Characterisation of engine exhaust particulate fingerprints and their contribution to air quality - VTT's contribution

Target of the European Commission project "Characterisation of engine exhaust particulate fingerprints and their contribution to air quality" was to identify the contribution of different engine technologies on ambient particulates through chemical mass balance modelling (CMB). The modelling requires as source information the evaluation of the feasibility of possible fingerprints from the analysis data obtained from particulates from several engine/vehicle technologies and similar data from ambient air particulates. Several technologies were selected for this project. VTT Energy was responsible of sampling and analysis of the particulate matter from heavy-duty diesel engine and spark-ignition vehicle. In the first phase of the project round-robin tests were carried out to find out, if the results from different laboratories are comparable with each other and to select analysis methods for actual samples. The analysis, which were selected for further work were SOF, PAH, fuel/lube, anions and metal analysis. The heavy-duty tests included three different load conditions with and without oxidation catalyst. The particulates were collected in two different size groups. The total particulates and fine particulates smaller than 2.5 µm were collected separately. The tests with sparkignition stoichiometric gasoline fuelled vehicle were carried out at two load conditions, with and without three-way-catalyst (TWC). In addition, European test cycle was used as a reference. Unleaded CEC reference gasoline was used in the tests with the spark-ignition vehicle with TWC. However, lead additive was added into gasoline for the tests without catalyst. Significant amount of sulphates were present in the particulates only in the conditions, where the catalyst was warm enough to generate sulphates from sulphur of the fuel. Bromide and chloride were found from the particulates of spark-ignition vehicle in the tests with leaded fuel. Profiles of the PAH compounds were rather different from the spark-ignition vehicle and diesel engine. Concentration of the heaviest PAH compounds in particulates from gasoline fuelled vehicle was high when compared with the particulates from diesel engine. Comparison of the metal analysis results from gasoline vehicle and diesel engine suffered from low level of metals in diesel particulate samples and disturbing effect of bromide and chloride in the gasoline particulate samples. However, it was noted e.g. that calcium was found only from the particulates from diesel engine.