Temporal Variations of O3 and NO x in the Urban Background Atmosphere of Nanjing, East China

Abstract

Rapid economic growth has given rise to a significant increase in ozone (O3)-precursor emissions in many regions of China. An improved understanding of O3 formation in response to different precursor emissions is imperative to address the highly nonlinear O3 problem and to provide a solid scientific basis for efficient O3 abatement in these regions. To this end, this study was performed in Nanjing using a set of observational data from June 1, 2013, to May 31, 2014. The results showed that O3 concentrations were positively correlated with wind speed and temperature and were significantly negatively correlated with relative humidity. The highest monthly daytime, nighttime, and daily average O3 concentrations were observed in summer with values of approximately 46, 18 and 30 ppb, respectively. The lowest O3 concentrations were observed in November through January with values as low as 17, 4, and 9 ppb for the daytime, nighttime, and daily concentrations, respectively. The highest daytime average NO and NO2 concentrations were observed in December, whereas the lowest concentrations were observed in July. A unimodal O3 peak was observed with the highest O3 levels in summer followed by spring and then autumn; the lowest levels observed in the winter. The O3 concentration reached maximum levels at 14:00 to 15:00 h (local standard time). It was found that the crossover occurred with approximately several hours difference with the earliest occurring in summer (06:00 h) followed by spring (08:00 h), autumn (09:00 h), and winter (10:30 h). Furthermore, the highest constant rate of O3 accumulation was observed in summer (5.6 ppb/h) followed by autumn (4.8 ppb/h), spring (4.5 ppb/h), and winter (2.7 ppb/h). The oxidant intercept ranged from 28.4 ppb in January to 58.6 ppb in June, although the slope also shows substantial variation from 0.18 in June to 0.67 in August. The weekend effect is stronger in spring and summer than in autumn and winter and is more intense on Sundays than on Saturdays. Thus, the decrease of O3 levels during weekends suggests that it may be NO x -sensitive.

Risk Reduction Behaviors Regarding PM2.5 Exposure among Outdoor Exercisers in the Nanjing Metropolitan Area, China

“…Nanjing, the capital city of Jiangsu Province, located in eastern China, is one of the most developed and fastest growing urbanized areas. With rapid social and economic development, Nanjing has been facing the challenges of severe air pollution [3,5,10,29,30,31,32,33,34]. There were 242 haze days (i.e., with horizontal visibility less than 10,000 m) in 2013 and increasing red alerts for severely high levels of air pollution were reported in 2015 [35].…”

Study on Coupled Relationship between Urban Air Quality and Land Use in Lanzhou, China

“…Previous research results provide significant theoretical and practical experience with regard to air quality distribution and driving factors, but those studies pay more attention to large-scale air quality in the whole country, urban agglomerations, and typical regions; there are few studies on the differences in air quality within cities, because most of the air quality data needed for the research come from satellite measurements and national environmental air quality monitoring sites [51]. Satellite measurements are usually obtained at a fixed time of the day to obtain the spatial distribution of atmospheric pollutant concentrations.…”

Tropospheric NO2 retrieval algorithm for geostationary satellite instruments: applications to GEMS

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