Light attenuation cross-section of black carbon in an urban atmosphere in northern China

- Two-year's EC contents and BC light attenuation cross-sections (σATN) in Xi'an were investigated.
- BC σATN exhibited pronounced seasonal variability, averaging 23.0 m2/g annually.
- σATN varied inversely with the ratios of EC/PM2.5, EC/[SO42−], and EC/[NO3−].
- The variations were mainly attributed to changes in EC loading and mixing mode of EC with sulfate.