Ground ozone variations at an urban and a rural station in Beijing from 2006 to 2017: Trend, meteorological influences and formation regimes

Due to complicated ozone formation regimes controlled by both ozone precursors and meteorological conditions, the underlying drivers for soaring ozone concentrations in Beijing were limitedly examined. With ground observation and remotely sensed data, the variation of ground ozone concentrations at an urban AT (Aoti) station and a rural YF (Yufa) station in Beijing was examined and a notable upward trend of ozone concentrations at both stations was found from 2006 to 2017. Following this, through a statistical model, the relative contribution of meteorological conditions to long-term ozone variations at both stations was calculated as 2%-3%, indicating anthropogenic emissions were the major cause for long-term ozone variations in Beijing. Meanwhile, short-term ozone variations could be influenced significantly by seasonal and synoptic meteorological conditions. Furthermore, the long-term variations of ozone formation regimes across Beijing were analyzed using OMI (Ozone Monitoring Instrument) retrieved HCHO VCDs (Vertical Column Densities)/NO2 VCDs, which were strongly correlated with ozone concentrations. The results suggested that the ozone formation regime for the AT urban station and YF rural station had changed from VOCs-limited and NOx-limited to VOCs-NOx-limited respectively. In this case, NOx-oriented emission-reduction measures for reducing PM2.5 concentrations might conversely enhance ozone concentrations in Beijing. Given the increasingly heterogeneous distribution of different ozone formation regimes across Beijing, emission-reduction strategies that balanced consider the reduction of VOCs and NOx emissions should be better designed and implemented according to local ozone formation regimes. (C) 2019 Elsevier Ltd. All rights reserved.