In this study, fine particulate matter (PM2.5) was collected inside the metal workshop located in the suburb of the City of Rijeka, Croatia. The high intensity of welding and plasma cutting is characteristic for this metal workshop and, therefore, high levels of very fine metal aerosols were expected. The fine aerosol sampling on thin Teflon filters and subsequent XRF elemental analysis were performed. The sampling in the workshop was conducted in two sampling periods in May and November 2016. In total, 64 samples were collected, out of which 28 were 12-hours samples and 36 were hourly samples. Additionally, Trotec Optical Particle Counter PC220 was used to measure concentrations for 6 different optical sizes (0.3 µm, 0.5 µm, 1 µm, 2.5 µm, 5 µm and 10 µm) to obtain the particle size distribution. The sample analysis was carried out with X-Ray Fluorescence technique at the Laboratory for Elemental Microanalysis at the Department of Physics, University of Rijeka. Heavy metals such as Ti, Cr, Mn, Fe, Ni, Cu, Zn and Pb were detected. The results were compared to the average daily concentrations measured in the city centre. Concentrations of all measured metals in indoor air in our study were significantly higher than in the samples collected outdoors. The highest indoor/outdoor ratio was obtained for Fe and Mn. Weekly and daily variations of heavy metal concentrations were also analysed. As expected, the results showed that weekly and diurnal variations of metal concentrations follow the work intensity in the workshop. The particle size distribution shows that sub-micron particles are present in much higher concentrations than coarse particles. This indicates the harmfulness of welding fumes.

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