Characteristics and sources of PM2.5 and carbonaceous species during winter in Taiyuan,China

Continuous observation of PM_2.5 was conducted in Taiyuan, a heavily polluted city in China, during high pollution season from December 2005 to February 2006. The results of this study showed that PM_2.5 and carbonaceous species pollution were serious during winter in Taiyuan. The organic carbon (OC) and element carbon (EC) were accounted for 18.6±11.2% and 2.9±1.6% of PM_2.5, respectively, which indicated that carbonaceous aerosols were key components for control fine particles pollution in Taiyuan. Coal combustion was a dominant source of OC and EC of PM_2.5 in the urban area of Taiyuan during winter. The impact of local and remote particle sources on urban air quality was assessed using PM_2.5 concentration rose and 3-day back trajectories of air masses arriving at Taiyuan. The meteorological conditions were found to affect the ambient concentrations of PM_2.5, OC, EC and OC/EC ratio.     

Characteristics of PM2.5 carbonaceous aerosol in the Sihwa industrial area,Korea

In order to investigate the characteristics of carbonaceous fine aerosols, PM_2.5 particulate samples were collected in the Sihwa industrial complex area between February 1998 and 1999 and in Seoul between 31 May and 9 June 1999, respectively. The carbonaceous species were analyzed by the selective thermal manganese dioxide oxidation (TMO) method. In Sihwa, average OC and EC concentrations for the entire data set were measured to be 9.8 and 1.8 μg m⁻³, respectively. The OC concentrations were higher than those measured in other urban environments. The EC concentrations were lower than those of other urban environments. The OC/EC ratio measured at the Sihwa area was higher than those at other urban and rural environments. Backward trajectories of sampled air masses were performed to find out the sources of those higher OC/EC levels. Enrichment in the organic compounds during winter periods can be explained by the combination of primary local emissions from the industrial complex area and long-range transport of organic species from outside the Sihwa area. High OC values in June resulted from primary anthropogenic emissions and secondary organic aerosol formation rather than the atmospheric transport of organic compounds from the outside. In urban area of Seoul, the OC and EC concentrations in PM_2.5 during the summer were higher than those measured at other urban atmospheres. OC/EC ratios obtained in Seoul were lower than Sihwa. It can be concluded that carbonaceous species in Seoul were mainly emitted from primary anthropogenic sources.     

Urban impacts on regional carbonaceous aerosols: Case study in central Texas

Rural and background sites provide valuable information on the concentration and optical properties of organic, elemental, and water-soluble organic carbon (OC, EC, and WSOC), which are relevant for understanding the climate forcing potential of regional atmospheric aerosols. To quantify climate- and air quality-relevant characteristics of carbonaceous aerosol in the central United States, a regional background site in central Texas was chosen for long-term measurement. Back trajectory (BT) analysis, ambient OC, EC, and WSOC concentrations and absorption parameters are reported for the first 15 months of a long-term campaign (May 2011–August 2012). BT analysis indicates consistent north–south airflow connecting central Texas to the Central Plains. Central Texas aerosols exhibited seasonal trends with increased fine particulate matter (<2.5 μm aerodynamic diameter, PM_2.5) and OC during the summer (PM_2.5 = 10.9 μg m^?3 and OC = 3.0 μg m^?3) and elevated EC during the winter (0.22 μg m^?3). When compared to measurements in Dallas and Houston, TX, central Texas OC appears to have mixed urban and rural sources. However, central Texas EC appears to be dominated by transport of urban emissions. WSOC averaged 63% of the annual OC, with little seasonal variability in this ratio. To monitor brown carbon (BrC), absorption was measured for the aqueous WSOC extracts. Light absorption coefficients for EC and BrC were highest during summer (EC MAC = 11 m² g^?1 and BRC MAE₃₆₅ = 0.15 m² g^?1). Results from optical analysis indicate that regional aerosol absorption is mostly due to EC with summertime peaks in BrC attenuation. This study represents the first reported values of WSOC absorption, MAE₃₆₅, for the central United States.

