Table 1.
Locations of the sampling sites.
Table 2.
Concentration of water-soluble ions (mean ± standard deviation in µg/m3) at sample sites in each season.
Table 3.
Comparison of annual ion concentrations in PM2.5 among major eastern Asian cities (µg/m3).
Figure 1.
Seasonal variation of water-soluble ions in the study area and at the control point.
Table 4.
Pearson correlation among study sites and control site by using seasonal average concentration multiples of study cities to background sites.
Figure 2.
Total anions versus total cations. (All data were included and categorized by season, p<0.001 for all regressions.).
Figure 3.
Ion enrichment in particulate matter of different sizes.
Table 5.
Seasonal [NO3−]/[SO42−] ratios in three cities in the North China Plain in 2013.
Table 6.
Vehicle amount and major energy consumption of 3 cities in 2012.