Sources Of Elemental Carbon Research Articles

Implementation of a high-resolution Source-Oriented WRF/Chem model at the Port of Oakland

A version of the Source-Oriented WRF/Chem (SOWC) model with 250 m spatial resolution (SOWC-HR) was developed and implemented to perform high resolution simulations over the community of Oakland, California, during March 2010. A multiscale set of nested domains was used to predict contributions to airborne particulate elemental carbon (EC) concentrations from ships, trains, and on-road diesel trucks. The final domain at 250 m resolution used Large Eddy Simulation (LES) to predict turbulent mixing at scales where traditional first order closure models are not valid. Results of the high resolution simulation with the nested LES (HR case) and without the nested LES (non-HR case) were compared to speciated particulate matter (PM) measurements and source contributions calculated using Positive Matrix Factorization (PMF). The PMF results showed that on-road diesel traffic was a major EC contributor, a result consistent with previous studies for Oakland. The average EC concentration predicted at the site by the SOWC-HR model was 0.42 μg m−3, with source contributions of 0.22 μg m−3 from on-road diesel, 0.05 μg m−3 from ship fuel combustion, 0.08 μg m−3 from trains, and 0.09 μg m−3 from other sources. Both simulation cases predicted similar total EC concentrations and source contributions at the sampling sites, but more substantial differences were predicted at other locations in the study region. The HR case predicted higher average and maximum hourly EC contributions from all sources compared the non-HR case. The greatest relative increase of maximum hourly EC was seen in the on-road diesel source, which increased by nearly a factor of 2 (3.74 μg m−3 to 6.69 μg m−3) when spatial resolution was increased from 1 km to 250 m. The SOWC-HR model predicted greater population-weighted EC concentrations from all sources when compared to the SOWC model without HR. The increase in period-averaged EC exposure from each source ranged from +1% to +17%, while the increase in maximum hourly EC exposure from each source ranged from +9% to +32%. This evaluation shows that resolving neighborhood scales through the representation of local mixing phenomena can significantly impact pollutant concentration predictions, especially when examining extreme exposures in a densely populated area with many sources and complex terrain.

The application of carbon-14 analyses to the source apportionment of atmospheric carbonaceous particulate matter: a review

Organic carbon (OC) and elemental carbon (EC) together constitute a substantial proportion of airborne particulate matter (PM). Insight into the sources of this major contributor to PM is important for policies to mitigate the impact of PM on human health and climate change. In recent years measurement of the abundance of the radioisotope of carbon ((14)C) in samples of PM by accelerator mass spectrometry has been used to help quantify the relative contributions from sources of fossil carbon and contemporary carbon. This review provides an introduction to the different sources of carbon within PM and the role of (14)C measurements, a description of the preparation of PM samples and of the instrumentation used to quantify (14)C, and a summary of the results and source apportionment methods reported in published studies since 2004. All studies report a sizable fraction of the carbonaceous PM as of non-fossil origin. Even for PM collected in urban locations, the proportions of non-fossil carbon generally exceed 30%; typically the proportion in urban background locations is around 40-60% depending on the local influence of biomass burning. Where values have been measured directly, proportions of non-fossil carbon in EC are lower than in OC, reflecting the greater contribution of fossil-fuel combustion to EC and the generally small sources of contemporary EC. Detailed source apportionment studies point to important contributions from biogenic-derived secondary OC, consistent with other evidence of a ubiquitous presence of heavily oxidized background secondary OC. The review concludes with some comments on current issues and future prospects, including progress towards compound-class and individual-compound-specific (14)C analyses.

