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

## TL;DR

This study investigates how ozone pollution in the Fen-Wei Plain is influenced by regional transport and provides insights into its formation mechanisms using observations and simulations.

## Contribution

The study provides first-hand evidence of ozone pollution evolution and highlights the impact of regional transport on ozone precursor sensitivity.

## Key findings

- O3 lidar profiles showed high-concentration layers exceeding 130 µg/m³ with downward transport to the surface.
- VOCs were dominated by OVOCs (>300 ppbv) and alkanes (>20 ppbv).
- Regional transport from Henan and Hubei contributed significantly to surface O3 enhancement.

## Abstract

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.