Shenzhen National Climate Observatory,Meteorological Bureau of Shenzhen Municipality,Shenzhen 518040 China;
Meteorological Observation Center,China Meteorological Administration,Beijing 100081 China;
Hong Kong Observatory,Hong Kong 999077 China;
School of Atmospheric Sciences,Sun Yat-sen University,Zhuhai 519082 China;
air quality; haze day; Shenzhen; water-soluble inorganic ions;