“…The concentration differences of K, Cr, Mn, Fe, Cu, and Pb during HP days and MP days were statistically significant ( p < 0.05) based on the Mann‐Whitney U test, while the differences of Ni, As, Se, and Zn during these two periods were not statistically significant. It is known that the local emissions of industrial activities, coal combustion, and biomass burning are lower in urban Beijing than in the areas outside Beijing in the BTH (Gao et al, ; Liu et al, ; Zhu et al, ); this is because a series of the strictest air pollution control measures were taken in the Beijing Municipality, including phasing out and/or relocation of highly polluting industries, reduction in coal consumption, and usage of clean energy. Consequently, during the highest polluted days, there was some decline in the concentrations of K, Cr, Mn, Fe, Ni, Zn, and Pb, which are closely associated with industrial emission and coal combustion.…”