资源环境科技发展态势分析平台

To better understand the formation of biogenic secondary organic aerosol (BSOA), aerosol samples with a 4 h time resolution were collected during summer and winter in the southeast of China, along with online measurements of trace gases, aerosol chemical compositions, and meteorological parameters. The samples were analyzed by gas chromatography–mass spectrometry for PM_2.5-bound secondary organic aerosol (SOA) tracers, including isoprene (SOA_I), $\mathit{\alpha }/\mathit{\beta }$-pinene (SOA_M), β-caryophyllene (SOA_C), and toluene (ASOA). The average concentrations of total SOA tracers in winter and summer were 38.8 and 111.9 ng m⁻³, respectively, with the predominance of SOA_M (70.1 % and 45.8 %), followed by SOA_I (14.0 % and 45.6 %), ASOA (11.0 % and 6.2 %) and SOA_C (4.9 % and 2.3 %). Compared to those in winter, the majority of BSOA tracers in summer showed significant positive correlations with O_x (O₃+NO₂) (r = 0.443–0.808), HONO (r = 0.299–0.601), ultraviolet (UV) (r = 0.382–0.588) and temperature (T) (r = 0.529–0.852), indicating the influence of photochemical oxidation under relatively clean conditions. However, in winter, BSOA tracers were significantly correlated with PM_2.5 (r = 0.407–0.867), NO${}_{\mathrm{3}}^{-}$ (r = 0.416–0.884), SO${}_{\mathrm{4}}^{\mathrm{2}-}$ (r = 0.419–0.813), and NH₃ (r = 0.440–0.757), attributed to the contributions of anthropogenic emissions. Major BSOA tracers in both seasons were linearly correlated with aerosol acidity (pH) (r = 0.421–0.752), liquid water content (LWC) (r = 0.403–0.876) and SO${}_{\mathrm{4}}^{\mathrm{2}-}$ (r = 0.419–0.813). The results indicated that acid-catalyzed reactive uptake onto sulfate aerosol particles enhanced the formation of BSOA. In summer, the clean air mass originated from the ocean, and chlorine depletion was observed. We also found that concentrations of the total SOA tracers were correlated with HCl (R²=0.545) and chlorine ions (r = 0.280–0.639) in PM_2.5, reflecting the contribution of Cl-initiated volatile organic compound (VOC) oxidations to the formation of SOA. In winter, the northeast dominant wind direction brought continental polluted air mass to the monitoring site, affecting the transformation of BSOA tracers. This implied that anthropogenic emissions, atmospheric oxidation capacity and halogen chemistry have significant effects on the formation of BSOA in the southeast coastal area.