Night-time ground-level ozone trends and variability over the urban sites
2019
Nor Azam Ramli | Syabiha Shith
This study evaluates the variation of night-time ground-level ozone (O₃), nitrogen dioxide (NO₂) and nitric oxide (NO) from year 2015 to 2016. During this period, the recorded maximum night-time ground-level O₃ was 55 ppb at Putrajaya (PT), which have more areas with higher brightness level compared to another urban site, Alor Setar (AS) at 21 ppb. Lower NO concentrations restricted the sinking agents, thus, reducing the depletion rates and resulted in O₃ to remain in the atmosphere. The contributor toward night-time ground-level O₃ concentration in the urban site was not only NO₂ concentration, as light pollution might enhance the O₃ formations. The photochemistry rate was commonly accounted to be zero due to the absence of photochemical reactions at night. However, the minimum photochemistry rate in both urban was recorded at the ranged from 1.50-2.70 ppb, indicating that O₃ was also titrated at night even though the value is not as high as during the day.
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