摘要：A number of time series from two local PM<sub>2.5</sub> monitoring stations were analyzed, for a small city, in North East Greece. They coincided with SARS-CoV-2 pandemic lockdowns and lifting restrictions. The aim of this analysis was to establish concentration exceedances and roughly apportion sources of the PM<sub>2.5</sub> concentration problem. This was established by analyzing 24-h filter samples of trace elements using WD-XRF. It was found that the restrictions and their lifting did not significantly affect these concentrations. The main problems were assigned to emissions from biomass burning central heating and Saharan dust episodes. The study results indicate that even in small cities the air quality as far as PM<sub>2.5</sub> is concerned can still be deleterious to the local population according to the WHO restricting levels but not according to the EU levels. The fact that PM<sub>2.5</sub> is not a single chemical pollutant makes matters more complicated and renders such concentration upper levels, of little significance.
