主要对天然挥发性有机物柠檬烯和柠檬烯氧化物在30%-80%(w)硫酸表面的非均相吸收反应进行了研究,借以评估天然挥发性有机物与大气环境中的酸性气溶胶的反应活性.采用自行搭建的配以单光子激光电离飞行时间质谱的湿壁流动反应管的设备对柠檬烯及其氧化物在硫酸表面的非均相吸收动力学进行了测定,计算了稳态摄取系数(γ)实验结果表明,柠檬烯氧化物在硫酸表面比只含有双键的柠檬烯的反应活性高,室温下柠檬烯氧化物在30%-50%(w)硫酸上对应的稳态摄取系数是(7.100±0.023)×10^(-5)-(8.150±0.162)×10^(-3).此外,还利用气相色谱-质谱(GC-MS)联用和电喷雾电离质谱(ESI-MS)对柠檬烯氧化物与硫酸的体相反应产物进行了研究,产物包括单萜烯、松油醇、水合萜二醇和水合萜二醇二硫酸酯.其中,水合萜二醇二硫酸酯作为有机硫酸酯的一种,能够改变气溶胶的吸湿性,增强云凝结核的活性,对于大气中灰霾的形成可能有明显的促进作用.
The heterogeneous uptake of limonene and limonene oxide (also known as 1,8-cineole) by a range of different aqueous sulfuric acid (H2SO4) solutions (30%-80% (w)) was investigated to develop an understanding of the reactivity of biogenic organic compounds in the atmosphere towards acidic aerosols. Experiments were performed using a rotating wetted-wall reactor coupled to a single photon ionization time-of-flight mass spectrometer. The heterogeneous uptake of the compounds into H2SO4 followed first-order kinetics and the corresponding steady-state uptake coefficients (y) were calculated for the first time. Limonene oxide was found to be more reactive than limonene towards H2SO4. Reactive uptake was observed for limonene oxide in acidic solution containing greater than 30% (w). The steady-state uptake coefficients of limonene oxide in 30%-50% (w) H2SO4 solutions at room temperature ranged from (7.100±0.023)× 10^(-5) to (8.150±0.162)× 10^(-3) . Furthermore, the reactions of limonene oxide with sulfuric acid in bulk solution were investigated using gas chromatography-mass spectrometry (GC-MS) and electron spray ionization-mass spectroscopy (ESI-MS). Analysis of the products revealed the presence of monoterpenes, terpineols, terpin hydrates, and terpin hydrate diorganosulfate from the bulk solution reaction of limonene oxide with H2SO4. The formation of significantly more hydrophobic organic compounds with lower volatilities suggested that limonene oxide is a significant precursor in the formation of atmospheric secondary organic aerosols. A transformation mechanism has been proposed based on the products.