Surface Trace Gases at a Rural Site between the Megacities of Beijing and Tianjin

• Published in: Atmospheric and oceanic science letters = Daqi-he-haiyang-kexue-kuaibao 2014, Vol.7 (3), p.230-235
• Main Author: RAN Lian LIN Wei-Li WANG Pu-Cai DENG Zhao-Ze
• Format: Article
• Language: English
• Subjects: 农村; 北京; 大城市; 天津; 微量气体; 氮氧化物浓度; 网站; 表面
• ISSN: 1674-2834; 2376-6123
• DOI: 10.1080/16742834.2014.11447166

The North China Plain （NCP） has recently faced serious air quality problems as a result of enhanced gas pollutant emissions due to the process of urbanization and rapid economic growth. To explore regional air pollu- tion in the NCP, measurements of surface ozone （O3）, nitrogen oxides （NOx）, and sulfur dioxide （SO2） were car- ried out from May to November 2013 at a rural site （Xianghe） between the twin megacities of Beijing and Tianjin. The highest hourly ozone average was close to 240 ppbv in May, followed by around 160 ppbv in June and July. High ozone episodes were more notable than in 2005 and were mainly associated with air parcels from the city cluster in the hinterland of the polluted NCP to the southwest of the site. For NOx, an important ozone precur- sor, the concentrations ranged from several ppbv to nearly 180 ppbv in the summer and over 400 ppbv in the fall. The occurrence of high NOx concentrations under calm condi- tions indicated that local emissions were dominant in Xianghe. The double-peak diurnal pattern found in NOx concentrations and NO/NOx ratios was probably shaped by local emissions, photochemical removal, and dilution re- sulting from diurnal variations of surface wind speed and the boundary layer height. A pronounced SO2 daytime peak was noted and attributed to downward mixing from an SO2-rich layer above, while the SO2-polluted air mass transported from possible emission sources, which differed between the non-heating （September and October） and heating （November） periods, was thought to be responsible for night-time high concentrations.