Abstract
Northeast China is an essential industrial development base in China and the regional air quality is severely affected by PM2.5 pollution. In this paper, spatial autocorrelation, trajectory clustering, hotspot analysis, PSCF and CWT analysis are used to explore the spatial pollution characteristics of PM2.5 and determine the atmospheric regional transmission pattern for 40 cities in Northeast China from 2016 to 2020. Analysis of PM2.5 concentration characteristics in the northeast indicates that the annual average value and total exceedance days of PM2.5 concentration in Northeast China showed a U-shaped change, with the lowest annual average PM2.5 concentration (31 μg/m3) in 2018, decreasing by 12.1% year-on-year, and the hourly PM2.5 concentration exploding during the epidemic lockdown period in 2020. A stable PM2.5 pollution band emerges spatially from the southwest to Northeast China. Spatially, the PM2.5 in Northeast China has a high degree of autocorrelation and a south-hot–north-cool characteristic, with all hotspots concentrated in the most polluted Liaoning province, which exhibits the H–H cluster pattern and hotspot per year. Analysis of the air mass trajectories, potential source contributions and concentration weight trajectories in Northeast China indicates that more than 74% of the air mass trajectories were transmitted to each other between the three heavily polluted cities, with the highest mean value of PM2.5 pollution trajectories reaching 222.4 μg/m3, and the contribution of daily average PM2.5 concentrations exceeding 60 μg/m3 within Northeast China. Pollution of PM2.5 throughout the Northeast is mainly influenced by short-range intra-regional transport, with long-range transport between regions also being an essential factor; organized integration is the only fundamental solution to air pollution.
Highlights
Atmospheric PM2.5 pollution is of great importance to the international community because of its harmfulness, extensive coverage and being difficult to manage
China [37]; the annual average PM2.5 concentration reached the lowest value in recent years
Using Getis–Ord Gi∗ to identify clustering areas with positive spatial autocorrelation, the results show that PM2.5 concentrations in Northeast China in the past five years have a clustering characteristic of being hot in the south and cold in the north
Summary
Atmospheric PM2.5 pollution is of great importance to the international community because of its harmfulness, extensive coverage and being difficult to manage. Health Organization has confirmed that PM2.5 is the most harmful to human health and that it can cause cancer [1], as well as respiratory and cardiopulmonary diseases [2], increasing the morbidity and mortality of many diseases [3]. In 2013, China’s State Council issued the “Action Plan for Prevention and Control of Air Pollution”, with the expectation to reduce PM2.5 pollution in five years. Compared with 2015, the number of cities with sub-standard PM2.5 concentrations and the ratio of heavily polluted days dropped by more than 18% and 25% separately in 2020, while the ratio of good air quality days in prefecture-level and above cities has reached 80%. Heavy pollution events are caused by a combination of high-intensity emissions and unfavorable meteorological conditions; the mobility of the atmospheric environment determines the regional transport characteristics of atmospheric pollutants, which can be transported from more polluted areas to downstream cities under the effect of meteorological factors, forming regional pollution, and becoming one of the important factors affecting
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