To investigate the impact of PM_2.5 chemical species on light scattering in autumn Xi'an, light scattering coefficient and PM_2.5 samples were collected daily in November 2012 at the Institute of Earth Environment, Chinese Academy of Sciences. The PM_2.5 water-soluble ionic species (Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, F^-, Cl^-, NO₃^- and SO₄^2-) and carbonaceous (organic carbon and elemental carbon) were analyzed to characterize their impacts on the light scattering coefficient. The average PM_2.5 during the sampling period was (195.4±83.5) μg·m^-3. The average light scattering coefficient was (579±387) Mm^-1, with high value at night and low value in the daytime. The concentration of PM_2.5 showed a strong correlation with light scattering coefficient, with a correlation coefficient of 0.85. The estimated light scattering efficiency of PM_2.5 was 3.09 m²·g^-1. Among the PM_2.5 chemical species, NH₄⁺, K⁺, SO₄^2- and OC had a strong correlation with light scattering coefficient, suggesting that they are the main contribution sources for light extinction coefficient. The revised IMPROVE equation was used to estimate chemical extinction (b_ext), which was lower than measured bsp, wet. Among the PM_2.5 chemical species, organics had the largest contribution to light extinction, accounting for 52.3%, followed by NH₄NO₃ (16.2%) and (NH₄)₂SO₄ (13.7%).

light scattering coefficient  /  PM_2.5 chemical species  /  visibility  /  light extinction coefficients