[Characterization of Water-soluble Ions in PM₂.₅ of Beijing During 2014 APEC].

The mass concentration of PM₂.₅ associated with its online and off-line water-soluble ions were obtained during 2014- 10- 2014-11. Secondary inorganic species NO₃⁻, SO₄²⁻ and NH₄⁺ were the major components of PM₂.₅ during different observation periods. The total concentration of NO₃⁻, SO₄²⁻ and NH₄⁺ was (26.8 ± 22.5) µg · m⁻³, which contributed (41.7 ± 8.5)% to PM₂.₅. The concentration of NO₃⁻ was higher than those of others and contributed most to PM₂.₅. The ions of NO₃⁻, SO₄²⁻ NH₄⁺ and Cl⁻ all showed three different periods during 2014 Beijing APEC, besides the different meteorological condition, the cumulative effect caused by local emissions and regional pollution could also not be ignored. Although the characteristics of water-soluble ions was different during different observation periods, there was no obvious acidification of PM₂.₅ in Beijing at the end of autumn and beginning of winter.