The characteristics of spatiotemporal distribution of PM2.5 in Henan Province, China

PM₂.₅ is the top issue of air pollution in Henan Province in China, especially in autumn and winter. In order to investigate its spatial and temporal distribution characteristics, monitoring data were collected in 17 cities and analyzed by using statistical methods and GIS tools. The results show that 57.16% of the entire days in 2015 met Chinese the national standard on the daily average concentration of PM₂.₅ in those 17 cities. However, 73.68% of the days in winter, 44.37% of the days in spring, 34.53% of the days in autumn, and 20.08% of the days in summer failed to meet the standard. Analysis shows the average concentration of PM₂.₅ on weekends was 8.04% higher than that of working days. The fact that the value of PM₂.₅/PM₁₀ was between 0.50 and 0.65 and that there was a high relevance between the PM₂.₅ concentration and SO₂ concentration suggests that the main air pollutants are coarse particles that are mainly released by coal burning. The positive correlation between PM₂.₅ and NO₂ reveals that vehicle exhaust emissions is another main reason for air pollution. Owing to the influence of the temperature and sunlight changes, the correlativity of PM₂.₅ concentrations and O₃ concentrations presents a remarkable difference in different seasons. The correlation coefficients are 0.003 for spring, 0.496**(p = 0.01) for summer, -0.353*(p = 0.05) for autumn, and -0.315*(p = 0.05) for winter, respectively. The method proposed in this paper has been verified and the research result is helpful for making relevant environmental policy.