Emission Factors Of Organic Carbon Research Articles

Effect of isothermal dilution on emission factors of organic carbon and n-alkanes in the particle and gas phases of diesel exhaust

To investigate the effect of isothermal dilution (30 °C) on emission factors (EFs) of semivolatile and nonvolatile compounds of heavy-duty diesel exhaust, we measured EFs for particulate matter (PM), organic carbon (OC), and elemental carbon (EC) in the particle phase, and EFs for n-alkanes in both the particle phase and the gas phase of exhaust produced under high-idle engine operating conditions at dilution ratios (DRs) ranging from 8 to 1027. The EC EFs did not vary with DR, whereas the OC EFs in the particle phase determined at DR = 1027 were 13% of the EFs determined at DR = 8, owing to evaporation of organic compounds. Using partitioning theory and n-alkane EFs measured at DR = 14 and 238, we calculated the distributions of compounds between the particle and gas phases at DR = 1760, which corresponds to the DR for tailpipe emissions as they move from the tailpipe to the roadside atmosphere. The gas-phase EF of a compound with a vapor pressure of 10−7 Pa was 0.01 μg kg−1-fuel at DR = 14, and this value is 1/330 the value derived at DR = 1760. Our results suggest that the EFs of high-volatility compounds in the particle phase will be overestimated and that the EFs of low-volatility compounds in the gas phase will be underestimated if the estimates are derived from data obtained at the low DRs and they are applied to the real world. Therefore, extrapolation from EFs derived at low DR values to EFs at atmospherically relevant DRs will be a source of error in predictions of the concentrations of particulate matter and gas-phase precursors to secondary organic aerosols in air quality models.

Emissions of volatile organic compounds and carbonyl compounds from residential coal combustion in China

Emissions of volatile organic compounds (VOCs) and carbonyls from residential coal combustion of five coals with different maturities were studied in a simulated room. The coals were burned in form of honeycomb briquettes in a domestic coal stove, one of the most common fuel/stove combinations in China. Through a dilution system, VOCs and carbonyls samples were collected by canisters and silica-gel cartridges and analyzed by gas chromatography and mass spectrum (GC/MS) and high performance liquid chromatography/ultraviolet (HPLC/UV), respectively. The results show that the bituminous coals with medium volatile matter content produce the highest emissions while the anthracite yields the lowest. Among the identified carbonyls from the coal smoke, the aromatic compounds (benzaldehyde, 2, 5-dimethylbenzaldehyde and p-tolualdehyde, m/o-tolualdehyde, benzene, m, p-xylene and trimethyl-benzene) were relatively abundant, which might be due to the molecular structure of the coal. For formaldehyde, aromatic carbonyls and aliphatic alkanes, their concentrations increase up to the maximum values and then decrease with increasing coal maturity. The total carbonyls and VOCs have the same tendency, which was observed for the emission factors of organic carbon (OC), elemental carbon (EC), particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) detected in the series study.

Measurements of Black and Organic Carbon Emission Factors for Household Coal Combustion in China: Implication for Emission Reduction

Household coal combustion is considered as the greatest emission source for black carbon (BC) and an important source for organic carbon (OC) in China. However, measurements on BC and OC emission factors (EF(BC) and EF(OC)) are still scarce, which result in large uncertainties in emission estimates. In this study, a detailed data set of EF(BC) and EF(OC) for household coal burning was presented on the basis of 38 coal/stove combination experiments. These experiments included 13 coals with a wide coverage of geological maturity which were tested in honeycomb-coal-briquette and raw-coal-chunk forms in three typical coal stoves. Averaged values of EF(BC) are 0.004 and 0.007 g/kg for anthracite in briquette and chunk forms and 0.09 and 3.05 g/kg for bituminous coal, respectively; EF(OC) are 0.06 and 0.10 g/kg for anthracite and 3.74 and 5.50 g/kg for bituminous coal in both forms, respectively. Coal maturity was found to be the most important influencing factor relative to coal's burning forms and the stove's burning efficiency, and when medium-volatile bituminous coals (MVB) are excluded from use, averaged EF(BC) and EF(OC) for bituminous coal decrease by 50% and 30%, respectively. According to these EFs, China's BC and OC emissions from the household sector in 2000 were 94 and 244 gigagrams (Gg), respectively. Compared with previous BC emission estimates for this sector (e.g., 465 Gg by Ohara et al., Atmos. Chem. Phys. 2007, 7, 4419-4444), a dramatic decrease was observed and was mainly attributed to the update of EFs. As suggested by this study, if MVB is prohibited as household fuel together with further promotion of briquettes, BC and OC emissions in this sector will be reduced by 80% and 34%, respectively, and then carbonaceous emissions can be controlled to a large extent in China.

