In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 22, No. 10 ( 2022-06-01), p. 7071-7085
Abstract:
Abstract. Strict air pollution control strategies have been implemented in recent decades in the North China Plain (NCP), previously one of the most polluted
regions in the world, and have resulted in considerable changes in emissions of air pollutants. However, little is so far known about the long-term
trends of the regional background level of NOx and SO2, along with the increase and decrease processes of regional
emissions. In this study, the seasonal and diurnal variations of NOx and SO2 as well as their long-term trends at a
regional background station in the NCP were characterized from 2004 to 2016. On average, SO2 and NOx mixing ratios were
5.7 ± 8.4 and 14.2 ± 12.4 ppb, respectively. The seasonal variations in SO2 and NOx mixing ratios
showed a similar pattern, with a peak in winter and a valley in summer. However, the diurnal variations in SO2 and NOx
mixing ratios greatly differed for all seasons, indicating different sources for SO2 and NOx and meteorological effects
on their concentrations. Overall, the annual mean SO2 exhibited a significant decreasing trend of −6.1 % yr−1
(R = −0.84, P 〈 0.01) from 2004 to 2016, which is very close to −6.3 % yr−1 of the annual SO2 emission in
Beijing, and a greater decreasing trend of −7.4 % yr−1 (R = −0.95, P 〈 0.01) from 2008 to 2016. The annual mean of
NOx showed a fluctuating rise of +3.4 % yr−1 (R = 0.38, P = 0.40) from 2005 to 2010, reaching the
peak value (16.9 ppb) in 2010, and then exhibited an extremely significant fluctuating downward trend of −4.5 % yr−1
(R = 0.95, P 〈 0.01) from 2010 to 2016. After 2010, the annual mean NOx mixing ratios correlated significantly
(R = 0.94, P 〈 0.01) with the annual NOx emission in North China. The decreasing rate (−4.8 % yr−1,
R = −0.92, P 〈 0.01) of the annual mean NOx mixing ratios from 2011 to 2016 at the Shangdianzi (SDZ) regional
atmospheric background station is lower than the one (−8.8 % yr−1, R = −0.94, P 〈 0.01) for the annual
NOx emission in the NCP and in Beijing (−9.0 % yr−1, R = −0.96, P 〈 0.01). This indicated that
surface NOx mixing ratios at SDZ had a weaker influence than SO2 on the emission reduction in Beijing and its surrounding
areas in the NCP. The increase in the number of motor vehicles led to an increase in traffic emissions for NOx. This study
supported conclusions from previous studies that the measures taken for controlling NOx and SO2 in the NCP in the past
decades were generally successful. However, NOx emission control should be strengthened in the future.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-22-7071-2022
DOI:
10.5194/acp-22-7071-2022-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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