both a split-less injector and a silica capillary- column, while the HRMS (Micromass Autospec Ultima, Manchester, UK) was fitted with a positive-electron impact (EI+) source. A resolution of 10,000 was used in the SIM mode. The temperature and electron energy were specified as 250 C and 35 ev, respectively. Since there should be one injection per analyte, a total of six injections were required for each exhaust sample for the analyses of PCDD/Fs, PBDEs, PCDEs, PBDD/Fs, PBBs, and PCBs. A more comprehensive study on the instrumental analysis is available in past investigations (Wang et al., 2003; Chang et al., 2013; Ying et al., 2014). 8

9 Quality assurance and Quality control (QA/QC) To clear off all the likely organic pollutants, the fiber glass filters were left in an oven at a temperature of 450 C for 8 hours before collection of the samples. Field and laboratory blank controls were incorporated into this study. The average concentrations of the POPs found in both the field and laboratory blank samples are presented in Table 2. The average concentrations of persistent organic pollutants (POPs) in the laboratory and field blank samples were low enough to be ignored since they were mostly below 5% of those in the exhaust samples from the diesel engine with the exception of PBDEs, which were below 2% of those in the exhaust samples. A prior leak detection test was performed for each fuel test between the inlet of the holder for the filter and the outlet of the flow-meter. A break through test using a three stage glass filter element was done for the PAHs. From the analysis, the third stage accounted for only between 0.409% and 4.37% of the 16 individual PAHs from all the three stages. Therefore, it was evident that the two stage glass filter element deployed for this study would ensure 95% trapping efficiency. To check the objectivity of the procedure applied in this investigation and compliance with the recovery criteria for the U.S. EPA Modified Methods 23 (70%-130%) (U.S. EPA, 2001), XAD-2 resin was mixed with PCDD/Fs surrogate standards pre-labeled with isotopes. Evaluations were then made based on the recovery rates for the PCDD/F surrogate standards, which had a range between 90% and 94%, implying that the procedure met the requirements. From the satisfactorily high recovery rates, the occurrence of PCDD/F breakthroughs could thus be ignored. The efficiency of collecting PBDD/Fs using the sampler was checked using the recovery rate of the corresponding PCDD/F replacement standard (Wang et al., 2007; Wang et al., 2008). Corrections for collection efficiency were not done for the other analytes reported in 195 this investigation. 9

10 A 13 C 12 -labeled internal standard was mixed with the sample in order to monitor the recovery during the analysis, as shown in Table 3. B Relevant standards for precision and recovery, surrogate, and internal standards for persistent organic pollutants were all met, as summarized in Table 4. Signal to noise ratios (S/N) of >3 and >10 were used as the limit of detection (LOD) and limit of quantification, respectively (Lin et al., 2017). The persistent organic pollutants that were below the detection limit for PAHs and PBDEs were assumed to have half of the limit of detection while for PBDD/Fs, PCDD/Fs, PCDEs PBBs and PCBs were all assumed to be zero. 3. Results and discussion 3.1. POPs Emissions from a diesel engine with changes in the injection timing Table 5 lists the POPs (PAHs, PCDD/Fs, PBDD/Fs, PBDEs, PBBs, and PCBs) emitted by diesel engines using the B2 fuel for two different injection timings. The toxicity of the POPs was expressed in terms of toxicity equivalent factors (TEFs) (Nisbet et al., 1992; Chang et al., 2014b). For the PBBs and PBDEs, discussions were based on mass concentrations only since TEFs are not yet widely accepted POPS emission for an injection at -8 For an injection timing of -8, which is the default injection timing for the engine, the mass concentrations of pollutants in the gaseous phase were 23.9 μg N -1 m -3 for PAHs, 585 pg N -1 m -3 for PCDD/Fs, 20.4 pg N -1 m -3 for PBDD/Fs, 3.72 μg N -1 m -3 for PBDEs, 1.09 pg N -1 m -3 for PBBs and 5.27 pg N -1 m -3 for PCBs. For the same settings, the mass concentrations of pollutants in the particle phase were μg N -1 m -3 for PAHs, pg N -1 m -3 for PCDD/Fs, pg N - 1 m -3 for PBDD/Fs, ng N -1 m -3 for PBDEs, and pg N -1 m -3 for PCBs. The particle 218 phase for PBBs was below the detection limit (Chao et al., 2014). The total mass concentrations 10

