Observations of new particle formation in urban air

Alam, Aftab; Shi, Ji Ping; Harrison, Roy M.

doi:10.1029/2001jd001417

Cited by 142 publications

(119 citation statements)

References 34 publications

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“…Their general characteristics have been reported in a number of studies (e.g. Alam et al, 2003;Charron et al, 2007Charron et al, , 2008Beddows et al, 2015;Vu et al, 2016) and can be summarised as follows: (i) particle modality at around 20 nm, (ii) higher frequency around noon in association with the peak in actinic flux intensities, (iii) clear seasonal cycles (higher average contribution levels in the summer, from June to September) and (iv) marked directionality from the westerly sectors, reflecting maritime atmospheric circulation regimes, with high wind speed and low PM 2.5 concentrations. A strong regional nucleation event occurred during the warm-period sampling campaign (starting on 7 September at 13:00 UTC and lasting for about 12 h).…”

Section: Analysis Of a Large Regional Nucleation Eventmentioning

confidence: 99%

Sources of sub-micrometre particles near a major international airport

Masiol

Harrison

et al. 2017

Atmos. Chem. Phys.

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Abstract. The international airport of Heathrow is a major source of nitrogen oxides, but its contribution to the levels of sub-micrometre particles is unknown and is the objective of this study. Two sampling campaigns were carried out during warm and cold seasons at a site close to the airfield (1.2 km). Size spectra were largely dominated by ultrafine particles: nucleation particles (< 30 nm) were found to be ∼ 10 times higher than those commonly measured in urban background environments of London. Five clusters and six factors were identified by applying k means cluster analysis and positive matrix factorisation (PMF), respectively, to particle number size distributions; their interpretation was based on their modal structures, wind directionality, diurnal patterns, road and airport traffic volumes, and on the relationship with weather and other air pollutants. Airport emissions, fresh and aged road traffic, urban accumulation mode, and two secondary sources were then identified and apportioned. The fingerprint of Heathrow has a characteristic modal structure peaking at < 20 nm and accounts for 30-35 % of total particles in both the seasons. Other main contributors are fresh (24-36 %) and aged (16-21 %) road traffic emissions and urban accumulation from London (around 10 %). Secondary sources accounted for less than 6 % in number concentrations but for more than 50 % in volume concentration. The analysis of a strong regional nucleation event showed that both the cluster categorisation and PMF contributions were affected during the first 6 h of the event. In 2016, the UK government provisionally approved the construction of a third runway; therefore the direct and indirect impact of Heathrow on local air quality is expected to increase unless mitigation strategies are applied successfully.

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Section: Analysis Of a Large Regional Nucleation Eventmentioning

confidence: 99%

Sources of sub-micrometre particles near a major international airport

Masiol

Harrison

et al. 2017

Atmos. Chem. Phys.

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“…The marine boundary layer (BL) provided evidence of homogeneous nucleation both in remote sites and near-coastal regions [Covert et al, 1992;Hoppel et al, 1994;Weber et al, 1998;Allen et al, 1999;O'Dowd et al, 1999]. New particles form also in urban environment, while the cases with low surface area of ambient aerosol are less frequent than in remote regions, and the direct emissions of UFP from road traffic and other sources make more difficult the observations of UFP generated by homogeneous nucleation [Kerminen and Wexler, 1996;Alam et al, 2003]. In addition, aircraft emissions in upper troposphere and lower stratosphere are also documented to be sources of UFP [Arnold et al, 1998;Yu et al, 1999;Kärcher et al, 2000].…”

Section: Introductionmentioning

confidence: 99%

Precipitation removal of ultrafine aerosol particles from the atmospheric boundary layer

Andronache

2004

J. Geophys. Res.

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[1] Ultrafine particles (UFP) formed in the boundary layer (BL) by nucleation processes need to grow up to a diameter d p $ 100 nm to become activated as cloud droplets (CD). The time required to reach d p = 100 nm is about 2-3 days for a typical growth rate of 5 nm h À1 . If precipitation occurs, most UFP are too small to become CD, and some particles are removed by scavenging processes. A model to estimate the UFP wet removal from the BL by rainfall and coagulation is presented. The scavenging coefficient that describes the decay of aerosol mass in various size bins is a function of aerosol size (d p ), rainfall rate (R), and BL background aerosol. The model is applied to determine the UFP 0.5-folding time (t 05 ) during rain events and results show that t 05 $ 1 hour for R $ 1 mm h À1 for newly created particles (d p < 10 nm) and t 05 $ 1 day for larger UFP (d p $ 10-100 nm). To infer the likelihood of UFP removal at a given location, the average time interval (Dt) between rain events with rainfall rate R = 1 mm h À1 at stations with different precipitation regimes was determined. Results show that on average, UFP are very effectively removed from the BL by below-cloud scavenging in tropical regions (Dt $ 1 day), removed to a significant extent in eastern U.S. regions (Dt $ 3 days), and are less likely to be removed in southwest U.S. regions (Dt $ 6-8 days), where the frequency of dry periods is high and UFP have sufficient time to grow.

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“…Also, nucleation mode particles are emitted from gasoline engines (Harris and Maricq, 2001). Aitken mode particles are emitted directly from traffic exhaust, or may result from condensational growth of nucleation mode particles (Kerminen and Wexler, 1996;Alam et al, 2003: Laakso et al, 2003b. Accumulation mode particles originate from industrial combustion and re-suspension from road beds.…”

Section: Introductionmentioning

confidence: 99%

Scavenging of ultrafine particles by rainfall at a boreal site: observations and model estimations

et al. 2006

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Abstract.Values of the scavenging coefficient determined from observations of ultrafine particles (with diameters in the range 10-510 nm) during rain events at a boreal forest site in Southern Finland between 1996 and 2001 were reported by Laakso et al. (2003a). The estimated range of the median values of the scavenging coefficient was [7×10 −6 −4×10 −5 ] s −1 , which is generally higher than model calculations based only on below-cloud processes (Brownian diffusion, interception, and typical phoretic and charge effects).In the present study, in order to interpret these observed data on scavenging coefficients from Laakso et al. (2003a), we use a model that includes below-cloud scavenging processes, mixing of ultrafine particles from the boundary layer (BL) into cloud, followed by cloud condensation nuclei activation and in-cloud removal by rainfall. The range of effective scavenging coefficient predicted by the new model, corresponding to wide ranges of values of its input parameters, are compared with observations. Results show that ultrafine particle removal by rain depends on aerosol size, rainfall intensity, mixing processes between BL and cloud elements, in-cloud scavenged fraction, in-cloud collection efficiency, and in-cloud coagulation with cloud droplets.The scavenging coefficients predicted by the new model are found to be significantly sensitive to the choice of representation of: (1) mixing processes; (2) raindrop size distribution; (3) phoretic effects in aerosol-raindrop collisions; and (4) cloud droplet activation. Implications for future studies of BL ultrafine particles scavenging are discussed.

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Observations of new particle formation in urban air

Cited by 142 publications

References 34 publications

Sources of sub-micrometre particles near a major international airport

Sources of sub-micrometre particles near a major international airport

Precipitation removal of ultrafine aerosol particles from the atmospheric boundary layer

Scavenging of ultrafine particles by rainfall at a boreal site: observations and model estimations

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