Modelling the vertical gradient of nitrogen dioxide in an urban area

Eeftens, Marloes and Odabasi, Danyal and Flückiger, Benjamin and Davey, Mark and Ineichen, Alex and Feigenwinter, Christian and Tsai, Ming-Yi. (2019) Modelling the vertical gradient of nitrogen dioxide in an urban area. Science of the Total Environment, 650 (1). pp. 452-458.

[img] PDF - Published Version
Restricted to Repository staff only

PDF - Accepted Version
Available under License CC BY-NC-ND (Attribution-NonCommercial-NoDerivatives).


Official URL: https://edoc.unibas.ch/65444/

Downloads: Statistics Overview


Introduction Land use regression models environmental predictors to estimate ground-floor air pollution concentration surfaces of a study area. While many cities are expanding vertically, such models typically ignore the vertical dimension. Methods We took integrated measurements of NO 2 at up to three different floors on the facades of 25 buildings in the mid-sized European city of Basel, Switzerland. We quantified the decrease in NO 2 concentration with increasing height at each facade over two 14-day periods in different seasons. Using predictors of traffic load, population density and street configuration, we built conventional land use regression (LUR) models which predicted ground floor concentrations. We further evaluated which predictors best explained the vertical decay rate . Ultimately, we combined ground floor and decay models to explain the measured concentrations at all heights. Results We found a clear decrease in mean nitrogen dioxide concentrations between measurements at ground level and those at higher floors for both seasons. The median concentration decrease was 8.1% at 10 m above street level in winter and 10.4% in summer. The decrease with height was sharper at buildings where high concentrations were measured on the ground and in canyon-like street configurations. While the conventional ground floor model was able to explain ground floor concentrations with a model R 2 of 0.84 (RMSE 4.1 μg/m 3 ), it predicted measured concentrations at all heights with an R 2 of 0.79 (RMSE 4.5 μg/m 3 ), systematically overpredicting concentrations at higher floors. The LUR model considering vertical decay was able to predict ground floor and higher floor concentrations with a model R 2 of 0.84 (RMSE 3.8 μg/m 3 ) and without systematic bias. Discussion Height above the ground is a relevant determinant of outdoor residential exposure, even in medium-sized European cities without much high-rise. It is likely that conventional LUR models overestimate exposure for residences at higher floors near major roads. This overestimation can be minimized by considering decay with height.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Ehemalige Einheiten Umweltwissenschaften > Meteorologie (Parlow)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Epidemiology and Public Health (EPH) > Environmental Exposures and Health > Physical Hazards and Health (Röösli)
UniBasel Contributors:Feigenwinter, Christian and Eeftens, Marloes and Flückiger, Benjamin
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
Identification Number:
edoc DOI:
Last Modified:04 Mar 2019 15:32
Deposited On:05 Oct 2018 13:13

Repository Staff Only: item control page