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.     

Chemical characteristics of principal PM2.5 species in Chongju,South Korea

Fine particles were collected over four seasons from October 1995 to August 1996 to evaluate the chemical characteristics of principal PM_2.5 components in Chongju, South Korea. The annual mean concentrations of PM_2.5 (d_p⩽2.5 μm), sulfate, nitrate, ammonium, elemental carbon (EC) and organic carbon (OC) were 44.2, 8.22, 3.63, 2.84, 4.44 and 4.99 μg m⁻³, respectively. The sum of the species measured from this study accounted for 50–62% of the PM_2.5 mass. Sulfate was the most abundant species and constituted 13–23% of the PM_2.5 mass. The EC and OC accounted for 17–28% of PM_2.5. The correlation between OC and EC was strong, and the annual mean ratio of OC/EC was 1.12, suggesting that OC measured in the Chongju area may be emitted directly in particulate form as a primary aerosol.     

Chemical composition of aerosols during a major biomass burning episode over northern Europe in spring 2006: Experimental and modelling assessments

The long-range transported smokes emitted by biomass burning had a strong impact on the PM_2.5 mass concentrations in Helsinki over the 12 days period in April and May 2006. To characterize aerosols during this period, the real-time measurements were done for PM_2.5, PM_2.5–10, common ions and black carbon. Moreover, the 24-h PM₁ filter samples were analysed for organic and elemental carbon (OC and EC), water-soluble organic carbon (WSOC), ions and levoglucosan. The Finnish emergency and air quality modelling system SILAM was used for the forecast of the PM_2.5 concentration generated by biomass burning. According to the real-time PM_2.5 data, the investigated period was divided into four types of PM situations: episode 1 (EPI-1; 25–29 April), episode 2 (EPI-2; 1–5 May), episode 3 (EPI-3; 5–6 May) and a reference period (REF; 24 March–24 April). EPI-3 included a local warehouse fire and therefore it is discussed separately. The PM₁ mass concentrations of biomass burning tracers—levoglucosan, potassium and oxalate—increased during the two long-range transport episodes (EPI-1 and EPI-2). The most substantial difference between the episodes was exhibited by the sulphate concentration, which was 4.9 (±1.4) μg m⁻³ in EPI-2 but only 2.4 (±0.31) μg m⁻³ in EPI-1 being close to that of REF (1.8±0.54 μg m⁻³). The concentration of particulate organic matter in PM₁ was clearly higher during EPI-1 (11±3.3 μg m⁻³) and EPI-2 (9.7±4.0 μg m⁻³) than REF (1.3±0.45 μg m⁻³). The long-range transported smoke had only a minor impact on the WSOC-to-OC ratio. According to the model simulations, MODIS detected the fires that caused the first set of concentration peaks (EPI-1) and the local warehouse fire (EPI-3), but missed the second one (EPI-2) probably due to dense frontal clouds.     

Assessment of road users’ elemental carbon personal exposure levels,London, UK

Little is known about particulate elemental carbon (EC) personal exposure levels, a key component of diesel exhaust, specifically in transport microenvironments. A method utilizing the optical properties of EC particles has been applied to personal exposure measurement filter samples. In a series of field studies carried out in London, UK, during 1999–2000 over 400 fine particle (PM_2.5) personal exposure level measurements were taken for journeys in bicycle, bus, car and underground rail transport microenvironments, along three main fixed routes. The particulate EC contribution to the PM_2.5 personal exposure was assessed indirectly by means of an optical technique and with the development and use of a size fraction specific and site-specific calibration curve. In this first EC personal exposure study of transport users geometric mean exposure levels in the summer field campaign were 11.2 μg m⁻³ (GSD=2.7) for cyclists, 13.6 μg m⁻³ (GSD=1.9) for bus passengers and 21.6 μg m⁻³ (GSD=2.1) for car drivers; corresponding exposure levels in the winter were 16.4 μg m⁻³ (GSD=1.8), 18.6 μg m⁻³ (GSD=2.3) and 27.3 μg m⁻³ (GSD=2.0), respectively. EC/PM_2.5 ratios were approximately 0.5–0.6 for bicycle and bus modes and 0.7–0.8 for the car mode. EC/PM_2.5 ratios for different routes ranged from approximately 0.7 for Route 1 to 0.4 for Route 3. Cyclists had the lowest exposure to EC, and car occupants the highest exposure. A large difference in exposure levels between a central high traffic density route and the other less central routes was observed. Particulate EC was a very significant proportion of the total PM_2.5 personal exposure and EC personal exposure levels were considerably higher than reported fixed site monitor EC concentrations.     

