Characterizations of Size-segregated Ultrafine Particles in Diesel Exhaust

Abstract

Size-segregated ultrafine particles (UFPs) in diesel exhaust were investigated to characterize carbonaceous substances, metals, and organic compounds originating from a medium-duty diesel engine dynamometer using the 13 driving mode. Organic carbon (OC) and elemental carbon (EC) peaked at 330-550 nm, but the OC/EC ratio showed two peaks in the ultrafine and accumulation modes. The distribution trend of metal elements was opposite to that of the size-segregated OC/EC ratio. The amounts of toxic Pb, As, and Cd were less than 0.03-2.5% in diesel exhaust particles (DEPs), but their cumulative fractions in the ultrafine mode exceeded 50%. Most organic compounds (76.6%) and alkanes (67.0%) were emitted in the accumulation mode (170-1000 nm). More than 70% of the identified polycyclic aromatic hydrocarbons (PAHs) were emitted in the accumulation mode (94-1000 nm), with phenanthrene being the most abundant. Two significant size ranges of toxicity equivalent quantity peaks in the ultrafine (34-66 nm) and accumulation (170-330 nm) modes were observed for the size-segregated DEPs. Contrary to the trends for PAHs and organic compounds, the identifiable nitrogen-containing polycyclic aromatic compounds were more abundant in the ultrafine mode. Overall toxicity was high as UFPs can be deposited with high efficiency throughout the human respiratory tract.

Emission Characteristics of Hazardous Air Pollutants from Medium-Duty Diesel Trucks Based on Driving Cycles

“…The toxicity equivalent factor (TEF) method is commonly used and is reliable for the evaluation of carcinogenicity of the identified PAHs. [14,15,18,38,39]. Since Nisbet and LaGoy (1992) put forward the concept of TEF based on the toxicity of PAHs (Table 9), benzo(a)pyrene is usually used as a reference compound to derive the TEQ of PAHs [14,15,18,38,39].…”

“…Many studies [13][14][15][16][17] have explored the characterization of PAHs in particles from diesel vehicles. A recent study reported that the PAH concentration in terms of toxic equivalency quantity (TEQ) associated with benzene ring number demonstrated two peak concentrations with respect to smaller ultrafine (> 66 nm) and quasiaccumulation (170-330 nm) size ranges [18]. Therefore, various domestic and overseas studies have been conducted on the toxicity, generation mechanisms, and occurrence paths of HAPs.…”

Emission Characteristics of Hazardous Air Pollutants from Medium-Duty Diesel Trucks Based on Driving Cycles

“…The toxicity equivalent factor (TEF) method is commonly used and is reliable for the evaluation of carcinogenicity of the identified PAHs. [14,15,18,40,41]. Since Nisbet and LaGoy (1992) put forward the concept of TEF based on the toxicity of PAHs (Table 9), benzo(a)pyrene is usually used as a reference compound to derive the TEQ of PAHs [14,15,18,40,41].…”

“…[14,15,18,40,41]. Since Nisbet and LaGoy (1992) put forward the concept of TEF based on the toxicity of PAHs (Table 9), benzo(a)pyrene is usually used as a reference compound to derive the TEQ of PAHs [14,15,18,40,41]. triplicate measurements with a standard deviation of (a) 0-0.32 µg/km for NEDC, 0.32-2.10 µg/km for NIER-9 (cold), 0-0.37 µg/km for WLTC, and 0-0.46 µg/km for NEDC; (b) 0-0.33 µg/km for WLTC, 0-0.24 µg/km for CVS-75, 0-2.99 µg/km for NIER-9 (cold); and 0-0.84 µg/km for NIER-9 (hot).…”

“…Many studies [13][14][15][16][17] have explored the characterization of PAHs in particles from diesel vehicles. A recent study reported that the PAH concentration in terms of the toxic equivalency quantity (TEQ) associated with the benzene ring number demonstrated two peak concentrations with respect to smaller ultrafine (>66 nm) and quasiaccumulation (170-330 nm) size ranges [18]. Therefore, various domestic and overseas studies have been conducted on the toxicity, generation mechanisms, and occurrence paths of HAPs.…”