Figure 1.

Morphology and phase behavior of PM_2.5 in Seoul and Beijing. (A) Optical images upon dehydration of PM_2.5 samples were the highest daily average concentration in Seoul and Beijing at 290 K. Illustrations are given for interpretation of the optical images. Light blue: single liquid mixed organic/inorganic phase; green and yellow: liquid organic-rich and liquid inorganic-rich phases, respectively; red: (semi)solid inorganic-rich phase; and dark blue: (semi)solid organic/inorganic phase. (B) Optical images at 293 K on pre-poking, poking, and post-poking of the same PM_2.5 filter samples as shown in (A). The solid black scale bars in (A) and (B) indicate 20 μm.