第七届青年地学论坛

Light absorption and radiative forcing of black carbon (BC) is influenced by both BC itself and its interactions with other aerosol chemical compositions. Although the changes in BC concentrations in response to emission reduction measures have been well documented, the influence of emission reductions on the light absorption properties of BC and its influence on BC-boundary-layer interactions has been less explored. In this study, we used the online coupled WRF-Chem model to examine how emission control measures during APEC affect the mixing state/light absorption of BC, and the associated implications for BC-PBL interactions. We found that both the mass concentration of BC and the BC coating materials declined during the APEC week, which reduced the light absorption and light absorption enhancement (E_ab) of BC. The reduced absorption aerosol optical depth (AAOD) during APEC were caused by both the declines in mass concentration of BC itself (52.0 %), and the lensing effect of BC (48.0 %). The reductions in coating materials (39.4 %) dominated the influence of lensing effect, and the reduced light absorption capability (E_ab) contributed 3.2 % to the total reductions in AAOD. Reduced light absorption of BC due to emission control during APEC enhanced planetary boundary layer height (PBLH) by 8.2 m. Different responses of PM_2.5 and O₃ were found to the changes in light absorption of BC. Reduced light absorption of BC due to emission reductions decreased near surface PM_2.5 concentrations but enhanced near surface O₃ concentrations in the North China Plain. These results suggest that current measures to control SO₂, NO_x, etc. would be efficient to reduce the absorption enhancement of BC, and to inhibit the feedback of BC on boundary layer. Yet enhanced ground O₃ might be a side effect of current emission control strategies. How to control emissions to offset this side effect of current emission control measures on O₃ should be an area of further focus.

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