A wide area of air pollutant impact downwind of a freeway during pre-sunrise hours

Hu, Shishan; Fruin, Scott; Kozawa, Kathleen; Mara, Steve; Paulson, Suzanne E.; Winer, Arthur M.

doi:10.1016/j.atmosenv.2009.02.033

Cited by 151 publications

(129 citation statements)

References 33 publications

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“…This is an important observation since it suggests that, in the receptor areas of the LAB, PM transported from central and west Los Angeles can contribute to higher and more sustained concentration levels even during the hours when local sources contribute minimally. These results are also consistent with the findings of Zhu et al (2006) and Hu et al (2009) both conducted in the LAB. The highest of morning concentrations were observed at USC and RUB, the two sites closest to freeways.…”

Section: Diurnal and Seasonal Variationssupporting

confidence: 82%

Inter-community variability in total particle number concentrations in the eastern Los Angeles air basin

et al. 2010

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Abstract. Ultrafine Particles (UFP) can display sharp gradients in their number concentrations in urban environment due to their transient nature and rapid atmospheric processing. The ability of using air pollution data generated at a central monitoring station to assess exposure relies on our understanding of the spatial variability of a specific pollutant associated with a region. High spatial variation in the concentrations of air pollutants has been reported at scales of 10s of km for areas affected by primary emissions. Spatial variability in particle number concentrations (PNC) and size distributions needs to be investigated, as the representativeness of a monitoring station in a region is premised on the assumption of homogeneity in both of these metrics. This study was conducted at six sites, one in downtown Los Angeles and five located about 40-115 km downwind in the receptor areas of Los Angeles air basin. PNC and size distribution were measured using Condensation Particle Counters (CPC) and Scanning Mobility Particle Sizer (SMPS). The seasonal and diurnal variations of PNC implied that PNC might vary significantly with meteorological conditions, even though the general patterns at the sites may remain generally similar across the year due to consistency of sources around them. Regionally transported particulate matter (PM) from upwind urban areas of Los Angeles lowered spatial variation by acting as a "homogenizing" factor during favorable meteorological conditions. Spatial variability also increased during hours of the day during which the effects of local sources predominate. The spatial variability associated with PNC (quantified using Coefficients of Divergence, CODs), averaged about 0.3, which was generally lower than that based on specific size ranges. Results showed an inverse relationship of COD with particles size, with fairly uniform values in the particle rangeCorrespondence to: C. Sioutas (sioutas@usc.edu) which is associated with regional transport. Our results suggest that spatial variability, even in the receptor regions of Los Angeles Basin, should be assessed for both PNC and size distributions, and should be interpreted in context of seasonal and diurnal influences, and suitably factored if values for exposure are ascertained using a central monitoring station.

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Section: Diurnal and Seasonal Variationssupporting

confidence: 82%

Inter-community variability in total particle number concentrations in the eastern Los Angeles air basin

et al. 2010

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“…We show here that traffic-emitted NCA increases the aerosol particle number concentrations in environments near traffic. Previous research has shown that particle concentrations decrease when moving away from the roadway; this effect is generally attributed to coagulation and dilution (2,26,34), although evaporation has been suggested as well (35). The scavenging time scale of diluted NCA is of the order of 20 min to reach the levels observed for urban background aerosol; thus, NCA can be transported for several kilometers before removal by loss processes, meaning that in urban areas, the traffic-originated NCA is likely ubiquitous and contributes significantly to the background levels.…”

Section: Tunnel Motorwaymentioning

confidence: 99%

“…Some studies have also shown that nanosized clusters have a role in engine emission formation (4,25). Research on particle number concentrations near traffic has shown highly elevated concentrations (of the order of 10 5 -10 6 ) of ultrafine particles near roadways (2,26), also indicating the likelihood of high concentrations of nanosized particles and clusters existing in such environments. However, up to now the measurement techniques suitable for their detection have not been applied in such environments, leaving the direct observation, formation, and effects of particles smaller than 3 nm unexplored.…”

mentioning

confidence: 99%

“…In densely populated areas, one of the most significant source of particles is traffic (1,2). Owing to their small size and complicated chemical and physical characteristics (3)(4)(5)(6), atmospheric particles resulting from traffic emissions pose a significant risk to human health (7)(8)(9)(10)(11)(12), and also contribute to anthropogenic forcing of climate (13,14).…”

mentioning

confidence: 99%

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Traffic is a major source of atmospheric nanocluster aerosol

