Based on the concentrations of the carbonaceous components and the typical organic tracers in 682 p.m._2.5 samples collected in Shanghai from 2012 to 2018, the temporal trends of the concentrations and potential sources of the secondary organic aerosols in PM_2.5 in Shanghai were investigated. The annual average concentrations of organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon (WSOC) all showed a decreasing trend along with the PM_2.5 concentration. The annual concentration of total carbon (TC) in 2018 (4.3 μg m⁻³) was about 34% of that in 2012. Compared with that in 2013, the concentrations of isoprene and sesquiterpene SOA tracers in 2018 decreased by 48% and 43%. Meanwhile, the concentration of monoterpene SOA tracers kept stable in 2 ng m⁻³ to 3 ng m⁻³, and the concentration of toluene SOA tracer decreased slightly from 1.3 ng m⁻³ in 2013 to 1.0 ng m⁻³ in 2018. Correlation analysis with levoglucosan suggested that biomass burning should be an important source of sesquitertene in Shanghai. It was found that the 2-MGA/2-MTLs ratio of the isoprene tracers was more strongly affected by the ambient temperature but not NOx in Shanghai. The concentration of secondary organic carbon (SOC) estimated with OC/EC-based, WSOC-based and tracer-based methods showed a decreasing trend during the study period, but the contribution of SOC to OC was increasing. Anthropogenic aromatic volatile organic compounds was the increasingly important contributor to the SOC in PM_2.5, and should be the key pollutants to be controlled to further improve the air quality in Shanghai.

基于2012-2018年上海采集的682个pm _2.5样品的含碳组分浓度和典型有机示踪剂，研究了上海PM _2.5二次有机气溶胶浓度和潜在来源的时间趋势。有机碳（OC）、元素碳（EC）和水溶性有机碳（WSOC）年均浓度均随PM _2.5浓度呈下降趋势。2018年总碳（TC）年浓度（4.3 μg m ^-3)约为2012年的34%。与2013年相比，2018年异戊二烯和倍半萜SOA示踪剂浓度分别下降48%和43%。同时，单萜SOA示踪剂的浓度稳定在2 ng m ^-3到3 ng m ^{-3 之间}，甲苯SOA示踪剂的浓度从2013年的1.3 ng m ^-3小幅下降到1.0 ng m ^-32018年与左旋葡聚糖的相关性分析表明，生物质燃烧应该是上海倍半萜烯的重要来源。发现异戊二烯示踪剂的 2-MGA/2-MTLs 比受环境温度的影响更大，但在上海不受 NOx 的影响。使用基于OC/EC、基于WSOC和基于示踪剂的方法估算的次生有机碳（SOC）浓度在研究期间呈下降趋势，但SOC对OC的贡献正在增加。人为芳香族挥发性有机化合物是 PM _{2.5 中}SOC 越来越重要的贡献者，应成为进一步改善上海空气质量需要控制的关键污染物。