Aerosol and NOx emission factors and submicron particle number size distributions in two road tunnels with different traffic regimes

[摘要] Measurements of aerosol particle number size distributions (18–700 nm), massconcentrations (PM2.5 and PM10) and NO_x were performed in the Plabutschtunnel, Austria, and in the Kingsway tunnel, United Kingdom. These twotunnels show different characteristics regarding the roadway gradient, thecomposition of the vehicle fleet and the traffic frequency. The submicronparticle size distributions contained a soot mode in the diameter range D=80–100 nmand a nucleation mode in the range of D=20–40 nm. In theKingsway tunnel with a significantly lower particle number and volumeconcentration level than in the Plabutsch tunnel, a clear diurnal variationof nucleation and soot mode particles correlated to the traffic density wasobserved. In the Plabutsch tunnel, soot mode particles also revealed adiurnal variation, whereas no substantial variation was found for thenucleation mode particles. During the night a higher number concentration ofnucleation mode particles were measured than soot mode particles and viceversa during the day. In this tunnel with very high soot emissions duringdaytime due to the heavy-duty vehicle (HDV) share of 18% and another 40%of diesel driven light-duty vehicles (LDV) semivolatile speciescondense on the pre-existing soot surface area rather than forming newparticles by homogeneous nucleation. With the low concentration of soot modeparticles in the Kingsway tunnel, also the nucleation mode particles exhibita diurnal variation. From the measured parameters real-world trafficemission factors were estimated for the whole vehicle fleet as well asdifferentiated into the two categories LDV and HDV. In the particle sizerange D=18–700 nm, each vehicle of the mixed fleet emits (1.50±0.08)×10¹⁴ particleskm^-1 (Plabutsch) and (1.26±0.10)×10¹⁴ particles km^-1 (Kingsway), while particle volumeemission factors of 0.209±0.008 cm³ km^-1 and0.036±0.004 cm³ km^-1, respectively, were obtained. PM1 emission factorsof 104±4 mg km^-1 (Plabutsch) and 41±4 mg km^-1(Kingsway) were calculated. Emission factors determined in this work were ingood agreement with results from other studies.

[学科分类] 大气科学