Implications:Background concentration and absorption measurements are essential in determining regional potential radiative forcing due to atmospheric aerosols. Back trajectory, chemical, and optical analysis of PM_2.5 was used to determine climatic and air quality implications of urban outflow to a regional receptor site, representative of the central United States. Results indicate that central Texas organic carbon has mixed urban and rural sources, while elemental carbon is controlled by the transport of urban emissions. Analysis of aerosol absorption showed black carbon as the dominant absorber, with less brown carbon absorption than regional studies in California and the southeastern United States.     

Seasonal and spatial trends in the sources of fine particle organic carbon in Israel,Jordan, and Palestine

A study of carbonaceous particulate matter (PM) was conducted in the Middle East at sites in Israel, Jordan, and Palestine. The sources and seasonal variation of organic carbon, as well as the contribution to fine aerosol (PM_2.5) mass, were determined. Of the 11 sites studied, Nablus had the highest contribution of organic carbon (OC), 29%, and elemental carbon (EC), 19%, to total PM_2.5 mass. The lowest concentrations of PM_2.5 mass, OC, and EC were measured at southern desert sites, located in Aqaba, Eilat, and Rachma. The OC contribution to PM_2.5 mass at these sites ranged between 9.4% and 16%, with mean annual PM_2.5 mass concentrations ranging from 21 to 25 ug m^?3. These sites were also observed to have the highest OC to EC ratios (4.1–5.0), indicative of smaller contributions from primary combustion sources and/or a higher contribution of secondary organic aerosol. Biomass burning and vehicular emissions were found to be important sources of carbonaceous PM in this region at the non-southern desert sites, which together accounted for 30%–55% of the fine particle organic carbon at these sites. The fraction of measured OC unapportioned to primary sources (1.4 μgC m^?3 to 4.9 μgC m^?3; 30%–74%), which has been shown to be largely from secondary organic aerosol, is relatively constant at the sites examined in this study. This suggests that secondary organic aerosol is important in the Middle East during all seasons of the year.     

Improving Source Apportionment of Fine Particles in the Eastern United States Utilizing Temperature-Resolved Carbon Fractions

Abstract

The objectives of this study were to examine the use of carbon fractions to identify particulate matter (PM) sources, especially traffic‐related carbonaceous particle sources, and to estimate their contributions to the particle mass concentrations. In recent studies, positive matrix factorization (PMF) was applied to ambient fine PM (PM_2.5) compositional data sets of 24‐hr integrated samples including eight individual carbon fractions collected at three monitoring sites in the eastern United States: Atlanta, GA, Washington, DC, and Brigantine, NJ. Particulate carbon was analyzed using the Interagency Monitoring of Protected Visual Environments/Thermal Optical Reflectance method that divides carbon into four organic carbons (OC): pyrolized OC and three elemental carbon (EC) fractions. In contrast to earlier PMF studies that included only the total OC and EC concentrations, gasoline emissions could be distinguished from diesel emissions based on the differences in the abundances of the carbon fractions between the two sources. The compositional profiles for these two major source types show similarities among the three sites. Temperature‐resolved carbon fractions also enhanced separations of carbon‐rich secondary sulfate aerosols. Potential source contribution function analyses show the potential source areas and pathways of sulfate‐rich secondary aerosols, especially the regional influences of the biogenic, as well as anthropogenic secondary aerosol. This study indicates that temperature‐resolved carbon fractions can be used to enhance the source apportionment of ambient PM_2.5.     

