Novel measurements of atmospheric iodine species by resonance fluorescence
Novel measurements of atmospheric iodine species by resonance fluorescence
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DOI：
10.1007/s10874-008-9108-z
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发表时间：
2008-05-01
影响因子：
2
通讯作者：
Bloss, William J.
中科院分区：
文献类型：
--
作者：
Bale, Catherine S. E.;Ingham, Trevor;Bloss, William J.
本文介绍了一种用于测量海洋边界层气相大气碘物种的现场仪器。利用微波放电灯产生的真空紫外共振荧光（RF），通过178-184 nm的（5 p（4）6s）-（5 p（5））跃迁，对碘原子进行了检测。该系统可以在两种模式下操作;要么直接测量环境碘原子，或测量环境空气中的总光不稳定碘负载，通过宽带可见光分解的光不稳定含碘物质，与随后的RF检测释放的碘原子。在这两种情况下，仪器都可以对探测到的物种进行现场测量，这有利于收集有关其当地来源和分布的信息。该仪器通过使用水银笔-射线灯从I-2的光解产生已知浓度的碘原子来校准。该仪器于2007年8月首次部署在梅斯头在西海岸的爱尔兰，从这个现场试验的初步结果。在一天中，测量到环境碘原子的水平高达22 +/- 4.8 ppt，与海带海藻床暴露时的最低潮汐相吻合。在几个夜间和白天的时间段，总的光不稳定碘负载也进行了测量，并发现与潮汐高度呈负相关。根据这些测量结果推断的I-2浓度表明Mace Head现场的水平为几百ppt。这些测量代表了对周围碘原子的首次直接观测和对大气中总的光不稳定碘的测量。
A field instrument has been developed for the purpose of measuring gas-phase atmospheric iodine species in the marine boundary layer. Vacuum UV resonance-fluorescence (RF), generated using a microwave discharge lamp, is employed to detect atomic iodine via the (5p(4)6s)-(5p(5)) transitions around 178-184 nm. The system can be operated in two modes; either to directly measure ambient iodine atoms, or to measure the total photolabile iodine loading of ambient air, through broadband visible photolysis of photolabile iodine-containing species, with subsequent RF detection of the iodine atoms released. In both cases the instrument allows for the in situ measurement of the species detected, which is advantageous for gathering information concerning their local sources and distribution. The instrument is calibrated through generation of a known concentration of iodine atoms from the photolysis of I-2 using a mercury pen-ray lamp. The instrument was deployed for the first time in August 2007 at Mace Head on the west coast of Ireland; initial results from this field trial are presented. Ambient iodine atoms were measured at levels up to 22 +/- 4.8 ppt during the day, coinciding with the lowest tides, when Laminaria seaweed beds were exposed. The total photolabile iodine loading was also measured during several night-time and day-time periods and was found to correlate inversely with tidal height. Inferred I-2 concentrations based on these measurements indicate levels of several hundred ppt at the Mace Head site. These measurements represent the first direct observations of ambient iodine atoms and measurement of total photolabile iodine in the atmosphere.