11 of pollutants determined in this study were 24.1 μg N -1 m -3 for PAHs, 586 pg N -1 m -3 for PCDD/Fs, 20.7 pg N -1 m -3 for PBDD/Fs, 3.79 ng N -1 m -3 for PBDEs, 1.09 pg N -1 m -3 for PBBs, and 5.35 pg N -1 m -3 for PCBs. The toxicity equivalence concentrations in the gaseous phase were μg BaP eq N -1 m -3 for PAHs, 3.34 pg I-TEQ N -1 m -3 for PCDD/Fs, pg TEQ N -1 m -3 for PBDD/Fs, and pg WHO-TEQ N -1 m -3 for PCBs. The toxicity equivalence concentrations in the particle phase were μg BaP eq N -1 m -3 for PAHs, pg I-TEQ N -1 m -3 for PCDD/Fs, and pg TEQ N -1 m -3 for PBDD/Fs. The total toxicity equivalence concentrations were μg BaP eq N -1 m -3 for PAHs, 3.37 pg I-TEQ N -1 m -3 for PCDD/Fs, pg TEQ N -1 m -3 for PBDD/Fs, and pg WHO-TEQ N -1 m -3 for PCBs POPS emission for an injection at -6 For an injection timing of -6, the mass concentrations of the pollutants in their gaseous phases were as follows: 34.5 μg N -1 m -3 for PAHs, 30.2 pg N -1 m -3 for PCDD/Fs, 51.8 pg N -1 m -3 for PCBs, 34.1 pg N -1 m -3 for PBDD/Fs, 68.2 pg N -1 m -3 for PBBs, and 26.6 ng N -1 m -3 for PBDEs. The mass concentrations of pollutants in the particle phase were μg N -1 m -3 for PAHs, 1.65 pg N -1 m -3 for PCDD/Fs, 8.72 pg N -1 m -3 for PBDD/Fs, ng N -1 m -3 for PBDEs, and pg N -1 m -3 for PCBs, whereas the PBBs were below the detection limit. The total mass concentrations of the pollutants were 34.8 μg N -1 m -3 for PAHs, 31.8 pg N -1 m -3 for PCDD/Fs, 42.8 pg μg N -1 m -3 for PBDD/Fs, 27.4 μg N -1 m -3 for PBDEs, 52.0 pg N -1 m -3 for PCBs, and 68.2 pg N -1 m -3 for PBBs. The toxicity equivalence concentrations in the gas phase were 1.39 μg BaP eq N -1 m -3 for PAHs, 2.75 pg I-TEQ N -1 m -3 for PCDD/Fs, pg TEQ N -1 m -3 for PBDD/Fs, and pg 241 WHO-TEQ N -1 m -3 for PCBs. The toxicity equivalence concentrations in the particle phase were 11

