1. Introduction
一、简介

In the lower atmosphere, iodine is involved in catalytic ozone destruction cycles and particle formation reactions that impact upon both the oxidising capacity of the atmosphere and the Earth's radiative balance.^1–7 Tropospheric ozone is a greenhouse gas and is harmful to both human health and vegetation, including food crops. As a key oxidant, ozone is also involved in reaction cycles that remove hydrocarbons from the troposphere. A detailed understanding of the controls on tropospheric ozone levels is thus a major goal in atmospheric chemistry. Atmospheric iodine chemistry also has potential to perturb the balance of other important species such as peroxy radicals and nitrogen oxides,^6,8 and may enhance rates of mercury oxidation and deposition at high latitudes.⁸ A key species in these chemical cycles is the iodine oxide (IO) radical, which may also be involved in particle nucleation events where levels are sufficiently high.^7,9–12 The particles formed in such events have potential to act as cloud condensation nuclei, and so can indirectly affect climate via impacts on the radiative properties of clouds. Iodine is also an essential nutrient for humans and many other animals, deficiency of which is the leading cause of preventable brain damage in children.¹³ Sea-to-air transfer, followed by atmospheric transport and deposition onto land, is an important pathway by which iodine can enter the human food chain. It is also a route by which radionuclides of iodine discharged (intentionally or accidentally) to the oceans from nuclear facilities may be returned to the terrestrial environment.
在低层大气中，碘参与催化臭氧破坏循环和颗粒形成反应，影响大气的氧化能力和地球的辐射平衡。 ^1-7对流层臭氧是一种温室气体，对人类健康和包括粮食作物在内的植被有害。作为一种关键的氧化剂，臭氧还参与从对流层去除碳氢化合物的反应循环。因此，详细了解对流层臭氧水平的控制是大气化学的一个主要目标。大气中的碘化学也有可能扰乱其他重要物质的平衡，例如过氧自由基和氮氧化物^6,8 ，并可能提高高纬度地区汞的氧化和沉积速率。 ⁸这些化学循环中的一个关键物质是氧化碘 (IO) 自由基，当水平足够高时，它也可能参与粒子成核事件。 ^7,9–12在此类事件中形成的粒子有可能充当云凝结核，因此可以通过影响云的辐射特性来间接影响气候。碘也是人类和许多其他动物的必需营养素，缺乏碘是导致儿童可预防的脑损伤的主要原因。 ¹³海空转移，然后是大气运输和沉​​积到陆地上，是碘进入人类食物链的重要途径。这也是从核设施（有意或无意）排放到海洋的碘放射性核素可能返回陆地环境的一条途径。

The oceans are the largest reservoir of iodine after the Earth's crust, containing a total of around 7.93 × 10¹⁰ tonnes.¹⁴ In seawater, the majority of iodine is found as one of two dissolved inorganic ions – iodide (I⁻) and iodate (IO₃⁻).¹⁵ The total amount of inorganic iodine (the sum of iodide and iodate) is close to constant across the oceans at ∼450 to 500 nM,^15–17 but the ratio of iodide to iodate varies with both geographical location and depth (see Section 3).
海洋是继地壳之后最大的碘储库，总储量约为 7.93 × 10 ¹⁰吨。 ¹⁴在海水中，大部分碘以两种溶解的无机离子之一的形式存在——碘化物 (I ⁻ ) 和碘酸根 (IO ₃ ⁻ )。 ¹⁵整个海洋中无机碘的总量（碘化物和碘酸盐的总和）接近恒定，约为 450 至 500 nM， ^15-17，但碘化物与碘酸盐的比例随地理位置和深度的不同而变化（见第 3 节） ）。

Sea-to-air exchange is the dominant source of iodine to the atmosphere^1,8 with an estimated global flux of the order of 10¹² g per year.^8,18 Until recently, fluxes of volatile organic iodine compounds (e.g. CH₃I, CH₂I₂) were thought to be the main source of iodine to the marine atmosphere (e.g.ref. 1, 4 and 11). However, it has become evident that known sources of organoiodines cannot sustain the observed concentrations of gas-phase iodine oxide,^6,19–22 and consequently there has been a resurgence of interest in the reactions of inorganic iodine compounds at the sea surface.
海空交换是大气中碘^1,8的主要来源，估计全球每年的碘通量约为 10 ¹²克。 ^8,18直到最近，挥发性有机碘化合物（例如CH ₃ I、CH ₂ I ₂ ）通量还被认为是海洋大气中碘的主要来源（例如参考文献1、4 和11 ）。然而，很明显，已知的有机碘来源无法维持观察到的气相氧化碘^6,19-22的浓度，因此人们对海面无机碘化合物的反应重新产生了兴趣。

