highly significantp < 0.01
The Relationship between Socioeconomic Factors and PM 2.5 in the Geographical Subareas From Figure 8 , a highly significant ( p < 0.01) positive correlation between socioeconomic factors and PM 2.5 was observed in North China, Northeast China and East China, indicating that GDPP, IVA, UPD and PCO played a vital role in North China, Northeast China and East China.