Assessment of the Characteristics and Influencing Factors of Ozone in Fuzhou, China, Using Wavelet Analysis

ABSTRACT

In recent years, ozone (O₃) air pollution has become a major problem—which is still increasing—in China. In this study, data on the O₃ concentration as well as on two of its influencing factors, meteorological parameters and traffic conditions, were collected in Fuzhou and then analyzed via wavelet transforms to evaluate the variation in O₃ concentration and its relationships with the factors. High concentrations appeared during spring and summer, and notable fluctuations occurred primarily from March till April, from June till July and during September. The level of O₃ exhibited significant positive correlations with the temperature and sunshine duration but negative ones with the relative humidity, precipitation and air pressure; additionally, it increased when the wind speed was low and fluctuated when the wind speed was high. The concentration was also significantly negatively correlated with the concentrations of O₃ precursors (NO_x and CO) and hence closely related to the traffic conditions, as the reduced vehicle speed during rush hour due to increased vehicle flow and traffic density led to higher precursor emissions in the vehicular exhaust. A prominent “weekend effect” was observed with the precursor levels, which displayed greater fluctuations during the weekdays than the weekends; the vehicle flow and the O₃ concentration.