EC Fractions Research Articles

Downwind O3 and PM2.5 speciation during the wildfires in 2002 and 2010

A series of wildfires in northern Quebec, early July 2002, and in southern Quebec, late May 2010, resulted in severe air pollution downwind. Downwind exposures were investigated to estimate the impact on outdoor and indoor environments. The plumes derived from the wildfires resulted in an increase of over 10 ppbv ozone (O3) concentrations in both major cities and rural areas, while O3 enhancement was not observed at locations adjacent to wildfire burning areas. Temporal trend in PM2.5 concentration showed a peak of 105.5 μg/m3 on July 7, 2002, while on May 31, 2010 the peak was 151.1 μg/m3 in Boston downwind. PM2.5 speciation showed similar trends between the episodes, along with spikes in the PM2.5/PM10 ratio, and in the concentrations of Black Carbon, ΔC (i.e., UV absorbing compounds minus Black Carbon), Organic Carbon (OC), potassium, and chlorine. OC was the most dominant constituent of the PM2.5 mass in the wildfires. The dominant specific carbon fractions include OC fraction 3, pyrolysis carbon, and EC fraction 1, likely due to pyrolysis of structural components of wood. Indoor PM2.5 peaks at two houses corresponded well with the ambient PM2.5 peak, along with the elemental composition, which could indicate an impact of wildfires on indoor air pollution exposure.

Carbonaceous Aerosols Emitted from Light-Duty Vehicles Operating on Gasoline and Ethanol Fuel Blends

This study examines the chemical properties of carbonaceous aerosols emitted from three light-duty gasoline vehicles (LDVs) operating on gasoline (e0) and ethanol-gasoline fuel blends (e10 and e85). Vehicle road load simulations were performed on a chassis dynamometer using the three-phase LA-92 unified driving cycle (UDC). Effects of LDV operating conditions and ambient temperature (-7 and 24 °C) on particle-phase semivolatile organic compounds (SVOCs) and organic and elemental carbon (OC and EC) emissions were investigated. SVOC concentrations and OC and EC fractions were determined with thermal extraction-gas chromatography-mass spectrometry (TE-GC-MS) and thermal-optical analysis (TOA), respectively. LDV aerosol emissions were predominantly carbonaceous, and EC/PM (w/w) decreased linearly with increasing fuel ethanol content. TE-GC-MS analysis accounted for up to 4% of the fine particle (PM2.5) mass, showing the UDC phase-integrated sum of identified SVOC emissions ranging from 0.703 μg km(-1) to 18.8 μg km(-1). Generally, higher SVOC emissions were associated with low temperature (-7 °C) and engine ignition; mixed regression models suggest these emissions rate differences are significant. Use of e85 significantly reduced the emissions of lower molecular weight PAH. However, a reduction in higher molecular weight PAH entities in PM was not observed. Individual SVOC emissions from the Tier 2 LDVs and fuel technologies tested are substantially lower and distributed differently than those values populating the United States emissions inventories currently. Hence, this study is likely to influence future apportionment, climate, and air quality model predictions that rely on source combustion measurements of SVOCs in PM.

Low-wind and other microclimatic factors in near-road black carbon variability: A case study and assessment implications

Airborne black carbon from urban traffic is a climate forcing agent and has been associated with health risks to near-road populations. In this paper, we describe a case study of black carbon concentration and compositional variability at and near a traffic-laden multi-lane highway in Cincinnati, Ohio, using an onsite aethalometer and filter-based NIOSH Method 5040 measurements; the former measured 1-min average black carbon concentrations and the latter determined the levels of organic and elemental carbon (OC and EC) averaged over an approximately 2-h time interval. The results show significant wind and temperature effects on black carbon concentration and composition in a way more complex than predicted by Gaussian dispersion models.Under oblique low winds, namely ux[=u×sin(θ)]∼ (0, −0.5 m s−1), which mostly occurred during morning hours, black carbon concentrations per unit traffic flow were highest and had large variation. The variability did not always follow Gaussian dispersion but was characteristic of a uniform distribution at a near-road distance. Under all other wind conditions, the near-road black carbon variation met Gaussian dispersion characteristics. Significant differences in roadside dispersion are observed between OC and EC fractions, between PM2.5 and PM10–2.5, and between the morning period and rest of the day. In a general case, the overall black carbon variability at the multi-lane highway can be stated as bimodal consisting of Gaussian dispersion and non-Gaussian uniform distribution. Transition between the two types depends on wind velocity and wind angle to the traffic flow. In the order of decreasing importance, the microclimatic controlling factors over the black carbon variability are: 1) wind velocity and the angle with traffic; 2) diurnal temperature variations due to thermal buoyancy; and 3) downwind Gaussian dispersion. Combinations of these factors may have created various traffic–microclimate interactions that have significant impact on near-road black carbon transport.

