Characteristics of carbonaceous aerosols in Beijing, China

Carbonaceous aerosols and PM10 were monitored from September 8 to November 30, 2002, in a semi-urban site (Tsinghua University) in Beijing. Daily concentrations of OC and EC ranged from 7.1 to 65.9 microgCm(-3) and from 1.3 to 26.1 microgCm(-3), with the overall average concentrations of 21.2 microgCm(-3) and 7.3 microgCm(-3), respectively. The diurnal variation of carbonaceous concentrations on 2 h basis presented two-peak trend, which was attributed to the cooperative effect of local meteorological conditions and anthropogenic sources such as traffic exhaust and human outdoor activities. Daily average OC/EC ratio varied between 1.5 and 5.3 with an average of 3.0. Strong correlation between OC and EC (R2=0.8) indicated that their main sources were common. The frequency of OC/EC ratio presented Gaussian normal distribution trend in fall, of which the peak value appeared in the range of 2.8-5. In winter, it presented bi-peak mode, with the first peak near 1.4-1.6, and the second between 2.8 and 5. The high value (2.8-5) implied the SOC formation in both seasons, and the low one probably suggested the primary OC/EC ratio from coal burning in winter. Averagely, PM10 and carbonaceous species exhibited higher concentrations in Wednesday than in other weekdays, which could be ascribed to the low wind speed (1.6 ms(-1)) and high humidity (62.9%). OC was the abundant component accounting for 76% of TC. OC and EC contributed 15% and 5% to PM10, respectively. The estimation on a minimum OC/EC ratio (1.5) basis showed that SOC accounted more than 50% for the total organic carbon. Even in winter, the SOC contribution to OC was also significant, as high as 40%.     

Annual and seasonal variability of ambient aerosols over an urban region in western India

Annual and seasonal variabilities in source contribution to total suspended particles (TSP) measured over an urban location in western India, Ahmedabad between May 2000 and January 2003 are examined in this study. Positive matrix factorization (PMF) resolved six factors including airborne regional dust, calcium carbonate rich dust, biomass burning/vehicular emissions, secondary nitrate/sulfate, marine aerosol, and smelter. In this study, non-parametric statistical tests including the Kruskal–Wallis analysis of variance (K–W ANOVA) and Spearman rank correlation (ρ) test were used to assess the annual and seasonal variations in factor contributions, and the influence of meteorology on these contributions, respectively. None of the factor contributions exhibited annual variations except airborne regional dust, and biomass burning/vehicular emissions factors. All of the factors exhibited seasonal variations. Several factor monsoon (July–September) median concentrations were significantly different from one or more of the other season medians. In general, it appeared that meteorological factors played a role in establishing the seasonal behavior of factor contributions. Factor contributions exhibited low to moderate correlations with meteorological parameters such as temperature, relative humidity, wind direction, and wind speed. Amongst all of the relationships, marine aerosol factor was reasonably well correlated with relative humidity (ρ = 0.73) and wind direction (ρ = 0.73) during the pre-monsoon season (March–May). This observation suggests that the aerosol transported by moisture laden winds from the Arabian sea contribute to this factor. The airborne regional dust factor was also moderately correlated with wind speed (ρ = 0.70) during the post-monsoon season. This relationship indicates that high regional dust concentrations are favored by high wind speeds and the resultant increase in dispersion.     

Sulfate and carbonaceous aerosols in Beijing China

Results of our aerosol study, performed during 1983–1984 in Beijing, demonstrate that ambient carbonaceous aerosols are derived principally from coal combustion. Different SO₂ oxidation processes have been observed in summer and winter. The winter sulfate appears to be produced locally and associated with products of incomplete combustion.     

Time-resolved measurements of PM2.5 carbonaceous aerosols at Gosan, Korea

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 microgC m-3, with a mean of 4.07+/- 2.60 microgC m-3, while the hourly average EC concentration ranged approximately from 0.04 to 8.19 .microgC m-3, with a mean of 1.35 +/- 0.71 microgC m-3, from May 28 to June 17, 2009. During the fall season, OC varied in the approximate range 0.9-9.6 microgC m-3, with a mean of 2.30 +/-0.80 microgC m-3, whereas EC ranged approximately from 0.01 to 5.40 microgC m-3, with a mean of 0.66 +/- 0.38 microgC 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.     

