Characteristics Of Carbonaceous Aerosols Research Articles

A two-year database of BC measurements at the biggest European crude oil pre-treatment plant: a comparison with organic gaseous compounds and PM10 loading

A two-year data-set of black carbon (BC) measurements collected in a site in South Italy close to the biggest European pre-treatment plant (COVA) of crude oil has been studied. The area named Val d'Agri, in Basilicata Region, is also crossed by the main road SS598. Data have been collected by using a 7 wavelength aethalometer allowing the measurement of equivalent black carbon (EBC) content, the estimation of Ångström absorption exponent (AAE), and the detection of organic fraction presence through UVPM (UV-absorbing particulate matter) quantity. Data have been analyzed to distinguish seasonal behaviors and characteristics of carbonaceous aerosols. No evident seasonal patterns have been observed for EBC concentrations with a mean value of 643±415ng/m3 and a large short-term variability, with frequent periods (few days or few weeks) of intense emissions associated to COVA activities. EBC averaged daily trends show two main peaks, one in the morning and one in the evening suggesting a contribution of traffic as a background source of BC on a long-term basis, due to the SS598 passing near the measurement site. On a four month period in 2013, a comparison with co-located PM10 concentrations data has been carried out showing a relevant contribution of EBC to the total particle loading at the site. Unlike EBC, AAE shows higher values (maximum value 1.3±0.3) during cold periods and lower values (minimum value 0.9±0.2) in the warmer seasons. Anti-correlation has been observed when comparing AAE with both solar radiation and temperature. In addition, enhanced values during night time for AAE average daily patterns have been observed despite the seasons, suggesting relevant additional sources of organic carbon other than traffic related to COVA emissions during the year. Moreover a good agreement, on a short-term basis, has been found among UVPM, benzene, toluene.

Characteristics of carbonaceous aerosols emitted from peatland fire in Riau, Sumatra, Indonesia (2): Identification of organic compounds

Smoke emitted from Indonesian peatland fires has caused dense haze and serious air pollution in Southeast Asia such as visibility impairment and adverse health impacts. To mitigate the Indonesian peatland fire aerosol impacts, an effective strategy and international framework based on the latest scientific knowledge needs to be established. Although several attempts have been made, limited data exist regarding the chemical characteristics of peatland fire smoke for the source apportionment. In order to identify the key organic compounds of peatland fire aerosols, we conducted intensive field studies based on ground-based and source-dominated sampling of PM2.5 in Riau Province, Sumatra, Indonesia, during the peatland fire seasons in 2012. Levoglucosan was the most abundant compound among the quantified organic compounds at 8.98 ± 2.28% of the PM2.5 mass, followed by palmitic acid at 0.782 ± 0.163% and mannosan at 0.607 ± 0.0861%. Potassium ion was not appropriate for an indicator of Indonesian peatland fires due to extremely low concentrations associated with smoldering fire at low temperatures. The vanillic/syringic acids ratio was 1.06 ± 0.155 in this study and this may be a useful signature profile for peatland fire emissions. Particulate n-alkanes also have potential for markers to identify impact of Indonesian peatland fire source at a receptor site.

Characteristics of carbonaceous aerosols in Beijing based on two–year observation

Both organic carbon (OC) and elemental carbon (EC) play an important role in climate change and human health. In the present work, OC and EC analysis was done for size segregated aerosols collected in Beijing during a period of two years (2009–2011). Both OC and EC concentrations exhibited a bimodal size distribution with the fine mode at 0.43–0.65 μm and the coarse mode at 4.7–5.8 μm. The carbonaceous species were prone to enrich in the fine particles, with 22.5±11.5 and 15.9±5.6 μg m-3 of OC and 2.7±1.5 and 1.1±0.7 μg m-3 of EC in the fine particles (PM2.1) and the coarse particles (PM>2.1), respectively. OC and EC accounted for 39.9% and 8.2%, respectively, of PM mass in <0.43 μm size range. The highest concentrations of carbonaceous species were noticed during winter. An increase in carbonaceous species between the two–year observations may be mainly attributed to the increasing vehicular exhaust in Beijing and the increasing emissions from coal combustion in neighboring provinces. The concentrations of secondary organic carbon (SOC) were the highest in PM2.1 for winter and the lowest in PM>2.1 for autumn. SOC averagely contributed to OC (56.5%) in the aerosols of Beijing during the two-–year observation.

