Abstract
In this work, a ground-based remote sensing instrument was used for observation of the trace gases NO2 and CHOCHO in Hefei, China. Excessive development and rapid economic growth over the years have resulted in the compromising of air quality in this city, with haze being the most prominent environmental problem. This is first study covering observation of CHOCHO in Hefei (31.783° N, 117.201° E). The observation period of this study, i.e., July 2018 to December 2018, is divided into three different categories: (1) clear days, (2) haze days, and (3) severe haze days. The quality of the differential optical absorption spectroscopy (DOAS) fit for both CHOCHO and NO2 was low during severe haze days due to a reduced signal to noise ratio. NO2 and CHOCHO showed positive correlations with PM2.5, producing R values of 0.95 and 0.98, respectively. NO2 showed strong negative correlations with visibility and air temperature, obtaining R values of 0.97 and 0.98, respectively. CHOCHO also exhibited strong negative correlations with temperature and visibility, displaying R values of 0.83 and 0.91, respectively. The average concentration of NO2, CHOCHO, and PM2.5 during haze days was larger compared to that of clear days. Diurnal variation of both CHOCHO and NO2 showed a significant decreasing trend in the afternoons during clear days due to photolysis, while during haze days these two gases started to accumulate as their residence time increases in the absence of photolysis. There was no prominent weekly cycle for both trace gases.
Highlights
China has been ranked near the bottom of the Global Environmental Sustainability Index due to its persistent and extensive air pollution [1]
In this study we primarily focused on retrieval of CHOCHO and NO2 from MAX-differential optical absorption spectroscopy (DOAS)
The quality of the DOAS fit is affected during severe haze days, which can be observed from the root mean square (RMS) and differential slant column densities (dSCDs) errors for both CHOCHO and NO2
Summary
China has been ranked near the bottom of the Global Environmental Sustainability Index due to its persistent and extensive air pollution [1]. Nitrogen dioxide (NO2 ) and glyoxal (CHOCHO) have significant roles in varying the chemistry of the troposphere [2]. Nitrogen dioxide may act as a precursor for the formation of aerosols under certain meteorological conditions. There have been some reported studies on monitoring air quality in China using MAX-DOAS instruments. Concentrations of tropospheric nitrogen dioxide were obtained using MAX-DOAS mounted at four different locations in Shanghai in 2010 during the Shanghai World Expo [18]. The effect of haze and non-haze conditions on the retrieval of CHOCHO from MAX-DOAS observations in Beijing has been investigated [20]. As a quick overview of the arguments discussed above, the current research claims the unique contribution of monitoring the air quality of Hefei, China.
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