Introduction to Special Issue – In-depth study of air pollution sources and processes within Beijing and its surrounding region (APHH-Beijing)
Authors: Shi Zongbo , Vu Tuan , Kotthaus Simone , Grimmond Sue , Harrison Roy M. , Yue Siyao , Zhu Tong , Lee James , Han Yiqun , Demuzere Matthias , Dunmore Rachel E. , Ren Lujie , Liu Di , Wang Yuanlin , Wild Oliver , Allan James , Barlow Janet , Beddows David , Bloss William J. , Carruthers David , Carslaw David C. , Chatzidiakou Lia , Crilley Leigh , Coe Hugh , Dai Tie , Doherty Ruth , Duan Fengkui , Fu Pingqing , Ge Baozhu , Ge Maofa , Guan Daobo , Hamilton Jacqueline F. , He Kebin , Heal Mathew , Heard Dwayne , Hewitt C. Nicholas , Hu Min , Ji Dongsheng , Jiang Xujiang , Jones Rod , Kalberer Markus , Kelly Frank J. , Kramer Louisa , Langford Ben , Lin Chun , Lewis Alastair C. , Li Jie , Li Weijun , Liu Huan , Loh Miranda , Lu Keding , Mann Graham , McFiggans Gordon , Miller Mark , Mills Graham , Monk Paul , Nemitz Eiko , O'Connor Fionna , Ouyang Bin , Palmer Paul  I. , Percival Carl , Popoola Olalekan , Reeves Claire , Rickard Andrew R. , Shao Longyi , Shi Guangyu , Spracklen Dominick , Stevenson David , Sun Yele , Sun Zhiwei , Tao Shu , Tong Shengrui , Wang Qingqing , Wang Wenhua , Wang Xinming , Wang Zifang , Whalley Lisa , Wu Xuefang , Wu Zhijun , Xie Pinhua , Yang Fumo , Zhang Qiang , Zhang Yanli , Zhang Yuanhang , Zheng Mei 
Published: October 2018

Abstract. APHH-Beijing (Atmospheric Pollution and Human Health in a Chinese Megacity) is an international collaborative project to examine the emissions, processes and health effects of air pollution in Beijing. The four research themes of APHH-China are: (1) sources and emissions of urban atmospheric pollution; (2) processes affecting urban atmospheric pollution; (3) exposure science and impacts on health; and (4) interventions and solutions to reduce health impacts. Themes 1 and 2 are closely integrated and support Theme 3, while Themes 1–3 provide scientific data for Theme 4 on the development of cost-effective solutions. A key activity within APHH-Beijing was the two month-long intensive field campaigns at two sites: (i) central Beijing, and (ii) rural Pinggu. The coordinated campaigns provided observations of the atmospheric chemistry and physics in and around Beijing during November–December 2016 and May–June 2017. The campaigns were complemented by numerical air quality modelling and air quality and meteorology data at the 12 national monitoring stations in Beijing. This introduction paper provides an overview of (i) APHH-Beijing programme, (ii) the measurement and modelling activities performed as part of it in Beijing, and (iii) the air quality and meteorological conditions during the two field campaigns. The winter campaign was characterized by high PM2.5 pollution events whereas the summer experienced high ozone pollution events. Air quality was poor during the winter campaign, but less severe than in the same period in 2015 when there were a number of major pollution episodes. PM2.5 levels were relatively low during the summer period, matching the cleanest periods over the previous five years. Synoptic scale meteorological analysis suggests that the greater stagnation and weak southerly circulation in November/December 2016 may have contributed to the poor air quality.