Source apportionment and seasonal variation of PM2.5 carbonaceous aerosol in the Beijing-Tianjin-Hebei Region of China

The seasonal variation of PM2.5 carbonaceous aerosol was investigated in Beijing and Tangshan cities of China. The characteristics of carbonaceous aerosol (e.g., organic carbon, OC and elemental carbon, EC) under different weather conditions and their source apportionment were also examined. The annual average PM2.5 concentration in the study area reached 95.6-197.3 μg/m(3), showing seasonal and spatial variation. The carbonaceous materials accounted for 17.3-21.2 % of the PM2.5, and they had a much higher content under haze weather condition. It was found that the PM2.5 contained more OC than EC. Principal component analysis (PCA) results indicated that the carbonaceous components came from mixed emission sources of coal combustion, vehicle exhaust, and biomass burning. In Beijing, the vehicle emission made a contribution of 63.0 % to the carbonaceous components of PM2.5 in summer, which is higher than that in Tangshan. While in Tangshan, the coal combustion made a contribution of 30.3 %, which is much higher than that in Beijing.

Size distribution characteristics of carbonaceous aerosol in a rural location in northwestern China

Size-segregated aerosol samples were collected in Dunhuang, China during 2012. The carbonaceous aerosols were quantified with the thermal/optical reflectance (TOR) method. In this study, two modes were observed in the size distribution of respective carbonaceous components. The first mode was the fine particle mode, and the second mode was in the coarse size range. OC, OP, and char showed a bimodal size distribution, with the fine particles as the major fraction in summer, autumn, and winter. Each of these components exhibited a similar seasonal pattern with the highest concentrations in winter and the lowest concentrations in summer. The highest soot (EC2 + 3, sum of EC2 and EC3) concentrations were in spring and the lowest concentrations were in fall, both in the fine and coarse modes. The correlations between different carbon fractions in size-segregated aerosol samples are discussed. OC and EC in Dunhuang are derived from coal combustion, biomass burning, and motor exhaust. The highest values of char/soot occurred in autumn, and lower values were found in the winter due to increased coal combustion.

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 (PM₂.₅: d < 2.5 μm) as well as associated carbonaceous aerosols. PM₂.₅ 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 PM₂.₅ 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 PM₂.₅ 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 PM₂.₅ 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 PM₂.₅ 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.

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, PM2.5) and OC during the summer (PM2.5 = 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 PM2.5 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.

Characteristics of carbonaceous aerosols emitted from peatland fire in Riau, Sumatra, Indonesia

Biomass burning is a significant source of fine particulate matter (PM2.5). Forest, bush, and peat fires in Kalimantan and Sumatra, Indonesia are major sources of transboundary haze pollution in Southeast Asia. However, limited data exist regarding the chemical characteristics of aerosols at sources. We conducted intensive field studies in Riau Province, Sumatra, Indonesia, during the peatland fire and non-burning seasons in 2012. We characterized PM2.5 carbonaceous aerosols emitted from peatland fire based on ground-based source-dominated sampling. PM2.5 aerosols were collected with two mini-volume samplers using Teflon and quartz fiber filters. Background aerosols were also sampled during the transition period between the non-burning and fire seasons. We analyzed the carbonaceous content (organic carbon (OC) and elemental carbon (EC)) by a thermal optical reflectance utilizing the IMPROVE_A protocol and the major organic components of the aerosols by a gas chromatography/mass spectrometry. PM2.5 aerosols emitted from peatland fire were observed in high concentrations of 7120 ± 3620 μg m−3 and were primarily composed of OC (71.0 ± 5.11% of PM2.5 mass). Levoglucosan exhibited the highest total ion current and was present at concentrations of 464 ± 183 μg m−3. The OC/EC ratios (36.4 ± 9.08), abundances of eight thermally-derived carbon fractions, OC/Levoglucosan ratios (10.6 ± 1.96), and Levoglucosan/Mannosan ratios (10.6 ± 2.03) represent a signature profile that is inherent in peatland fire. These data will be useful in identifying contributions from single or multiple species in atmospheric aerosol samples collected from peatland fires.