PM2.5 carbon measurements in two urban areas: Seoul and Kwangju,Korea

24-h PM_2.5 carbonaceous samples were collected between 27 November and 9 December 1999 in Seoul, and between 7 and 20 June 2000 in Kwangju to investigate characteristics of carbonaceous species, and the relationship between elemental carbon (EC) and Aethalometer-based black carbon (BC) measurements. 5-min PM_2.5 BC and criteria air pollutant data were also measured using the Aethalometer and ambient air monitoring system. The PM_2.5 samples were analyzed for EC and OC using a selective thermal manganese dioxide oxidation (TMO) method. The daily average EC and OC concentrations in Seoul were higher in the winter than in the summer (Atmos. Environ. 35 (2001a) 657). It was found that difference between ambient BC levels in the two cities was not directly proportional to the population ratio (∼8) or diesel traffic ratio (∼5.9) since particulate matter or BC concentration is strongly influenced by a result of varying traffic and meteorological conditions at the site. Using the primary OC/EC ratio approach, the results suggest that most of the measured OC in Kwangju is of primary origin during the summer. In Seoul, the observed OC includes additional secondary organic aerosol during the wintertime conditions. The relationship between the 24-h TMO-EC and Aethalometer BC measurements in PM_2.5 reflected very good agreement for the two urban sites, with correlation coefficients of R²=0.99 and 0.92, and BC/EC slopes of 0.93 and 1.07, respectively. It was found that comparing TMO-EC to BC at a different location in Korea, a different scaling factor was needed.     

Sources and characteristics of carbonaceous aerosol in two largest cities in Pearl River Delta Region,China

PM_2.5 samples were collected at five sites in Guangzhou and Hong Kong, Pearl River Delta Region (PRDR), China in both summer and winter during 2004–2005. Elemental carbon (EC) and organic carbon (OC) in these samples were measured. The OC and EC concentrations ranked in the order of urban Guangzhou > urban Hong Kong > background Hong Kong. Total carbonaceous aerosol (TCA) contributed less to PM_2.5 in urban Guangzhou (32–35%) than that in urban Hong Kong (43–57%). The reason may be that, as an major industrial city in South China, Guangzhou would receive large amount of inorganic aerosol from all kinds of industries, however, as a trade center and seaport, urban Hong Kong would mainly receive organic aerosol and EC from container vessels and heavy-duty diesel trucks. At Hong Kong background site Hok Tsui, relatively lower contribution of TCA to PM_2.5 may result from contributions of marine inorganic aerosol and inland China pollutant. Strong correlation (R²=0.76–0.83) between OC and EC indicates minor fluctuation of emission and the secondary organic aerosol (SOA) formation in urban Guangzhou. Weak correlation between OC and EC in Hong Kong can be related to the impact of the long-range transported aerosol from inland China. Averagely, secondary OC (SOC) concentrations were 3.8–5.9 and 10.2–12.8 μg m⁻³, respectively, accounting for 21–32% and 36–42% of OC in summer and winter in Guangzhou. The average values of 4.2–6.8% for SOA/ PM_2.5 indicate that SOA was minor component in PM_2.5 in Guangzhou.     

Carbonaceous aerosol over a Pinus taeda forest in Central North Carolina,USA

Organic aerosol is the least understood component of ambient fine particulate matter (PM_2.5). In this study, organic and elemental carbon (OC and EC) within ambient PM_2.5 over a three-year period at a forested site in the North Carolina Piedmont are presented. EC exhibited significant weekday/weekend effects and less significant seasonal effects, in contrast to OC, which showed strong seasonal differences and smaller weekend/weekday effects. Summer OC concentrations are about twice as high as winter concentrations, while EC was somewhat higher in the winter. OC was highly correlated with EC during cool periods when both were controlled by primary combustion sources. This correlation decreased with increasing temperature, reflecting higher contributions from secondary organic aerosol, likely of biogenic origin. PM_2.5 radiocarbon data from the site confirms that a large fraction of the carbon in PM_2.5 is indeed of biogenic origin, since modern (non-fossil fuel derived) carbon accounted for 80% of the PM_2.5 carbon over the course of a year. OC and EC exhibited distinct diurnal profiles, with summertime OC peaking in late evening and declining until midday. During winter, OC peaked during the early morning hours and again declined until midday. Summertime EC peaked during late morning hours except on weekends. Wintertime EC often peaked in late PM or early AM hours due to local residential wood combustion emissions. The highest short term peaks in OC and EC were associated with wildfire events. These data corroborate recent source apportionment studies conducted within 20 km of our site, where oxidation products of isoprene, α-pinene, and β-caryophyllene were identified as important precursors to organic aerosols. A large fraction of the carbon in rural southeastern ambient PM_2.5 appears to be of biogenic origin, which is probably difficult to reduce by anthropogenic controls.     

