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Variation and co-variation of PM10, particle number concentration, NOx and NO2 in the urban air - Relationships with wind speed, vertical temperature gradient and weather type

Journal article
Authors Maria Grundström
Claudia S. Hak
Deliang Chen
Mattias Hallquist
Håkan Pleijel
Published in Atmospheric Environment
Volume 120
Pages 317-327
ISSN 1352-2310
Publisher Elsevier Ltd
Publication year 2015
Published at Department of Earth Sciences
Department of Biological and Environmental Sciences
Department of Chemistry and Molecular Biology
Pages 317-327
Language en
Keywords Atmospheric stability, Lamb weather types, NO2, NOx, PM10, PNC, Proxy, Urban air pollution, Wind, Air pollution, Atmospheric temperature, Balloons, Pollution, Speed, Temperature, Thermal gradients, Urban planning, Urban growth, nitric oxide, nitrogen dioxide, air pollutant, air quality, Article, environmental temperature, hypothesis, meteorology, particle size, particulate matter, priority journal, risk assessment, seasonal variation, Sweden, urban area, velocity, weather, wind speed
Subject categories Meteorology and Atmospheric Sciences, Environmental chemistry


Atmospheric ultrafine particles (UFP; diameter < 0.1 μm) represent a growing global health concern in urban environments and has a strong link to traffic related emissions. UFP is usually the dominating fraction of atmospheric particle number concentrations (PNC) despite being a minor part of total particle mass. The aim of this study was to empirically investigate the relationship between PNC and other air pollutants (NOX, NO2 and PM10) in the urban environment and their dependence on meteorology and weather type, using the Lamb Weather Type (LWT) classification scheme. The study was carried out in Gothenburg, Sweden, at an urban background site during April 2007-May 2008. It was found that daily average [PNC] correlated very well with [NOx] (R2 = 0.73) during inversion days, to a lesser extent with [NO2] (R2 = 0.58) and poorly with [PM10] (R2 = 0.07). Both PNC and NOx had similar response patterns to wind speed and to the strength of temperature inversions. PNC displayed two regimes, one strongly correlated to NOx and a second poorly correlated to NOx which was characterised by high wind speed. For concentration averages based on LWTs, the PNC-[NOx] relationship remained strong (R2 = 0.70) where the windy LWT W deviated noticeably. Exclusion of observations with wind speed >5 ms-1 or ΔT < 0 °C from LWTs produced more uniform and stronger relationships (R2 = 0.90; R2 = 0.93). Low wind speeds and positive vertical temperature gradients were most common during LWTs A, NW, N and NE. These weather types were also associated with the highest daily means of NOx (~30 ppb) and PNC (~10 000 # cm-3). A conclusion from this study is that NOx (but not PM10) is a good proxy for PNC especially during calm and stable conditions and that LWTs A, NW, N and NE are high risk weather types for elevated NOx and PNC. © 2015.

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