[Comparison Test Between On-line Monitoring of Water-soluble Ions and Filter-based Manual Methods for PM_2.5]

Concentrations of water-soluble ions were measured in Beijing during 2014 for comparison of URG online monitoring systems and filter-based manual methods. The differences of four main ions components in spring, summer, autumn and winter were compared. The total concentrations of eight ions measured by URG online were higher than those of filter-based manual method. There was no significant differences among the annual concentrations of Cl^-,NO₃^-,Mg²⁺ and Ca²⁺ obtained by the two methods, while the concentrations of SO₄^2-,NH₄⁺,Na⁺,K⁺ from online were higher than those from filter. NO₃^-,SO₄^2-,Cl^- had good correlations in autumn and winter, and NH₄⁺ only had better fitting performance in winter.