Exposure of PM2.5 and EC from diesel and gasoline vehicles in communities near the Ports of Los Angeles and Long Beach,California

The Ports of Los Angeles and Long Beach are the entry point for almost half of all cargo containers entering the United States. The use of diesel trucks to move Port-related goods has raised significant public health concerns associated with black carbon and other air pollutants. It is difficult to reliably estimate people's exposure to vehicle-related pollutants due to the narrow impact zone of traffic, usually within 200–300 m downwind of major roadways. Previous studies suffer from the lack of traffic count data on surface streets and the lack of neighborhood-level population data. We examined seasonal and annual average exposures of particulate matter less than 2.5 μm (PM_2.5) and elemental carbon (EC) at a neighborhood scale for communities heavily impacted by diesel trucks near these ports. We assembled a traffic-activity database that distinguishes gasoline and diesel vehicles on both freeways and surface streets, by consolidating information from several sources, including our own field measurements. The CALINE4 model was used to estimate residential exposure of the study population to PM_2.5 and EC. Parcel property data were used to allocate Census block group (BG) population to increase spatial resolution. The annual average PM_2.5 and EC exposure due to local traffic was 3.8 and 0.4 μg m^?3, respectively. On average, surface streets contributed a little more than freeways (55% vs. 45% for EC and 57% and 43% for PM_2.5). Light-duty vehicles contributed significantly more than heavy-duty trucks for PM_2.5 (61% vs. 39%), but slightly less than heavy-duty trucks for EC (49% vs. 51%). Community mean population exposure was similar using parcel, census block, and BG population data, but extreme values and standard deviations varied significantly at different spatial resolutions. The intake fraction for the study population was in the range of 1.0–2.2 × 10^?5 by vehicle type, roadway type, and season.     

Characteristics of vertical profiles and sources of PM2.5, PM10 and carbonaceous species in Beijing

In August 2003 during the anticipated month of the 2008 Beijing Summer Olympic Games, we simultaneously collected PM₁₀ and PM_2.5 samples at 8, 100, 200 and 325 m heights up a meteorological tower and in an urban and a suburban site in Beijing. The samples were analysed for organic carbon (OC) and elemental carbon (EC) contents. Particulate matter (PM) and carbonaceous species pollution in the Beijing region were serious and widespread with 86% of PM_2.5 samples exceeding the daily National Ambient Air Quality Standard of the USA (65 μg m⁻³) and the overall daily average PM₁₀ concentrations of the three surface sites exceeding the Class II National Air Quality Standard of China (150 μg m⁻³). The maximum daily PM_2.5 and PM₁₀ concentrations reached 178.7 and 368.1 μg m⁻³, respectively, while those of OC and EC reached 22.2 and 9.1 μg m⁻³ in PM_2.5 and 30.0 and 13.0 μg m⁻³ in PM₁₀, respectively. PM, especially PM_2.5, OC and EC showed complex vertical distributions and distinct layered structures up the meteorological tower with elevated levels extending to the 100, 200 and 300 m heights. Meteorological evidence suggested that there exist fine atmospheric layers over urban Beijing. These layers were featured by strong temperature inversions close to the surface (<50 m) and more stable conditions aloft. They enhanced the accumulation of pollutants and probably caused the complex vertical distributions of PM and carbonaceous species over urban Beijing. The built-up of PM was accompanied by transport of industrial emissions from the southwest direction of the city. Emissions from road traffic and construction activities as well as secondary organic carbon (SOC) are important sources of PM. High OC/EC ratios (range of 1.8–5.1 for PM_2.5 and 2.0–4.3 for PM₁₀) were found, especially in the higher levels of the meteorological tower suggesting there were substantial productions of SOC in summer Beijing. SOC is estimated to account for at least 33.8% and 28.1% of OC in PM_2.5 and PM₁₀, respectively, with higher percentages at the higher levels of the tower.     

