Fig. 3.

Diurnal curves of (A) and (B) HONO, (C) and (D) NO, (E) and (F) NO₂, (G) and (H) PM_2.5, (I) and (J) HONO/NO₂ ratio, (K) and (L) CO, (M) and (N) O₃, (O) and (P) PBL height on clean days (c_PM2.5 < 50 μg m⁻³) and pollution days (c_PM2.5 ≥ 50 μg m⁻³ and RH < 90%). The black lines are the diurnal curves before CNY and the red ones are during & after CNY. The shadows indicate standard errors (±1σ). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)