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

Testing av utslippsfaktorer for vedfyring i AirQUIS. En sensitivitetsstudie for PM2.5 i Oslo.

Utslipp fra vedfyring gir et av de største bidragene til partikkelutslipp i Norge, men det er en del usikkerhet rundt utslippstallene og hvor mye vedfyring bidrar til de bakkenære konsentrasjonene. Det er gjort spredningsberegninger for Oslo for å vurdere utslipp fra vedfyring og teste ulike parametere som er knyttet opp mot denne kilden. Det er vært testet for 3 ulike vinterperioder for å se på meteorologisk variasjon (Basisberegninger), med nye utslippsfaktorer fra SINTEF (scenario SINTEF), kraftig kutt i utslippene (scenario Forbruk) og med en ny fordeling av utslippet over døgnet (scenario TID). Modellen overestimerer klart bidraget fra vedfyring i basisberegningene som inkluderer det største utslippet for vedfyring i denne studien. Selv med bruk av nye utslippsfaktorer fra SINTEF som gir mindre utslipp og som gir et noe bedre resultat enn de tidligere faktorene, er det fortsatt klart at utslippene fra vedfyring gir for høye konsentrasjoner, spesielt på kvelden. I kombinasjon med resultatene fra andre scenarioberegninger vurderer vi det til at utslippene ikke er riktige hverken i mengde eller fordeling i tid og rom

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

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

Vurdering av luftkvalitet. Måledataanalyse og litteraturstudie.

NILU - Norsk institutt for luftforskning har på oppdrag fra Klima- og forurensningsdirektoratet (Klif) gjort en vurdering av nasjonal luftkvalitet og en virkemiddelanalyse. Det er analysert data fra flere byer i Norge og det er valgt byer av ulik størrelse for å få et bredt grunnlag til analysen. Det er analysert for NOx, NO2, PM10, PM2,5, SO2 og benzen. Dette arbeidet gir et bedre grunnlag til å planlegge videre arbeid med luftkvalitet og vurdering av grenseverdier