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Study on Distribution and Transport of SO2 and NO2 in North China Plain using Mobile DOAS

This study investigates the spatial and temporal distribution of SO2 and NO2 in the North China Plain (NCP) using mobile Differential Optical Absorption Spectroscopy (DOAS) instruments. The study aims to understand the sources and influence of these pollutants on Beijing's air quality, as well as estimate pollutant emissions and study their transport processes.

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Study on Distribution and Transport of SO2 and NO2 in North China Plain using Mobile DOAS

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  1. 7th International DOAS Workshop 6-8 July 2015, Brussels Study on distribution and transport of precursors SO2 and NO2 in North China Plain using mobile DOAS Pinhua Xie, Ang Li, Fengcheng Wu, Zhaokun Hu,Fusheng Mou, Jie Zhang, Hao Chen, Jin Xu, Jianguo Liu, Wenqing Liu Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences

  2. Introduction Mobile DOAS instruments Field Campaigns - CAREBEIJING 2013 Results and Discussions Summary Outline

  3. Introduction China is facing with the regional and complex air pollution 2014/02/19－26 (Beijing) 2013/12/01－07 (YRD) 2013/10/17－21 (XI’an) PM2.5 Number of days of haze >100

  4. Introduction SO2, NO2 are important precursors of PM2.5 PM2.5 Chemical Compositions: SO42- and NO3- contribute nearly 50% to PM2.5 WANG et al, 2014, SCIENCE CHINA Many SO2 and NO2 sources locate in North China Plain, strongly affected the air quality of Beijing under specific wind field. Wu et al., 2011, ACP In order to know better about the sources and their influence to Beijing, it is necessary to investigate the spatial and temporal distribution of SO2 and NO2 in NCP. Zhang et al., 2014, ACP Su Fuqinget al, 2004

  5. Introduction Mobile DOAS • Estimation of pollutant emissions from point sources or fugitive emission sources (such as: city, industrial area etc.) • Regional distributions of pollutants (SO2, NO2 etc. ) • Transport process in combination with trajectory model • Validation of satellite data Mobile DOAS was used to investigate the distribution of SO2 and NO2 VCDs, transport in in North China Plain (NCP).

  6. Mobile DOAS instruments Weather Station Mobile DOAS Instrument (I) -zenith observation Mobile DOAS Temperature stabilizer △＜±0.1℃ Telescope • Our mobile DOAS system include: • Telescope: 80mm diameter and 170mm focal length, field of view about 0.1° • a UV/VIS detector spectrometer unit: • -Ocean Optics HR2000 spectrometer, spectral resolution 0.6nm, wavelength range: 290nm~420nm • - temperature stabilizer: precision ±0.1℃ • GPS • miniature weather station: wind speed, wind direction, temperature, humidity, and pressure • DC +12V battery: +12V direct current is converted to AC by a power converter to power the entire system

  7. Mobile DOAS instruments Spectral Analysis –zenith observation fit for NO2 and SO2 recorded at 13:04 on 12 June, 2013 The spectrum in the “clean area” is chosen as the Frauenhofer reference spectrum which contains minimum concentration of SO2 and NO2. The reference spectrum can be corrected by MAX-DOAS if it is setup along the mobile DOAS measurement route,

  8. Mobile DOAS instruments Mobile DOAS Instrument (II)-Mobile MAX-DOAS Mobile DOAS with Stabilized Platform • Obtained the absolute VCD • Detected more gas due to slant light-path absorption • aerosol and trace gas profile retrieval (dependence on experimental environment) GPS antenna 1 high precision turntable attitude feedback GPS antenna 2 Gyroscope+GPSPID  Stabilized Platform Specification: Elevation angle: 90°, 20° (30°,15°….) Spectral range: 290~420nm Gas: SO2, NO2, O4, HCHO, BrO,…. Precision of gyroscope: 0.1°, azimuth angle: 0.5°, elevation angle: 0.3°.

