Atmospheric aerosol compositions in China: spatial/temporal variability, chemical signature, regional haze distribution and comparisons with global aerosols

摘要

From 2006 to 2007, the daily concentrations of major inorganic water-solubleconstituents, mineral aerosol, organic carbon (OC) and elemental carbon (EC)in ambient PM samples were investigated from 16 urban, rural and remotesites in various regions of China, and were compared with global aerosolmeasurements. A large difference between urban and rural chemical specieswas found, normally with 1.5 to 2.5 factors higher in urban than in ruralsites. Optically-scattering aerosols, such as sulfate (~16%), OC(~15%), nitrate (~7%), ammonium (~5%) and mineralaerosol (~35%) in most circumstance, are majorities of the totalaerosols, indicating a dominant scattering feature of aerosols in China. Ofthe total OC, ~55%–60% can be attributed to the formation ofthe secondary organic carbon (SOC). The absorbing aerosol EC only accountsfor ~3.5% of the total PM. Seasonally, maximum concentrations ofmost aerosol species were found in winter while mineral aerosol peaks inspring. In addition to the regular seasonal maximum, secondary peaks werefound 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 aerosolcomponents in China. Aerosol acidity was normally neutral in most of urbanareas, but becomes some acidic in rural areas. Based on the surfacevisibility observations from 681 meteorological stations in China between1957 and 2005, four major haze areas are identified with similar visibilitychanges, namely, (1) Hua Bei Plain in N. China, and the Guanzhong Plain; (2)E. China with the main body in the Yangtze River Delta area; (3) S. Chinawith most areas of Guangdong and the Pearl River Delta area; (4) The Si ChuanBasin in S.W. China. The degradation of visibility in these areas is linkedwith the emission changes and high PM concentrations. Such quantitativechemical characterization of aerosols is essential in assessing their rolein atmospheric chemistry and weather-climate effects, and in validatingatmospheric models.