Analysis of the air pollution climate of a central urban roadside supersite: London, Marylebone Road

Kamara, Adams A.; Harrison, Roy M.

doi:10.1016/j.atmosenv.2021.118479

Cited by 20 publications

(4 citation statements)

References 49 publications

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“…London, Marylebone Road (LMR) is located in a street canyon on a six-lane highway with 80,000–90,000 vehicles per day. An analysis of the many air pollution datasets collected at this site is presented by Kamara and Harrison 34 . The other site, in the central urban background, is London, North Kensington (LNK), located at about 4 km from the LMR site.…”

Section: Methodsmentioning

confidence: 99%

Non-linearity of secondary pollutant formation estimated from emissions data and measured precursor-secondary pollutant relationships

et al. 2022

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In order to predict the impacts of reductions in air pollutant emissions, it is important to know whether secondary pollutant concentrations will decline in direct proportion to the reduction in their precursor, referred to as linearity. Trends in airborne concentrations of nitrate, sulfate, and SOC at sites in southern England are compared with emissions and concentration trends for sulfur dioxide (SO2), oxides of nitrogen (NOx), and non-methane VOC, and show some increased ratios of concentrations to emissions, strongly suggestive of non-linearity in the primary-secondary pollutant relationships for nitrate, but not the other pollutants. Analysis of a further 20-year dataset from the AGANET network shows a decline of nitrate concentrations significantly lower than that of NOx emissions and ambient NOx concentrations. For sulfate, the decline lies between that of emissions and airborne concentrations of SO2. Back trajectory analysis and Potential Source Contribution Function mapping for 2014–2018 show that the highest concentrations of secondary constituents in southern England are associated with air masses originating in mainland Europe, with 42% of sulfate, 55% of nitrate, and 35% of SOC estimated to be associated with air masses entering the UK from the European mainland.

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Section: Methodsmentioning

confidence: 99%

Non-linearity of secondary pollutant formation estimated from emissions data and measured precursor-secondary pollutant relationships

et al. 2022

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“…The monitoring stations surroundings also include six lanes of traffic (three in each direction of travel), two footpaths, and scant vegetation. Analyses of air quality data from this site have been reported by Kamara and Harrison (2021).…”

Section: Budapest Hungarymentioning

confidence: 99%

Insights into the sources of ultrafine particle numbers at six European urban sites obtained by investigating COVID–19 lockdowns

Rowell,

Brean,

Beddows

et al. 2024

Preprint

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Abstract. Lockdown restrictions in response to the COVID–19 pandemic led to the curtailment of many activities and reduced emissions of primary air pollutants. Here, we applied Positive Matrix Factorization to particle size distribution (PSD) data from six monitoring sites (three urban background and three roadside) between four European cities (Helsinki, Leipzig, Budapest, and London) to evaluate how particle number concentrations (PNCs) and their sources changed during the respective 2020 lockdown periods compared to the reference years 2014–2019. A number of common factors were resolved between sites, including nucleation, road traffic semi–volatile fraction (road trafficsvf), road traffic solid fraction (road trafficsf), diffuse urban (woodsmoke + aged traffic), ozone–associated secondary aerosol (O3–associated SA), and secondary inorganic aerosol (SIA). Nucleation, road traffic, and diffuse urban factors were the largest contributors to mean PNCs during the reference years and respective lockdown periods. However, SIA factors were the largest contributors to particle mass concentrations, irrespective of environment type. Total mean PNCs were lower at two of the urban background and all roadside sites during lockdown. Nucleation and road trafficsvf factors response to lockdown restrictions were highly variable, although road trafficsf factors were consistently lower at roadside sites. The responses of diffuse urban factors were largely consistent and were mostly lower at urban background sites. Secondary aerosols (O3-associated SA and SIA) exhibited extensive reductions to their mean PNCs at all sites. These variegated responses to lockdowns across Europe point to a complex network of sources and aerosol sinks contributing to PSDs.

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“…Deep urban canyons are commonly found in major cities. These are places where limited air exchange leads to poor air quality [1], regardless of the wide range of turbulenceinduced fluctuating concentrations [2]. At the base of the canyon, the wind speeds can be low, even if the traffic-generated turbulence is strong.…”

Section: Introductionmentioning

confidence: 99%

NOx and CO Fluctuations in a Busy Street Canyon

2021

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Busy street canyons can have a large flow of vehicles and reduced air exchange and wind speeds at street level, exposing pedestrians to high pollutant concentrations. The airflow tended to move with vehicles along the canyon and the 1-s concentrations of NO, NO2 and CO were highly skewed close to the road and more normally distributed at sensors some metres above the road. The pollutants were more autocorrelated at these elevated sensors, suggesting a less variable concentration away from traffic in the areas of low turbulence. The kerbside concentrations also showed cyclic changes approximating nearby traffic signal timing. The cross-correlation between the concentration measurements suggested that the variation moved at vehicle speed along the canyon, but slower vertically. The concentrations of NOx and CO were slightly higher at wind speeds of under a metre per second. The local ozone concentrations had little effect on the proportion of NOx present as NO2. Pedestrians on the roadside would be unlikely to exceed the USEPA hourly guideline value for NO2 of 100 ppb. Across the campaign period, 100 individual minutes exceeded the guidelines, though the effect of short-term, high-concentration exposures is not well understood. Tram stops at the carriageway divider are places where longer exposures to higher levels of traffic-associated pollutants are possible.

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Analysis of the air pollution climate of a central urban roadside supersite: London, Marylebone Road

Cited by 20 publications

References 49 publications

Non-linearity of secondary pollutant formation estimated from emissions data and measured precursor-secondary pollutant relationships

Non-linearity of secondary pollutant formation estimated from emissions data and measured precursor-secondary pollutant relationships

Insights into the sources of ultrafine particle numbers at six European urban sites obtained by investigating COVID–19 lockdowns

NOx and CO Fluctuations in a Busy Street Canyon

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