  9. Field Campaigns CAREBEIJING 2013 field campaign Beijing China Zhuozhou 5 Tianjin 1 4 Baoding 3 • Routes： • 5 routes  1 cycle —Beijing-Shijiazhuang —Shijiazhuang-Dezhou —Dezhou-Baoding-Cangzhou —Cangzhou-Zhuozhou —Zhuozhou-Beijing • 10:00-14:00 —Stable boundary layer — battery endurance • June 11th-July 16th , 2013 • All routes are expressways Cangzhou Shijiazhuang Dezhou 2 Jinan

  10. The mobile platform also equipped some point instruments, like gaseous analyzers (SO2, NOx, CO etc.) and aerosol instruments (PM2.5, PM10 etc.) Inner vehicle Inlet system • Wind: • southerly wind (11 Jun~15 Jun, 24 Jun~26 Jun), • northerly wind (17 Jun~21 Jun, 2 Jul~ 7Jul) • Weather condition: clear or cloudy • Cloud Fraction≤0.4：11 Jun~13 Jun，18 Jun，25 Jun~26 Jun，3 Jul，6 Jul， total 8 days Roof of vehicle

  11. Results and Discussions • CAREBEIJING 2013 field campaign • Distributions of SO2 and NO2 VCD over NCP • - Distributions over whole NCP • - Spatial and temporal variations @ different routes (southwest route and southeast route) @ different wind field (south and north) • Validation of OMI NO2

  12. Results and Discussions Beijing • Distributions of SO2 and NO2 VCD over NCP • Distributions over whole NCP Beijing Southerly wind Tianjin 11 Jun.~15 Jun. 11 Jun.~15 Jun. Tianjin Shijiazhuang Shijiazhuang SO2 NO2 JiNan JiNan • The VCDs of SO2 and NO2 are affected by the cities. The VCDs increase near the cities. • Some hot spots are found, like close to JiNan • Serious air pollution in Hebei(southwest route). The VCD over southwest region is higher than those over southeast.

  13. Results and Discussions • Distributions of SO2 and NO2 VCD over NCP • Distributions over whole NCP Beijing Beijing Northerly wind Tianjin 17 Jun.~21 Jun. 17 Jun.~21 Jun. Tianjin Shijiazhuang Shijiazhuang JiNan • The VCDs of SO2 and NO2 reduce under northerly wind. • The hot spot near the Ji’Nan disappear under the northerly wind. SO2 JiNan NO2

  14. Results and Discussions • Distributions of SO2 and NO2 VCD over NCP Spatial and temporal variations @ southwest and southeast measurement route Beijing Southwest measurement route: Beijing-Baoding-Shijiazhuang Southerly wind: 6.11, 6.24 Northerly wind: 6.17, 7.2 Tianjin Baoding Southeast measurement route: Dezhou-Tianjin-Beijing Southerly wind: 6.13, 6.14, 6.26,7.4, 7.6 Northerly wind: 6.20 Shijiazhuang Dezhou

  15. Results and Discussions • Distributions of SO2 and NO2 VCD over NCP Spatial and temporal variations @ southwest measurement route SO2 VCD (mobile DOAS) SO2 surface concentration • The SO2 VCD and near-surface concentration under southerly windare 2.60 and 1.24 times of that under northerly wind, respectively. The SO2 VCDs have a distinct variations under southerly and northerly wind. It shows high elevated point sources along the southwest route. • According to the “Box-chart”, the peak value indicates the elevated sources exist along the southwest measurement route. • The upper layer SO2 existed, which can be transported to Beijing. 6.24 7.2 6.11 6.17

  16. Results and Discussions • Distributions of SO2 and NO2 VCD over NCP Spatial and temporal variations @ southwest measurement route NO2 concentration from point instrument NO2 VCD from mobile DOAS • The difference of NO2 VCD for southerly and northerly wind is lower than SO2. • NO2 mainly located near surface.

  17. Results and Discussions • Distributions of SO2 and NO2 VCD over NCP Spatial and temporal variations @ southwest measurement route Southerly wind SO2 SO2 Northerly wind Beijing Beijing Beijing Beijing 石家庄 Shijiazhuang Shijiazhuang Shijiazhuang Shijiazhuang 6.11 6.24 6.17 7.2 • Southwest route is a transport route. The air quality of Beijing is affected by the transport from southern area.

