Iodine chemistry in the troposphere and its effect on ozone
Iodine chemistry in the troposphere and its effect on ozone
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DOI：
10.5194/acp-14-13119-2014
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发表时间：
2014-12
影响因子：
6.3
通讯作者：
A. Saiz‐Lopez;R. Fernández;C. Ordóñez;D. Kinnison;J. G. Martin;J. Lamarque;S. Tilmes
中科院分区：
文献类型：
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作者：
A. Saiz‐Lopez;R. Fernández;C. Ordóñez;D. Kinnison;J. G. Martin;J. Lamarque;S. Tilmes
抽象的。尽管碘化学对对流层的氧化能力有潜在影响，但活性碘的分布及其对对流层臭氧的影响仍然是全球大气中几乎未被探索的方面。在这里，我们提出了一个全面的全球模拟实验，旨在估计无机碘负荷的下限和上限及其对对流层臭氧的影响。进行了两组模拟，没有和有光分解的IxOy氧化物（即I2 O2，I2 O3和I2 O 4），以确定无机碘负载的范围，分配和影响在对流层。我们的结果表明，在对流层中上部，白天最丰富的碘是原子碘，年平均热带丰度为（0.15-0.55）pptv。我们提出了一个“热带碘原子环”的存在，它在赤道的热带对流层上层（约11-14公里）达到顶峰，并延伸到亚热带（30° N-30° S）。热带地区的年平均日间I / IO比大于3，在强对流区域发生剧烈隆升事件期间，该比高达约20。我们计算出催化碘反应对对流层臭氧损失总速率（IOx损失）的综合贡献比溴和氯的综合循环大2-5倍。如果将IxOy光解计算在内，IOx损失分别代表海洋边界层（MBL）、自由对流层（FT）和对流层上部（UT）热带年度臭氧损失的约27%、14%和27%的上限，而整个热带对流层的下限约为9%。我们的结果表明，碘是全球海洋UT和热带MBL中第二强的臭氧消耗家族。我们建议：（i）碘源及其化学需要包括在全球对流层化学模型中，（ii）旨在量化对流层碘收支的实验计划应包括测量原子碘的策略，和（iii）需要实验室方案来表征较高碘氧化物的光化学性质，以确定其在大气中的归宿，因为它们可能主导卤素-催化了对流层臭氧层的破坏
Abstract. Despite the potential influence of iodine chemistry on the oxidizing capacity of the troposphere, reactive iodine distributions and their impact on tropospheric ozone remain almost unexplored aspects of the global atmosphere. Here we present a comprehensive global modelling experiment aimed at estimating lower and upper limits of the inorganic iodine burden and its impact on tropospheric ozone. Two sets of simulations without and with the photolysis of IxOy oxides (i.e. I2O2, I2O3 and I2O4) were conducted to define the range of inorganic iodine loading, partitioning and impact in the troposphere. Our results show that the most abundant daytime iodine species throughout the middle to upper troposphere is atomic iodine, with an annual average tropical abundance of (0.15–0.55) pptv. We propose the existence of a "tropical ring of atomic iodine" that peaks in the tropical upper troposphere (~11–14 km) at the equator and extends to the sub-tropics (30° N–30° S). Annual average daytime I / IO ratios larger than 3 are modelled within the tropics, reaching ratios up to ~20 during vigorous uplift events within strong convective regions. We calculate that the integrated contribution of catalytic iodine reactions to the total rate of tropospheric ozone loss (IOx Loss) is 2–5 times larger than the combined bromine and chlorine cycles. When IxOy photolysis is included, IOx Loss represents an upper limit of approximately 27, 14 and 27% of the tropical annual ozone loss for the marine boundary layer (MBL), free troposphere (FT) and upper troposphere (UT), respectively, while the lower limit throughout the tropical troposphere is ~9%. Our results indicate that iodine is the second strongest ozone-depleting family throughout the global marine UT and in the tropical MBL. We suggest that (i) iodine sources and its chemistry need to be included in global tropospheric chemistry models, (ii) experimental programs designed to quantify the iodine budget in the troposphere should include a strategy for the measurement of atomic I, and (iii) laboratory programs are needed to characterize the photochemistry of higher iodine oxides to determine their atmospheric fate since they can potentially dominate halogen-catalysed ozone destruction in the troposphere.