Light-absorbing carbon in Europe – measurement and modelling, with a focus on residential wood combustion emissions

Abstract. The atmospheric concentration of elemental carbon (EC) in Europe during the six-year period 2005–2010 has been simulated with the EMEP MSC-W model. The model bias compared to EC measurements was less than 20% for most of the examined sites. The model results suggest that fossil fuel combustion is the dominant source of EC in most of Europe but that there are important contributions also from residential wood burning during the cold seasons and, during certain episodes, also from open biomass burning (wildfires and agricultural fires). The modelled contributions from open biomass fires to ground level concentrations of EC were small at the sites included in the present study, <3% of the long-term average of EC in PM10. The modelling of this EC source is subject to many uncertainties, and it was likely underestimated for some episodes. EC measurements and modelled EC were also compared to optical measurements of black carbon (BC). The relationships between EC and BC (as given by mass absorption cross section, MAC, values) differed widely between the sites, and the correlation between observed EC and BC is sometimes poor, making it difficult to compare results using the two techniques and limiting the comparability of BC measurements to model EC results. A new bottom-up emission inventory for carbonaceous aerosol from residential wood combustion has been applied. For some countries the new inventory has substantially different EC emissions compared to earlier estimates. For northern Europe the most significant changes are much lower emissions in Norway and higher emissions in neighbouring Sweden and Finland. For Norway and Sweden, comparisons to source-apportionment data from winter campaigns indicate that the new inventory may improve model-calculated EC from wood burning. Finally, three different model setups were tested with variable atmospheric lifetimes of EC in order to evaluate the model sensitivity to the assumptions regarding hygroscopicity and atmospheric ageing of EC. The standard ageing scheme leads to a rapid transformation of the emitted hydrophobic EC to hygroscopic particles, and generates similar results when assuming that all EC is aged at the point of emission. Assuming hydrophobic emissions and no ageing leads to higher EC concentrations. For the more remote sites, the observed EC concentration was in between the modelled EC using standard ageing and the scenario treating EC as hydrophobic. This could indicate too-rapid EC ageing in the model in relatively clean parts of the atmosphere.

Identification of the Sources and Geographic Origins of Black Carbon using Factor Analysis at Paired Rural and Urban sites

Black carbon particles, composed of forms of elemental carbon (EC), contribute significantly to regional and global warming. The origins of EC were examined in southeastern Canada as part of a source apportionment study using positive matrix factorization (PMF), performed on long-term PM2.5 chemical speciation data collected at two paired rural and urban sites. Comparisons of the urban and rural sites revealed a previously unrecognized EC-rich factor that accounted for 41-56% of the total EC in this region. This factor was characterized by the more thermally stable EC fractions that exhibit strong light absorption characteristics. While these EC fractions are often attributed to local diesel emissions, this interpretation was rejected for several reasons. The EC-rich factor was present in similar temporal patterns at both the high-traffic urban and low-traffic rural sites across this 600 km region. The geographic origins of the EC-rich factor were found to be Ohio and Western Pennsylvania regions with heavy industry and multiple coal-based electrical generating stations. The direct radiative forcing due to this EC-rich factor was roughly estimated to be +0.2 W m(-2), which represented a substantial portion of the aerosol induced warming in the region. Thus, this region was impacted by an important unidentified source of EC associated with long-range transport.

Chemical and morphological characteristics of indoor and outdoor particulate matter in an urban environment

Chemical characterization of suspended particulate matter (SPM) measured inside a naturally ventilated school building (indoor) and at an adjacent roadway (outdoor) in Chennai city was performed during monsoon, winter and summer seasons. The daily average indoor SPM concentrations in monsoon, winter and summer seasons were 158.18, 170.08 and 149.63 μg m−3, respectively. Indoor and outdoor samples were analyzed for 11 inorganic ions using ion chromatography and 28 elements by inductively coupled plasma optical emission spectrometry. Results indicated the dominance of SO42− (10.89 μg m−3) followed by NH4+ (5.62 μg m−3), NO3− (5.35 μg m−3), Na+ (4.35 μg m−3) Ca2+ (4.08 μg m−3) and Cl- (3.47 μg m−3) ions in the indoor SPM. In the outdoor SPM, SO42−, NO3− and NH4+ ions concentration were slightly higher while Ca2+, K+ and Mg2+ ions concentrations were higher in indoors. Among the elements, crustal element (Al, Fe, Ca, K, Mg and Na) concentrations were much higher (92.7% of the total elemental concentration) in indoor environment than those of toxic elements (Ba, Cr, Cu, Mn, Mo, Ni, Sr, Ti, V and Zn) emitted from vehicles. Analysis of elemental carbon (EC) and organic carbon (OC) components in indoor and outdoor PM indicated the predominance of OC. The indoor/outdoor (I/O) ratios for EC = 0.70 and OC = 0.82, indicating no significant indoor emission sources of OC and EC. To characterize the morphology, indoor and outdoor filters were examined by Scanning Electron Microscopy coupled with energy dispersive X-ray spectrometry. Soot and Al–Si rich particles were mostly found in indoor and outdoor SPM. The presence of toxic elements and soot particles in the indoor PM confirms the contributions of vehicular emissions from the adjacent motorway.

