Ground-level O₃ pollution in the Pearl River Delta region (PRD) is closely related to anthropogenic, natural emissions and regional transport. However, the interactions among different sources and natural intervention in modulating anthropogenic management have not been comprehensively assessed. Here, the WRF-CMAQ-MEGAN modeling system was utilized to simulate an O₃ episode over PRD. The integrated source apportionment method (ISAM) and brute-force top-down combined with factor separation approach (BF-TD-FSA) were applied to quantify source contributions, impacts of individual or multiple sources on O₃, and decouple interactions among various emissions; additionally, based on ISAM, O₃ isopleths visualized MDA8 O₃ response of different source types to anthropogenic perturbations. ISAM concluded considerable MDA8 O₃ contributions of regional transport in PRD/NPRD (non-PRD areas in Guangdong province) (38.8%/35.7%), followed by anthropogenic (32.7%/24.8%), BVOC (biogenic volatile organic compounds, 23.8%/20.3%) and SNO (soil NO, ~4%) emissions. Compared to concentrated anthropogenic contributions, widespread natural contributions were observed across their source areas and along the transport pathways. The BF-TD also revealed that regional transport had the largest impact (>90 μg m^-3) on MDA8 O₃ while anthropogenic and BVOC emissions greatly affected downwind PRD (64.5 and 7.7 μg m^-3). Negative synergy between anthropogenic and natural emissions (especially BVOC emission) suggested potential natural-induced intensification of anthropogenic impact during O₃ management. The MDA8 O₃ isopleths further demonstrated significant BVOC-induced reward and regional transport-induced penalty for anthropogenic NO_x (ANO_x) emission control benefits, leading to additional maximum MDA8 O₃ decrease and increase by -27.5 and 13.8 μg m^-3 in polluted high-emission grids. The natural-induced reward effect could impose loose requirements on anthropogenic reduction (decreased by 13.3%~17.7%) if there were no regional transport-induced control penalty. It is advisable to prioritize ANO_x control and seek collaboration on air quality management with neighboring provinces to maximize the natural-induced control reward and achieve desired targets with minimal human efforts.

 

臭氧,人为调控