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.     

PM2.5 particles and size-segregated ionic species measured during fall season in three urban sites in Korea

Twelve hours integrated fine particles (PM_2.5) and 24-h average size-segregated particles were collected to investigate the chemical characteristics and to determine the size distribution of ionic species during October–December 1999 in three cities of different urban scale; Chongju, Kwangju, and Seoul, Korea. Concentrations of 5-min PM_2.5 black carbon (BC) and hourly criteria air pollutants (PM₁₀, CO, NO_x, SO₂, and O₃) were also measured using the Aethalometer and ambient air monitoring system, respectively.Highest PM_2.5 mass concentrations at Chongju, Kwangju, and Seoul sites were 63.0, 77.9, and 143.7 μg m⁻³, respectively. For the time period when highest PM_2.5 mass occurred, BC level out of PM_2.5 chemical species was highest at both Chongju and Kwangju, and highest NO₃⁻ (23.6 μg m⁻³) followed by BC (23.1 μg m⁻³) were observed at Seoul site, indicating that highest PM_2.5 pollution is closely associated with the traffic emissions. Strong relationships of Fe with BC and Zn at both Kwangju and Seoul sites support that the Fe and Zn measured there are originated partly from same source as BC, i.e. diesel traffics. However, it is suggested that the Fe measured at Chongju is most likely derived from dispersion of soil dust.The size distributions of SO₄²⁻, NO₃⁻, and NH₄⁺ ionic species indicated similar unimodal distributions at all sampling sites. However, different unimodal patterns in the accumulation mode size range with a peak in the smaller size (0.28–0.53 μm, condensation mode) in both Kwangju and Seoul, and in the relatively larger size (0.53–1.0 μm, droplet mode) in Chongju, were found. The potassium ion under the study sites dominates in the fine mode, and its size distribution showed unimodal character with a maximum in the size range 0.56–1.0 μm.     

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.     

Spatial variation of mass concentration of roadside suspended particulate matter in metropolitan Hong Kong

This study conducted roadside particulate sampling to measure the total suspended particulate (TSP), PM₁₀ (particles <10 μm in aerodynamic diameter) and PM_2.5 (particles <2.5 μm in aerodynamic diameter) mass concentration in 11 urbanized and densely populated districts in Hong Kong. One hundred and thirty-three samples were obtained to measure the mass concentrations of TSP, PM₁₀ and PM_2.5. According to these results, the TSP, PM₁₀ and PM_2.5 mass concentrations varied from 94.85 to 301.63 μg m⁻³, 67.67 to 142.68 μg m⁻³ and 50.01 to 125.12 μg m⁻³, respectively. The PM_2.5/PM₁₀ ratio of all samples was 0.82 which ranged from 0.62 to 0.95. The PM levels and PM ratios in metropolitan Hong Kong significantly fluctuated from site-to-site and over time. The PM_2.5 mass concentration in different districts corresponding to urban industrial, new town, urban residential and urban commercial were 77.64, 87.50, 106.96 and 88.54 μg m⁻³, respectively. The PM_2.5 level is high in Hong Kong, and for individual sampling, more than 60% daily measurements exceeded the NAAQS. The mass fraction of PM_2.5 in PM₁₀ and TSP is relatively high when compared with overseas studies.     

