But go with your logic.
https://smartairfilters.com/en/blog/less-pm25-pollution-higher-floors/?srsltid=AfmBOoo3xnZLYZLqJzkP_CUQRBU6CS_LIYW9gBg0kdRyOoA-lfE_k4ra
this one states that pn 2.5 actually increases with height
https://www.researchgate.net/publication/337793709_Vertical_Variation_of_Carbonaceous_Aerosols_with_in_the_PM25_Fraction_in_Bangkok_Thailand
The analysis of data obtained in this study shows that average values of PM2.5 at observation heights of 30 m, 75 m, and 110 m increased slightly with height and were 6.21 ± 2.45, 8.12 ± 3.65, and 9.03 ± 3.93 µg m–3, respectively. OC concentrations at these observation heights were 4.13 ± 2.65, 4.01 ± 4.07, and 4.11 ± 3.58 µg m–3, respectively, and corresponding EC concentrations were 1.02 ± 0.84, 1.07 ± 0.95, and 0.50 ± 0.70 µg m–3.