Submicron particle-bound mercury in university teaching rooms: A summer study from two polish cities

The goal of the study was to determine the concentrations of submicron particulate matter (PM₁) and of the mercury contained in it (Hg_p) in the air in two teaching rooms in two Polish cities, Gliwice and Warsaw. The levels of atmospheric particulate matter (PM) differ greatly between these two cities. The relations between the indoor (I) and outdoor (O) 24-h concentrations for each PM₁ and Hg_p were determined and, based on the conclusions, an attempt was made to identify the main sources of the indoor Hg_p in both cities. During the whole measuring period (April-June 2015), in both Warsaw and Gliwice, the 24-h outdoor PM₁ concentrations were slightly higher than the indoor ones (outdoor and indoor averages were equal to 19.3 μg m^-3 and 14.5 μg·m^-3, respectively, in Gliwice and to 13.2 μg·m^-3 and 9.5 μg·m^-3 inWarsaw). In Gliwice, the indoor concentrations of Hg_p (2.4 pg·m^-3 to 27.7 pg·m^-3) were much higher than the outdoor ones (1.1 pg·m^-3 to 6.1 pg·m^-3); in Warsaw the average concentrations of Hg_p were equal to 1.4 pg m^-3 indoors and outdoors. The 24-h concentrations of Hg_p and the 24-h I/O ratios for Hg_p varied more intensely in Gliwice than in Warsaw throughout the whole measuring period. InWarsaw, the teaching room Hg_p came mainly from the infiltration of atmospheric (outdoor) Hg_p. In Gliwice, a part of the indoor Hg_p infiltrated into the teaching room with the outdoor PM₁ that most probably was then enriched with gaseous indoor Hg, what resulted in the relatively high indoor Hg_p concentrations.