Comparison and implications of PM2.5 carbon fractions in different environments

The concentrations of PM2.5 carbon fractions in rural, urban, tunnel and remote environments were measured using the IMPROVE thermal optical reflectance (TOR) method. The highest OC1 and EC1 concentrations were found for tunnel samples, while the highest OC2, OC3, and OC4 concentrations were observed for urban winter samples, respectively. The lowest levels of most carbon fractions were found for remote samples. The percentage contributions of carbon fractions to total carbon (TC) were characterized by one peak (at rural and remote sites) and two peaks (at urban and tunnel sites) with different carbon fractions, respectively. The abundance of char in tunnel and urban environments was observed, which might partly be due to traffic-related tire-wear. Various percentages of optically scattering OC and absorbing EC fractions to TC were found in the four different environments. In addition, the contribution of heating carbon fractions (char and soot) indicated various warming effects per unit mass of TC. The ratios of OC/EC and char/soot at the sites were shown to be source indicators. The investigation of carbon fractions at different sites may provide some information for improving model parameters in estimating their radiative effects.

Assessment of carbon fractions of aerosols collected under gravity settling at two different heights in the Delhi region

To understand height, location and season-specific variability in the composition and amount of different carbon fractions present in aerosols, samples were collected under gravity settling at two different heights (5feet and 30feet) from ground at nine different locations in the Delhi region, over the time span of 1year. Sample collection height, not only determined the mass of different carbon fractions present but also their distribution (TC:OC:EC). Carbon forms estimated in aerosol samples carry signatures of location-specific characteristic of activity, particularly when the samples are collected close to ground. The EC fractions in aerosol samples collected at 30feet height suggested no location-specificity whereas the OC fractions detected in the aerosol samples manifested variability with location, change of season, and the height at which the samples were collected. The analysis of the estimated OC/EC ratios suggested that the some fraction of OC may have arisen from the process of secondary organic carbon (SOC) formation in the atmosphere. Fractal dimensions of carbonaceous aggregates present in aerosols were also determined for different seasons, during summer and winter months it varies from 1.5 to 2.0±0.05. The average diameters of the primary particles were also measured, constituting the aggregates, ranged between 24 and 57nm.

Source Apportionment of Carbonaceous Particulate Matter in a Shanghai Suburb Based on Carbon Isotope Composition

In this article, a new approach was established to estimate the fractional contributions of soil dust, biomass burning, biogenic emissions, coal burning, and vehicle exhaust to the carbonaceous particulate matter by carbon isotope and linear regression techniques of OC-K+ (organic carbon) and OC-EC (elemental carbon). Using the method described herein, the fractional distributions of these sources were quantitatively determined for the OC and semiquantitatively for the EC in the size-resolved particles (size ranges: 7.2 μm) collected in Jiading District, a suburb of Shanghai, China. Distinct size distribution of contributions of these sources to the OC and EC was observed. Generally, biomass burning contributed a large fraction to OC in the smaller particles and biogenic emissions shared a bigger fraction to OC in the larger particles. Soil dust made contributions solely to the OC, for no EC fraction was found in the soil dust. OC from coal burning concen...

