深圳大气有机硝酸酯粒径分布特征和来源研究

于2021年3月30日至2021年4月17日利用超高分辨率气溶胶飞行时间质谱(Long-ToF-AMS),对深圳城市大气中的颗粒态有机硝酸酯(pON)开展高精度分析. 基于两种估算pON的方法,计算得出pON对有机气溶胶(OA)的贡献占比为5.08%~11.00%.pON的日变化特征显示,其高值主要出现在夜间时段(19:00~6:00).pON在夜间时段与氧化程度较低的二次有机气溶胶(LO-OOA)相关性最高,说明pON来源生成可能与夜间的新鲜二次生成相关.此外,小粒径段颗粒物对pON贡献显著,进一步证明了夜间时段新鲜生成了较多的pON.本研究还进一步比对了环境样品中与pON相关的离子类型(C_xH_yN_p⁺和C_xH_yO_zN_p⁺)及实验室模拟的特征质谱,结果显示深圳市pON生成的前体VOCs可能与植物排放和生物质燃烧过程联系更为密切.

Sizing and source characterization of particulate organic nitrates based on long time-of-flight aerosol mass spectrometer (Long-ToF-AMS) in Shenzhen

In this study, a long time-of-flight aerosol mass spectrometer (Long- ToF-AMS) was applied to characterize particulate organic nitrates (pON) during March 30^th to April 17^th in 2021 at Shenzhen. Using cross-validation estimated methods, we calculated pON accounting for 5.08%~11.00% in total OA. The diurnal pattern with nighttime higher mass loading for pON and the best correlation with less-oxidized oxygenated OA (LO-OOA) at night indicated that pON formation might be more associated with nighttime fresh secondary formation. The high-resolution size distribution of pON showed they contained a substantial fraction of smaller size particles, further confirming the contributions from primary aerosols or newly formed secondary aerosols at night. Additionally, the potential precursors for pON formation was further explored based on comparison analysis between mass spectrum of our ambient data and the laboratory generated pON using different precursors. The results implied that volatile organic compounds (VOCs) emitted from biogenic sources and biomass burning were potential precursors for pON formation in Shenzhen.