Source apportionment of PM10, organic carbon and elemental carbon at Swiss sites: An intercomparison of different approaches

In this study, the results of source apportionment of particulate matter (PM10), organic carbon (OC), and elemental carbon (EC) — as obtained through different approaches at different types of sites (urban background, urban roadside, and two rural sites in Switzerland) — are compared. The methods included in this intercomparison are positive matrix factorisation modelling (PMF, applied to chemical composition data including trace elements, inorganic ions, OC, and EC), molecular marker chemical mass balance modelling (MM-CMB), and the aethalometer model (AeM).At all sites, the agreement of the obtained source contributions was reasonable for OC, EC, and PM10. Based on an annual average, and at most of the considered sites, secondary organic carbon (SOC) is the component with the largest contribution to total OC; the most important primary source of OC is wood combustion, followed by road traffic. Secondary aerosols predominate in PM10. All considered techniques identified road traffic as the dominant source of EC, while wood combustion emissions are of minor importance for this constituent.The intercomparison of different source apportionment approaches is helpful to identify the strengths and the weaknesses of the different methods. Application of PMF has limitations when source emissions have a strong temporal correlation, or when meteorology has a strong impact on PM variability. In these cases, the use of PMF can result in mixed source profiles and consequently in the under- or overestimation of the real-world sources. The application of CMB models can be hampered by the unavailability of source profiles and the non-representativeness of the available profiles for local source emissions.This study also underlines that chemical transformations of molecular markers in the atmosphere can lead to the underestimation of contributions from primary sources, in particular during the summer period or when emission sources are far away from the receptor sites.

A methodology for elemental and organic carbon emission inventory and results for Lombardy region, Italy

This paper presents a methodology and its application for the compilation of elemental carbon (EC) and organic carbon (OC) emission inventories. The methodology consists of the estimation of EC and OC emissions from available total suspended particulate matter (TSP) emission inventory data using EC and OC abundances in TSP derived from an extensive literature review, by taking into account the local technological context. In particular, the method is applied to the 2008 emissions of Lombardy region, Italy, considering 148 different activities and 30 types of fuels, typical of Western Europe. The abundances estimated in this study may provide a useful basis to assess the emissions also in other emission contexts with similar prevailing sources and technologies.The dominant sources of EC and OC in Lombardy are diesel vehicles for EC and the residential wood combustion (RWC) for OC which together account for about 83% of the total emissions of both pollutants. The EC and OC emissions from industrial processes and other fuel (e.g., gasoline, kerosene and LPG) combustion are significantly lower, while non-combustion sources give an almost negligible contribution. Total EC+OC contribution to regional greenhouse gas emissions is positive for every sector assuming whichever GWP100 value within the range proposed in literature. An uncertainty assessment is performed through a Monte Carlo simulation for RWC, showing a large uncertainty range (280% of the mean value for EC and 70% for OC), whereas for road transport a qualitative analysis identified a narrower range of uncertainty.