Concentrations of carbonaceous species in particles at Seoul and Cheju in Korea

Concentrations of elemental carbon (EC) and organic carbon (OC) in particles at Seoul and Cheju Island, Korea were observed in 1994. PM₁₀ and PM_2.5 were collected by a modified SCAQS (Southern California Air Quality Study) sampler from Seoul during June 1994 and PM_2.5 were collected by a low-volume sampler at Cheju Island during July and August 1994. The selective thermal oxidation method with MnO₂ catalyst was used for analysis. The EC concentrations from Seoul were higher than those at Los Angeles, USA during the SCAQS study while the OC concentrations were comparable to those during the SCAQS study. At Cheju Island, the OC concentrations were higher than those at other clean areas in the world but the EC concentrations were lower than or comparable to those at other clean areas in the world. The OC to EC ratios of Seoul suggest that the carbonaceous species are mostly from primary emission sources. In Cheju, during July 1994 air pollutant levels were high and it was suggested that atmospheric transformation/transport of organics and biogenic emissions were main sources of carbonaceous species in particles. The carbonaceous species levels were low during August 1994 and it was suggested that the levels could be considered as marine background concentrations in the region during summer.     

Calibration and Certification of Audit Devices for Transmissometers

Abstract

Speciated fine particulate matter (PM_2.5) data collected as part of the Speciation Trends Network at four sites in the Midwest (Detroit, MI; Cincinnati, OH; Indianapolis, IN; and Northbrook, IL) and as part of the Interagency Monitoring of Protected Visual Environments program at the rural Bondville, IL, site were analyzed to understand sources contributing to organic carbon (OC) and PM_2.5 mass. Positive matrix factorization (PMF) was applied to available data collected from January 2002 through March 2005, and seven to nine factors were identified at each site. Common factors at all of the sites included mobile (gasoline)/secondary organic aerosols with high OC, diesel with a high elemental carbon/OC ratio (only at the urban sites), secondary sulfate, secondary nitrate, soil, and biomass burning. Identified industrial factors included copper smelting (North–brook, Indianapolis, and Bondville), steel/manufacturing with iron (Northbrook), industrial zinc (North–brook, Cincinnati, Indianapolis, and Detroit), metal plating with chromium and nickel (Detroit, Indianapolis, and Bondville), mixed industrial with copper and iron (Cincinnati), and limestone with calcium and iron (Bondville). PMF results, on average, accounted for 96% of the measured PM_2.5 mass at each site; residuals were consistently within tolerance (±3), and goodness–of–fit (Q) was acceptable. Potential source contribution function analysis helped identify regional and local impacts of the identified source types. Secondary sulfate and soil factors showed regional characteristics at each site, whereas industrial sources typically appeared to be locally influenced. These regional factors contributed approximately one third of the total PM_2.5 mass, on average, whereas local mobile and industrial sources contributed to the remaining mass. Mobile sources were a major contributor (55–76% at the urban sites) to OC mass, generally with at least twice as much mass from nondiesel sources as from diesel. Regional OC associated with secondary sulfate and soil was generally low.     