Emission factors of PM species based on freeway measurements and comparison with tunnel and dynamometer studies

Emission factors of various particle species from light- and heavy-duty vehicles (LDVs and HDVs, respectively), including organic and elemental carbon (OC and EC), sulfate, polycyclic aromatic hydrocarbons (PAHs), hopanes, steranes, trace metals, elements, and particle number (PN), were estimated based on roadway measurements. Sampling campaigns were conducted at two different roadways: the CA-110 highway (where only gasoline-powered vehicles are allowed), and the I-710 freeway (where about 20% of the total number of vehicles are diesel-powered trucks). The particulate matter (PM) emission factors determined in these roadways were compared to those reconstructed from recent source emission data from the Caldecott tunnel [Phuleria, H.C., Geller, M.D., Fine, P.M., Sioutas, C., 2006. Size-resolved emissions of organic tracers from light- and heavy-duty vehicles measured in a California roadway tunnel. Environmental Science and Technology 40 (13), 4109–4118], and those from previous tunnel and chassis dynamometer studies. Very good agreement between estimated and reconstructed emission factors was found for PN, EC, sulfate, high-molecular-weight (MW) PAHs, hopanes and steranes. This suggests that PM-speciated chemical data collected at roadsides can be used to calculate reliable emission factors for several important particle species at other locations characterized by a similar mix of on-road motor vehicles. The agreement between our results and other studies in the emission factors of trace elements and metals varied from very good (for species such as Cu, Mo, Ba, Pb) to poor (for species such as Mg, Fe, Ca), probably because the atmospheric concentrations of the latter elements are associated with both traffic and non-traffic sources, and the relative abundances of Mg, Ca, and Fe in road dust varies considerably across locations. The emission factors of OC and EC were clearly the highest for HDVs, and those of PAHs, hopanes, and steranes from our roadway measurements were well within the range of values reported in the literature from tunnel and dynamometer studies. The approach presented in this paper allows for a straight-forward estimation of PM emission factors from ambient, near-freeway measurements. Although the uncertainties inherent in the method proposed here must be acknowledged (e.g. assumptions were made to estimate the average fleet composition and the total carbon content in the vehicles’ exhaust), our results are generally in very good agreement with those in the available literature for most non-labile PM species.

Fine particle emission factors from vehicles in a highway tunnel: Effects of fleet composition and season

In-use, fuel-based motor vehicle emission factors were determined using measurements made in a highway tunnel in Pittsburgh, Pennsylvania. Concentrations of PM 2.5 mass, CO, CO 2, and NO x were measured continuously. Filter-based measurements included PM 2.5 mass, organic and elemental carbon (OC and EC), inorganic ions and metals. Fuel-based emission factors for each pollutant were calculated using a fuel-carbon balance. The weekday traffic volume and fleet composition varied in a consistent diurnal pattern with the estimated fraction of fuel consumed by heavy-duty diesel vehicle (HDDV) traffic ranging from 11% to 36%. The emission rate of most species showed a significant dependence on sample period. NO x , PM 2.5, EC and OC emission factors were significantly larger during the early morning, truck-dominated period. Emissions of particulate metals associated with brake wear (Cu, Sb, Ba and potentially Ga) were emitted at higher rates during the rush-hour period, which is characterized by slower, stop-and-go traffic. Emission rates of crustal elements (Fe, Ca, Mg, Li), Zn and Mn were highest during the early-morning period when there was more heavy-truck traffic. A seasonal shift in average OC/EC ratio for the rush-hour period was observed; fall and summer OC/EC ratios are 1.0±0.6 and 0.26±0.06, respectively. Potential causes for this shift are increased partitioning of semi-volatile organic compounds into the gas phase during the summer months and/or effects of seasonal changes in fuel formulation. Emission factors for HDDV and light-duty vehicles (LDV) classes were estimated using a linear regression of emission factor as a function of fleet composition. The extrapolated emission factors generally agree with previously published measurements, though a substantial range in published values is noted.