Meteorological characteristics associated with air pollution in Xiong’an, China

Abstract

In April 2017, the central government of China announced it would establish the Xiong’an New Area in Hebei Province, as part of measures to advance the coordinated development of the Beijing-Tianjin-Hebei (BTH) region. The area is expected to become an innovative, market-driven green city; thus, it is urgent to address its environmental issues before urban construction begins. This study involved a systematic analysis of atmospheric pollutants PM2.5, PM10, CO, SO2, NO2, and O3, and their relationship to meteorological parameters in the Xiong’an area for a continuous period from May 2016 to April 2017. It used observations of 2-m temperature, 2-m relative humidity, and 10-m wind speed along with measurements of the concentration of these six criteria pollutants in Anxin, Rongcheng, and Xiongxian taken on an hourly basis. Results revealed that the Xiong’an area experienced severe air pollution, with heavy aerosol loadings. The annual averaged concentrations of PM2.5 and PM10 were 101.3 and 144.2 μg m−3, respectively, significantly exceeding the Grade II standard of the Chinese Ambient Air Quality Standards. The maximum 24-h average concentrations of PM2.5 and PM10 were 540.1 and 642.1 μg m−3, respectively. Distinct seasonal trends were observed for PM2.5 and PM10, with the maximum concentrations occurring in winter and the minimum in summer. Other trace gaseous pollutants, including CO, SO2, and NO2 demonstrated similar seasonal variations. Contrarily, O3 demonstrated a reversed seasonal trend, with concentration peaking in summer, decreasing in spring and fall, and at its lowest in winter. Seasonal variations of atmospheric pollutants were modulated by the seasonal variations in pollutant emissions, but they were also strongly related to meteorological conditions. The relatively cool thermal conditions and low wind speeds in fall and winter can limit the development of the planetary boundary layer and the horizontal transport of pollutants. Such conditions may be partially responsible for the higher concentrations of the primary pollutants during these seasons. On the contrary, secondary pollutant O3 exhibited positive correlations with temperature. When the pollutants PM2.5 or PM10 exceeded standards, the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to calculate 24-h air mass backward trajectories ending at Xiong’an area (115.95°E, 39.0°N, 100 m AGL). The trajectories travelled backwards over the Beijing area, the Tianjin-Tangshan region, and the south of Hebei Province, with each area accounting for 34.9%, 25.0%, and 59.9% of the total, respectively. This spatial distribution suggests that pollutants released from adjacent regions may be transported to the Xiong’an area, and play a role in exacerbating the level of pollutants. Thus, joint efforts to reduce emissions in the whole BTH region are necessary to control the heavy pollution in Xiong’an. Overall, this study of air pollution in Xiong’an provides insight into the fundamental role of meteorological parameters in relation to different air pollutants. These key findings can enhance the accuracy of forecasting air pollution, and provide scientific support for policy makers who seek its mitigation.