Characterization of Carbonaceous Species of Ambient PM2.5 in Beijing,China

Abstract

One-week integrated fine particulate matter (i.e., particles <2.5 μm in diameter; PM_2.5) samples were collected continuously with a low-flow rate sampler at a downtown site (Chegongzhuang) and a residential site (Tsinghua University) in Beijing between July 1999 and June 2000. The annual average concentrations of organic carbon (OC) and elemental carbon (EC) at the urban site were 23.9 and 8.8 μg m^?3, much higher than those in some cities with serious air pollution. Similar weekly variations of OC and EC concentrations were found for the two sampling sites with higher concentrations in the winter and autumn. The highest weekly variations of OC and EC occurred in the winter, suggesting that combustion sources for space heating were important contributors to carbonaceous particles, along with a significant impact from variable meteorological conditions. High emissions coupled with unfavorable meteorological conditions led to the max weekly carbonaceous concentration the week of November 18–25, 1999. The weekly mass ratios of OC:EC ranged between 2 and 4 for most samples and averaged 2.9, probably suggesting that secondary OC (SOC) is present most weeks. The range of contemporary carbon fraction, based on the C14 analyses of eight samples collected in 2001, is 0.330–0.479. Estimated SOC accounted for ～38% of the total OC at the two sites. Average OC and EC concentrations at Tsinghua University were 25% and 18%, respectively, higher than those at Chegongzhuang, which could be attributed to different local emissions of primary carbonaceous particles and gaseous precursors of SOC, as well as different summer photochemical intensities between the two locations.     

Sources and characteristics of carbonaceous aerosols at Agra “World heritage site” and Delhi “capital city of India”

Agra, one of the oldest cities “World Heritage site”, and Delhi, the capital city of India are both located in the border of Indo-Gangetic Plains (IGP) and heavily loaded with atmospheric aerosols due to tourist place, anthropogenic activities, and its topography, respectively. Therefore, there is need for monitoring of atmospheric aerosols to perceive the scenario and effects of particles over northern part of India. The present study was carried out at Agra (AGR) as well as Delhi (DEL) during winter period from November 2011 to February 2012 of fine particulate (PM_2.5: d?<?2.5 μm) as well as associated carbonaceous aerosols. PM_2.5 was collected at both places using medium volume air sampler (offline measurement) and analyzed for organic carbon (OC) and elemental carbon (EC). Also, simultaneously, black carbon (BC) was measured (online) at DEL. The average mass concentration of PM_2.5 was 165.42?±?119.46 μg m^?3 at AGR while at DEL it was 211.67?±?41.94 μg m^?3 which is ~27 % higher at DEL than AGR whereas the BC mass concentration was 10.60 μg m^?3. The PM_2.5 was substantially higher than the annual standard stipulated by central pollution control board and United States Environmental Protection Agency standards. The average concentrations of OC and EC were 69.96?±?34.42 and 9.53?±?7.27 μm m^?3, respectively. Total carbon (TC) was 79.01?±?38.98 μg m^?3 at AGR, while it was 50.11?±?11.93 (OC), 10.67?±?3.56 μg m^?3 (EC), and 60.78?±?14.56 μg m^?3 (TC) at DEL. The OC/EC ratio was 13.75 at (AGR) and 5.45 at (DEL). The higher OC/EC ratio at Agra indicates that the formation of secondary organic aerosol which emitted from variable primary sources. Significant correlation between PM_2.5 and its carbonaceous species were observed indicating similarity in sources at both sites. The average concentrations of secondary organic carbon (SOC) and primary organic carbon (POC) at AGR were 48.16 and 26.52 μg m^?3 while at DEL it was 38.78 and 27.55 μg m^?3, respectively. In the case of POC, similar concentrations were observed at both places but in the case of SOC higher over AGR by 24 in comparison to DEL, it is due to the high concentration of OC over AGR. Secondary organic aerosol (SOA) was 42 % higher at AGR than DEL which confirms the formation of secondary aerosol at AGR due to rural environment with higher concentrations of coarse mode particles. The SOA contribution in PM_2.5 was also estimated and was ~32 and 12 % at AGR and DEL respectively. Being high loading of fine particles along with carbonaceous aerosol, it is suggested to take necessary and immediate action in mitigation of the emission of carbonaceous aerosol in the northern part of India.     

