泰山夏季PM2.5中生物源SOA的分子组成及影响因素

为探究泰山夏季PM_2.5中生物源二次有机气溶胶（BSOA）的分子组成、昼夜变化特征、及影响因素，于2016年7~8月在泰山山顶进行PM_2.5样品采集，并对碳质组分、无机离子和BSOA示踪物进行分析.结果表明，元素碳（EC）和左旋葡聚糖质量浓度处于较低水平且昼夜差异较小（t检验，P < 0.05），表明采样期间泰山山顶气溶胶受人为污染排放的影响较小.BSOA示踪物的总质量浓度呈昼高夜低的变化特征，表明白天较强的温度和太阳辐射使得气溶胶的氧化程度比夜间强.其中，异戊二烯类SOA示踪物的质量浓度最高达（77.64±51.79）ng/m³，其次为单萜烯类和倍半萜烯类SOA示踪物，分别为（33.68±21.29）和（6.97±3.28）ng/m³.基于示踪物-产率法估算得出SOC_异戊二烯对有机碳（OC）的贡献率（15.3%）最高.由BSOA示踪物与RH（R￡-0.45）和pH_is（R￡-0.53）的负相关性可知，高湿条件可以降低气溶胶的酸度进而抑制BSOA通过酸催化氧化反应的形成.由BSOA与温度和人为源指示物（左旋葡聚糖和EC）的相关性分析得出，采样期间泰山地区BSOA主要受当地BVOCs氧化反应的影响，而受长距离传输人为污染源的影响较小.

Molecular compositions and affecting factors of biogenic SOA in PM2.5 from Mount Taishan during the summer

To investigate the molecular composition, diurnal variation, and influencing factors of biogenic secondary organic aerosols (BSOA) in PM_2.5 from Mt. Tai during summer time, PM_2.5 samples were collected during July and August of 2016. The samples were determined for molecular distributions of carbonaceous compounds, inorganic ions and the tracers of BSOA (isoprene, monoterpene and sesquiterpene derived SOA). The results showed that the mass concentrations of elemental carbon (EC) and levoglucosan were in lower level and did not exhibit significant diurnal variations, suggesting that the effect of anthropogenic pollution during the sampling period was minor. The concentrations of BSOA tracers were higher in daytime than those in nighttime, indicating that the daytime aerosols were more photochemically aged than those in night time due to the higher temperature and stronger solar radiation. Isoprene SOA tracers (77.64±51.79)ng/m³] was the dominant species, followed by monoterpene (33.68±21.29)ng/m³] and sesquiterpene (6.97±3.28)ng/m³] SOA tracers. Based on tracer-yield method, the contribution rate (15.3%) of isoprene derived secondary organic carbon (SOC) to OC was the highest. The BSOA tracers presented significant negative correlations with relative humidity (RH) (R￡-0.45) and particle in-situ pH (pH_is) (R￡-0.53), suggesting that higher RH can suppress the acid-catalyzed formation of BSOA because of the lower aerosol acidity due to dilution. The correlations of BSOA with temperature and anthropogenic pollutants (e.g., levoglucosan and EC) suggested that BSOA were largely derived from the local oxidation of biogenic VOCs rather than long-range transport.