Characterization of carbonaceous aerosols over Delhi in Ganga basin: seasonal variability and possible sources

The mass concentration of carbonaceous species, organic carbon (OC), and elemental carbon (EC) using a semicontinuous thermo-optical EC-OC analyzer, and black carbon (BC) using an Aethalometer were measured simultaneously at an urban mega city Delhi in Ganga basin from January 2011 to May 2012. The concentrations of OC, EC, and BC exhibit seasonal variability, and their concentrations were ～2 times higher during winter (OC 38.1?±?17.9 μg m^?3, EC 15.8?±?7.3 μg m^?3, and BC 10.1?±?5.3 μg m^?3) compared to those in summer (OC 14.1?±?4.3 μg m^?3, EC 7.5?±?1.5 μg m^?3, and BC 4.9?±?1.5 μg m^?3). A significant correlation between OC and EC (R?=?0.95, n?=?232) indicate their common emission sources with relatively lower OC/EC ratio (range 1.0–3.6, mean 2.2?±?0.5) suggests fossil fuel emission as a major source of carbonaceous aerosols over the station. On average, mass concentration of EC was found to be ～38 % higher than BC during the study period. The measured absorption coefficient (b_abs) was significantly correlated with EC, suggesting EC as a major absorbing species in ambient aerosols at Delhi. Furthermore, the estimated mass absorption efficiency (σ_abs) values are similar during winter (5.0?±?1.5 m² g^?1) and summer (4.8?±?2.8 m² g^?1). Significantly high aerosol loading of carbonaceous species emphasize an urgent need to focus on air quality management and proper impact assessment on health perspective in these regions.     

Identification,abundance and seasonal variation of anthropogenic organic aerosols from a mega-city in China

PM_2.5 aerosols were collected in Nanjing, a typical mega-city in China, during summer and winter 2004 and were characterized for aromatic and cyclic compounds using a GC/MS technique to understand the air pollution problem. They include polycyclic aromatic hydrocarbons (PAHs), hopanes, phthalates and hydroxy-PAHs (OH-PAHs). PAHs, hopanes and OH-PAHs presented higher concentrations in winter (26–178, 3.0–18, and 0.013–0.421 ng m⁻³, respectively) than in summer (12–96, 1.6–11, and 0.029–0.171 ng m⁻³, respectively) due to an enhanced coal burning for house heating and atmospheric inversion layers developed in the cold season. In contrast, phthalates are more abundant in summer (109–368 ng m⁻³, average 230 ng m⁻³) than in winter (33–390 ng m⁻³, average 170 ng m⁻³) due to an enhanced evaporation from plastics during the hot season and the subsequent deposition on the pre-existing particles. Generally, all the identified compounds showed higher concentrations in nighttime than in daytime due to inversion layers and increased emissions from heavy-duty trucks at night. PAHs, hopanes and phthalates in Nanjing aerosols are 5–100 times more abundant than those in Los Angeles, USA, indicating a serious air pollution problem in the city. Concentrations of OH-PAHs are 1–3 orders of magnitude less than their parent PAHs and comparable to those reported from other international cities. Source identification using diagnostic ratios of the organic tracers suggests that PAHs in Nanjing urban area are mainly derived from coal burning, whereas hopanes are more attributable to traffic emissions.     

Measurements of ozone and nonmethane hydrocarbons at Chichi-jima island,a remote island in the western Pacific: long-range transport of polluted air from the Pacific rim region

Chichi-jima island is located in the Pacific about 1000 km from the Japanese main island and is an ideal remote observatory from which to assess the long-range transport of polluted air from East Asia. The ozone concentration was measured from August 1997 to August 1998. Owing to the air mass change, the seasonal variation of ozone shows a distinct character: low concentration (about 13 ppbv) for the maritime air mass during the summer, and high concentration (about 40 ppbv) for the continental air mass during the winter. To assess the contribution of the long-range transport of polluted air during winter, nonmethane hydrocarbons were also measured in December 1999. Using backward trajectory analysis, the transport time of the air mass from the source area in the Pacific rim region was calculated for each sample. The concentration of hydrocarbons shows a clear negative correlation against the transport time. This analysis clearly shows the transport of polluted air, emitted in East Asia, to the Pacific during the winter. The plots of suitable hydrocarbon pairs showed that the decrease of hydrocarbon concentrations during winter is mainly caused by the mixing with clean background air.     

