Diesel emissions

Figure 7.1. Diesel emissions standards from EuroII to EuroV on a four-axis space corresponding to the pollutants soot particles, HC, NO and CO.

Nitro polycyclic aromatic hydrocarbons are environmental contaminants which have been detected in airborne particulates, coal fly ash, diesel emission and carbon black photocopier toners. These compounds are metabolized Tn vitro to genotoxic agents through ring oxidation and/or nitroreduction. The details of these metabolic pathways are considered using 4-nitrobiphenyl, 1- and 2-nitronaphthalene, 5-nitro-acenaphthene, 7-nitrobenz[a]anthracene, 6-nitro-chrysene, 1-nitropyrene, 1,3-, 1,6- and 1,8-dinitro-pyrene, and 1-, 3- and 6-nitrobenzo[a] pyrene as examples ... 

A wide variety of nitro PAHs have been isolated from different environmental sources including airborne particulates (27-34), coal fly ash (35-37), diesel emission particulates (38-41) and carbon black photocopier toners (42-43). Their presence has also been suggested in the smoke from nitrate-fortified cigarettes (44). The structures of the most commonly detected nitro PAHs are shown in Figure 1 and in each instance it is the kinetically-favored isomer that is found. 

Several methods have been developed to estimate the exposure to such emissions. Most methods are based on either ambient air quality surveys or emission modeling. Exposure to other components of diesel emissions, such as PAHs, is also higher in occupational settings than it is in ambient environments. The principles of the techniques most often used in exhaust gas analysis include infrared (NDIR and FTIR), chemiluminescence, flame ionization detector (FID and fast FID), and paramagnetic methods. 

Diesel emissions contain low concentrations of carbon monoxide and hydrocarbons. The major problem with diesel emissions are nitric oxides and particles as these are the most difficnlt to rednce. 

Gallagher J, George M, Kohan M, et al. 1993. Detection and comparison of DNA adducts after in vitro and in vivo diesel emission exposures. Environmental Health Perspectives 99 225-228. 

Alternatively (or initially) the mixture is treated as a whole and tested in its crude state. The advantage of this strategy includes the relevancy of the tested sample to its environmental counterpart, decreased potential for artefact formation, and inclusion of combined effects of chemicals in the mixture. Moreover if the mixture is representative of others in its class (e.g., diesel emissions from different sources would share certain characteristics), it may be possible to extrapolate results across samples. This method also circumvents the labor-intensive process of individual testing of multiple chemicals. But sometimes a complex mixture is too cytotoxic to be tested directly in a bioassay. Furthermore, it may be incompatible with the test system because of the physical matrix. Other disadvantages include the inability to specify the constituent of the mixture responsible for the toxicity, as well as potential masking effects (e.g., the masking of mutagenicity by cytotoxicity). 

As an example of typical experimental data, Fig. 10.32 is a GC-MS selected ion monitoring (SIM) profile (m/z 247) for the nitrofluoranthenes and nitropy-renes in an extract of ambient particles collected in southern California (Arey et al., 1988b). The 1-nitropyrene (1-NP) and 3-nitrofluoranthene (3-NF) presumably are from diesel emissions (Tables 10.33 and 10.34), but the dominance of 2-nitrofluoranthene and 2-nitropyrene reflects a second major source. 

Rosenkranz, H. S., Mutagenic Nitroarenes, Diesel Emissions, Particulate-Induced Mutations and Cancer An Essay on Cancer-Causation by a Moving Target, Mutat. Res., 367, 65-72 (1996). 

Tokiwa, H., T. Otofuji, R. Nakagawa, K. Horikawa, T. Maeda, N. Sano, I. Izumi, and H. Otsuka, Dinitro Derivatives of Pyrene and Fluoranthene in Diesel Emission Particulates and Their Tumorigenicity in Mice and Rats, in Carcinogenic and Mutagenic Effects of Diesel Engine Exhaust (N. Ishinishi, A. Koizumi, R. O. McClellan, and W. Stober, Eds.), pp. 253-270, Elsevier, Amsterdam/New York, 1986. 

For a description of some of the issues involved in motor vehicle emissions control, see Calvert et al. (1993), for those involving diesel emissions, see Walsh (1995), and for motorcycle emisions compared to passenger cars, see Chan et al. (1995). 

Absorption by particles, for example acetylene smoke (Roessler and Faxvog, 1979a) and diesel emissions (Faxvog and Roessler, 1979), has been measured by the photoacoustic method. 

Gas Chromatography-Mass Spectrometric Characterization of Polynuclear Aromatic Hydrocarbons in Particulate Diesel Emissions... 

Diesel emission particulates, mostly of respirable size, are assuming increased importance as a source of atmospheric particulate pollutants. They may also present significant hazard in certain working environments such as bus garages and mines. 

GC-M3) is described for characterization of particulate-bound PAHs in diesel emissions. The term PAH will refer to the parent and alkyl-substituted PAHs. The analytical methodology may also be adaptable to other types of sample matrices. 

CHOUDHURY Scan and bush PA Hs in Diesel Emissions 1 I (cont.) Compound... 

In a later phase of work, the formic acid concentration in mine air subject to diesel emissions was measured. The expected concentrations were about one hundred times lower than those found in engine exhaust. The efficiency of the collection scheme was again measured under these conditions of challenge concentration (0.06 mg/m3). The collection efficiency was found to be 92.2% at this level (Table IV). 

Two ion chromatographic techniques were utilized to quantify formic acid in both diesel engine exhaust and mine air subjected to diesel emissions. A commonly used anion separation system utilizing a weak borate eluent adequately separated the acids of interest in diesel exhaust. It was, however, affected by the presence of strong acids during subsequent consecutive analyses. 

In order to preclude this problem and the necessary frequent regeneration of the anion system s suppressor column, an ion chromatography exclusion scheme was utilized. Samples collected in a mine environment were reliably concentrated by freeze-drying and then analyzed on an ICE system with dilute hydrochloric acid eluent. The precision of the ICE method was experimentally determined to be 2.5% in a concentration range of 1 to 10 yg/mL. The accuracy was not independently determined but good precision and recovery yield confidence that measured values are within 5% of the true value. No interferences were observed in the ICE system due to strong acids, carbonic acid or other water soluble species present in mine air subject to diesel emissions. 

Lawter, J. R. Kendall, D. A. "Effects of Diesel Emissions on Coal Mine Air Quality" Final Report, U.S. Bureau of Mines Contract J0166009, 1977. 

Johnson, T. V. Diesel emission control technology-2003 in review. SAE Technical Paper No. 2004-01-0070 (2004). 

---