Abstract:
In order to investigate the variation profile of air pollutant concentrations in the Nanjing urban area in winter, real-time monitoring data on
φ(CO),
φ(O
3),
φ(NO
2),
φ(SO
2),
ρ(PM
2.5) and
ρ(PM
10) from air quality automatic monitoring stations, as well as the synchronous meteorological data, were used in this study. The concentration level and variation profile of air pollutants in the Nanjing urban area in winter 2014 (from December 2014 to February 2015) were analyzed. The effects of meteorological conditions on air quality during emission reduction measures during the Spring Festival of 2015 were investigated. The results indicated that during the observation period, both daily mean values and hourly mean values of
φ(CO) and
φ(O
3) were below the grade Ⅱ standard in China′s
Ambient Air Quality Standards (GB 3095-2012). Daily mean values of
ρ(PM
2.5),
ρ(PM
10),
φ(NO
2) and
φ(SO
2) exceeded the limits by 44%, 38%, 34% and 2%, respectively.
ρ(PM
2.5) and
ρ(PM
10) reached maximal daily average values of 231 and 283 μg/m
3, respectively, which were 3.1 times and 1.9 times the grade Ⅱ standard. The daily variation indicated that
φ(CO) and
φ(NO
2) values presented bimodal patterns in the morning and evening, which was related to pollutant discharge from traffic rush in the morning and evening. Variation trend of
φ(O
3) values appeared as an obvious single peak, with peak value appearing in the afternoon. Variation trend of
φ(SO
2) values presented a single peak, with the concentration at night lower than that in the daytime. Variation trend of
ρ(PM
2.5) and
ρ(PM
10) values generally showed synchronous bimodal pattern, with the peak values appearing at around 10:00 and 22:00. In the urban area of Nanjing, pollutant concentrations during the weekend were overall higher than those on the workdays. In particular, the values of
φ(CO),
φ(NO
2) and
ρ(PM
2.5) during the weekend were significantly higher than those on the workdays, with an obvious ′weekend effect′ observed. Since the emission reduction measures were adopted in Nanjing during the Spring Festival of 2015, serious accumulation of pollutants in Nanjing was not observed, despite poor weather conditions, indicating the important contribution of emission reduction measures towards the improvement of air quality.
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