Abstract:

To better understand the chemical make-ups of PM_2.5 in Shanghai, samples have been collected at a typical suburban site in Shanghai in four seasons with a high-volume PM_2.5 sampler. Mass concentrations and compositions of carbon-, nitrogen- and sulphur-containing components in the PM_2.5 samples have been measured with different instruments including elemental analyzer, thermal/optical carbon analyzer, ion chromatograph, and chemical oxidation-UV spectrophotometer, and the result from the different methods were compared. The seasonal variations and influencing factors of the concentrations of these components were investigated. Furthermore, methods for the estimation of the mass concentrations of carbon-, nitrogen- and sulphur-containing components in PM_2.5 in Shanghai with the C, N, S concentrations from the elemental analyzer was developed. Results show that mass concentrations of total carbon in PM_2.5 in Shanghai in spring, summer, autumn and winter are 14.26, 10.44, 11.89 and 24.35 ug·m^-3 respectively, 8.72, 3.07, 5.07 and 17.09 ug·m^-3 respectively for nitrogen, while 6.50, 4.06, 3.66 and 6.00 ug·m^-3 respectively for sulphur. Most of the carbon in PM_2.5 in Shanghai exists as organic and elemental carbon, and the contribution of inorganic carbon is very small. Most of the nitrogen in PM_2.5 in Shanghai appears in the form of water-soluble inorganic components, while most of the sulphur-containing components appear in the form of water-soluble sulphate. Elemental analyzer could be used effectively to study the mass concentrations and compositional characteristics of the carbon-containing, nitrogen-containing and sulphur-containing components in PM_2.5.

Key words: PM_2.5, elemental analyzer, ions, seasonal variation, Shanghai