Characteristics And Source Apportionment Of Atmospheric Particles In Changsha City

The pH value and concentrations of water-soluble salts in Atmospheric PM10 and PM2.5 aerosol were analyzed quantitatively at three sampling sites in Changsha City. The results showed that SO₄^2-, NO₃^-, NH₄⁺ and Ca²⁺ were the major ionic species and existed in the form of (NH₄)₂SO₄, Ca(NO₃)₂ and CaSO₄ in particles. The concentrations of PM10, PM2.5, NH₄⁺ and K⁺ were higher in daytime than in nighttime, but that of SO₄^2- and NO₃^- was on the contrary. The particles especially PM2.5 aerosol was slightly acidic. Coarse mode dominated the size distributions of crustal elements; SO₄^2-, NH₄⁺ and K⁺ were mostly concentrated in the fine particle ranges; and bimodal types characterized the size distributions of NO₃^- and Cl-.The secondary formations from SO2 to SO₄^2- was present, The formations of NO₃^- from NO₂ weakly occurred compared to that of SO₄^2- maybe due to deficiency of NH₄⁺ . Stationary emissions were the dominant source in Changsha city indicated by the NO₃^-/SO₄^2- ratio of lower than 1. The concentration of nine metallic elements such as Fe, Mn, Pb, Zn, K, Ca, Al, Na, Mg were measured by Atomic Absorption Spectrometer. Enrichment factor method was used for studying sources of the particulates. Results showed that Pb, Zn and Ca were obviously enriched; Mn was partly enriched; K,Mg,Fe,Na were not enriched. In order to assay the TSP-element-constitute database better, applying SPSS for Windows statistics analysis software to carry out factor analysis, the results showed that there are four main TSP pollution sources in Changsha in spring. The contribution rates of the four sources were roughly estimated that construction dust was 75.618%, vehicle dust was 9.536%, soil dust was 5.898%, waste material combustion was 4.676%. Scanning Electron Microscopy and Energy- Dispersive X-ray were used to study microstructure of the atmospheric particles samples in Changsha City. The results showed that particles were mostly irregular; spherical, cylindrical and aggregate were the major species in regular shaped particles. Thirteen elements were detected in samples. Dust, fly ash and mineral particles such as gypsum were the main ingredient in atmospheric particles.