Chemical Characteristics and Health Risk Assessment of Fine Particulate Matter from Typical Emission Source in Xi’an, Northwestern China

To establish and complete the source profile of fine particulate matter (PM_2.5) in a Chinese megacity- Xi’an, the morphology, chemical characteristics and health risks of PM_2.5 emitted from different sources were explored. In this study, scanning electron microscope, inductively coupled plasma mass spectrometer, ion chromatograph and carbon analyzer were utilized to analyze and determine the source emission PM_2.5 samples. The results showed that PM_2.5 emitted from stationary source was mostly regular spherical, while the dust including soil wind dust and urban dust was practically irregular and with large size. PM_2.5 of mobile source was aggregated porous carbonaceous particles, and of biomass burning was floc or lamellar. Si was regarded as the marker of soil wind dust PM_2.5. Si and SO₄²⁻ accounted for a relatively high proportion in urban dust PM_2.5 (52.2% and 27.9%). Ca could be used as the tracer of construction cement dust due to its high mass fraction. Compared to other sources, mobile source showed higher NO₃⁻ proportion while biomass burning was dominated by Na and K. Attributed to relatively higher OC/EC in Xi’an than other cities, the secondary pollution was more serious. The health risk assessment results showed that the risk of Cr through inhalation route was 10^− 6~10^− 4 for a stationary source, which was over the threshold. In particular, the non-carcinogenic risk and carcinogenic risk of children were all higher than adults.