Aerosol characterisation at the FEBUKO upwind station Goldlauter (I): Particle mass,main ionic components,OCEC, and mass closure

This contribution presents characterisation efforts of the gas phase and particle phase main components during the FEBUKO orographic cloud passage experiments in autumn 2001 and 2002 in the Thüringer Wald (Germany). Three events out of a total of 14 were chosen as the best events considering all meteorological conditions. Gas phase and size-segregated particle phase data obtained from physical (dry size distribution) and chemical (particle mass, main ions, OCEC, and water-soluble metals) measurements are presented for the upwind site. The total particulate mass concentration (PM₁₀) was found to be between 8 and 17 μg m⁻³. Particles with an aerodynamic diameter up to 1.2 μm contribute about 80% of the mass concentration. About 90% of the total ion concentration consists of nitrate, sulphate and ammonium. The OC concentration in all three events amounts to about 1.0 μg m⁻³, whereas EC concentrations were between 0.40 and 1.0 μg m⁻³. The contribution of OC and EC to stage mass ranged from 5% to 35% and from 2% to 17%, respectively. The water content of particles was estimated to be 16–18%. Physical and chemical mass closure is discussed in detail and the results are in a reasonable agreement. The complex data set obtained for each event can be used in the initialisation of models for the multiphase processes during and after the cloud passage of the characterised air mass.     

Comparative analysis of organic and elemental carbon concentrations in carbonaceous aerosols in three European cities

Sampling and analysis of carbonaceous compounds in particulate matter presents a number of difficulties related to artefacts during sampling and to the distinction between organic (OC) and elemental carbon (EC) during analysis. Our study reports on a comparative analysis of OC, EC and WSOC (water-soluble organic carbon) concentrations, as well as sampling artefacts, for PM2.5 aerosol in three European cities (Amsterdam, Barcelona and Ghent) representing Southern and Western European urban environments. Comparability of results was ensured by using a single system for sample analysis from the different sites. OC and EC concentrations were higher in the vicinity of roads, thus having higher levels in Amsterdam (3.9–6.7 and 1.7–1.9 μg m⁻³, respectively) and Barcelona (3.6–6.9 and 1.5–2.6 μg m⁻³) than in Ghent (2.7–5.4 and 0.8–1.2 μg m⁻³). A relatively larger influence of secondary organic aerosols (SOA), as deduced from a larger OC/EC ratio, was observed in Ghent. In absolute sense, WSOC concentrations were similar at the three sites (1.0–2.3 μg m⁻³). Positive artefacts were higher in Southern (11–16% of the OC concentration in Barcelona) than in Western Europe (5–12% in Amsterdam, 5–7% in Ghent). During special episodes, the contribution of carbonaceous aerosols from non-local sources accounted for 67–69% of the OC concentration in Western Europe, and for 44% in Southern Europe.     

Characterisation of fresh particulate vehicular exhausts near a Paris high flow road

