Abstract:
Meteorological factors have an important influence on ozone (O
3) concentration. In order to explore the characteristics and causes of near-surface O
3 pollution in Henan Province, based on the datasets of ambient air quality monitoring stations and national basic ground climate stations in Henan Province from 2014 to 2020, this study examined the spatial-temporal characteristics of O
3 pollution in Henan Province and the relationship between O
3 and precursors and meteorological factors, and the potential sources of O
3 in Henan Province are also explored. The results showed that: (1) In terms of temporal characteristics, the annual mean O
3 concentration of a maximum daily 8h average (O
3-8 h) in Henan Province was generally reduced from 2014 to 2020, showing an "M" type temporal evolution. For the seasonality of O
3-8 h concentration, it was highest in summer and decreased sequentially in spring, autumn, and winter, while both the concentration of O
3-8 h and the number of days exceeding the standard reached their peaks in June. In terms of spatial characteristics, the concentration of O
3 is generally lower in northern than in southern China, and lower in western than in eastern China, and the areas with high concentrations are concentrated in southern Henan Province. (2) The concentration of O
3-8 h was significantly negatively correlated with the precursor NO
2 and with the CO concentration. (3) Seeing from the perspective of meteorological factors, O
3-8 h concentration is positively correlated with air temperature and negatively correlated with relative humidity, which indicates that high temperature (≥26 ℃) and low humidity (≤40%) are favorable for the increasing of O
3-8 h concentration. Affected by the prevailing northerly winds in autumn and winter, the O
3-8 h concentration in Henan Province showed a spatial pattern of low values in the north and high values in the south in autumn and winter, and the prevailing southerly wind in summer is conducive to the formation and maintenance of O
3 in Henan Province. (4) In the summer of 2019, the main source areas of O
3 and precursors increased gradually and changed from both inside and outside the province to mainly outside the province. Affected by the boundary cities and topographic conditions, O
3 in Henan Province accumulated locally in summer. The Study shows that the near-surface O
3 pollution in Henan Province has significant spatial and temporal distribution characteristics, the pollution degree is generally reduced, the precursors of O
3 and meteorological factors (temperature, relative humidity, wind) have significant effects on O
3, and O
3 transport paths and potential sources change with time in summer.