Aerosols have a significant impact on both direct and indirect radiative effects and are considered to be one of the largest contributors to the uncertainty in global climate change assessment. In this study, continuous one-year-round in-situ observations of aerosol optical properties were conducted in the southeastern coastal city of Xiamen, China, and the effects of chemical composition on aerosol optical properties were analyzed to assess the environmental and climate effects of aerosols. The scattering coefficient (σ_sp), absorption coefficient (σ_ap), single scattering albedo (SSA) showed significant seasonal variations. The σ_sp and σ_ap showed obvious bimodal diurnal patterns, with peaks occurring in the morning peak and evening, while the diurnal patterns of SSA were reversed. The results of the chemical component-based estimation reconstruction of σ_sp illuminated that OM, NH₄NO₃, (NH₄)₂SO₄ were the main contributors to the σ_sp. The concentration weighted trajectory (CWT) method was used to characterize the contributing sources of each chemical component affecting σ_sp. The main contributing source areas were elucidated and varied slightly with species and season. The wind dependence analysis reflected that σ_ap was mainly influenced by local emissions, while σ_sp was affected by both local emissions and regional transport. The contribution sources of σ_sp and σ_ap were investigated using potential source contribution function (PSCF) method. The contributing source of σ_sp and σ_ap in Xiamen were clarified, and varied slightly with seasonal differences. This study revealed the aerosol optical properties in the southeastern coastal urban areas of China and provided a scientific basis for the estimation of the factors affecting climate change.

Diurnal variations of σ_sp, σ_ap, SSA and PM_2.5 mass concentrations from September 2020 to August 2021.