Simultaneous continuous measurements of PM_2.5, PM₁₀, black carbon mass (BCae), Black smoke (BS) and particle number density (N) were conducted in the close vicinity of a high traffic road around Paris during a three-month period beginning in August 1997. In parallel some aerosol collection was performed on filters in order to assess the black carbon (BC), organic carbon (OC) and water soluble organic fractions (WSOC) of the freshly emitted traffic aerosols. The high hourly concentrations of PM_2.5 (39±20 μg m⁻³), BCae (14±7 μg m⁻³), and N (220,000±115,000 cm⁻³), were found to be well correlated with each other. On average PM_2.5 represented 66±13% of PM₁₀ and appears to be composed primarily of BC (43±20%). On the contrary no correlation was found between PM_2.5 and the coarse (PM₁₀–PM_2.5) mass fractions which was attributed to resuspension processes by vehicles. Black carbon mass concentrations obtained from both filter analyses (BC) and Aethalometre data (BCae) show a good agreement suggesting that the Aethalometre calibration based on a black carbon specific attenuation coefficient (σ) of 19 m² g⁻¹ is well adapted to nearby roadside measurements. Daily BC (used as a surrogate for fine particles) concentrations and wind speed were found to be anti-correlated. Average daily variations of BC could be related to traffic intensity and regime as well as to the boundary layer height. As expected for freshly emitted traffic aerosols, filter analyses indicated a high BC/TC ratio (29±5%) and a low mean WSOC/OC ratio (12.5±5%) for the bulk aerosol. For these two ratios no day/night differences were observed, the sampling station being probably too close to traffic to evidence photochemical modification of the aerosol phase. Finally, a linear relationship was found between BC and BS hourly concentrations (BC=0.10×BS+1.18; r²=0.93) which offers interesting perspectives to retrieve BC concentrations from existing BS archives.     

Properties of organic matter in PM2.5 at Changdao Island,China—A rural site in the transport path of the Asian continental outflow

Fifty-five seasonal PM_2.5 samples were collected March 2003–January 2004 at Changdao, a resort island located at the demarcation line between Bohai Sea and Yellow Sea in Northern China. Changdao is in the transport path of the continental aerosols heading toward the Pacific Ocean in winter and spring due to the East Asia Monsoon. Solvent-extractable organic compounds (SEOC), organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon (WSOC) were analyzed for source identification based on molecular markers. This data set provides useful information for the downstream site researchers of the Asian continental outflow. Total carbon (TC, OC+EC) was ∼18 μg m⁻³ in winter, ∼9 μg m⁻³ in spring and autumn and a large part of the TC was WSOC (33% in winter, >45% in the other seasons). Winter and spring were the high SEOC seasons with n-fatty acids the highest at ∼290 and ∼170 ng m⁻³, respectively, followed by n-alkanes at ∼210 and ∼90 ng m⁻³, and polycyclic aromatic hydrocarbons (PAHs) were also at high at ∼120 and ∼30 ng m⁻³. High WSOC/TC, low C_18:1/C₁₈ of fatty acids, and low concentrations of labile PAHs such as benzo(a)pyrene, together with back trajectory analysis suggested that the aerosols were aged and transported. PAHs, triterpane and sterane distributions provided evidence that coal burning was the main source of the continental outflow. The detection of levoglucosan and β-sitosterol in nearly all the samples showed the impact of biomass burning.     

Field validation of a semi-continuous method for aerosol black carbon (aethalometer) and temporal patterns of summertime hourly black carbon measurements in southwestern PA

Two methods for measuring aerosol elemental carbon (EC) are compared. Three-hour integrated carbon samples were collected on quartz filters during the summer of 1990 in Uniontown, PA, primarily during episodes of elevated particulate pollution levels. These samples were analyzed for EC and organic carbon (OC) using a thermo/optical reflectance (TOR) method. Aerosol black carbon (BC) was measured using an Aethalometer, a semi-continuous optical absorption method. The optical attenuation factor for ambient BC was supplied by the instrument manufacturer. Three-hour average concentrations were calculated from the semi-continuous BC measurements to temporally match the EC/OC integrated quartz filter samples. BC and EC concentrations are highly correlated over the study period (R²=0.925). The regression equation is BC (μg m^-3)=0.95 (±0.04) EC−0.2 (±0.4). The means of 3 h average measurements for EC and BC are 2.3 and 2.0 μg m^-3, respectively, average concentrations of EC and BC ranged from 0.6 to 9.4 and 0.5 to 9.0 μg m^-3 respectively. TOR OC and EC concentrations were not highly correlated (R²=0.22). The mean OC/EC ratio was 1.85.The 10-week Aethalometer hourly dataset was analyzed for daily and weekly temporal patterns. A strong diurnal BC pattern was observed, with peaks occurring between 7 a.m. and 9 a.m. local time. This is consistent with the increase in emissions from ground level combustion sources in the morning, coupled with poor dispersion before daytime vertical mixing is established. There was also some indication of a day-of-week effect on BC concentrations, attributed to activity of local ground level anthropogenic sources. Comparison of BC concentrations with co-located measurements of coefficient of haze in a separate field study in Philadelphia, PA, during the summer of 1992 showed good correlation between the two measurements (R²=0.82).     