The chemical composition and sources of PM2.5 during the 2009 Chinese New Year's holiday in Shanghai

China is virtually shut down during the week-long Chinese New Year's holiday. This implies that the anthropogenic emissions would be greatly decreased during the period thus providing an opportunity to study the air quality in China under reduced emissions, and the drastic emission changes during a short period of time allows the comparison of source contributions under significantly different conditions. Seventeen PM2.5 samples were collected during the 2009 Chinese New Year's holiday in Shanghai to study the composition and sources of the fine particles. Organic carbon (OC), elemental carbon (EC), eight water-soluble ions, fourteen metals and solvent extractable organic compounds (SEOC) including alkanes, hopanes, polycyclic aromatic hydrocarbons (PAHs) and fatty acids were measured. Diagnostic PAH ratios, correlation analysis of OC, EC, n-alkanes, hopanes and PAHs showed that vehicle emissions were the main source of n-alkanes and EC, and an important source of the locally emitted particulate PAHs in urban Shanghai, while coal burning should be the main source of the transported PAHs from the inland areas. The composition of n-fatty acids also provided some clue on the significance of the contribution by kitchen activities. In the New Year's Eve's sample, 75% of the particle mass was estimated to be from fireworks, and K+, SO42−, Cl−, OC, Al and Ba were the main components. Firework fine particles had high OC/EC ratio and low NO3−/SO42− ratio.

Carbonaceous aerosols in China: top-down constraints on primary sources and estimation of secondary contribution

Abstract. We simulated elemental carbon (EC) and organic carbon (OC) aerosols in China and compared model results to surface measurements at Chinese rural and background sites, with the goal of deriving "top-down" emission estimates of EC and OC, as well as better quantifying the secondary sources of OC. We included in the model state-of-the-science Chinese "bottom-up" emission inventories for EC (1.92 TgC yr−1) and OC (3.95 TgC yr−1), as well as updated secondary OC formation pathways. The average simulated annual mean EC concentration at rural and background sites was 1.1 μgC m−3, 56% lower than the observed 2.5 μgC m−3. The average simulated annual mean OC concentration at rural and background sites was 3.4 μgC m−3, 76% lower than the observed 14 μgC m−3. Multiple regression to fit surface monthly mean EC observations at rural and background sites yielded the best estimate of Chinese EC source of 3.05 ± 0.78 TgC yr−1. Based on the top-down EC emission estimate and observed seasonal primary OC/EC ratios, we estimated Chinese OC emissions to be 6.67 ± 1.30 TgC yr−1. Using these top-down estimates, the simulated average annual mean EC concentration at rural and background sites was significantly improved to 1.9 μgC m−3. However, the model still significantly underestimated observed OC in all seasons (simulated average annual mean OC at rural and background sites was 5.4 μgC m−3), with little skill in capturing the spatiotemporal variability. Secondary formation accounts for 21% of Chinese annual mean surface OC in the model, with isoprene being the most important precursor. In summer, as high as 62% of the observed surface OC may be due to secondary formation in eastern China. Our analysis points to four shortcomings in the current bottom-up inventories of Chinese carbonaceous aerosols: (1) the anthropogenic source is underestimated on a national scale, particularly for OC; (2) the spatiotemporal distributions of emissions are misrepresented; (3) there is a missing source in western China, likely associated with the use of biofuels or other low-quality fuels for heating; and (4) sources in fall are not well represented, either because the seasonal shifting of emissions and/or secondary formation are poorly captured or because specific fall emission events are missing. In addition, secondary production of OC in China is severely underestimated. More regional measurements with better spatiotemporal coverage are needed to resolve these shortcomings.

The implication of carbonaceous aerosol to the formation of haze: Revealed from the characteristics and sources of OC/EC over a mega-city in China

The characteristics and sources of organic carbon (OC) and elemental carbon (EC) in PM 2.5 in 2006–2007 as well as their impact on the formation of heavy haze in Shanghai were investigated. Daily average concentrations of OC and EC ranged from 1.8 to 20.1 μg m −3 and 0.5–7.8 μg m −3 with averages of 7.2 and 2.8 μg m −3, respectively. The carbonaceous aerosol (OC plus EC) contributed to ∼27.2% of the total mass of PM 2.5 on annual average. Obvious seasonal variation was observed in both OC and EC. The percentage of secondary organic carbon (SOC) contributed to OC was in a range of 2.4–66.8%, with an average of 40.1%. Three types of haze were classified based on their chemical composition. OC, EC, SO 2/NO 2 (in turn, SO 4 2−/NO 3 −) were responsible for the formation of the three types of haze, respectively. The carbonaceous aerosol was one of the key factors in the formation of haze. Local emissions were the dominant sources of OC and EC in warm seasons, and long-range transport had a significant contribution to OC and EC in PM 2.5 in spring and winter in Shanghai.

