[Seasonal Variation and Source Analysis of the Water-soluble Inorganic Ions in Fine Particulate Matter in Suzhou].

A total of 87 daily PM samples were collected in the urban area of Suzhou city during 2015, representing spring, summer, autumn, winter, respectively. Mass concentration of PM was analyzed gravimetrically. Water-soluble inorganic ions, including F, Cl, NO, SO, Na, NH, K, Mgand Ca, were determined by ion chromatography. The average mass concentration of PM was (74.26±38.01) μg·m. The seasonal variations of PM concentrations decreased in the order of winter > spring > autumn > summer. The average total mass concentrations of 9 ions was (43.95±23.60) μg·m, and the order of concentration of ions was NO > SO > NH > Na > Cl > K > Ca > F > Mg. Seasonal variation of ion concentrations was significant, with the highest concentration observed in winter and the lowest in summer. The secondary inorganic species, including SO, NO and NH (SNA) were the major components of the water-soluble ions in PM. SNA's correlations with each other were significant. SO, NO and NH were probably in the form of NHNO and (NH)SO. The [NO]/[SO] ratio approaching to 1 implied that mobile sources were as important as stationary sources. Ion balance calculations indicated strong correlations between anion and cation equivalents. The PM was acidic. Industrial emission, combustion process, secondary formation and fugitive dust were the major sources of the water-soluble ions in PM.