中文摘要：

在2015年7~11月,选取我国珠江三角洲北部的广东南岭国家大气背景站为观测点,应用预浓缩-气相色谱/质谱联用等仪器进行连续在线监测,研究了大气中异戊二烯的浓度水平、干湿季变化、昼夜变化及其影响因素,并初步探讨了高浓度O3污染天气以及典型台风天气过程对森林大气异戊二烯含量变化的影响.结果表明,广东南岭森林大气异戊二烯的平均浓度为(0.173±0.171)×10-9,低于国内其它大气背景站.湿季异戊二烯浓度高于干季,分别为(0.261±0.178)×10-9和(0.080±0.089)×10-9.白天(06:00~18:00)异戊二烯浓度[(0.247±0.332)×10-9]远高于夜晚[(0.071±0.129)×10-9],异戊二烯浓度于06:00开始稳步升高,午后14:00达到峰值,之后逐渐降低.异戊二烯浓度水平与温度呈正指数相关关系,且湿季温度对异戊二烯浓度水平影响更加显著(R2=0.308).O3污染日异戊二烯的日均浓度[(0.257±0.128)×10-9]水平普遍高于非O3污染日[(0.158±0.173)×10-9],然而O3污染日异戊二烯的光化学降解反应相对更为活跃.对台风“杜鹃”的分析表明,台风天气过程中外来污染气团的输送会导致森林大气异戊二烯含量显著增加.

英文摘要：

Isoprene emissions from forest are important precursors of tropospheric ozone and secondary organic aerosols.To study the background concentration and variation characteristics of isoprene at a subtropical forest(Shaoguan,Nanling)in southern China,4-month online measurements of isoprene emissions and meteorological parameters were conducted in July-November2015.The results show that the overall daily average concentration of isoprene at the forest was(0.173±0.171)×10-9,with(0.261±0.178)×10-9in the wet season and(0.080±0.089)×10-9ppbv in the dry season.Isoprene concentration is much higher during daytime(6:00-18:00)than nighttime,with an average of0.247±0.332ppbv and(0.071±0.129)×10-9,respectively.It began to rise steadily from6:00,and gradually decreased after the peak at14:00.Isoprene concentrations were positively exponential functional related to temperature,and in the wet season,the temperature had greater influence on isoprene emission.Isoprene concentrationsduring the O3episode days[(0.257±0.128)×10-9]were much higher than during the non-O3episode days[(0.158±0.173)×10-9],suggesting that the photochemical degradation was more active during the O3episode days.In addition,it was found that typhoon(e.g.Dujuan)would lead to increase in isoprene emissions due to the transportation of air pollutants to the forest.