Contribution of long range transport to local fine particulate matter concerns

Abstract We have utilized the Particulate Matter Source Apportionment Technology (PSAT) in PMCAMx (a regional chemical transport model) to quantify the contributions from local emissions and short range (under 100 km), mid range (100–550 km) and long range (over 550 km) pollutant transport to both primary and secondary particulate matter concentrations using the Eastern United States as a test case. We have studied these contributions for two urban (Pittsburgh, Pennsylvania and Atlanta, Georgia) and one rural area (Great Smoky Mountains National Park) during all seasons. The local emissions impacts to elemental carbon (EC) in major urban areas were found to be substantial with approximately 50% of the EC coming from local sources and 80% emitted within 200 km of the receptor. The local sources are even more important during the night contributing around 60% of the EC and then dropping to around 40% during the early afternoon. The EC in the rural Great Smoky Mountains was mainly the result of sources 100–550 km away. The seasonal variation of the EC source area contributions is small. There was also little difference between high and low EC concentration days. The contributions to secondary aerosol species were found to be more regional with more than 50% of the sulfate and secondary organic aerosol (SOA) originating from SO2 and VOC sources that were more than 200 km away from the receptor. The importance of sources further away increased during the winter because of the lower photochemical activity. While mid range transport dominated in the summer the sulfate and SOA levels in all areas, long range transport became the most important sulfate and SOA source during the winter in the colder Northeastern US and of sulfate in the warmer South.

Estimation of the contributions of long range transported aerosol in East Asia to carbonaceous aerosol and PM concentrations in Seoul, Korea using highly time resolved measurements: a PSCF model approach

The contributions of long range transported aerosol in East Asia to carbonaceous aerosol and particulate matter (PM) concentrations in Seoul, Korea were estimated with potential source contribution function (PSCF) calculations. Carbonaceous aerosol (organic carbon (OC) and elemental carbon (EC)), PM(2.5), and PM(10) concentrations were measured from April 2007 to March 2008 in Seoul, Korea. The PSCF and concentration weighted trajectory (CWT) receptor models were used to identify the spatial source distributions of OC, EC, PM(2.5), and coarse particles. Heavily industrialized areas in Northeast China such as Harbin and Changchun and East China including the Pearl River Delta region, the Yangtze River Delta region, and the Beijing-Tianjin region were identified as high OC, EC and PM(2.5) source areas. The conditional PSCF analysis was introduced so as to distinguish the influence of aerosol transported from heavily polluted source areas on a receptor site from that transported from relatively clean areas. The source contributions estimated using the conditional PSCF analysis account for not only the aerosol concentrations of long range transported aerosols but also the number of transport days effective on the measurement site. Based on the proposed algorithm, the condition of airmass pathways was classified into two types: one condition where airmass passed over the source region (PS) and another condition where airmass did not pass over the source region (NPS). For most of the seasons during the measurement period, 249.5-366.2% higher OC, EC, PM(2.5), and coarse particle concentrations were observed at the measurement site under PS conditions than under NPS conditions. Seasonal variations in the concentrations of OC, EC, PM(2.5), and coarse particles under PS, NPS, and background aerosol conditions were quantified. The contributions of long range transported aerosols on the OC, EC, PM(2.5), and coarse particle concentrations during several Asian dust events were also estimated. We also investigated the performance of the PSCF results obtained from combining highly time resolved measurement data and backward trajectory calculations via comparison with those from data in low resolutions. Reduced tailing effects and the larger coverage over the area of interest were observed in the PSCF results obtained from using the highly time resolved data and trajectories.