Positive sampling artifacts of organic carbon fractions for fine particles and nanoparticles in a tunnel environment

The positive artifacts in particulate organic carbon fractions for fine particles (PM2.5) and nanoparticles (PM0.1) were characterized in a tunnel environment by using the QBQ (a quartz filter behind a quartz filter) method. The OC concentrations of the backup quartz filters ranged from 3.56 to 11.38μgm−3 with the average of 6.70μgm−3 for PM2.5, and from 2.62 to 7.27μgm−3 with the average of 4.64μgm−3 for PM0.1. The most abundant species on the backup quartz filters was OC1 for both PM2.5 and PM0.1, accounting for 56.9% and 41.1% of the measured organic carbon, respectively. Most of EC fractions (EC1–EC3) on the backup filters for PM2.5 and PM0.1 were below the minimum detection limit. Therefore, only OC contributed to positive artifacts distinctly with the average percentage of 21.7% and 48.0% for PM2.5 and PM0.1, respectively. The artifacts for four organic carbon fractions ranged from 36.1% (OC1) to 4.4% (OC4) for PM2.5 and from 68.0% (OC1) to 31.9% (OC4) for PM0.1. The uncorrected OC/EC ratios on the front quartz filters were higher by as much as 30% and 107% for PM2.5 and PM0.1 than those corrected for positive organic artifacts, respectively. That is, much higher percentage of positive artifacts was found for PM0.1 OC fractions on the front filters. The comparison of the present and previous studies shows that OC positive artifacts vary widely among various PM fractions and sampling sites attributing to many factors that are worth investigating in the future.

남천(Nandina domestica) 열매 분획 추출물의 항산화 효과

This study was carried out to compare the antioxidative effects of various Nandina domestica fruits extracts. Organic fractions, including n-hexane, chloroform, ethyl acetate, and butanol fractions, were obtained from the water and ethanol extracts of N. domestica fruits. The phenolic compound content of the EE fraction was 922.22 mg/g. The flavonoid compound content was highest in the EB fraction (282.49 mg/g). The electron-donating ability was highest (93%) in the WA and EH fractions at 0.1 mg/mL. The SOD-like activity was showed the highest in the EA fraction (56.36%), and EH and EC both showed higher than 50% activity. The nitrite-scavenging ability of the EC fraction at 1.0 mg/mL under pH 1.2 conditions was 82.03%. The xanthine oxidase inhibitory activities of all the fractions, except WE, were higher than 90% at 0.5 mg/mL. The effect of tyrosinase inhibition was highest in the WE fraction (46.75%). These results show that the N. domestica fruits fractions contained high levels of polyphenol and flavonoid compounds, along with excellent antioxidative effects. This suggests that N. domestica fruits can be used as a functional material.

Stable carbon isotopes in aerosols from Chinese cities: Influence of fossil fuels

Stable carbon isotope ratios were determined for the OC and EC fractions of PM 2.5 collected from 14 Chinese cities in January and June/July of 2003. The period-averaged isotope values ( δ 13 C) varied from −26.90‰ to −23.08‰ for OC and −26.63‰ to −23.27‰ for EC. A strong correlation ( R 2 = 0.70, p < 0.0001) between δ 13 C OC and δ 13 C EC was found in winter but not summer. Winter vs. summer differences for δ 13 C OC and δ 13 C EC were greater for the seven northern cities (∼1 to 3‰) than the seven southern cities (<1‰). Comparisons with isotopic signatures of putative sources suggest that the carbonaceous PM 2.5 was mainly from fossil fuels, especially coal combustion and motor vehicle emissions; the northern cities in particular were strongly impacted by coal combustion during winter. Studies of stable carbon isotopes in OC and EC are potentially useful for identifying sources for carbonaceous PM 2.5 , and this approach may be a useful new tool for the study of air pollution. ► Stable carbon isotope ratios were determined for OC and EC in PM 2.5 from Chinese cities. ► The isotopic signatures indicate that coal combustion and motor vehicle exhaust were the major sources for the carbonaceous aerosols. ► Stable carbon isotopes can be useful for distinguishing among major sources for carbonaceous PM 2.5 .