12 μg BaP eq N -1 m -3 for PAHs, pg I-TEQ N -1 m -3 for PCDD/Fs, and pg TEQ N -1 m -3 for PBDD/Fs, whereas the PCBs were below the detection limit. The total toxicity equivalence concentrations were 1.40 μg BaP eq N -1 m -3 for PAHs, 2.90 pg I-TEQ N -1 m -3 for PCDD/Fs, pg TEQ N -1 m -3 for PBDD/Fs, and pg WHO-TEQ N -1 m -3 for PCBs Influence of injection timing on the emission of pollutants The default injection timing for the heavy diesel engine used in this study was -8, but when the injection timing was changed from -8 to -6, the concentration of CO and PM exhibited an increasing trend, as presented in Table 6. The emission of the two pollutants is an indication of lower combustion temperatures as a result of incomplete combustion and hence a subsequent increase in emissions of organic toxic pollutants is likely to be associated with this change in injection timing. For the two injection timings, that is -8 and -6, the main organic toxic pollutants were in their gas phase (Tsai et al., 2015). Application of an after treatment such as a diesel oxidation catalyst would be a viable solution solve this emission problem; however, this is not possible when the temperatures of the exhaust gas are very low (Dober et al., 2008). When the injection timing was changed from -8 to -6, the gas and solid phases of all pollutants increased with the exception of the PCDD/Fs. The increase in the pollutants in the solid phase was relatively higher than that occurring in the gaseous phase. Incomplete combustion could be the possible cause of the increase in PM concentration. Pollutants were easily adsorbed in particulate matter, so the increase of solid phase pollutants was higher than that of gas phase pollutants. From the results, it can be observed that the change in injection timing from -8 to -6 led to a subsequent increase in the mass concentration of most of the pollutants, where the rate of increase ranged between 1.44 times and 62.6 times. The 264 accompanying increase in the toxicity equivalence ranged between 2.04 and Unlike the 12

13 other pollutants, the total mass and toxicity equivalence for PCDD/Fs decreased when the injection timing was changed from -8 to -6, but the decrease in the toxicity equivalent was much smaller than that of the total mass. Figure 1 shows the PCDD/Fs profile for the two different injection timings of -8 and -6, respectively. The proportion of PCDD/Fs with a low chlorine number increased significantly after the injection timing was changed to -6, which indicated that de novo regeneration existed in the flue gas (Tsai et al., 2018). Therefore, it was speculated that changing the injection angle to -6 would potentially make it easier to produce PCDD/Fs with higher toxicity. Although NOx emissions can be reduced by changing the injection timing from -8 to -6, the combustion efficiency will be reduced, and the emission of organic toxic pollutants will be increased. Although the change in injection timing from -8 to -6 can reduce PCDD/Fs emissions, it will lead to the formation of PCDD/Fs with high toxicity and a low chlorine number, which indicates that this control technology has an overall negative impact on emissions from diesel engines. 4. Conclusions The change in the injection timing from -8 to -6 caused an increase in the concentration of both CO and PM. This is a clear indication of the occurrence of incomplete combustion, which caused the formation of toxic organic pollutants during combustion. Consequently, there was a significant increase in both the gaseous and particulate phases of toxic organic pollutants except for the PCDD/Fs. The gaseous phase contributed a major share of the total organic toxic pollutants as compared to the solid phase. The mass concentration increment for each pollutant ranged between 1.44 and 62.6, and the increasing toxicity equivalence ranged between 2.04 and Overall, the change in fuel injection timing from -8 to -6 had adverse effects in terms of 13

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21 Aerosol Air Qual. Res. 15: Ying, E.M.Y., Wang, L.C., Lin, S.L., Chang-Chien G. P. (2014). Validation and characterization of persistent organic pollutant emissions from stack flue gases Table 1. of an electric arc furnace by using a long-term sampling system (AMESA ). Aerosol Air Qual. Res. 14: Properties of the diesel engine under investigation Item Hino W06E Configuration In-line 6-cylinder Stroke 118 mm Broe Air intake 104 mm Naturally aspirated 21

22 Compression ratio 17.9 Type of fuel injection system Injection type Bosch A type Direct injection 469 Fuel injection pressure kpa Injection timing Displacement Max torque Max power EGR Boundary condition Ambient air temperature Ambient air pressure 15 o Before top dead center 6.0 L rpm rpm No C Ambient air humidity % Table 2. Field and laboratory blank results. Approximate 101 kpa (1 atm) Analytes Field blank Laboratory blank PAHs (μg) PCDD/Fs (pg) PCBs (pg) ND PCDEs (pg) ND PBDD/Fs (pg) ND PBBs (pg) ND ND ND ND ND ND ND PBDEs (pg)

