Impacts of Cross-Regional Transport on Ozone Pollution in the Fen-Wei Plain: Insights from Multi-Source Observations...

Unfavorable terrain conditions and intensive emissions have led to a deteriorating trend of ozone (O₃) pollution in the Fenwei Plain (FWP), which has attracted increasing attention. However, the lack of observations and Volatile Organic Compound (VOC) component observation data has seriously constrained an in-depth understanding of the formation mechanisms of O₃ pollution. The multi-source observations conducted in this study provides first-hand evidence for characterizing the evolution of O₃ pollution in the FWP. O₃ lidar vertical profiles reported high-concentration layers exceeding 130 µg/m³, O₃ vertical flux high-concentration layers exceeding -50 µg/(m²⋅s), confirming downward transport to the surface. The VOCs components were dominated by Oxygenated Volatile Organic Compounds (OVOCs) (>300 ppbv) and alkanes (>20 ppbv). O₃ source apportionment technology analysis indicated transport from the Henan (HN) and Hubei (HB) contributed 24.99% and 40.02% of surface O₃ enhancement. Interestingly, a close linkage between O₃ precursor sensitivity (OPS) variations and contribution from potential source regions was noticed. Large contributions from HN and HB drove the OPS toward a VOC-limited regime, with a concurrent drop in the HCHO/NO₂ indicator to 1.73. Our results underscore the great importance of the impacts of regional transport on OPS from different source areas when formulating strategies for regional joint prevention and control.