제주도 고산지역 탄소 성분의 특성 분석 - 유기탄소의 열광학적 특성 및 유기성분 중심으로

Abstract Ground-based measurements were conducted from August 25 to September 8 of 2011 for understandingcharacteristics of carbonaceous aerosols measured at Gosan. Chemical components and their sources werediscussed by analysis of organic compounds with identification of primary and secondary products in particulatematter. Thus, organic carbon (OC) and elemental carbon (EC) based on the carbonaceous thermal distribution(CTD), which provides detailed carbon signature characteristics relative to analytical temperature, was used toimprove the carbon fractionation of the analytical method. In addition, organic compounds by gas chromatographytechnique with the backward trajectories were discussed for characteristics of carbonaceous aerosols. Different air-masses were classified related to the OC thermal signatures and the organic molecular markers such as aromaticacids and PAHs. We concluded that the aging process was influenced by the long-range transport from East Seaarea. Key words : Organic, Organic compounds, OC, EC

Characteristics of carbonaceous aerosol in the region of Beijing, Tianjin, and Hebei, China

More than 400 PM2.5 samples were collected at four urban sites in Beijing (BJ), Tianjin (TJ), Shijiazhuang (SJZ), and Chengde (CD), and also one site in Shangdianzi (SDZ), which was used as a regional background station, over four seasons from 2009 to 2010. The organic carbon (OC) and elemental carbon (EC) in each sample were analyzed. The average annual concentrations were 71.8–191.2 μg m−3 for PM2.5, 10.8–26.4 μg m−3 for OC, and 3.9–9.7 μg m−3 for EC at the five sites. OC and EC concentrations were lower in the spring and summer and much higher in the autumn and winter, mainly due to aerosol emissions from additional fuel combustion for heating. OC/EC ratios were lowest in the summer and highest in the winter at SDZ, BJ, TJ, and SJZ. These seasonal trends indicate that the characteristics of carbonaceous aerosol pollution were spatially similar and season-dependent in the plain area of Beijing, Tianjin, and Hebei (BTH). An EC tracer method was used to calculate the concentrations for secondary organic carbon (SOC); SOC concentrations were also higher in the autumn and winter and lowest during the summer at all five sites. A stable atmosphere and low temperatures, which were more frequent during the winter and autumn, facilitated the accumulation of air pollutants and accelerated the condensation or adsorption of volatile organic compounds in the BTH area. Over the past ten years (1999–2009), Beijing had observed a decrease in the EC concentrations during every season and a remarkable reduction in aerosol emissions from coal combustion for heating.

Carbonaceous aerosol and its characteristics observed in Tokyo and south Kanto region

Due to enforcing vehicle emission reduction requirements in Japan, particulate matter (PM) concentration, especially elemental carbon (EC) concentration in roadside atmosphere, obviously decreased in the last decade. In spite of the previous vehicle emission reduction, EC concentration was not shown a clear decrease, recently. To achieve the PM2.5 environmental standard, measurements based on emission source contribution are desirable. However, source apportionment of carbonaceous aerosol was ambiguous because chemical components are complicated, and the components change through photochemical reaction.The goal of this study is to determine source apportionment for carbonaceous aerosols. Examination of PM2.5 was performed in south Kanto including Tokyo in the summer of 2008 and the winter of 2009. Emissions from the industrial area around Tokyo Bay and the agricultural northern area showed transportation and accumulation due to the seasonal prevailing wind. The emissions formed a geographical distribution due to photochemical reactions. The characteristics of carbonaceous aerosol were obtained using carbon profile analysis and carbon isotope analysis, including the source information such as fossil fuel emission origin, vegetation origin, and combustion product, photochemical reaction product, etc.Soot-EC was found as a substance with fossil fuel origin which did not contain biomass combustion matter, and since it is stable, there was no observed difference by site and a uniform concentration was observed in winter. It became apparent from the carbon isotope analysis using 14C that the carbon from the biomass origin involved 29% in total carbon in the summer, and 48% in winter even at Kudan of central Tokyo.