Particulate matter in the indoor air of classrooms—exploratory results from Munich and surrounding area

Numerous epidemiological studies have demonstrated the association between particle mass (PM) concentration in outside air and the occurrence of health related problems and/or diseases. However, much less is known about indoor PM concentrations and associated health risks. In particular, data are needed on air quality in schools, since children are assumed to be more vulnerable to health hazards and spend a large part of their time in classrooms.On this background, we evaluated indoor air quality in 64 schools in the city of Munich and a neighbouring district outside the city boundary. In winter 2004–2005 in 92 classrooms, and in summer 2005 in 75 classrooms, data on indoor air climate parameters (temperature, relative humidity), carbon dioxide (CO₂) and various dust particle fractions (PM₁₀, PM_2.5) were collected; for the latter both gravimetrical and continuous measurements by laser aerosol spectrometer (LAS) were implemented. In the summer period, the particle number concentration (PNC), was determined using a scanning mobility particle sizer (SMPS). Additionally, data on room and building characteristics were collected by use of a standardized form. Only data collected during teaching hours were considered in analysis. For continuously measured parameters the daily median was used to describe the exposure level in a classroom.The median indoor CO₂ concentration in a classroom was 1603 ppm in winter and 405 ppm in summer. With LAS in winter, median PM concentrations of 19.8 μg m⁻³ (PM_2.5) and 91.5 μg m⁻³ (PM₁₀) were observed, in summer PM concentrations were significantly reduced (median PM_2.5=12.7 μg m⁻³, median PM₁₀=64.9 μg m⁻³). PM_2.5 concentrations determined by the gravimetric method were in general higher (median in winter: 36.7 μg m⁻³, median in summer: 20.2 μg m⁻³) but correlated strongly with the LAS-measured results. In explorative analysis, we identified a significant increase of LAS-measured PM_2.5 by 1.7 μg m⁻³ per increase in humidity by 10%, by 0.5 μg m⁻³ per increase in CO₂ indoor concentration by 100 ppm, and a decrease by 2.8 μg m⁻³ in 5–7th grade classes and by 7.3 μg m⁻³ in class 8–11 compared to 1–4th class. During the winter period, the associations were stronger regarding class level, reverse regarding humidity (a decrease by 6.4 μg m⁻³ per increase in 10% humidity) and absent regarding CO₂ indoor concentration. The median PNC measured in 36 classrooms ranged between 2622 and 12,145 particles cm⁻³ (median: 5660 particles cm⁻³).The results clearly show that exposure to particulate matter in school is high. The increased PM concentrations in winter and their correlation with high CO₂ concentrations indicate that inadequate ventilation plays a major role in the establishment of poor indoor air quality. Additionally, the increased PM concentration in low level classes and in rooms with high number of pupils suggest that the physical activity of pupils, which is assumed to be more pronounced in younger children, contributes to a constant process of resuspension of sedimented particles. Further investigations are necessary to increase knowledge on predictors of PM concentration, to assess the toxic potential of indoor particles and to develop and test strategies how to ensure improved indoor air quality in schools.     