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.     

The oxidation and long-range transport of sulphur dioxide in a remote region

The flux of sulphur dioxide has been measured in the plume of a remotely situated smelter (Mount Isa, Australia) at distances of up to 1000 km from the source. These measurements were made with an airborne correlation spectrometer in plumes ranging in age from 1.0 to 42.5 h, the latter corresponding to a photolytic age of almost two periods of daylight. Ground-based experiments were also performed to determine the rate of dry deposition of sulphur dioxide in the area situated about 500 km from the source.The implications of an error in the deposition velocities, reported by Milne J.W., Roberts D.B. and Williams D.J. (Atmos. Envir. 13, 373–380, 1979.), are considered. The average velocity for the Mount Isa region is higher than that previously employed by Roberts D. B and Williams D.J. (Atmos. Envir. 13, 1485–1489, 1979). Along with a reassessment of the diurnal model and the average mixing height encountered by Roberts and Williams, this necessitates a reduction in the estimate of the photochemical oxidation rate of sulphur dioxide from 0.25 to 0.15%h⁻¹, when averaged over 24 h.It is shown in this study that the rate of loss of sulphur dioxide from the plume out to the furthest distances measured can be accounted for by the combined processes of atmospheric oxidation and dry deposition, as determined by Roberts and Williams for much shorter distances (< 260 km). The lifetime of sulphur dioxide in the region under study is shown to be fourteen days, with about half of the loss being due to atmospheric oxidation.     

Spatial and seasonal variations of polycyclic aromatic hydrocarbons in Haihe Plain, China

A dynamic fugacity model was developed to simulate the spatial and seasonal variations of PAHs in Haihe Plain, China. The calculated and measured concentrations exhibited good consistency in magnitude with deviations within a factor of 4 in air and 2 in soil. The spatial distributions of PAHs in air were mainly controlled by emission while the seasonal variations were dominated by emission and gas-particle partition. In soil, the spatial distributions of PAHs were controlled by the soil organic carbon content while the seasonal variations were insignificant. The severest soil contamination was observed in Shanxi and followed by the southwest of Hebei province. Transfer fluxes of total PAHs between air and soil were calculated. The spatial distribution of air-to-soil flux was closely related to the landcover while the soil-to-air flux changed with soil organic matter content. Monte Carlo simulation was done to evaluate the uncertainty of the estimated results in air.     

Impact of anthropogenic emissions and open biomass burning on regional carbonaceous aerosols in South China

Carbonaceous aerosols were studied at three background sites in south and southwest China. Hok Tsui in Hong Kong had the highest concentrations of carbonaceous aerosols (OC = 8.7 ± 4.5 μg/m³, EC = 2.5 ± 1.9 μg/m³) among the three sites, and Jianfeng Mountains in Hainan Island (OC = 5.8 ± 2.6 μg/m³, EC = 0.8 ± 0.4 μg/m³) and Tengchong mountain over the east edge of the Tibetan Plateau (OC = 4.8 ± 4.0 μg/m³, EC = 0.5 ± 0.4 μg/m³) showed similar concentration levels. Distinct seasonal patterns with higher concentrations during the winter, and lower concentrations during the summertime were observed, which may be caused by the changes of the regional emissions, and monsoon effects. The industrial and vehicular emissions in East, Southeast and South China, and the regional open biomass burning in the Indo-Myanmar region of Asia were probably the two major potential sources for carbonaceous matters in this region.     

Atmospheric carbonaceous aerosols over grasslands of central Europe and a Boreal forest

A labour-intensive analytical technique was applied to atmospheric particulate matter samples collected in a German urban/industrial influenced grassland location (Melpitz) and in a Finnish forest area (Hyyti?l?) in order to achieve a detailed chemical speciation of the organic content. The representative nature of the solvent and water-extractable fractions was determined. The organic compounds identified in the solvent extracts are represented by primary compounds with both anthropogenic and biogenic origin, which mainly derive from the vegetation waxes and from petrogenic sources. Secondary products resulting from the oxidation of volatile organic compounds were also detected. The German meadow presented the highest levels of sugars and acidic compounds in the water extracts, whilst polyols were the most abundant class in the Finnish forest. The major compounds of these classes were malic acid, mannitol, arabitol, glucose and sucrose. Levoglucosan was also found in the water extract.     

