The concentration and isotopic composition of particulate-bound mercury (PBM) on both PM_2.5 and PM₁₀ were simultaneously measured (24 months) in a typical subtropical coastal suburb of Xiamen bay (SCXB), southern China. The results showed that most mercury was concentrated in PM_2.5 and small particulates enriched heavier isotopes of mercury more than lighter ones. Negative Δ¹⁹⁹Hg values and slightly positive Δ²⁰⁰Hg values were observed in both PM_2.5 and PM₁₀. PBM input sources were identified with isotopic compositions and meteorological data using the NOAA HYSPLIT model. It revealed that biomass combustion is the main source of particulate mercury in SCXB, and the two other sources are urban anthropogenic emissions and potential marine sources. Seasonal variations in isotopic composition and correlation analysis suggested that PBM in SCXB mainly originate from inland after long-distance transportation in spring and under the influence of oceanic air masses in summer. The Δ¹⁹⁹Hg/Δ²⁰¹Hg ratios in all samples (1.01 ± 0.05, 2SE) indicated that the photoreduction of Hg(II) in the aerosol was the main reaction process of PBM transformation in the atmosphere. Seasonal variations in Δ²⁰⁰Hg values were also found, indicating the possibility of even mass independent fractionation in tracing the mercury sources.