Over het atmosferische gedrag en de emissie van submicrone verkeersaerosolen

Abstract

Different processes can influence the perticle size distribution of fresh automobile aerosols. Dispersion, deposition and polydispers coagulation according to Fuchs (1964) are discussed. The monodispers coagulation theory of Davies (1979) and the formula describing the gradient coagulation are extended to polydispers aerosols. Also a critical review is given of the behavious of submicron particles under the influence of the relative humidity and the reentrainment of these particles by tubulence.A survey is given of the electrical aerosolanalyzer and condensation nucleus counter. The control and comparison of these instruments is treated next. After that a literature review of the particle size distributions of traffic aerosols and the emissions which can be calculated from these distributions is presented.The emission in particles/km per vehicle can be derived from the size distribution measurements of aerosols and tracergas concentrations along a road, because the dispersion is known for the tracergas. As the aerosol samples were taken at different distances from the road, with different residence times, the velocity of coagulation and deposition can be deduced. Also one model is used to describe the three processes dispersion, deposition and coagulation. With the measurements along a road an experimental verification of this model was possible.The measured particle size distributions in a tunnel were a steady state concentration. The loss of aerosol bij dispersion, deposition and coagulation is compensated by the traffic emission. With this steady state concentration and the emission by traffic found during the roadexperiments the coagulation constant of submicron particles can be calculated. As a conclusion from these calculations a preference can be given to the theory of DAVIES (1979) above the theory of FUCHS (1964) describing the value of the coagulation constant. With a model that describes the steady state concentration in the tunnel as a function of the emission and removal mechanisms the traffic emission in the tunnel could be calculated.The emissions from the road and tunnel experiments have been evaluated and are in a reasonable agreement. The following emission in particles per vehicle is presented with a variation coefficient between 20% for the bigger particles and 70% for particles of 0.01 μm