The North China Plain (NCP) has been experiencing severe airpollution problems with rapid economic growth and urbanisation. Many fieldand model studies have examined the distribution of air pollutants in theNCP, but convincing results have not been achieved, mainly due to a lack ofdirect measurements of pollutants over large areas. Here, we employed amobile laboratory to observe the main air pollutants in a large part of theNCP from 11 June to 15 July 2013. High median concentrations of sulfurdioxide (SO) (12 ppb), nitrogen oxides (NO) (NO + NO;452 ppb), carbon monoxide (CO) (956 ppb), black carbon (BC;5.5 µg m) and ultrafine particles (28 350 cm) weremeasured. Most of the high values, i.e. 95 percentile concentrations, weredistributed near large cities, suggesting the influence of local emissions.In addition, we analysed the regional transport of SO and CO,relatively long-lived pollutants, based on our mobile observations togetherwith wind field and satellite data analyses. Our results suggested that, forborder areas of the NCP, wind from outside this area would have a dilutingeffect on pollutants, while south winds would bring in pollutants that haveaccumulated during transport through other parts of the NCP. For the centralNCP, the concentrations of pollutants were likely to remain at high levels,partly due to the influence of regional transport by prevalent south–northwinds over the NCP and partly by local emissions.
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