Black and Organic Carbon Emission Inventories: Review and Application to California

Particulate black or elemental carbon (EC) (black carbon [BC]) and organic carbon (OC) affect climate, visibility, and human health. Several “top-down” and “bottom-up” global emission inventories for these components have compiled country-wide emission factors, source profiles, and activity levels that do not necessarily reflect local conditions. Recent estimates of global BC and OC emissions range from 8 to 24 and 33 to 62 Tg (1012 g) per year, respectively. U.S. BC emissions account for 5.6% of the global total emissions. Uncertainties in global BC emission estimates are a factor of 2 or more. The U.S. National Emissions Inventory is well documented, but its major source categories are not easily related to EC- and OC-emitting source subcategories. California’s bottom-up emission inventory is easily accessible at many levels of detail and provides an example of how sources can be regrouped for speciated emission rates. PM2.5 (particulate matter with aerodynamic diameters < 2.5 µm) emissions from these categories are associated with EC and OC source profiles to generate California’s speciated emissions. A BC inventory for California of 38,731 t/yr was comparable to the 33,281 t/yr estimated from a bottom-up global BC inventory. However, further examination showed substantial differences among subcategories, with the global inventory BC from fossil fuel combustion at two-thirds that from the California inventory and the remainder attributed to biomass burning. Major discrepancies were found for directly emitted OC, with the global inventory estimating more than twice that of the California inventory. Most of the discrepancy was due to differences in open biomass burning (wildfires and agricultural waste) for which carbon emissions are highly variable. BC and OC emissions are sensitive to the availability and variability of existing source profiles, and profiles more specific to fuels and operating conditions are needed to increase emission accuracy.

Elemental carbon and sulfate aerosols over a rural mountain site in the northeastern United States: Regional emissions and implications for climate change

The effect of elemental carbon (EC) on global as well as regional climate forcing is potentially very important. However, the EC data for northeastern U.S. is sparse. Daily EC concentrations, [EC], and [SO 4 ] were measured in the northeastern U.S. at a regionally representative rural site, Whiteface Mountain (WFM; 44.366°N, 73.903°W, 1.5 km amsl, above mean sea level), New York (NY), for 1997. The air mass origin was determined using 6-h backward in time air trajectories obtained from the Hybrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT 4). [EC] and [SO 4 ] were highly variable and influenced by synoptic–scale meteorology (rainy vs dry periods). The maximum daily [EC] and [SO 4 ] were 364 ± 55 and 28,800 ± 3000 ng m −3 , respectively. [EC] and [SO 4 ] also showed seasonal variations at WFM. Occurrences of high daily [EC] were mainly in spring months, while peak daily [SO 4 ] concentrations occurred in summer months. This behavior of aerosols is due to the fact that the sources of EC and SO 4 are not the same and also due to the enhanced photochemical activity during summer months that increased the production of SO 4 from SO 2 . High [EC] and [SO 4 ] values were associated with westerly air flow from the industrialized Midwestern U.S. Sector analysis using HYSPLIT 4 air trajectories showed that regions lying between the southwest and northwest of the WFM contributed 81% and 83% of the [EC] and [SO 4 ], respectively. The monthly net direct radiative forcing for shortwave (SW) due to EC and SO 4 aerosols at the top of the atmosphere (TOA) varied from −0.05 to −0.50 W m −2 , with an annual average of −0.20 ± 0.15 W m −2 that gives a net cooling effect. Average net radiative forcing at WFM for clear sky is lower than the global average radiative forcing reported by IPCC ( Foster and Ramaswamy, 2007 ).

Synthesis of LiFePO4 / C Composite Particles by Gas–Solid Phase Reaction and Their Electrochemical Properties

composite particles were prepared by a gas–solid phase reaction. The precursor particles for the olivine compounds were prepared by an intimate mixing of , , and and by calcination at in a atmosphere. Then, they were heated up to a predetermined temperature under a constant flow of hydrocarbon gas, which is a source of elemental carbon. The adjustment of the temperature enabled us to obtain the composite particles with few magnetic impurities (the spontaneous magnetization was less than 0.01 emu/g) as well as good electrical conductivity (the compact conductivity was higher than ). The composite particles, synthesized under the optimized condition, showed a reversible capacity greater than 150 mAh/g at a low current density of 0.1 C. Simultaneously, they also exhibited a superior performance in both cycle stability and rate capability.

