Wang Fengyang, Hu Renzhi, Chen Hao, Xie Pinhua, Wang Yihui, Li Zhiyan, Jin Huawei, Liu Jianguo, Liu Wenqing
Opt Express. 2019 Apr 15;27(8):A419-A435. doi: 10.1364/OE.27.00A419.
A ground-based system for measuring tropospheric OH radical based on laser-induced fluorescence (AIOFM-LIF) was developed in this work. In this system, ambient air is expanded through a 0.4 mm nozzle to low pressure in a detection chamber, where OH radical is irradiated by the 308 nm laser pulse at a repetition rate of 8.5 kHz. Then, the resultant fluorescence corresponding to the AΣ(υ=0)←XΠ(ν=0) transition at 308 nm is detected using gated photon counting. The AIOFM-LIF system was integrated into a mobile observing platform for the field observation following the series of laboratory characterization. A portable standard OH radical source by water photolysis-ozone actinometry was established and optimized for accurate system calibration. The factors affecting the system sensitivity were quantified. It was shown that the ultimate system sensitivity is 9.9 × 10 cps (molecules cm) mw; the minimum detection limits are (1.84 ± 0.26) × 10 cm and (3.69 ± 0.52) × 10 cm at night and noon, respectively; and the whole error of AIOFM-LIF system is about 16%. Then, the system was deployed in Shenzhen, China, during the "A comprehensive STudy of the Ozone foRmation Mechanism in Shenzhen" (STORM) campaign. Valid OH radical concentrations for 31 days were obtained, and the peak of the daily average concentration was 6.6 × 10 cm around 12:00. And a high correlation (R = 0.77) between OH and j(OD) was also observed in this field campaign. The relationship between OH concentration and NOx was attentively discussed. The deployment of AIOFM-LIF system in STORM campaign has demonstrated its capability of measuring tropospheric OH radical with high sensitivity and accuracy in a polluted environment.
本工作开发了一种基于激光诱导荧光的地面对流层OH自由基测量系统（AIOFM-LIF）。在该系统中，环境空气通过0.4毫米喷嘴在检测室内膨胀至低压，在检测室内，OH自由基被308纳米激光脉冲以8.5千赫兹的重复频率照射。然后，使用门控光子计数检测对应于308纳米处AΣ(υ=0)←XΠ(ν=0)跃迁的荧光。在一系列实验室表征之后，AIOFM-LIF系统被集成到一个移动观测平台上进行实地观测。建立并优化了一种基于水光解-臭氧光化学分析法的便携式标准OH自由基源，用于精确的系统校准。对影响系统灵敏度的因素进行了量化。结果表明，系统的最终灵敏度为9.9×10 cps（分子·厘米）/毫瓦；夜间和中午的最低检测限分别为(1.84±0.26)×10¹²厘米⁻³和(3.69±0.52)×10¹²厘米⁻³；AIOFM-LIF系统的整体误差约为16%。然后，该系统在中国深圳的“深圳臭氧形成机制综合研究”（STORM）活动期间进行了部署。获得了31天的有效OH自由基浓度，日平均浓度峰值在12:00左右为6.6×10¹²厘米⁻³。在这次实地活动中还观察到OH与j(OD)之间具有高度相关性（R = 0.77）。详细讨论了OH浓度与氮氧化物之间的关系。AIOFM-LIF系统在STORM活动中的部署证明了其在污染环境中高灵敏度和高精度测量对流层OH自由基的能力。