Commuter exposure to particulate matter in public transportation modes in Hong Kong

This study examined commuter’s exposure to respirable suspended particulate matters while commuting in public transportation modes. The survey was conducted between October 1999 and January 2000 in Hong Kong. A total of eight public transportation modes, that are bus, tram, public light bus, taxi, ferry, Kowloon–Canton Railway, Mass Transit Railway and Light Rail Transit, were selected in the study. They were grouped into four categories: (T1) railway transport; (T2) non-air-conditioned roadway transport; (T3) air-conditioned roadway transport and (T4) marine transport. Both PM₁₀ and PM_2.5 levels were investigated. The results indicate that the particulate level is greatly affected by the mode of transport as well as the ventilation system of the transport. The overall average PM₁₀ concentration level in T2 (147 μg m⁻³) is the highest and is followed by T4 (81 μg m⁻³) and T3 (65 μg m⁻³). The PM₁₀ level in T1 (50 μg m⁻³) is the lowest. Notably, the commuter exposure in tram (175 μg m⁻³) is the highest among all the monitored commuting modes. Commuting modes such as railway and air-conditioned vehicle are recommended as a substitute for non-air-conditioned vehicle. The PM_2.5 to PM₁₀ ratio in transports ranged from 63% to 78%. Higher PM_2.5 to PM₁₀ ratio is found in vehicles with air-conditioning system. For the double deck vehicle, higher PM₁₀ level has resulted in the lower deck. The average upper-deck to lower-deck PM₁₀ ratio is 0.836, 0.751 and 0.738 in air-conditioned bus, non-air-conditioned bus and non-air-conditioned tram, respectively. Typical concentration profiles in different transports are also presented.     

Emission factors of PAHs,methoxyphenols, levoglucosan,elemental carbon and organic carbon from simulated wheat and Kentucky bluegrass stubble burns

Emission factors (EFs) of pollutants from post-harvest agricultural burning are required for predicting downwind impacts of smoke and inventorying emissions. EFs of polycyclic aromatic hydrocarbons (PAH), methoxyphenols (MP), levoglucosan (LG), elemental carbon (EC) and organic carbon (OC) from wheat and Kentucky bluegrass (KBG) stubble burning were quantified in a US EPA test burn facility. The PAH and MP EFs for combined solid+gas phases are 17±8.2 mg kg⁻¹ and 79±36 mg kg⁻¹, respectively, for wheat and 21±15 mg kg⁻¹ and 35±24 mg kg⁻¹, respectively, for KBG. LG, particulate EC and artifact-corrected OC EFs are 150±130 mg kg⁻¹, 0.35±0.16 g kg⁻¹ and 1.9±1.1 g kg⁻¹, respectively, for wheat and 350±510 mg kg⁻¹, 0.63±0.056 g kg⁻¹ and 6.9±0.85 g kg⁻¹, respectively, for KBG. Positive artifacts associated with OC sampling were evaluated and remedied with a two-filter system. EC and OC accounted for almost two-thirds of PM_2.5 mass, while LG accounted for just under 3% of the PM_2.5 mass. Since EFs of these pollutants generally decreased with increasing combustion efficiency (CE), identifying and implementing methods of increasing the CEs of burns would help reduce their emissions from agricultural field burning. PAH, OC and EC EFs are comparable to other similar studies reported in literature. MP EFs appear dependent on the stubble type and are lower than the EFs for hard and softwoods reported in literature, possibly due to the lower lignin content in wheat and KBG.     

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.     

