Chemical Characterizations of PM10 Profiles for Major Emission Sources in Xining, Northwestern China

The chemical profiles of emission sources are indispensable for source apportionment using receptor models. To develop current knowledge of PM10 profiles, the chemical composition of major emission sources were analyzed in Xining. Samples of geological sources (soil dust, road dust and construction derived dust) and industrial fly ash were collected from representative portions using a plastic dustpan and brush and sampled on filters through a re-suspension chamber. Samples of coal combustion source and vehicle exhaust were collected directly on the filters using a dilution stack sampler. Chemical analysis included inductively coupled plasma mass spectrometry for 19 elements (Na, P, K, As, Rb, Mo, Cd, Sn, Sb, La, V, Cr, Mn, Co, Ni, Cu, Zn, T1, and Pb), inductively coupled plasma optical emission spectrometry for 7 elements (Al, Sr, Mg, Ti, Ca, Fe, and Si), ion chromatography for water-soluble ions (Na+, K+, Mg2+, Ca2+, F-, Cl-, NO3- and SO42-) and thermal/optical reflectance analysis for carbonaceous species. Crustal elements (Si, Al, Ca, Fe) predominated in geological sources, whereas trace elements (Pb, Cd, Cr, Zn and Ni) were predominant in industrial fly ash. An abundance of carbon and SO42- was present in coal-combustion source and vehicle exhaust. The coal-combustion boilers were a source of trace elements (Ti, Co, Sr, Sb, Tl). High concentrations of Pb and OC in soil indicated the strong influence of agriculture activities in Xining. Comparison of vehicle exhaust profiles indicated that natural gas was high environmental friendliness in comparison with petroleum products used as motor vehicles fuel. Differences in EC, Cd and NO3- between natural gas-powered and gasoline- or diesel-powered vehicle exhaust can be used to differentiate the two types of vehicle emission sources. Differences in source profiles and indicator species between Xining and other cities suggest that source profiles should be developed locally and updated frequently.