Real-Time Observation on Water-Soluble Ions of PM2.5 in Beijing under the Influences of Different Air Masses in Summer

摘要

To further understand the variations of water-soluble ions in PM_(2.5) in Beijing, the authors observed their concentrations continuously and in high temporal resolution by the system for rapid collection of fine particles and ion chromatography (RCFP-IC) during 12–18 July 2010. These results combined with those of earlier backward trajectory research are used analyzed to determine the causes of concentration changes in water-soluble ions under the influences of two kinds of air masses in summer. The results indicate that concentrations of NO_(3)~(?), SO_(4)~(2?), and NH_(4)~(+) were influenced strongly by the continental air mass than by the marine air mass. Cl~(?) and Na~(+) were not changed significantly. Because the sources of K~(+), Mg~(2+), and Ca~(2+) are mainly concentrated on land, their concentration levels were slightly higher under the control of continental air mass than that of the marine air mass. Variations of NO_(2)~(?) during the observation differed from those of other ions; its concentration was significantly higher under the influence of marine air mass. Moreover, the authors obtain the diurnal variations of eight water-soluble inorganic ions including NH_(4)~(+), K~(+), Mg~(2+), Ca~(2+), Cl~(?), NO_(2)~(?), NO_(3)~(?), and SO_(4)~(2?). Diurnal variations of NH_(4)~(+), NO_(3)~(?), and Cl~(?) showed single peak, which appeared before noon, while SO_(4)~(2?) showed two peaks that appeared during rush hours. Those of Mg~(2+), Ca~(2+), and K~(+) showed single peak that appeared in the afternoon. That of NO_(2)~(?) showed with a peak appearing at sunrise and a valley appearing at sunset.