Rönkkö

Kuuluvainen

Karjalainen

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

203

132

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In densely populated areas, traffic is a significant source of atmospheric aerosol particles. Owing to their small size and complicated chemical and physical characteristics, atmospheric particles resulting from traffic emissions pose a significant risk to human health and also contribute to anthropogenic forcing of climate. Previous research has established that vehicles directly emit primary aerosol particles and also contribute to secondary aerosol particle formation by emitting aerosol precursors. Here, we extend the urban atmospheric aerosol characterization to cover nanocluster aerosol (NCA) particles and show that a major fraction of particles emitted by road transportation are in a previously unmeasured size range of 1.3-3.0 nm. For instance, in a semiurban roadside environment, the NCA represented 20-54% of the total particle concentration in ambient air. The observed NCA concentrations varied significantly depending on the traffic rate and wind direction. The emission factors of NCA for traffic were 2.4·10 15 (kg fuel ) −1 in a roadside environment, 2.6·10 15 (kg fuel ) −1 in a street canyon, and 2.9·10 15 (kg fuel ) −1 in an on-road study throughout Europe. Interestingly, these emissions were not associated with all vehicles. In engine laboratory experiments, the emission factor of exhaust NCA varied from a relatively low value of 1.6·10 12 (kg fuel ) −1 to a high value of 4.3·10 15 (kg fuel ) −1 . These NCA emissions directly affect particle concentrations and human exposure to nanosized aerosol in urban areas, and potentially may act as nanosized condensation nuclei for the condensation of atmospheric low-volatile organic compounds.nanocluster aerosol | atmospheric aerosol | combustion-derived nanoparticles | air pollution | traffic emission D etailed characterization of aerosol sources is required to understand climate impacts and health effects of atmospheric aerosols, as well as to develop technologies and policies capable of mitigating air pollution in urbanized areas. In densely populated areas, one of the most significant source of particles is traffic (1, 2). Owing to their small size and complicated chemical and physical characteristics (3-6), atmospheric particles resulting from traffic emissions pose a significant risk to human health (7-12), and also contribute to anthropogenic forcing of climate (13,14). Previous research on vehicular emissions has demonstrated the presence of soot and ash (3, 15) and solid sub-10-nm core particles (4-6) in primary emissions from vehicles and engines and their variation, depending on vehicle technologies (4, 6), the properties of fuels and lubricant oils (15, 16), and driving conditions (15-17). In addition to particles, exhaust typically contains species that reside in the gaseous phase in the undiluted high-temperature exhaust (5, 18, 19) but condense or even nucleate to the particle phase immediately after the exhaust is released to the atmosphere. Here, we term such aerosols delayed primary aerosols, because particle precursors exist already in the u...

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“…Other temporal variations that were not accounted for included wind speed and direction, atmospheric stability, mixing height and topography, all factors which may influence air pollution exposure (Hagler et al 2009;Hagler et al 2010;Hitchins et al 2000;Hu et al 2009). …”

Section: Discussionmentioning

confidence: 99%

Investigating the relationship between environmental factors and respiratory health outcomes in school children using the forced oscillation technique

Boeyen

Callan

Blake

et al. 2017

International Journal of Hygiene and Environmental Health

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The environmental factors which may affect children’s respiratory health are complex, and the influence and significance of factors such as traffic, industry and presence of vegetation is still being determined. We undertook a cross-sectional study of 360 school children aged 5–12 years who lived on the outskirts of a heavy industrial area in Western Australia to investigate the effect of a range of environmental factors on respiratory health using the forced oscillation technique (FOT), a non-invasive method that allows for the assessment of the resistive and reactive properties of the respiratory system. Based on home address, proximity calculations were used to estimate children’s exposure to air pollution from traffic and industry and to characterise surrounding green space. Indoor factors were determined using a housing questionnaire. Of the outdoor measures, the length of major roads within a 50 m buffer was associated with increased airway resistance (Rrs8). There were no associations between distance to industry and FOT measures. For the indoor environment the presence of wood heating and gas heating in the first year of life was associated with better lung function. The significance of both indoor and outdoor sources of air pollution and effect modifiers such as green space and heating require further investigation

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A wide area of air pollutant impact downwind of a freeway during pre-sunrise hours

Cited by 151 publications

References 33 publications

Inter-community variability in total particle number concentrations in the eastern Los Angeles air basin

Inter-community variability in total particle number concentrations in the eastern Los Angeles air basin

Traffic is a major source of atmospheric nanocluster aerosol

Investigating the relationship between environmental factors and respiratory health outcomes in school children using the forced oscillation technique

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