Mass concentration and elemental composition of indoor PM2.5 and PM10 in University rooms in Thessaloniki, northern Greece

The mass concentration and the elemental composition of PM2.5 and PM10 were measured in 40 rooms (mainly offices or mixed office-lab rooms, and photocopying places) of the Aristotle University of Thessaloniki, northern Greece. A total of 27 major, minor and trace elements were determined by ED-XRF analysis. The PM2.5/PM10 concentration ratios averaged 0.8±0.2, while the corresponding elemental ratios ranged between 0.4±0.2 and 0.9±0.2. The concentrations of PM2.5 and PM10 were significantly higher (by 70% and 50%, respectively) in the smokers’ rooms compared to the non-smokers’ places. The total elemental concentrations were also higher in the smokers’ rooms (11.5 vs 8.2 μg m−3 for PM2.5, and 10.3 vs 7.6 μg m−3 for PM2.5−10). Fine particle concentrations (PM2.5) were found to be quite proportional to smoking strength. On the contrary, the two environments exhibited similar coarse (PM2.5−10) particle fractions not related to the number of cigarettes smoked. A slight decrease of particle concentrations with increasing the floor level was also observed, particularly for PM2.5, suggesting that high-level floors are less impacted by near ground-level sources like traffic emissions. Finally, the removal efficiency of air purification systems was evaluated.