During 2006 and 2007, the daily concentrations of major water-soluble constituents, mineral aerosol, organic carbon (OC) and elemental carbon (EC) in ambient PM₁₀ samples were investigated from 16 urban, rural and remote sites in various regions of China, and were compared with global aerosol. A large difference between urban and rural chemical species was found, normally with 1.5 to 2.5 factors higher in urban than in rural sites. Optically-scattering aerosols such as sulfate (~16%), OC (~15%), nitrate (~7%) and ammonium (~5%) consist of ~50% of the total aerosols with another ~35% from mineral aerosol also having a certain degree of scattering ability, indicating a dominant scattering feature of aerosols in China. Of the total OC, ~55%–60% can be attributed to the secondary organic carbon (SOC). The absorbing aerosol EC accounts for ~3.5% of the total PM₁₀. Seasonally, maximum concentrations of most aerosol species are found in winter while mineral aerosol also peaks in spring. Second peaks were found for sulfate and ammonium in summer and for OC and EC in May and June. This can be considered as a typical seasonal pattern in various aerosol components in China. Aerosol acidity is normally neutral in most of urban areas, but becomes somewhat acidic in rural areas. Based on the surface visibility from 681 meteorological stations in China during 1957–2005, four major haze areas are also identified with similar visibility changes, namely, (1) Hua Bei Plain in N. China, plus the Guanzhong Plain; (2) E. China with the main body in the Yangtze River Delta area; (3) S. China with most areas of Guangdong and the Pearl River Delta area; (4) The Si Chuan Basin in S. W. China. The degradation of visibility in these areas is linked with the emission changes and high PM concentrations. Such quantitative chemical characterization of aerosols is essential in assessing their role in atmospheric chemistry and weather-climate effects, and in validating atmospheric models