Seasonal trends and light extinction effects of PM_2.5 chemical composition from 2021 to 2022 in a typical industrial city of central China

This study investigates the concentrations, chemical compositions, and sources of PM_2.5 in Huangshi, China. Daily average PM_2.5 levels ranged from 8.43 to 193.08 μg m⁻³, with an annual mean of 54.13 μg m⁻³, exceeding China's annual secondary standard of 35 μg m⁻³. Seasonal mean concentrations peaked in winter and were lowest in summer. Organic carbon (OC) and elemental carbon (EC) had annual means of 4.89 μg m⁻³ and 0.94 μg m⁻³, respectively. Water-soluble inorganic ions (WSIIs) accounted for 52.17% of PM_2.5, with NO₃⁻, SO₄²⁻, and NH₄⁺ being the major components. The NO₃⁻/SO₄²⁻ ratio averaged 1.65, indicating a transition from coal combustion to vehicle emissions as the primary pollution source. Chemical mass reconstruction revealed that NH₄NO₃, (NH₄)₂SO₄, and organic matter (OM) accounted for 65.3% of PM_2.5 mass. Seasonal variations in light extinction (b_ext) highlighted the impact of secondary inorganic salts on visibility, with an annual average b_ext of 346.30 ± 246.98 Mm⁻¹. Airmass clusters and potential source region analysis suggested PM_2.5 and its components were primarily originated from local and nearby regions. These findings underscore the effectiveness of local pollution control measures, changing pollution sources, and the necessity for targeted emission controls to improve air quality and visibility in urban areas.