Optical and thermal characteristics of carbonaceous aerosols measured at an urban site in Gwangju,Korea, in the winter of 2011

Carbonaceous components (organic carbon [OC] and elemental carbon [EC]) and optical properties (light absorption and scattering) of fine particulate matter (aerodynamic diameter <2.5 μm; PM_2.5) were simultaneously measured at an urban site in Gwangju, Korea, during the winter of 2011. OC was further classified into OC1, OC2, OC3, and OC4, based on a temperature protocol using a Sunset OC/EC analyzer. The average OC and EC concentrations were 5.0 ± 2.5 and 1.7 ± 0.9 μg C m^?3, respectively. The average single-scattering albedo (SSA) at a wavelength of 550 nm was 0.58 ± 0.11, suggesting that the aerosols observed in the winter of 2011 had a local warming effect in this area. During the whole sampling period, “stagnant PM” and “long-range transport PM” events were identified. The light absorption coefficient (b_abs) was higher during the stagnant PM event than during the long-range transport PM event due to the existence of abundant light-absorbing OC during the stagnant PM event. In particular, the OC2 and OC3 concentrations were higher during the stagnant PM event than those during the long-range transport event, suggesting that OC2 and OC3 might be more related to the light-absorbing OC. The light scattering coefficient (b_scat) was similar between the events. On average, the mass absorption efficiency attributed to EC (σ_EC) was 9.6 m² g^?1, whereas the efficiency attributed to OC (σ_OC) was 1.8 m² g^?1 at λ = 550 nm. Furthermore, the σ_EC is comparable among the PM event days, but the σ_OC for the stagnant PM event was significantly higher than that for the long-range transport PM event (1.7 vs. 0.5).

Implications: Optical and thermal properties of carbonaceous aerosol were measured at Gwangju, and carbonaceous aerosol concentration and optical property varied between “stagnant PM” and “long-range transport PM” events. More abundant light absorbing OC was observed during the stagnant PM event.     

Characteristics and diurnal variations of NMHCs at urban,suburban, and rural sites in the Pearl River Delta and a remote site in South China

The Pearl River Delta (PRD) is one of the most industrialized and urbanized regions in China. With rapid growth of the economy, it is suffering from deteriorating air quality. Non-methane hydrocarbons (NMHCs) were investigated at urban and suburban sites in Guangzhou (GZ), a rural site in PRD and a clean remote site in South China, in April 2005. Additional roadside samples in GZ and Qingxi (QX, a small industrial town in PRD), ambient air samples at the rooftop of a printing factory in QX and exhaust samples from liquefied petroleum gas (LPG)—fueled taxis in GZ were collected to help identify the source signatures of NMHCs. A large fraction of propane (47%) was found in exhaust samples from LPG-fueled taxis in GZ and extremely high levels of toluene (2.0–3.1 ppmv) were found at the rooftop of the printing factory in QX. Vehicular and industrial emissions were the main sources of NMHCs. The effect of vehicular emission on the ambient air varied among the three PRD sites. The impact of industrial emissions was widespread and they contributed greatly to the high levels of aromatic hydrocarbons, especially toluene, at the three PRD sites investigated. Leakage from vehicles fueled by LPG contributed mainly to the high levels of propane and n-butane at the urban GZ site. Ethane and ethyne from long-range transport and isoprene from local biogenic emission were the main contributors to the total hydrocarbons at the remote site. Diurnal variations of NMHCs showed that the contribution from vehicular emissions varied with traffic conditions and were more influenced by fresh emissions at the urban site and by aged air at the suburban and rural sites. Isoprene from biogenic emission contributed largely to the ozone formation potential (OFP) at the remote site. Ethene, toluene and m/p-xylene were the main contributors to the OFP at the three PRD sites.     