Fine carbonaceous aerosol characteristics at a coastal rural site in the Central Mediterranean as given by OCEC online measurements

In order to know the variability and to understand the sources of carbonaceous aerosol in the Central Mediterranean area, a two month (May and June 2010) field campaign was carried out at Trisaia ENEA Research Centre (Italy). The semi-continuous measurements of organic carbon (OC) and elemental carbon (EC) showed one order of magnitude variation during the campaign, with very low EC concentrations. The diurnal variation of EC was similar to the diurnal variation of NO2 concentration, of number concentration of aerosol particles with diameters between 0.25 and 2.5μm and of traffic flow while the diurnal variation of OC was more related to the meteorological conditions. The increase of OC observed early in the morning may be due to an increase of the secondary organic aerosol (SOA) fraction, in low wind conditions, increasing solar radiation and in the presence of air masses rich in volatile organic compounds (VOC) transported from the NW, and due to the presence of primary biological aerosol particles such as bacteria, spores and pollen.

Time-Resolved Measurements of PM2.5 Carbonaceous Aerosols at Gosan, Korea

ABSTRACT In order to better understand the characteristics of atmospheric carbonaceous aerosol at a background site in Northeast Asia, semicontinuous organic carbon (OC) and elemental carbon (EC), and time-resolved water-soluble organic carbon (WSOC) were measured by a Sunset OC/EC and a PILS-TOC (particle-into-liquid sampler coupled with an online total organic carbon) analyzer, respectively, at the Gosan supersite on Jeju Island, Korea, in the summer (May 28–June 17) and fall (August 24–September 30) of 2009. Hourly average OC concentration varied in the range of approximately 0.87–28.38 μgC m−3, with a mean of 4.07 ± 2.60 μgC m−3, while the hourly average EC concentration ranged approximately from 0.04 to 8.19 μgC m−3, with a mean of 1.35 ± 0.71 μgC m−3, from May 28 to June 17, 2009. During the fall season, OC varied in the approximate range 0.9–9.6 μgC m−3, with a mean of 2.30 ± 0.80 μgC m−3, whereas EC ranged approximately from 0.01 to 5.40 μgC m−3, with a mean of 0.66 ± 0.38 μgC m−3. Average contributions of EC to TC and WSOC to OC were 26.0% ± 9.7% and 20.6% ± 7.4%, and 37.6% ± 23.5% and 57.2% ± 22.2% during summer and fall seasons, respectively. As expected, clear diurnal variation of WSOC/OC was found in summer, varying from 0.22 during the nighttime up to 0.72 during the daytime, mainly due to the photo-oxidation process. In order to investigate the effect of air mass pathway on the characteristics of carbonaceous aerosol, 5-day back-trajectory analysis was conducted using the HYSPLIT model. The air mass pathways were classified into four types: Continental (CC), Marine (M), East Sea (ES) and Korean Peninsula (KP). The highest OC/EC ratio of 3.63 was observed when air mass originated from the Continental area (CC). The lowest OC/EC ratio of 0.79 was measured when air mass originated from the Marine area (M). A high OC concentration was occasionally observed at Gosan due to local biomass burning activities. The contribution of secondary OC to total OC varied approximately between 8.4% and 32.2% and depended on air mass type. IMPLICATIONS Organic material contributes approximately 20–90% of the total fine particulate mass concentration at different sites over the world depending on location and season. Organic carbon consists of hundreds of compounds with a wide range of chemical and optical properties. A better understanding of the chemical characteristics of carbonaceous aerosol influenced by increasing anthropogenic pollution in the downwind regions of the East Asian continent is needed in order to determine their impacts on regional air quality and climate change.

Characteristics of carbonaceous aerosol in PM2.5: Pearl Delta River Region, China

