J. Z. Ma 1, W. Wang 2, Y. Chen 1, H. J. Liu 2, P. Yan 1, G. A. Ding 1, M. L. Wang 1, J. Sun 1, and J. Lelieveld 3 1 Chinese Academy of Meteorological Sciences, Beijing, China; 2 Chinese Research Academy of Environmental Sciences, Beijing, China; 3 Max Planck Institute for Chemistry, Mainz, Germany TOAR Workshop –27 January 2016, Beijing Spatial Distribution Characteristics of Air Pollutants and Atmospheric Oxidation Capacity over North China

Outline 1. Motivation of this study 2. Overview of field experiment in spring Important measurement and modeling results 4. Conclusions Outline 1. Motivation of this study 2. Overview of field experiment in spring Important measurement and modeling results 4. Conclusions Spatial Distribution Characteristics of Air Pollutants and Atmospheric Oxidation Capacity over North China TOAR Workshop 1.03, 25–27 January 2016, Beijing

Increase in tropospheric NO 2 over North China observed from space (Richter et al., Nature, 2005 Hilboll et al., ACP, 2013) The estimated regional NO 2 emissions are about 5% of the global anthropogenic NO 2 emissions (B. Zhao et al., ACP, 2012) North China “Huabei” ( 华北 ) in Chinese (32-42 ºN of eastern China) A pollution hot spot ! North China “Huabei” ( 华北 ) in Chinese (32-42 ºN of eastern China) A pollution hot spot !

T. Wang et al., GRL, 2006 High ozone episodes (with 1-hr O 3 mixing ratio exceeding 120 ppbv) were frequently observed in urban plumes from Beijing during summertime, with a maximum level of 286 ppbv ! High ozone episodes (with 1-hr O 3 mixing ratio exceeding 120 ppbv) were frequently observed in urban plumes from Beijing during summertime, with a maximum level of 286 ppbv ! 286 ppbv The year of 2005

CO emission rates Wind direction rose J. Xu et al., ACP, 2011 SDZ: Shangdianzi SY: Shun Yi BL: Bao Lian FT: Feng Tai Ozone pollution is synchronism in the urban and rural areas of Beijing. The ozone peak values are found to lag behind one site after another along the route of prevailing wind from SW to NE, due to the transport of both O 3 and its precursors. 20 June – 16 September 2007 NO X O 3

M. Shao et al., JGR, 2009 VOCs plays a key role in ozone formation. Measurements of NMHCs and OVOCs at several sites in Beijing and near by provinces show high variability of VOC mixing ratios and chemical speciation. August 2006

A.J. Ding et al., ACP, 2008 Dufour et al., ACP, 2010 MOZAIC aircraft data analysis shows that O 3 in the lower troposphere over Beijing had a strong positive trend (~2% per year from 1995 to 2005). Strong photochemical pollution and regional pollution transport resulted in lower tropospheric O 3 maximum especially in the spring-summer period, and similar results were obtained by IASI satellite data analysis. August 2006 MOZAIC IASI

Significant increasing trends of tropospheric ozone residue (TOR) during were found over North China (Huabei), with a maximum rate of 1.10 DU per decade for summer. X.B. Xu and W. L. Lin et al., Adv. Clim. Change Res., 2010

NSFC Key Project: Impact of Air Pollution on Aerosols & Cloud Microphysics in North China (IPAC-NC ) (1) to investigate 3-D synchronous distributions of gaseous pollutants, aerosols and cloud microphysical parameters; (2) to assess primarily the impact of air pollution on aerosols and cloud microphysics in North China.

Beijing Zhangjiakou Shijiazhuang Xin’an station Shangdianzi station 17 research flights (60 hrs) Tianjin Yun-12 IPAC-NC Field Campaign (2 April-16 May 2006) Tangshan Bohai Gulf

Primary emissions in the central area of North China (Huabei) Percentage contributions from different sources to the NO x mixing ratios in the PBL during IPAC-NC as estimated by our RCTM with a tracer-tagging technique B. Zhao et al., ACP, 2012

Model (GRAPES) simulated wind fields and spatial distributions of pollution emitted from major urban centers of Huabei. The model predicts an air pollution pool over the larger Beijing, Tianjin and Tangshan area, where IPAC-NC aircraft measurements took place. Beijing Tangshan Tianjin

The spatial distributions of the major gaseous pollutants measured by aircraft. Widespread high pollutants’ mixing ratios were observed. For instance, over the highly polluted area, SO 2 even reached up to ppbv in the PBL, much higher than at the surface. NO x CO O x O 3 NO SO 2 Below 1.5km Above 1.5km

A decreasing tendency of NO, NOx* and CO with increasing altitude. SO 2 shows a maximum at ~0.5 km altitude. The tendency of O 3 with altitude is not so clear. Changes in the size distributions of number density and surface area concentration of aerosols with altitude are different.

Our chemical box-model simulations, constrained by the measurements, suggest a maximum in the vertical profiles of OH and HO 2 at an altitude of ~1 km over the polluted area of Huabei, due to the combined effective photolysis of ozone and the recycling of radicals in the photochemistry of NO 2, CO, VOC and SO 2. BASE: standard simulation; NO_S: BASE without considering SO 2 related reactions; NO_H: BASE without considering heterogeneous reactions of OH and HO 2 on aerosol surfaces ‘1.3*CH2O’: BASE with a 30% increase of CH 2 O. NCAR’s MM model simulations HO 2 P(O 3 )-L(O 3 ) OH

In addition to reactive hydrocarbons and CO, the oxidation of SO 2 causes significant ozone production over Huabei (up to ~13% or 2.0 ppbv h -1 at 0.8 km altitude). In the upper part of the boundary layer and in the lower free troposphere, high CO and SO 2 compete with relatively less NO 2 in reacting with OH, being efficiently recycled through HO 2, preventing a net loss of HO x radicals. without HO 2 formation with HO 2 formation

New particle formation and growth The high OH levels tend to promote the formation of semi- and low-volatile species such as inorganic and organic acids through the oxidation of SO 2, NO 2 and VOCs. The aerosol formation rate through the condensation of H 2 SO 4 is estimated to be 2-8 g cm -3 h -1 during the IPAC-NC campaign period, with a maximum at about 0.8 km altitude. Condensation on primary emitted particles

Conclusions Strong pollution emissions from urban and industrial centers tend to accumulate in the lower atmosphere over the central area of Huabei; Enhanced levels of OH and HO 2 radicals are found to be associated with the high pollution concentrations; The lower atmosphere over Huabei is not only strongly polluted, but also acts as an oxidation pool, with pollutants undergoing very active photochemistry over this part of China.

谢谢！ Thank you for your attention ！