Attainment Flip-Flops and the Achievability of the Ozone Air Quality Standard

Abstract

This paper presents the results of the first reported study on fine particulate matter (PM) chemical composition at Salamanca, a highly industrialized urban area of Central Mexico. Samples were collected at six sites within the urban area during February and March 2003. Several trace elements, organic carbon (OC), elemental carbon (EC), and six ions were analyzed to characterize aerosols. Average concentrations of PM with aerodynamic diameter of less than 10 μm (PM₁₀) and fine PM with aerodynamic diameter of less than 2.5 μm (PM_2.5) ranged from 32.2 to 76.6 μg m^-3 and 11.1 to 23.7 μg m^-3, respectively. OC (34%), SO₄ ⁼ (25.1%), EC (12.9%), and geological material (12.5%) were the major components of PM_2.5. For PM₁₀, geological material (57.9%), OC (17.3%), and SO₄ ⁼ (9.7%) were the major components. Coarse fraction (PM₁₀ –PM_2.5), geological material (81.7%), and OC (8.6%) were the dominant species, which amounted to 90.4%. Correlation analysis showed that sulfate in PM_2.5 was present as ammonium sulfate. Sulfate showed a significant spatial variation with higher concentrations to the north resulting from predominantly southwesterly winds above the surface layer and by major SO₂ sources that include a power plant and refinery. At the urban site of Cruz Roja it was observed that PM_2.5 mass concentrations were similar to the submicron fraction concentrations. Furthermore, the correlation between EC in PM_2.5 and EC measured from an aethalometer was r² = 0.710. Temporal variations of SO₂ and nitrogen oxide were observed during a day when the maximum concentration of PM_2.5 was measured, which was associated with emissions from the nearby refinery and power plant. From cascade impactor measurements, the three measured modes of airborne particles corresponded with diameters of 0.32, 1.8, and 5.6 μm.     

Source apportionment of fine particles at urban background and rural sites in the UK atmosphere

Airborne fine particulate matter (PM_2.5) has been collected at two sites in the West Midlands conurbation, UK, representing urban background and rural locations. Chemical analyses have been carried out for major anions, trace metals, total OC and EC, and for individual organic marker species including n-alkanes, hopanes, PAHs, organic acids and sterols. Source apportionment has been conducted using both a pragmatic mass closure model and the US EPA chemical mass balance (CMB) model. The pragmatic mass closure model is well able to account for the measured PM_2.5 mass in terms of chemical/source components, and the chemical mass balance model has been used to apportion the carbonaceous component of the aerosol. The dominant components of PM_2.5 at both sites are secondary inorganic (sulphate and nitrate) and carbonaceous particles. The CMB model shows the latter to arise mainly from road traffic sources, with smaller contributions from vegetative detritus, wood smoke, natural gas, coal, and dust/soil. The CMB model also identifies an important component of the organic aerosol not associated with these primary sources, which correlates very strongly with secondary organic aerosol estimated from the OC/EC ratio. The split between different automotive source types does not relate well to UK emission inventories, and may indicate that CMB source profiles from North American studies and different carbon analysis protocols may lead to erroneous conclusions.     

Multi-year hourly PM2.5 carbon measurements in New York: Diurnal,day of week and seasonal patterns

Multi-year hourly measurements of PM_2.5 elemental carbon (EC) and organic carbon (OC) from a site in the South Bronx, New York were used to examine diurnal, day of week and seasonal patterns. The hourly carbon measurements also provided temporally resolved information on sporadic EC spikes observed predominantly in winter. Furthermore, hourly EC and OC data were used to provide information on secondary organic aerosol formation. Average monthly EC concentrations ranged from 0.5 to 1.4 μg m^?3 with peak hourly values of several μg m^?3 typically observed from November to March. Mean EC concentrations were lower on weekends (approximately 27% lower on Saturday and 38% lower on Sunday) than on weekdays (Monday to Friday). The weekday/weekend difference was more pronounced during summer months and less noticeable during winter. Throughout the year EC exhibited a similar diurnal pattern to NO_x showing a pronounced peak during the morning commute period (7–10 AM EST). These patterns suggest that EC was impacted by local mobile emissions and in addition by emissions from space heating sources during winter months. Although EC was highly correlated with black carbon (BC) there was a pronounced seasonal BC/EC gradient with summer BC concentrations approximately a factor of 2 higher than EC. Average monthly OC concentrations ranged from 1.0 to 4.1 μg m^?3 with maximum hourly concentrations of 7–11 μg m^?3 predominantly in summer or winter months. OC concentrations generally correlated with PM_2.5 total mass and aerosol sulfate and with NO_x during winter months. OC showed no particular day of week pattern. The OC diurnal pattern was typically different than EC except in winter when OC tracked EC and NO_x indicating local primary emissions contributed significantly to OC during winter at the urban location. On average secondary organic aerosol was estimated to account for 40–50% of OC during winter and up to 63–73% during summer months.     