Estimating the impact of Saharan dust on the year 2001 PM10 record of Rome,Italy

This paper evaluates the role of Saharan dust advection in the exceeding of the PM₁₀ thresholds in the city of Rome, Italy. To this purpose, a series of observations and model forecasts recorded in the year 2001 are analysed and discussed. Lidar profiles collected over 168 days of the year are employed to both assess the presence and magnitude of Saharan dust layers over the city and to evaluate the depth of the planetary boundary layer. Backtrajectories are used to verify the Saharan origin of the lidar-sounded air masses. Model predictions of the presence of Saharan dust over the area are employed to fill the time gaps between lidar observations. PM₁₀ and carbon monoxide records of both a city background (Villa Ada) and a heavy traffic station (Magna Grecia) are cross-analysed with the dust events record and meteorological data. The analysis shows that: (1) Saharan dust was advected over Rome on about 30% of the days of 2001; (2) mean contribution of Saharan dust transport events to daily PM₁₀ levels was of the order of 20 μg m⁻³; (3) at the urban background station of Villa Ada, the Saharan contribution caused the surpassing of the maximum number of days in excess of 50 μg m⁻³ fixed by the current legislation (35 per year). Conversely, at the heavy traffic station of Magna Grecia the Saharan contribution was not determinant at causing the observed large exceeding of that limit, as well as of the maximum yearly average of 40 μg m⁻³; (4) 25% of the Saharan advection days (of the order of 100/year at Rome) led to a PM₁₀ increase >30 μg m⁻³, 4% caused an increase >50 μg m⁻³, thus leading on their own to surpassing the 50 μg m⁻³ daily limit.     

Source contributions to carbonaceous aerosols in the Tennessee Valley Region

Sources of carbonaceous aerosols collected from three sites of Chattanooga, TN (CH), Muscle Shoals, AL (MS), and Look Rock, TN (LR) in the Tennessee Valley Region (TVR) were apportioned using both organic tracer-based chemical mass balance (CMB) modeling and radiocarbon (¹⁴C) measurement and the results were compared. Eight sources were resolved by CMB, among which wood combustion (averaging 0.92 μg m⁻³) was the largest contributor to primary organic carbon (OC) concentrations, followed by gasoline exhaust (0.35 μg m⁻³), and diesel exhaust (0.18 μg m⁻³). The identified primary sources accounted for 43%, 71%, and 14% of measured OC at CH, MS, and LR, respectively. Contributions from the eight primary sources resolved by CMB could explain 107±10% of ambient elemental carbon (EC) concentrations, with diesel exhaust (66±32%) and wood combustion (37±33%) as the most important contributors. The fossil fractions in total carbon determined by ¹⁴C measurements were in reasonably good agreement with that in primary (OC+EC) carbon apportioned by CMB in the MS winter samples. The comparison between the ¹⁴C and CMB results revealed that contemporary sources dominated other OC in the TVR, especially in summertime (84% contemporary).     

The use of receptor modelling and emission inventory data to explain the downward trend in UK PM10 concentrations

Statistically significant downward trends in measured UK annual mean PM₁₀ concentrations have been observed at eight out of the nine urban background monitoring sites between the start of monitoring in 1992 or 1993 and 2000.Site-specific projections of the individual components of measured PM₁₀ concentrations have been derived for the period 1992–2000 at three monitoring sites from receptor modelling results for 1999 monitoring data. Measured annual average PM₁₀ concentrations declined to between 71% and 66% of the 1992 values during this period at the sites studied. The largest contributions to the decline in total PM₁₀ are from secondary particles at London Bloomsbury (40%, 3.4 μg m⁻³, tapered element oscillating microbalance (TEOM)), stationary sources at Belfast Centre (53%, 4.6 μg m⁻³, TEOM) and roadside traffic emissions at Bury Roadside (49%, 5.0 μg m⁻³, TEOM). The good agreement between the projected total PM₁₀ concentrations and measured values for the years 1992–2000 indicate that the combination of the receptor model and the site-specific projections provide a suitably robust method for predicting future PM₁₀ concentrations and the quantification of the impact of possible future policy measures to reduce PM₁₀ concentrations. The good agreement between the projections and measured concentration also provides a useful verification of the trends in emissions inventory estimates for the 1990s.Projections of estimated PM₁₀ concentrations have also been calculated for the London Bloomsbury site for the period from 1970 to 1991. Annual mean concentrations are predicted to have been in the range from 30 to 35 μg m⁻³, TEOM from 1977 to 1991 but much higher at values between 39 and 46 μg m⁻³, TEOM in the early 1970s.