Fluorescence Properties and Chemical Composition of Fine Particles in the Background Atmosphere of North China

To understand the aerosol characteristics in a regional background environment, fine-particle (PM_2.5, n = 228) samples were collected over a one-year period at the Shangdianzi (SDZ) station, which is a Global Atmospheric Watch regional background station in North China. The chemical and optical characteristics of PM_2.5 were analyzed, including organic carbon, elemental carbon, water-soluble organic carbon, water-soluble inorganic ions, and fluorescent components of water-soluble organic matter. The source factors of major aerosol components are apportioned, and the sources of the fluorescent chromophores are further analyzed. The major chemical components of PM_2.5 at SDZ were \rmNO_3^- , organic matter, \rmSO_4^2- , and \rmNH_4^+ . Annually, water-soluble organic carbon contributed 48% ± 15% to the total organic carbon. Secondary formation (52%) and fossil fuel combustion (63%) are the largest sources of water-soluble organic matter and water-insoluble organic matter, respectively. In addition, three humic-like and one protein-like matter were identified via parallel factor analysis for excitation–emission matrices. The fluorescence intensities of the components were highest in winter and lowest in summer, indicating the main impact of burning sources. This study contributes to understanding the chemical and optical characteristics of ambient aerosols in the background atmosphere.