Concentrations and distributions of carbonaceous species in ambient particles in Kaohsiung City,Taiwan

Concentrations and distributions of elemental carbon (EC) and organic carbon (OC) in particles were measured in Kaohsiung City, Taiwan. PM₁₀ and PM_2.5 samples were collected using a dichotomous sampler from November 1998 to April 1999 and were analyzed for carbonaceous species with an elemental analyzer. The concentrations of carbonaceous species in Kaohsiung City were comparable to those at other urban locations in the world. On average, carbonaceous species accounted for 21.2% of the PM_2.5 and 18.1% of the PM₁₀. It was found that organic carbon dominated the carbonaceous species and was 72.2 and 70.4% of total carbon (TC) for PM_2.5 and PM₁₀. The secondary organic carbon formed through the volatile organic compound gas-to-particle conversion was estimated from the minimum ratio between elemental and organic carbon obtained in this study, and was found to constitute 40.0 and 32.4% of the total organic carbon particle for PM_2.5 and PM₁₀ (or 6.6 and 4.5% of the total particle mass).     

Estimations of primary and secondary organic carbon formation in PM2.5 aerosols of Santiago City,Chile

High concentration of fine airborne particulates is considered one of the major environmental pollutants in Santiago, the Chilean Capital city, which in 1997 was declared a PM₁₀ saturated zone. To date there is no control of the amounts of fine and coarse aerosols concentrations and the source and chemical characterizations of the PM_2.5 particulates in the carbonaceous fractions are not well known even though this fraction could be represented almost the 50% in mass of the PM_2.5.In this work, we present for the first time determinations of primary organic aerosol (POA) and secondary organic aerosol composition (SOA) fractions of the total mass of PM_2.5 particulates collected in the urban atmosphere of Santiago City. Our purpose is to know the anthropogenic contributions to the formation of SOA. To accomplish this we used the elemental carbon (EC) and organic carbon (OC) determinations developed by automatic monitoring stations installed in the city during the period 2002–2005, with a particular analysis of the summer time occurred in February 2004. Based on the EC tracer method, we have estimated the POA and SOA fraction and our data permit us to estimate the SOA reaching up to 20% of total organic aerosol matter, in good agreement to other measurements observed in large cities of Europe and U.S.A.     

Characterization of carbonaceous species in PM2.5 in Xi'an during spring

The characterization of carbonaceous species in PM_2.5 during a spring period in a suburb of Xi'an, China was investigated. PM_2.5 samples were collected on quartz filters and analyzed for organic carbon (OC) and elemental carbon (EC). The thermal optical reflectance method was used. The minimum OC/EC ratio method was used to estimate the concentration of secondary organic carbon (SOC). The distribution of eight carbon fractions was investigated as well. The average mass concentrations of OC and EC were 15.90 and 8.38 μg/m³, respectively. The average OC/EC ratio ranged from 1.16 to 3.16 with an average value of 2.25. This implies the existence of SOC in PM_2.5. The mean SOC concentration was 7.20 μg/m³, accounting for 45.28% of total OC. This result suggests that SOC is a significant component of OC in the suburb of Xi'an. Results from the distribution of eight carbon fractions revealed that emissions from motor vehicle, coal combustion, and road dust were the main source of carbonaceous particles in the sampling period.