Simultaneous measurements of atmospheric organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon (WSOC) were made at four sampling sites, namely Guangzhou (GZ), Zhaoqing (ZQ), PolyU Campus (PU) and Hok Tsui (HT), in the Pearl River Delta (PRD) region between 14 August 2006 and 28 August 2007. The highest concentrations of total carbon (TC) were found at the medium-scale roadside site (PU) and the lowest were found at the regional-scale site (HT). Among the four sampling sites, the average WSOC at ZQ showed the highest concentrations, while the lowest were seen at HT. OC and EC concentrations revealed spring/summer minima and autumn/winter maxima at all sites except PU, which had a consistently high EC concentration all over the year. The highest WSOC/OC ratio was found at ZQ with an average of 0.41, suggesting that the OC was more oxidized in the atmosphere of the semi-rural site. The lowest WSOC/OC was found at the roadside site of PU. Moreover, the WSOC/OC ratio increased in autumn, when the photochemical reactions are the most active in the PRD region. This can be attributed to aging and atmospheric processing of the organic compounds during their transportation, or to the formation of secondary organic aerosol (SOA). Average annual secondary organic carbon (SOC) concentrations in PM2.5 were estimated to be 2.2 and 3.5μgm−3 for GZ and ZQ, comprising 33.5% and 42.8% of the corresponding OC concentrations, respectively. The results indicate that SOC is significant in the PRD region, and its formation mostly occurs within the region.

Carbonaceous Aerosol Characteristics in Outdoor and Indoor Environments of Nanchang, China, during Summer 2009

ABSTRACT A study of carbonaceous aerosol was initiated in Nanchang, a city in eastern China, for the first time. Daily and diurnal (daytime and nighttime) PM2.5 (particulate matter with aerodynamic diameter ≤2.5 μm) samples were collected at an outdoor site and in three different indoor environments (common office, special printing and copying office, and student dormitory) in a campus of Nanchang University during summer 2009 (5–20 June). Daily PM10 (particulate matter with aerodynamic diameter ≤10 μm) samples were collected only at the outdoor site, whereas PM2.5 samples were collected at both indoor and outdoor sites. Loaded PM2.5 and PM10 samples were analyzed for organic and elemental carbon (OC, EC) by thermal/optical reflectance following the Interagency Monitoring of Protected Visual Environments—Advanced (IMPROVE-A) protocol. Ambient mass concentrations of PM10 and PM2.5 in Nanchang were compared with the air quality standards in China and the United States, and revealed high air pollution levels in Nanchang. PM2.5 accounted for about 70% of PM10, but the ratio of OC and EC in PM2.5 to that in PM10 was higher than 80%, which indicated that OC and EC were mainly distributed in the fine particles. The variations of carbonaceous aerosol between daytime and nighttime indicated that OC was released and formed more rapidly in daytime than in nighttime. OC/EC ratios were used to quantify secondary organic carbon (SOC). The differences in SOC and SOC/OC between daytime and nighttime were useful in interpreting the secondary formation mechanism. The results of (1) OC and EC contributions to PM2.5 at indoor sites and the outdoor site; (2) indoor–outdoor correlation of OC and EC; (3) OC–EC correlation; and (4) relative contributions of indoor and outdoor sources to indoor carbonaceous aerosol indicated that OC indoor sources existed in indoor sites, with the highest OC emissions in I2 (the special printing and copying office), and that indoor EC originated from outdoor sources. The distributions of eight carbon fractions in emissions from the printer and copier showed obviously high OC1 (>20%) and OC2 (∼30%), and obviously low EC1−OP (a pyrolyzed carbon fraction) (<10%), when compared with other sources. IMPLICATIONS Ambient PM2.5 and PM10 in Nanchang showed serious pollution levels. OC and EC were mainly distributed in the fine particle fraction. Interestingly, daytime and nighttime carbonaceous aerosol and SOC and SOC/OC values were compared and indicated that OC was released and formed more rapidly in daytime. From analysis of the distribution of OC and EC, indoor–outdoor correlation, OC–EC correlation, and the relative contributions of indoor and outdoor sources to indoor carbonaceous aerosol, we confirmed the presence of indoor OC sources and limited indoor EC sources. Carbon fractions in emissions from the printer and copier showed obviously high OC1 and OC2 contributions and low EC1−OP percentages. The study contributes a significant reference for the control of indoor carbonaceous sources.

