Road salt emissions: A comparison of measurements and modelling using the NORTRIP road dust emission model

AbstractDe-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

NORTRIP emission model user guide.

The NORTRIP emission model has been developed at NILU, in conjunction with other Nordic institutes, to model non-exhaust traffic induced emissions. This short summary document explains how to run the NORTRIP model from the MATLAB environment or by using the executable user interface version. It also provides brief information on input files and the model architecture

Modelling non-exhaust emissions of PM10 in Oslo. Impact of traffic parameters and road maintenance activities using the NORTRIP model.

This report was requested by the Norwegian Public Roads Administration (Statens vegvesen) to provide information concerning non-exhaust traffic emissions in Oslo and the impact of various traffic parameters and road maintenance activities on these emissions. This report provides the results of calculations made with the NORTRIP model, a recently developed emission model for calculating non-exhaust emissions. The sensitivity of the modelled emissions to traffic parameters such as studded tyre share and fraction of heavy duty vehicles is investigated. In addition the impact of salting and cleaning is addressed

NORTRIP model development and documentation: NOn-exhaust Road TRaffic Induced Particle emission modelling.

The NORTRIP model is the result of research efforts carried out by a number of Nordic institutes to improve our understanding and ability to model non-exhaust traffic emissions and has been developed through the Nordic Council of Ministers project NORTRIP (NOn-exhaust Road Traffic Induced Particle emissions). The NORTRIP model is a process based non-exhaust emission model that is intended for application without site specific empirical factors. It takes into account direct wear emissions, the build up of mass on the road surface, the suspension of this mass, as well as the application and suspension of salt and sand. It combines a road dust sub-model with a road moisture sub-model in order to properly describe the retention of dust on the road surface. The model can be applied for assessment purposes and for the management and evaluation of abatement strategies regarding road wear, salting and sanding. The model development and its documentation, along with its application to a large number of Nordic datasets, is described in detail in this report

Modelling non-exhaust emissions of PM10 in Oslo. Impact of the environmental speed limit using the NORTRIP model.

This report was requested by the Norwegian Public Roads Administration (Statens vegvesen) to provide information concerning non-exhaust traffic emissions in Oslo and the impact of changes in environmental speed limits on these emissions. This report provides the results of calculations made with the dispersion model EPISODE coupled to the NORTRIP road dust emission model, a recently developed emission model for calculating non-exhaust emissions. The change in modelled emissions due to changes in environmental speed limit are calculated for two different speed scenarios, where 'speed limit' and 'realistic speed' changes are compared. In addition the impact of the environmental speed limit is compared to other road dust control measures involving studded tyre share and heavy duty vehicle reduction, taken from a previous report

Luftkvalitetskart av NO2 og PM10 for byområdet Stavanger, Sandnes, Randaberg og Sola (Nord-Jæren). Oppsummeringsrapport.

Denne rapporten beskriver og presenterer luftkvalitetskart av NO2 og PM10 som er blitt laget for området Nord-Jæren, som innbefatter kommunene Stavanger, Sandnes, Randaberg og Sola

Air quality maps of NO2 and PM10 for the region including Stavanger, Sandnes, Randaberg and Sola (Nord-Jæren). Documentation of methodology.

This report documents the methodology used to make air quality maps of NO2 and PM10 for the region Nord-Jæren, which includes the municipalities of Stavanger, Sandnes, Randaberg and Sola. It provides support documentation for the summary report OR 57/2013

The role of air quality modelling in particulate matter management in cities. Results from the Air Implementation Pilot

The European Commission and the EEA agreed to reinforce efforts to improve knowledge on implementation of air quality legislation through a joint pilot project. The Air Implementation Pilot run from March 2012 to June 2013 and aimed at better understanding the challenges cities faced in implementing air quality policy. Twelve European cities were selected and invited to join the project. One of the focus of the Pilot project was to assess the use of models for air quality assessment and management, share experiences, and identify needs for further guidance. The results of the analysis of modelling practices are presented in this work. More than 20 different models have been used for air quality assessment and management in these cities. The main purposes for which cities applied models are air quality assessment, quantification of source contribution and long term planning. The cities have found models helpful and the outputs have been used in urban air quality assessment and management, including the evaluation of strategies to reduce PM ambient levels. However, the cities found difficulties in the application of models as for instance the quality and availability of input data or the validation and uncertainty estimation of the model results