Concentrations and sources of carbonaceous aerosol in the atmosphere of Summit,Greenland

High-volume PM_2.5 samples were collected at Summit, Greenland for approximately six months from late May through December of 2006. Filters were composited and analyzed for source tracer compounds. The individual organic compounds measured at Summit are orders of magnitude smaller than concentrations measured at other sites, including locations representative of remote oceanic, and remote and urban continental aerosol. The measured tracers were used to quantify the contribution of biomass burning (0.6–0.9 ng C m^?3), vegetative detritus (0.3–0.9 ng C m^?3), and fossil fuel combustion (0.1–0.8 ng C m^?3) sources, 4% of OC total, to atmospheric organic carbon concentrations at the remote location of Summit, Greenland. The unapportioned organic carbon (96%) during the early summer period correlates well with the fraction of water soluble organic carbon, indicating secondary organic aerosol as a large source of organic carbon, supported by the active photochemistry occurring at Summit. To the author's knowledge, this paper represents the first source apportionment results for the polar free troposphere.     

Patterns and Concentrations of PM10 in a Mountainous Basin Region

ABSTRACT

In this study, continuous data of PM₁₀ (particles with aerodynamic diameter <10 u,m) concentration measurements for a 4-yr period were analyzed. These measurements have been carried out in the Eordea Basin, an industrial area in the northwestern mountainous region of Greece. The annual, monthly, and diurnal patterns are presented and investigated regarding the prevailing meteorological conditions and atmospheric processes that affect the ambient concentrations of PM₁₀. The effect of wind on controlling PM₁₀ concentration is also discussed. Based on the data analysis, an attempt is made to provide useful information about air quality levels, taking into account U.S. Environmental Protection Agency air quality standards.     

Concentrations and fluxes of tin in aerosols and rain

The concentration of tin in atmospheric aerosols has been measured at land and ship based sites in the northern and southern hemispheres. Tin concentrations in the northern hemisphere are up to three orders of magnitude greater than those in the southern hemisphere, indicating the importance of anthropogenic inputs to the atmospheric tin cycle. In aerosols sampled in Tallahassee, Florida, tin is correlated with soot carbon in air masses originating in the central U.S., but is not correlated with locally produced soot carbon. Rainwaters collected in Tallahassee, Florida have been analyzed for dissolved tin and major ions. Factor analysis of the results indicates a continental and pollution source for tin. The dissolved fraction of tin in rain represents only a minor component of the deposition flux of tin. Rates of deposition of atmospheric tin are consistent with estimated fluxes of tin to the atmosphere.     

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).     

On the variability of Black Smoke and carbonaceous aerosols in the Netherlands

The study addresses the characteristics of elemental carbon (EC) and organic carbon (OC) distributions in the Netherlands by using Black Smoke (BS) data in combination with dedicated measurements and modelling. The BS levels indicate a large-scale background concentration over the Netherlands with low spatial variability and a gradient with highest levels (∼9 μg m⁻³) in the south gradually decreasing to the north-west (∼5.5 μg m⁻³). The BS concentrations at rural sites in the Netherlands are highly correlated due to common (diffuse) sources and large-scale meteorology. Superimposed on the regional background are the contributions of local/urban sources. Urban and rural BS levels show a distinct variation over the week with minimum levels on Sundays.BS levels do not reflect a real concentration as they are obtained via an optical measurement in combination with an outdated calibration curve to arrive at total suspended particles (TSP). We have found that the relation between BS and EC in the Netherlands is linear and highly correlated but dependent on station type. Application of these relations to the BS time series yields a gradient in the rural background EC concentration from 0.5 μg m⁻³ in the north to 0.7 μg m⁻³ in the south of the Netherlands. The relationship between OC and BS appears to be location specific and is determined by the BS–EC relation in combination with a characteristic OC/EC ratio. OC/EC ratios are ∼5 at regional background sites and ∼2 at traffic locations. Minimum OC/EC ratios at the traffic sites reflect the primary OC/EC ratio of traffic. We argue that estimation of secondary organic aerosol by assuming the minimum OC/EC ratio to be a proxy for the primary OC/EC is not allowed since this approach does not account for sources with high OC/EC ratios. Based on European scale modelling and the measured data, we estimate that national sources contribute ∼40–60% to Dutch EC levels.The rather costly and laborious EC measurements provide a better indicator of the carbonaceous fraction in ambient particulate matter (PM) but the cheap BS method may provide valuable information on spatial distribution of EC when used in combination with validation sites to characterise the EC–BS relationship.