Temporal variations of elemental carbon in Beijing

Concentrations of elemental carbon (EC), carbon monoxide (CO), and carbon dioxide (CO2) were measured in Beijing between 2005 and 2006. EC was measured every hour with a semicontinuous thermal optical analyzer. The observed concentrations were rather uniform over a distance of about 50 km from the observation site. The annual average concentrations of EC and CO were 6.9 μgC m−3 and 1120 parts per billion by volume, respectively. The concentrations of these species increased with decreasing near‐surface wind speed (WS). The slopes of the CO‐CO2, EC‐CO2, and EC‐CO correlations are used to estimate major EC and CO sources. In the weak wind regime (WS ≤ 2.0 m s−1), the median EC, ΔEC/ΔCO2, and ΔEC/ΔCO (except for winter) increased in the late evening and remained high until early morning. The traffic of heavy duty diesel trucks during nighttime was about 20 times higher than that during daytime. These results indicate a dominant contribution of exhaust from diesel vehicles to the nighttime EC. In winter, the nighttime CO and ΔCO/ΔCO2 ratio were largely higher than those in the other seasons. The most likely cause is the increase in the CO emissions from the exhaust of gasoline vehicles at low temperature. The ΔEC/ΔCO2 ratio in winter was lower than that in fall, indicating no significant additional EC emissions. The diurnal variations of EC, CO, CO2, and ΔEC/ΔCO were similar between weekdays and weekends. The slopes of the CO‐CO2‐EC correlations are compared with the CO‐CO2‐EC ratios derived from a published emission inventory in the Beijing area.

Fossil and non-fossil sources of organic carbon (OC) and elemental carbon (EC) in Göteborg, Sweden

Abstract. Particulate matter was collected at an urban site in Göteborg (Sweden) in February/March 2005 and in June/July 2006. Additional samples were collected at a rural site for the winter period. Total carbon (TC) concentrations were 2.1–3.6 μg m−3, 1.8–1.9 μg m−3, and 2.2–3.0 μg m−3 for urban/winter, rural/winter, and urban/summer conditions, respectively. Elemental carbon (EC), organic carbon (OC), water-insoluble OC (WINSOC), and water-soluble OC (WSOC) were analyzed for 14C in order to distinguish fossil from non-fossil emissions. As wood burning is the single major source of non-fossil EC, its contribution can be quantified directly. For non-fossil OC, the wood-burning fraction was determined independently by levoglucosan and 14C analysis and combined using Latin-hypercube sampling (LHS). For the winter period, the relative contribution of EC from wood burning to the total EC was &gt;3 times higher at the rural site compared to the urban site, whereas the absolute concentrations of EC from wood burning were elevated only moderately at the rural compared to the urban site. Thus, the urban site is substantially more influenced by fossil EC emissions. For summer, biogenic emissions dominated OC concentrations most likely due to secondary organic aerosol (SOA) formation. During both seasons, a more pronounced fossil signal was observed for Göteborg than has previously been reported for Zurich, Switzerland. Analysis of air mass origin using back trajectories suggests that the fossil impact was larger when local sources dominated, whereas long-range transport caused an enhanced non-fossil signal. In comparison to other European locations, concentrations of levoglucosan and other monosaccharide anhydrides were low for the urban and the rural site in the area of Göteborg during winter.

Seasonal variation of PM&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; main constituents in two valleys of the French Alps. I: EC/OC fractions

Abstract. Daily PM10 samples were collected at two urban sites within two valleys in the French Alps (Chamonix and St Jean de Maurienne) during a period of two and a half years. The carbonaceous species EC (elemental carbon) and OC (organic carbon) were analysed to investigate the possible sources of EC and OC, and their seasonal variations. Mean OC concentrations are in the very high range of concentrations measured for other European sites, and represent at least one third of the PM10 mass on each site. On the basis of the comparison between EC and OC concentrations with several tracers, we were able to show that their main sources are local primary combustion sources. Biomass burning emissions (residential heating) have a significant impact on OC concentrations while heavy duty traffic emissions have an impact only on EC concentrations. Finally, we estimated the contribution of SOA (secondary organic carbon) to OC, using the EC-to-OC primary ratio method (Castro et al., 1999) and demonstrated that the calculation of SOA mass with this method is highly uncertain, if the hypothesis of a constant primary EC-to-OC ratio is not very closely examined.

