Road salt emissions: A comparison of measurements and modelling using the NORTRIP road dust emission modelShow others and affiliations
2016 (English)In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 141, p. 508-522Article in journal (Refereed) Published
Abstract [en]
De-icing of road surfaces is necessary in many countries during winter to improve vehicle traction. Large amounts of salt, most often sodium chloride, are applied every year. Most of this salt is removed through drainage or traffic spray processes but a certain amount may be suspended, after drying of the road surface, into the air and will contribute to the concentration of particulate matter. Though some measurements of salt concentrations are available near roads, the link between road maintenance salting activities and observed concentrations of salt in ambient air is yet to be quantified. In this study the NORTRIP road dust emission model, which estimates the emissions of both dust and salt from the road surface, is applied at five sites in four Nordic countries for ten separate winter periods where daily mean ambient air measurements of salt concentrations are available. The model is capable of reproducing many of the salt emission episodes, both in time and intensity, but also fails on other occasions. The observed mean concentration of salt in PM10, over all ten datasets, is 4.2 μg/m3 and the modelled mean is 2.8 μg/m3, giving a fractional bias of −0.38. The RMSE of the mean concentrations, over all 10 datasets, is 2.9 μg/m3 with an average R2 of 0.28. The mean concentration of salt is similar to the mean exhaust contribution during the winter periods of 2.6 μg/m3. The contribution of salt to the kerbside winter mean PM10 concentration is estimated to increase by 4.1 ± 3.4 μg/m3 for every kg/m2 of salt applied on the road surface during the winter season. Additional sensitivity studies showed that the accurate logging of salt applications is a prerequisite for predicting salt emissions, as well as good quality data on precipitation. It also highlights the need for more simultaneous measurements of salt loading together with ambient air concentrations to help improve model parameterisations of salt and moisture removal processes. © 2016 The Authors
Place, publisher, year, edition, pages
Elsevier Ltd , 2016. Vol. 141, p. 508-522
Keywords [en]
Air quality, Modelling, Non-exhaust emissions, Particulate matter, Road salt, Dust, Models, Roads and streets, Salt removal, Transportation, Ambient air concentration, Comparison of measurements, Exhaust emission, Road dust emissions, Road salts, Sensitivity studies, Simultaneous measurement, Precipitation (chemical), sodium chloride, ambient air, atmospheric pollution, concentration (composition), numerical model, road, seasonal variation, traffic emission, air monitoring, Article, exhaust gas, highway, measurement, precipitation, priority journal, road salt emission, vapor pressure, winter
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:ri:diva-61323DOI: 10.1016/j.atmosenv.2016.07.027Scopus ID: 2-s2.0-84978511831OAI: oai:DiVA.org:ri-61323DiVA, id: diva2:1715996
Note
Funding details: Nordisk Ministerråd, KOL-1408; Funding text 1: We would like to acknowledge the Nordic Council of Ministers through the project ‘NORTRIP-2’ (Project number KOL-1408) for their financial support of this project. We would also like to acknowledge the following institutes for providing data for this study: The Norwegian Public Roads Administration for traffic and road salting data; the Finnish Meteorological Institute (FMI) for meteorological data and regional background salt concentration data (Utö and Virolahti); Destia Oy and the Centre for Economic Development, Transport and the Environment for road maintenance data at Kehä III; the Finnish Transport Agency for traffic data at Kehä III; the City of Helsinki for traffic and road maintenance data at Hämeentie; the Danish Metrological Institute for providing precipitation data from Copenhagen; Kim N. Sørensen from Copenhagen Municipality for the provision of winter road maintenance data in Copenhagen.
2022-12-052022-12-052023-06-07Bibliographically approved