Carbonaceous aerosol characteristics over a Pinus taeda plantation: Results from the CELTIC experiment

Carbonaceous particles smaller than 2.5 μm aerodynamic diameter (PM 2.5 ) were collected in July, 2003 over a Loblolly Pine plantation at Duke Forest, NC during the C hemical E mission, L oss, T ransformation and I nteractions within C anopies (CELTIC) field study. Organic (OC) and elemental (EC) carbon in PM 2.5 ranged from 1.4–6.3 and 0.08–0.41 μg C m −3 , respectively, and concentrations measured above and below the pine canopy were in good agreement. Ambient OC was lower (<3 μg C m −3 ) during cooler periods (daytime maximum temperatures < 28 °C) and for periods following precipitation events, and was higher (>3 μg C m −3 ) during warm humid periods. Radiocarbon analysis indicates that on average 83% (range 78–91%) of the PM 2.5 carbon was derived from contemporary (biogenic VOC and biomass burning) sources. This is higher than previous estimates from urban and suburban sites, and in good agreement with recently published data from other rural sites throughout the U.S. The estimates of contemporary PM 2.5 carbon may represent a lower limit for this site since the sampler was located above the center of a 30 meter diameter plot fumigated with 200 ppm CO 2 derived from fossil carbon sources. However, this effect is likely to be negligible. The regression relationship between OC/EC ratios and percent biogenic carbon in aerosol is very similar to those observed in recent summertime data from Tennessee and Florida. However, our values for both OC/EC and percent biogenic carbon are higher than those observed in the latter studies, likely due to the more rural character of the site. Simple box model estimates indicate that biogenic VOC (BVOC) emissions measured at the site provide sufficient reactive carbon sources to account for the observed levels of aerosol biogenic carbon. The magnitude and temporal pattern in the box model secondary organic aerosol estimates correlate well with the ambient aerosol carbon measurements. The model estimates of the relative contribution of isoprene , α-pinene, and β-caryophyllene oxidation to PM 2.5 carbon are in reasonable agreement with a study recently conducted at a nearby site where aerosol tracers of these compounds were quantitatively analyzed in ambient PM 2.5 . Pinic acid concentrations in the below-canopy PM 2.5 during CELTIC (from another recently published study) similarly suggest a significant contribution of α-pinene oxidation to PM 2.5 carbon. The biomass burning tracers potassium and levoglucosan yielded fire contribution estimates to PM 2.5 consistent with their respective published emission factors. These estimates indicate that biomass burning accounted for 1 to 5% (0.015 to 0.30 μg C m −3 ) of the PM 2.5 carbon during CELTIC.

Characteristics of carbonaceous aerosols in ambient PM 10 and PM 2.5 particles in Dar es Salaam, Tanzania

Ambient daytime and nighttime PM 10 and PM 2.5 samples were collected in parallel at a kerbside in Dar es Salaam in August and September 2005 (dry season) and in April and May 2006 (wet season). All samples were analyzed for the particulate matter mass, for organic, elemental, and total carbon (OC, EC, and TC), and for water-soluble OC (WSOC). The average PM 10 and PM 2.5 mass concentrations and associated standard deviations were 76 ± 32 µg/m 3 and 26 ± 7 µg/m 3 for the 2005 dry season and 52 ± 27 µg/m 3 and 19 ± 10 µg/m 3 for the 2006 wet season campaign. On average, TC accounted for 29% of the PM 10 mass and 49% of the PM 2.5 mass for the 2005 dry season campaign and the corresponding values for the 2006 wet season campaign were 35% and 59%. There was little difference between the two campaigns for the WSOC/OC ratios with the PM 2.5 fraction having higher ratios than the PM 10 fraction during each campaign. Also for EC/TC higher ratios were noted in PM 2.5 than in PM 10, but the ratios were substantially larger in the 2006 wet season than in the 2005 dry season. The large EC/TC ratios (means 0.22–0.38) reflect the substantial impact from traffic at Dar es Salaam, as was also apparent from the clear diurnal variation in OC levels, with higher values during the day. A simple source apportionment approach was used to apportion the OC to traffic and charcoal burning. On average, 70% of the PM 10 OC was attributed to traffic and 30% to charcoal burning in both campaigns. A definite explanation for the substantially larger EC/TC ratios in the 2006 campaign as compared to the 2005 campaign is not available.