Relationship between Elemental Carbon, Total Carbon, and Diesel Particulate Matter in Several Underground Metal/Non-metal Mines

Elemental carbon (EC) is currently used as a surrogate for diesel particulate matter (DPM) in underground mines since it can be accurately measured at low concentrations and diesels are the only source of submicrometer EC in underground mines. A disadvantage of using EC as a surrogate for DPM is that the fraction of EC in DPM is a function of various engine parameters and fuel formulations, etc. In order to evaluate how EC predicts DPM in the underground mining atmosphere, measurements of total carbon (TC; representing over 80% of the DPM) and EC were taken away from potential interferences in four underground metal/non-metal mines during actual production. In a controlled atmosphere, DPM mass, TC, and EC measurements were also collected while several different types of vehicles simulated production with and without different types of control technologies. When diesel particulate filters (DPFs) were not used, both studies showed that EC could be used to predict DPM mass or TC. The variability of the data started to increase at TC concentrations below 230 microg/m3 and was high (> +/- 20%) at TC concentrations below 160 microg/m3, probably due to the problem with sampling organic carbon (OC) at these concentrations. It was also discovered that when certain DPFs were used, the relationship between DPM and EC changed at lower DPM concentrations.

Relationships Between Personal, Indoor, and Outdoor Levels of Sulfate, Elemental Carbon, and PM2.5 for a Cohort of Individuals With Cardiopulmonary Disease

SM4-PD-14 Background: Previous exposure studies have validated the use of ambient fine particulate matter (PM2.5) measurements as surrogates of exposure in PM time-series epidemiologic studies. It is uncertain, however, whether ambient measurements of specific PM components are equally good surrogates. Panel exposure assessment studies provide a direct means of exploring the strength of the relationships between personal, home indoor, home outdoor, and ambient particulate levels. For this study, we conducted a panel study measuring personal, home indoor, home outdoor, and ambient site concentrations of PM2.5 as well as its components, sulfate, and elemental carbon (EC), for individuals with cardiopulmonary disease. We examined particulate pollutant associations among the microenvironments by season and subject. Methods: Simultaneous 24-hour integrated personal, home indoor, and home outdoor PM2.5, SO42−, and EC concentrations were measured in 25 single-family homes during the summer and winter. All homes and subjects were measured for 7 consecutive days. Integrated 24-hour PM2.5, sulfate, and EC samples were also measured at a central monitoring site. Results: A total of 210 person-days of exposure data were collected. We found ambient sulfate to be strongly correlated with personal and home indoor sulfate for all individuals without an indoor source of sulfate in the home. Outdoor or ambient sulfate accounted for approximately 80% of the variability in personal and indoor sulfate concentrations, despite the fact that absolute exposure to sulfate was at times considerably lower than outdoor levels. In contrast to the results for sulfate, personal/indoor, and outdoor/ambient associations for EC and PM2.5 were weaker, likely due to indoor and/or local sources of EC and PM2.5. There were relatively weak EC outdoor-ambient associations, especially during the summer (mean home-specific Spearman's correlation coefficient = 0.26), indicating a greater degree of spatial heterogeneity for this pollutant. Discussion and Conclusions: These findings provide further evidence that ambient sulfate monitors may serve as good indicators of correlations, but not absolute exposures, to particles of ambient origin for particle health effects studies. The spatial variability of EC was notable in this study, although our results did not show stronger personal-outdoor associations compared with personal-ambient associations. These findings suggest that, for this metropolitan area, locating monitors closer to participants’ homes may not be effective when trying to assess personal EC exposure in future studies. Our results also indicate that housing characteristics are likely the central driving factor determining the strength of the personal-outdoor or personal-ambient relationships for PM2.5 and these 2 components.