Point Measurement of Reactive Iodine Species by Resonance Fluorescence

我们大气的组成对我们日常生活的许多方面负有责任，例如污染的传播和我们的气候。大气的组成取决于天然和人造化合物的排放，以及转化这些化合物的化学反应。这项研究旨在加深我们对海洋地区大气中碘物种的一些化学过程的了解。众所周知，海洋生物会向大气中释放含碘的化合物。在阳光下，这些化合物可以被分解，释放出它们所含的碘原子，然后发生影响海洋大气的化学反应：碘物种可以影响大气处理污染物排放的能力，例如全球变暖气体甲烷，因为它们可以改变引发碳氢化合物降解的氧化剂物种的浓度。最近的研究还表明，在某些条件下，气相碘物种可以在大气中凝聚形成直径几纳米的新颗粒。在爱尔兰西海岸的梅斯海德研究站进行的测量中，探测到了新粒子的爆发。这些颗粒会增加云形成的倾向，因为它们是水蒸气凝结的焦点。由于云层在白天将太阳辐射反射回太空，并在夜间将热量聚集在接近地球表面的地方，海洋碘排放可能会影响我们的天气和气候。这项研究旨在回答有关这些过程的一个基本问题：海洋大气中含碘化合物的浓度和分布是什么？这项研究将由利兹大学化学学院的威廉·布洛斯博士和德韦恩·希尔德教授进行，在那里将开发一种新的检测碘物种的仪器，该仪器基于一种名为共振荧光的技术，这种技术灵敏、专门检测碘原子，并且可以精确校准。该仪器将能够测量海洋大气中存在的几种碘物种，这将极大地提高我们对沿海岸线和开阔海洋的碘化学作用的了解。该仪器将在利兹进行测试，并在爱尔兰梅斯黑德研究站进行试验部署。一个特别的目标将是确定碘物种是否仅限于狭窄的沿海区域，或者如果它们是在公海上以可观的水平被发现--如果是后者，那么上述过程将对大气成分产生重大影响。现场测量还将用于测试数值模式中使用的化学机制，这些模式旨在预测未来大气的组成。

The composition of our atmosphere is responsible for many aspects of our everyday life, such as the spread of pollution and our climate. Atmospheric composition is determined by emissions of natural and man-made compounds, and by chemical reactions which transform those compounds. This research fellowship aims to develop our understanding of some of the chemical processes involving iodine species which occur in the atmosphere in marine areas. Marine organisms are known to release iodine-containing compounds into the atmosphere. In the presence of sunlight, these compounds can be broken down releasing the iodine atoms they contain, which can then undergo chemical reactions which affect the marine atmosphere: Iodine species can affect the ability of the atmosphere to process pollutant emissions such as the global warming gas methane, as they can change the concentrations of the oxidant species which initiate the degradation of hydrocarbons. Recent research has also shown that under certain conditions, gas-phase iodine species can condense to form new particles in the atmosphere, a few nanometres in diameter. Bursts of new particles have been detected during measurements conducted at Mace Head Research Station on the west coast of Ireland. These particles can increase the tendency for clouds to form, as they act as focal points for water vapour to condense upon. As clouds reflect solar radiation back into space during the day, and trap heat close to the earth's surface at night, marine iodine emissions could affect both our weather and climate. This research aims to answer a fundamental question about these processes: -What are the concentrations and distribution of iodine-containing compounds in the marine atmosphere ? The research will be carried out by Dr William Bloss & Professor Dwayne Heard in the School of Chemistry in the University of Leeds, where a new instrument for the detection of iodine species will be developed, based upon a technique called resonance fluorescence, which is sensitive, specifically detects iodine atoms and can be accurately calibrated. The instrument will be able to measure several of the iodine species present in the marine atmosphere, which will greatly improve our understanding of the role of iodine chemistry along the coastline and over the open ocean. The instrument will be tested in Leeds, and during a trial deployment at Mace Head Research Station in Ireland. A particular aim will be to determine if the iodine species are restricted to a narrow coastal region, or if they are found over the open ocean at appreciable levels - if the latter, then the processes described above will have a significant impact upon atmospheric composition. The field measurements will also be used to test the chemical mechanisms used in numerical models which aim to predict the future composition of the atmosphere.