Preferential degradation of aromatic hydrocarbons in kerosene by a microbial consortium

Numerous studies on the biodegradation of petroleum products using total petroleum hydrocarbons (TPH) have been carried out; however, the biodegradation of equivalent carbon number (EC) based hydrocarbon fractions in mineral oil has attracted little attention. This study investigated the ability of a microbial consortium to degrade the EC fractions in kerosene, which was used as a representative mineral oil. Based on the cloning and sequencing of the 16S rRNA gene, the microbial community was predominantly identified as Betaproteobacteria of the genera Achromobacter, Alcaligenes, and Cupriavidus. Degradation experiments in sealed 120-ml vials containing 1% (w v −1) kerosene revealed that aromatic fractions were degraded faster than aliphatic fractions. Aromatic fractions EC >7–8 and EC >8–10 were completely degraded after three days while aliphatic fractions EC >6–8 and EC >8–10 were only partially degraded. The aromatic EC >10–12 fraction was the third most degraded, and the aliphatic EC >10–12 and EC >12–16 fractions were the least degraded fractions. The first-order rate constants for the aromatic fractions ranged from 0.12 d −1 to 0.51 d −1 and from 0.06 d −1 to 0.32 d −1 for the aliphatic fractions. The microbial consortium preferentially utilized aromatic fractions, which are more toxic than aliphatic fractions. This finding is useful when considering risk-based bioremediation: A microbial community could potentially degrade the more toxic aromatic hydrocarbon components in petroleum-contaminated environments.

Characterization of carbon fractions for atmospheric fine particles and nanoparticles in a highway tunnel

Fine particles (PM 2.5) and nanoparticles (PM 0.1) were sampled using Dichotomous sampler and MOUDI, respectively, in Xueshan Tunnel, Taiwan. Eight carbon fractions were analyzed using IMPROVE thermal-optical reflectance (TOR) method. The concentrations of different temperature carbon fractions (OC1–OC4, EC1–EC3) in both PM 2.5 and PM 0.1 were measured and the correlations between OC and EC were discussed. Results showed that the ratios of OC/EC were 1.26 and 0.67 for PM 2.5 and PM 0.1, respectively. The concentration of EC1 was found to be more abundant than other elemental carbon fractions in PM 2.5, while the most abundant EC fraction in PM 0.1 was found to be EC2. The variation of contributions for elemental carbon fractions was different among PM 2.5 and PM 0.1 samples, which was partly owing to the metal catalysts for soot oxidation. The correlations between char-EC and soot-EC showed that char-EC dominated EC in PM 2.5 while soot-EC dominated EC in PM 0.1. Using eight individual carbon fractions, the gasoline and diesel source profiles of PM 0.1 and PM 2.5 were extracted and analyzed with the positive matrix factorization (PMF) method.

Particulate carbon in precipitation at European background sites

The particulate carbon content of precipitation was investigated in samples collected at five background sites located over a west-east European transect, from the Azores, in the mid-Atlantic Ocean, to the Hungarian plain, in central Europe. Sampling was performed on an event basis and the particulate carbon (elemental carbon, EC, and water insoluble organic carbon, WIOC) content was concentrated on quartz filters for the subsequent analysis by a thermal optical method in order to separate the EC and WIOC fractions. The average EC concentrations range from low values at the Azores (2.8±4.3 μg C L −1) and at the high mountain site of Sonnblick (5.2±3.7 μg C L −1) to high values at the more inland sites of Schauinsland (28±38 μg C L −1) and K-Puszta (24±24 μg C L −1). The average WIOC concentrations range from 98±56 μg C L −1 at the coastal site of Aveiro and 113±78 μg C L −1 at the Azores to 358±194 μg C L −1 at the continental site of K-Puszta. These results are discussed in terms of factors affecting the spatial distribution of particulate carbon, such as emissions from surrounding areas and prevalent meteorological conditions. EC is found to be a minor contributor to total particulate carbon present in rain and snow samples (from 2.5% to 15%). This is particularly true at the remotes sites, where the EC contribution to total particulate carbon is <6.5%, consistent with a negligible impact of anthropogenic combustions locally. The EC and WIOC scavenging ratios were estimated and compared with those of sulfate, also evaluated at the same sampling sites. The results indicated that EC is removed from the atmosphere by wet deposition less efficiently than WIOC, and in turn this species is removed less efficiently than sulfate.