  18. Results and Discussions • Distributions of SO2 and NO2 VCD over NCP Spatial and temporal variations @ southeast measurement route SO2 VCD from mobile DOAS SO2 surface concentration • Low scatted sources in the southeast route.

  19. Results and Discussions • Distributions of SO2 and NO2 VCD over NCP Spatial and temporal variations @ southeast measurement route NO2 concentration from point instrument NO2 VCD from mobile DOAS NO2 mainly located near surface, from traffic

  20. Results and Discussions • Distributions of SO2 and NO2 VCD over NCP Spatial and temporal variations @ southeast measurement route • High emissions in the southwest is in accordance with our observation (left figure). • Elevated sources are the major contributors to SO2 along southwest measurement route. • Southwest measurement route is a transport route for Beijing. • Low area sources are the contributors to SO2 along southeast measurement route southwest route southeast route Spatial distributions of anthropogenic SO2 in and around Beijing with horizontal resolution of 12 by 12 km2 cited by Wang et al., ACP, 2014

  21. Results and Discussions 2. Validation of OMI NO2 • Cloud fraction ≤0.4 • Grid resolution= 0.1 • Jun 11, 12, 13, 18, 25, 26, July 3 and July 6 total 8 days

  22. Results and Discussions 2. Validation of OMI NO2 Mobile DOAS and OMI can capture the high and low value simultaneously.

  23. Results and Discussions 3. Validation of OMI NO2 The both datasets have a good agreement, with correlation coefficient R2=0.65.

  24. HOPE J3A 2014 field campaign • Routes： • Two cycle —Beijing 5th Ring Road (98.58km) —Beijing 6th Ring Road (192km） 10:00-14:00 November 3th 2014 – January 12th 2015 Weather condition: clear or cloudy Dominated Wind field: north

  25. Observation of NO2 distribution and emission flux during APEC APEC A decrease in NO2 emission during the APEC, which caused by the strict control policies.

  26. Results and Discussions Identification of emission source @ Beijing 5th and 6th Ring Road HOPE J3A 2014 field campaign SO2 NO2 NO2 NO2 NO2 NO2 VCD（ppmm） Beijing 6th Ring Road NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 2014年12月21日 2014年11月3日 2014年12月31日 2014年12月21日 Beijing 6thRing Road 2014年11月7日 • The vehicle exhaust is the major source of NO2 in Beijing. • The distribution of NO2 VCD of western 6th ring road is affected by the industrial source near Mentougou Area, which resulted in local NO2 VCD increase.

  27. Summary • In NCP, the SO2 and NO2 VCDs are higher along the southwest route than that along southeast route. However, the near-surface concentrations are higher along southeast route. • Southwest route is a important transport pathway to affect air quality in Beijing. High elevated point sources are the major contributors to SO2 along southwest route. Low area sources are the contributors to SO2 along southeast route. • Vehicle emission is main source of NO2. The SO2 and NO2 VCD enhance simultaneously indicates there is coal-combustion source. • In Beijing City, SO2 is most transported from surrounding area whereas the NO2 is from local traffic. • There is a good agreement between OMI and mobile DOAS. The correlation coefficient is R2=0.65. • Mobile DOAS is a potential powerful tool for pollutant distribution investigation , tracking the plume as well as satellite validation. • .

  28. Case: “Tracking Haze” experimental observation(11 Oct.~18 Oct., 2014 ) Hefei-Zhengzhou-Wuhan-Hefei-JiNan • The distributions of SO2 and NO2 are characterized by mobile DOAS rapidly. • The SO2 and NO2 VCD was greatly influenced by the heavy industrial source emission. The emission sources are identified using this scanning measurement, like heavy emission sources are found in Wuhan.

  29. Thank you for your attention! Acknowledgements: We would like to thank Prof. Zhu’s group (Peking University) for arrangement of the experiments and providing the data from point instruments during the CAREBEIJING 2013 field campaign. Anhui Institute of Optics & Fine Mechanics, Chinese Academy of Sciences

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