Pearson correlation among study sites and control site by using seasonal average concentration multiples of study cities to background sites.

(The bold numbers were calculated based on PM10, and the regular numbers were based on PM2.5). (4 seasons, 9 ions, n = 36, pPearson correlation among study sites and control site by using seasonal average concentration multiples of study cities to background sites.（加粗数值以PM10为计算基准，常规数值以PM2.5为计算基准）。本数据集涵盖4个季节、9种离子，样本量n=36；以研究城市相较于背景监测点的季节平均浓度倍数为依据，计算各研究点位与对照点位间的Pearson相关系数。