Plasma LCAT Activity and Lipid Subfraction Composition in Obese Beagles Undergoing Weight Loss

The relationship between lecithin:cholesterol acyltransferase (LCAT) activity and weight loss in dogs was investigated. Four experimental weight-loss diets were fed to 12 obese female beagles for 56 days in a partial crossover design (n = 6). High- (HGI) or low- (LGI) glycemic index starch and diacylglycerol or triacylglycerol oils were combined to compose experimental diets with similar fatty acid profiles. Food intake and body weights were measured daily and weekly, respectively. Fasted blood samples were drawn at day 0, day 28, and day 56 to measure plasma LCAT activity and total (TC), unesterified (UC), and esterified (EC) cholesterol concentrations, and for fatty acid analysis of the phospholipid (PL) and EC fractions. The LGI groups lost more weight than the HGI groups due to starch digestibility differences. An HGI starch effect on TC and UC concentrations was observed but was unrelated to weight loss. LCAT activities increased over time but were not different after controlling for percentage weight loss. However, a positive linear correlation was found between LCAT and UC concentrations in all groups. Plasma PL fatty acid profiles reflected the diets fed, but increases in 16 and 18 carbon saturated and monounsaturated fatty acids in all groups appeared to be an effect of fatty acid mobilization from storage sites. Both plasma PL and EC fatty acid profiles were similar with both acylglycerol types and EC fatty acids reflected linoleic acid specificity with minimal diet or time effects.

Sequential chemical oxidation and aerobic biodegradation of equivalent carbon number-based hydrocarbon fractions in jet fuel.

Remediation of petroleum mixtures is complicated by the differing environmental degradabilities of hundreds of individual hydrocarbons in the mixtures. By grouping the individual hydrocarbons into a few fractions based on equivalent carbon number (EC), the present study examined the chemical and biological degradation of the fractions. With or without prechemical oxidation (25 days) by three oxidants (KMnO4, H202, MgO2), sterile and live microcosms were constituted with aquifer samples for aerobic biodegradation (134 days) of JP-4 jet fuel. Eighty-seven hydrocarbons were recovered and grouped into nine EC fractions. The apparent removal and actual transformation rate constants were estimated for both chemical and biological degradations. The data show that prechemical oxidations facilitated removal of total petroleum hydrocarbons (TPH) (up to 80%) within shorter times (<50 days) than biological alone. KMnO4 and H202 were better oxidants in terms of mass reduction in shorter times yet to some extent inhibited the subsequent microbial activity. MgO2 was a moderate oxidant with less inhibition of microbial activity. Selective degradation of the EC fractions was observed for both chemical and biological processes. The biological processes were much less effective than the prechemical oxidations in transforming aromatic fractions, the more toxic fractions. The favorable substrates (i.e., aliphatic EC approximately 10) for microbial growth were also those most subject to chemical oxidation. The results suggest that for remediation of petroleum contaminants, sequential chemical and biological technologies may surpass biological alone and more moderate oxidants such as MgO2 may be better candidates. More work is needed on the optimal dose and residence time for applied oxidants and on the application to engineering design and formulation of cleanup standards.

