Using a mobile laboratory to characterize the distribution and transport of sulfur dioxide in and around Beijing

Abstract

Megacities are places with intensive human activity and energy consumption. To reduce air pollution, many megacities have relocated energy supplies and polluted industries to their outer regions. However, regional transport then becomes an important source of air pollution in megacities. To improve air quality before and during the 2008 Beijing Olympics, a wide range of control strategies were implemented, including the relocation of polluting industries. High sulfur dioxide (SO<sub>2</sub>) concentrations were occasionally observed during this period. Potential sources from southern regions of Beijing were indicated by backward trajectories model and urban/rural stationary measurements, but direct evidence was lacking. Here we used a mobile laboratory to characterize the spatial distribution and regional transport of SO<sub>2</sub> to Beijing during the Campaign for Air Quality Research in Beijing and the Surrounding Region (CAREBEIJING)-2008. Among the five days chosen for the case studies during the Olympic air pollution control period, four had high SO<sub>2</sub> concentrations (6, 20 August and 3, 4 September 2008) while one had low SO<sub>2</sub> concentration (11 September 2008). The average values of SO<sub>2</sub> during the low SO<sub>2</sub> concentration day were 3.9 ppb, much lower than during the high concentration days (7.8 ppb). This result implied an impact by regional transport from outside Beijing. During these days, we captured transport events of SO<sub>2</sub> from areas south of Beijing, with a clear decrease in SO<sub>2</sub> concentrations southeast of the 6th to 4th Ring Roads around Beijing and along the 140 km highway from Tianjin to Beijing. The influx of SO<sub>2</sub> through the 4th to 6th Ring Roads ranged from 2.1 to 4.6 kg s<sup>−1</sup> on 4 September and 0.2 to 1.6 kg s<sup>−1</sup> on 20 August 2008. The differences of influx in days were due to the variations of emission changes, transport directions and dilutions. Locally emitted SO<sub>2</sub> from a source located along Jingshi Highway outside the southwest section of the 5th Ring Road of Beijing was identified using wind field data generated by the Weather Research and Forecasting model and the measured particle size distribution, with an estimated flux of 0.1 kg s<sup>−1</sup> to Beijing. Estimated uncertainties for SO<sub>2</sub> influx were approximately 31%

Air pollutant emissions from Chinese households: A major and underappreciated ambient pollution source

“…When the prevailing wind is southerly, air pollutants from Hebei, Shandong, and Henan are transported to Beijing (15,16), and the contribution of emissions from surrounding regions to PM 2.5 in Beijing has been found to be 34-39% (14,15). Our study also finds that regional air quality management is critical.…”

Investigations of temporal and spatial distribution of precursors SO<sub>2</sub> and NO<sub>2</sub> vertical columns in the North China Plain using mobile DOAS

“…Aside from gaseous pollutant instruments, some aerosol instruments, such as GRIMM and Dusttrak for PM 2.5 and a Fast Mobility Particle Sizer, were also available on board for analysis of particle size distribution. The details of the setup and performance of the instruments are described in Wang et al (2009Wang et al ( , 2011.…”

“…Meanwhile, regional variation of gases, particle pollutants, and other factors which influence pollution characteristics has been detected using airborne measurement . Also, based on measurements using a mobile laboratory, Wang et al (2011) analyzed the regional distribution of SO 2 in Beijing and its surrounding areas and estimated transport flux from the outside to Beijing . Model simulations, another method, can obtain distribution, transboundary transport fluxes, and major transport channels of Beijing in combination with meteorological data .…”

Distribution and sources of air pollutants in the North China Plain based on on-road mobile measurements

“…A number of mobile laboratory measurements (Johansson et al, 2008;Li et al, 2009;Wang et al, 2009Wang et al, , 2011 and aircraft measurements (Huang et al, 2010;Zhang et al, 2011Zhang et al, , 2009Zhang et al, , 2014 have been used to determine pollution distributions, mainly within the megacity of Beijing. There have been several reports of model and satellite studies on the air pollution distribution in the NCP, or even the whole of China (Wei et al, 2011;Zhao et al, 2013;Ying et al, 2014;Ding et al, 2015Ding et al, , 2009).…”