Research;
Institute,;
Shandong;
University,;
Jinan;
250100,;
China;
of;
Environmental;
Science;
and;
Engineering,;
Shandong;
University,;
Jinan;
250100,;
China;
Research;
Academy;
of;
Environmental;
Sciences,;
Beijing;
100012,;
China;
indoor; air; quality; indoor; outdoor; ratios; size; distributions; particles; with; aerodynamic; diameter≤2; 5μm; (PM2; 5); water-soluble; ions;