Department of Chemistry and Environmental Research Institute, University College Cork, Cork, Ireland.
Environ Sci Technol. 2012 Oct 2;46(19):10413-21. doi: 10.1021/es204534v. Epub 2012 Aug 30.
Tidally exposed macroalgae emit large amounts of I(2) and iodocarbons that produce hotspots of iodine chemistry and intense particle nucleation events in the coastal marine boundary layer. Current emission rates are poorly characterized, however, with reported emission rates varying by 3 orders of magnitude. In this study, I(2) emissions from 25 Laminaria digitata samples were investigated in a simulation chamber using incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS). The chamber design allowed gradual extraction of seawater to simulate tidal emersion of algae. Samples were exposed to air with or without O(3) and to varying irradiances. Emission of I(2) occurred in four distinct stages: (1) moderate emissions from partially submerged samples; (2) a strong release by fully emerged samples; (3) slowing or stopping of I(2) release; and (4) later pulses of I(2) evident in some samples. Emission rates were highly variable and ranged from 7 to 616 pmol min(-1) gFW(-1) in ozone-free air, with a median value of 55 pmol min(-1) gFW(-1) for 20 samples.
潮汐暴露的大型藻类会大量排放 I(2) 和碘碳化合物，从而在沿海海洋边界层中产生碘化学和强烈的颗粒成核热点。然而，目前的排放率特征描述很差，报告的排放率相差 3 个数量级。在这项研究中，使用非相干宽带腔增强吸收光谱法（IBBCEAS）在模拟室中研究了 25 个裙带菜样本的 I(2)排放。该腔室设计允许逐步提取海水，以模拟藻类的潮汐暴露。样品暴露在有氧或无氧以及不同辐照度的环境中。I(2)的排放分为四个不同阶段：(1)部分浸没样品的适度排放；(2)完全暴露的样品的强烈释放；(3)I(2)释放的减缓或停止；以及 (4)在一些样品中明显的后期 I(2)脉冲。排放率高度可变，范围从 7 到 616 pmol min(-1) gFW(-1)，在 20 个样本中，中位数为 55 pmol min(-1) gFW(-1)。
