Which aerosol type dominate the impact of aerosols on ozone via changing photolysis rates?

The impact of aerosols on ozone via influencing photolysis rates is a combined effect of absorbing aerosols (AA) and scattering aerosols (SA). However, AA and SA show different optical properties and influence photolysis rates differently, which then cause different impacts on ozone. Till now, the dominate factor is disconfirmed, which is largely due to the impact of SA on ozone not reaching to a consistent conclusion. In this study, the WRF-Chem model was implemented to simulate the air pollutants over the North China Plain (NCP). The impacts of AA and SA on ozone via influencing photolysis rates were quantitatively isolated and analyzed. Our results also demonstrated the decreasing effect of AA on ozone within planet boundary layer (PBL) which is consistent with the conclusions of previous studies. But for SA, it decreased the ozone chemical contribution (CHEM) near surface but increased which in the upper layers of PBL, that enlarge the ozone vertical gradients. In this case, more vertical exchanges of ozone would occur with the effect of vertical mixing motion of atmosphere, then the opposite CHEM variations were counteracted with each other and finally led to very slight changes in ozone within PBL. Thus, it can be summarized that AA dominate this impact of aerosols on ozone. Reducing AA could cause a general increase in ozone (ΔO) over the NCP. Based on the aerosol levels of this case, ΔO would be seen over 86 % of the areas in the NCP when reducing AA by 3/4 and ΔO was more significant in the megacities. Our study highlights the different relationships between ozone and aerosol types, which suggests that more attentions should be paid on aerosol types, especially AA, when making the synergetic control strategy of aerosols and ozone in China.