춘천과 서울에서 측정한 PM2.5내 탄소성분의 농도 특성에 관한 연구

<TEX>$PM_{2.5}$</TEX> samples were collected from December 2005 through November 2007 in two cities including Chuncheon and Seoul in order to investigate the characteristics of carbonaceous aerosol. The average <TEX>$PM_{2.5}$</TEX> concentration in Seoul (<TEX>$43.2{\mu}g/m^3$</TEX>) was approximately 1.2 times higher than that measured in Chuncheon (<TEX>$36.1{\mu}g/m^3$</TEX>), however there was no statistical difference on <TEX>$PM_{2.5}$</TEX> concentration between those two cities. Backward trajectories were passing through Seoul area before arriving Chuncheon for about half of the samples, and <TEX>$PM_{2.5}$</TEX> largely increased in Chuncheon when back-trajectories originated from Seoul area. Total carbon (TC) was calculated as sum of OC and EC, contributing 20.5% and 29.2% to total <TEX>$PM_{2.5}$</TEX> mass in Chuncheon and Seoul, respectively. The average ratio of secondary organic carbon (SOC) to total OC was 40% at both sites, and the highest SOC concentration was observed in summer probably due to enhanced volatilization of organic species and active photochemical reaction. J value was calculated to determine if acidic condition affected the increase of secondary organic carbon. In both Chuncheon and Seoul SOC/OC ratios were fairly enhanced when J<100% of acidic condition.

Characteristics of Carbonaceous Aerosol at a Near–Highway-Traffic Sampling Site During Spring 2006

The concentrations for mass, organic carbon (OC), and elemental carbon (EC) of fine (PM2.5) and inhalable (PM10) particulates were studied at a near–highway-traffic sampling site during March 6 to April 1, 2006, around central Taiwan. The primary OC/EC ratio approach is applied to assess the contribution of secondary organic aerosol (SOA) to the PM2.5 and PM10 mass at the near–highway-traffic sampling site. The mass average concentrations of PM2.5 and inhalable () PM10 particulates were found to be 67.5 μ g m−3 and 107.9 μ g m−3, respectively, during sampling period. Furthermore, analytical results indicated that the average OC and EC concentrations were 10.22 and 3.88 mg m−3, respectively, in PM2.5 particulates. The average OC and EC concentrations were 11.57 and 4.56 mg m−3, respectively, in PM10 particulates. The average mass concentration ratio of PM2.5to PM10 particulates was 1.6 during sampling period. The results also reflected that PM2.5 particulate concentrations were the primary species (average approximately 61%). Additionally, the OC/EC ratio of both PM10 and PM2.5 particulates was at all times greater than 1.7, indicating that OC constituted 66%–79% of total carbon (TC). Experimental results demonstrated that direct emissions of primary organic aerosol (POA) are greater than emissions of carbonaceous material (EC aerosol) for either PM10 or PM2.5 particles. In addition, the results also reflected that OC concentration was the major species at this sampling site.

Chemical characteristics of carbonaceous aerosols during dust storms over Xi’an in China

Characterization of carbonaceous aerosols including CC (carbonate carbon), OC (organic carbon), and EC (elemental carbon) were investigated at Xi’an, China, near Asian dust source regions in spring 2002. OC varied between 8.2 and 63.7 µg m−3, while EC ranged between 2.4 and 17.2 µ m−3 during the observation period. OC variations followed a similar pattern to EC and the correlation coefficient between OC and EC is 0.89 (n=31). The average percentage of total carbon (TC, sum of CC, OC, and EC) in PM2.5 during dust storm (DS) events was 13.6%, which is lower than that during non-dust storm (NDS) periods (22.7%). CC, OC, and EC accounted for 12.9%, 70.7%, and 16.4% of TC during DS events, respectively. The average ratio of OC/EC was 5.0 in DS events and 3.3 in NDS periods. The OC-EC correlation (R2=0.76, n=6) was good in DS events, while it was stronger (R2=0.90, n=25) in NDS periods. The percentage of water-soluble OC (WSOC) in TC accounted for 15.7%, and varied between 13.3% and 22.3% during DS events. The distribution of eight carbon fractions indicated that local emissions such as motor vehicle exhaust were the dominant contributors to carbonaceous particles. During DS events, soil dust dominated the chemical composition, contributing 69% to the PM2.5 mass, followed by organic matter (12.8%), sulfate (4%), EC (2.2%), and chloride (1.6%). Consequently, CC was mainly entrained by Asian dust. However, even in the atmosphere near Asian dust source regions, OC and EC in atmospheric dust were controlled by local emission rather than the transport of Asian dust.