Mass balance of free tropospheric aerosol at the Puy de Dôme (France) in winter

The size‐segregated chemical composition of aerosols was investigated during winters 2000 and 2001 at Puy de Dôme (1465 m above sea level, France), a site most of the time located in the free troposphere. Aerosols have been sampled using low‐pressure cascade impactors (Electrical Low Pressure Impactor (ELPI) and Small Deposition Impactor (SDI) 13 and 12 stages) and analyzed for inorganic (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3−, and SO42−) and organic (HCOO−, CH3COO−, and C2O42−) ions, organic and elemental carbon (OC and EC), insoluble dust, and total mass. Under cloudy conditions, the sampling includes interstitial aerosol as well as the residue of evaporated cloud droplets. Aerosols (and residues of cloud droplets) were sampled in different air masses, which can be classified into three different categories according to their aerosol load and composition: background (BG), anthropogenic (ANT), and specific events (EV) that include advection of Saharan dust and upward transport from the polluted boundary layer to the site. On the basis of the presence or absence of coarse sea‐salt particles, a further classification permits us to distinguish air masses that have or have not been exposed to the ocean. A closed mass balance is achieved on submicron ranges (mean departure of 18.5%) for the three main air mass categories, providing a reliable description of main aerosol types in the west European free troposphere. The total aerosol mass at 50% relative humidity is close to 2.7 ± 0.6 μg m−3 in BG, 5.3 ± 1.0 μg m−3 in ANT, and 15 to 22 μg m−3 in EV air masses. The aerosol mass distribution generally exhibits two submicron modes (Acc1 at 0.2 ± 0.1 μm and Acc2 at 0.5 ± 0.2 μm geometric mean diameter (calculated for every impactor stage) and a supermicron mode (2 ± 1 μm). Aerosols exhibit a high degree of external mixing with carbonaceous (EC and OC) and ionic species associated with Acc1 and Acc2. Concentrations of light carboxylates and mineral dust never exceed 4% of the total content of analyzed compounds, except for a Saharan dust event during which the contribution of insoluble dust reaches 26% of the total aerosol mass. Depending on the sampled air mass, bulk water‐soluble inorganic species and carbonaceous material account for 25–70% and 15–60% of the total mass, respectively. The OC fraction is higher in air masses with low aerosol load (53%, 32%, and 22% for BG, ANT, and EV, respectively). Conversely, the EC fraction is enhanced from 4% in BG to 10% in ANT and 14% in EV. The inorganic fraction is more abundant in EV (55%) and ANT (60%) than in BG (40%) air masses as a result of enhanced nit .

The influence of dietary fat source (sunflower oil or olive oil) on LDL composition and serum lipid levels in miniature swine ( Sus scrofa)

A total of 24 miniature swine ( Sus scrofa) were fed with two diets of 9% fat content, differing only in the quality of the fat source (sunflower oil and olive oil). Two groups of animals were fed for a 12-week period, and the other two groups were fed for a 50-week period. After the two experimental periods, the influence of the dietary fat on serum lipids and protein and fatty acid composition of isolated LDLs was studied. In the short term, the serum cholesterol level was slightly higher in the olive oil group but, with the time of adaptation to the diet, serum levels of TC, FC and PL increased significantly in the sunflower group. In the long term, LDL and HDL were also significantly higher in the sunflower group when compared to the monounsaturated diet. In the sunflower group, PROT/TC and PROT/LIP ratios decreased significantly with the experimental period, while in the olive oil group they increased, due to the decrease in EC and TG fractions. The LDL particle in the olive group contained fewer saturated fatty acids and more monounsaturated fatty acids, specially oleic acid, than the LDL in the sunflower group. The changes found in chemical and fatty acid compositions of LDL, according to the saturation degree of the predominant fat of the diet, could alter its cellular metabolism.

Fractionation of ragweed extract by semicontinuous electrophoresis-convection

A systematic study of the stationary and positively charged components of low ragweed pollen, extracted at pH 5, has been carried out in the Tiselius electrophoresis apparatus over a pH range of 2.9–8.6. Three positively charged components were identified as well as “immobile” material. Simplified fractions of dialyzed pH 5 extracts of low ragweed pollen were prepared by the “semicontinuous” technique of electrophoresis-convection. These fractions were active and had retained their original specificity, according to tests carried out in sensitized areas of normal skin. The most highly simplified preparation, Bottom-1 of extract XLVI, was comprised of a single, almost stationary component when examined at pH 5.5. Doubt is cast on the homogeneity of this fraction, however, by the fact that its counterpart in the whole extract was resolved into two components by extending the analysis to 11 hr. By means of cross-tests among the several EC fractions in sensitized skin, it has been possible to estimate the relative potencies of individual electrophoretic constituents of our pH 5 extract. Although the activity per mg. N of the essentially immobile material was no greater than that of the slowest positively charged component, the electrophoretic area of the former was so much larger that it must have contributed the major activity to the pollen. While activity was demonstrated for another positively charged substance of high mobility, none could be unequivocally assigned to a constituent of intermediate positive charge or to negatively charged material.