23 Table 3. The internal standards applied for this study Analytes PAHs PCDD/Fs PCBs PCDEs PBDD/Fs PBBs PBDEs Homologue d 8 -Nap, d 10 -Acp, d 10 -PA, d 12 -CHR, and d 12 -PER 13 C 12-2,3,7,8-TeCDD, HxCDD, 13 C 12-2,3,7,8-TeCDF, 13 C 12-1,2,3,7,8-PeCDD, 13 C 12-1,2,3,7,8-PeCDF, 13 C 12-1,2,3,6,7,8-13 C 12-1,2,3,6,7,8-HxCDF, 13 C 12-1,2,3,4,6,7,8-HpCDD, 13 C 12 -OCDD, 13 C 12-1,2,3,4,6,7,8-HpCDF 13 C 12 -PCB-77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, and C 12 -CDE-37, 86, 141, and C 12-2,3,7,8-TeBDF, 13 C 12-1,2,3,7,8-PeBDF, 13 C 12-2,3,4,7,8-PeBDF, 13 C 12-1,2,3,4,7,8-HxBDF, 13 C 12-1,2,3,4,6,7,8-HpBDF, 13 C 12 -OctBDF, 13 C 12-2,3,7,8-TeBDD, HxBDD, 13 C 12 -OctBDD 13 C 12-1,2,3,7,8-PeBDD, 13 C 12-1,2,3,7,8,9-HxBDD, 13 C 12 -PBB-52, 153, 194, and C 12 -BDE-28, 47, 99, 154, 153,183, 197, 207, C 12-1,2,3,4,6,7,8-13 C 12-1,2,3,4,6,7,8-HpBDD, 23

24 473 Table 4. The recovery of standards and the respective criteria Standard Analytes Homologue Recovery Criteria PAHs All % % PAR Surrogate Standards Internal PCDD/Fs All % % PCBs All % % CDE % % PCDEs PBDD/Fs PBBs CDE % % CDE-99, CDE-141, CDE % % CDE % % tetra through hepta % % Octa % Di % % tetra through octa % % PBDEs All % % PCDD/Fs PAHs 37 Cl 4-2,3,7,8-TeCDD, 13 C 12-2,3,4,7,8- PeCDF, 13 C 12-1,2,3,4,7,8-HxCDD, % % 13 C 12-1,2,3,4,7,8-HxCDF, 13 C 12-1,2,3,4,7,8,9-HpCDF Standards PCDD/Fs ( 13 C 12 - d 8 -Nap, d 10 -Acp, d 10 -PA, d 12 -CHR, and % % d 12 -PER tetra through hexa % % hepta and octa % % labeled) PCBs All % % PBDD/Fs tetra through hepta % % 24

25 474 Recovery standard PBDEs Octa % % BDE-28, 47, 99, 154, 153,183, 197, % % 207, 209 PCDD/Fs 13 C 12-1,2,3,7,8,9-HxCDF % % 25

26 Table 5. Concentration of toxic organic pollutants in the exhaust gas Gas phase Particle phase Total Gas-Particle phase concentration -6 o /-8 o -8 o -6 o -8 o -6 o -8 o -6 o Ratio Ratio Ratio PAHs PCDD/Fs PCBs PBDD/Fs mass (μg/nm 3 ) total BaPeq (μg/nm 3 ) mass (pg/nm 3 ) I-TEQ (pg I-TEQ/Nm 3 ) mass (pg/nm 3 ) WHO-TEQ (pg WHO- TEQ/Nm 3 ) N.D. N.D mass (pg/nm 3 ) TEQ (pg I-TEQ/Nm 3 ) PBBs mass (pg/nm 3 ) N.D. N.D

27 PBDEs mass (ng/nm 3 )

28 1 2 Table 6. Injection Timing Emission factors for CO, PM 2.5, and NO X from the diesel engine CO (g/kwh) PM 2.5 (g/kwh) NO X (g/kwh) -6 deg deg

29 3 4 Fig. 1. Three- PCDD/Fs congener profile with injection timings of -8 and -6 29