**4. Conclusions**

The article presents the results of the analysis of the physical properties and chemical composition of particles emitted by a diesel and gasoline engine. The research focused not only on data obtained from particulate matter analyzer but also related to the chemical analysis of particulate matter from the tested engines, which allowed for comparing chemical composition and properties of particles emitted from diesel engine and petrol engine. There were three chemical analyses: Fourier Transform Infrared Spectroscopy, Scanning Electron Microscope with Energy Dispersive Spectroscopy, and Evolution Gas Analysis, which is a very extended analysis compared to the available studies. The diesel engine was mounted on an engine dynamometer; therefore, it was possible to analyze it in depth. In the case of the petrol engine, it was mounted on a scooter; therefore, a chassis dynamometer was used. The diesel engine emitted particles in the range of 50–120 nm. With the increase in the engine load, the specific emission of particulate matter increased. Increasing the load also resulted in an increase in the specific emission of the number and mass (particles per kilogram of fuel burnt). Additionally, the tests included the results before and after regeneration of the diesel particulate filter. In the case of a gasoline engine running without load, the emission of particles smaller than 30 nm was mainly observed. Increasing load of the gasoline engine resulted in an increase in both the concentration of particles and their diameter (average diameter to 90 nm).

Particles emitted from the Diesel and petrol engine differ in the size, number, and the chemical composition. PMs emitted from the Diesel engine are smaller, and more carbon black is emitted than in the case of petrol engine. It is a huge challenge to study the exact composition of PMs collected on the filters. Very accurate techniques were used in this paper, and it is possible to estimate the PMs chemical composition. EGA, SEM-EDS, and FTIR results show the differences of PMs chemical composition emitted from the Diesel and petrol engine. It can be concluded that PMs emitted from petrol engine agglomerate. The chemical composition is similar; however, for the Diesel engine, more carbon black is emitted. In case of both engines, sulfur compounds are observed.

On the basis of the conducted experimental studies, the following conclusions can be presented:


**Author Contributions:** Conceptualization, R.J. and B.S.; methodology, R.J., B.S., I.K. and J.M.; software, R.J., B.S., I.K. and J.M.; validation, R.J. and B.S., formal analysis, R.J.; investigation, B.S.; resources, R.J.; data curation, R.J., B.S., I.K., J.M. and P.K.; writing—original draft preparation, R.J., B.S., I.K., J.M. and P.K., writing—review and editing, R.J.; visualization, B.S., I.K. and J.M.; supervision, R.J.; project administration, R.J.; funding acquisition, R.J. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research subject was carried out with the use of equipment funded by the project CePT, reference: POIG.02.02.00-14-024/08, financed by the European Regional Development Fund within the Operational Programme "Innovative Economy" for 2007–2013.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