At the air–sea interface, dissolved iodide (I⁻) reacts with gas phase ozone to liberate molecular iodine via reactions (R1) and (R2) below:^18,23,24
在海气界面，溶解的碘化物 (I ⁻ ) 与气相臭氧发生反应，通过以下反应(R1)和(R2)释放分子碘： ^18,23,24 I⁻ + O₃ + H⁺ → HOI + O₂
I ⁻ + O ₃ + H ⁺ → HOI + O ₂ (R1) HOI + I⁻ + H⁺ → I₂ + H₂O
HOI + I ⁻ + H ⁺ → I ₂ + H ₂ O (R2)

Reaction (R1) is one of a number of processes known to destroy ozone in the surface ocean,²⁵ which together are thought to be responsible for the observed atmospheric ozone deposition velocity to the oceans being 40 times greater than that predicted from physical dissolution alone.²⁶ Deposition to the sea surface is a significant ozone sink, accounting for around one third of total global ozone dry deposition flux (600–1000 Tg O₃ per year).²⁷ Estimates of the contribution of reaction (R1) to the chemical enhancement of ozone deposition range from 20%²⁸ to almost 100%.²⁵
反应(R1)是已知会破坏海洋表层臭氧的众多过程之一， ²⁵人们认为这些过程共同导致观测到的大气臭氧沉积到海洋的速度比仅通过物理溶解预测的速度快 40 倍。 ²⁶海面沉积是一个重要的臭氧汇，约占全球臭氧干沉积通量总量的三分之一（每年 600-1000 Tg O ₃ ）。 ²⁷反应(R1)对臭氧沉积化学增强的贡献估计范围从 20% ²⁸到几乎 100%。 ²⁵

The reactive iodine (HOI and I₂) released to the atmosphere as a result of reactions (R1) and (R2) is photolysed to yield iodine atoms, which in turn react with ozone in the gas phase to form iodine oxide.^1,8 This gas phase chemistry represents a catalytic loss pathway for tropospheric ozone. Carpenter et al.²⁹ recently demonstrated that reactions (R1) and (R2) could explain around 75% of the iodine oxide levels measured over the tropical Atlantic. Inclusion of these reactions in atmospheric chemistry models has subsequently yielded good agreement between observed levels of molecular iodine and iodine oxide at Cape Verde,²⁰ and reasonable agreement between modelled and observed iodine oxide levels over the eastern Pacific.³⁰
由于反应(R1)和(R2)而释放到大气中的活性碘(HOI和I ₂ )被光解产生碘原子，碘原子又与气相中的臭氧反应形成氧化碘。 ^1,8这种气相化学代表了对流层臭氧的催化损失途径。卡彭特等人。 ²⁹最近证明，反应(R1)和(R2)可以解释热带大西洋上空测量到的约 75% 的氧化碘水平。将这些反应纳入大气化学模型后，佛得角观测到的分子碘和氧化碘水平之间取得了良好的一致性， ²⁰东太平洋上空的模拟和观测到的氧化碘水平也取得了合理的一致性。 ³⁰

The strength of the reactive iodine source and the ozone deposition flux are related to sea surface iodide concentration,^24,29,31 so to estimate the significance of these processes requires an accurate representation of sea surface iodide concentrations. Iodide concentrations are not constant at the sea surface; observations in different locations vary by approximately one order of magnitude (see Section 3). Measurements of iodide are sparse compared to parameters such as salinity or nutrient concentrations, and aqueous iodine species cannot yet be detected by either remote sensing or easily automated methods. The scarcity of oceanic iodide measurements and need for a synthesis of iodine biogeochemistry relevant to the atmospheric chemistry community has been highlighted in a number of recent publications.^21,32 In the absence of comprehensive global and regional iodide data sets, sea surface iodide concentrations have instead been estimated as a function of more readily available oceanographic variables, specifically nitrate^27,32 and chlorophyll-a,^32,33 in the context of quantifying large-scale ozone deposition. Sea surface temperature has also been used as proxy for iodide concentration in order to estimate iodine emissions.³⁰
活性碘源的强度和臭氧沉降通量与海面碘化物浓度相关， ^24,29,31因此，要估计这些过程的重要性，需要准确表示海面碘化物浓度。海面的碘化物浓度并不恒定；不同地点的观测结果相差大约一个数量级（见第 3 节）。与盐度或营养物浓度等参数相比，碘化物的测量结果很少，并且还无法通过遥感或简单的自动化方法检测含水碘物质。最近的许多出版物都强调了海洋碘化物测量的稀缺性以及对与大气化学界相关的碘生物地球化学合成的需求。 ^21,32在缺乏全面的全球和区域碘化物数据集的情况下，海面碘化物浓度被估算为更容易获得的海洋学变量的函数，特别是硝酸盐^27,32和叶绿素-a, ^32,33量化大规模臭氧沉降。海面温度也被用作碘化物浓度的替代指标，以估算碘排放量。 ³⁰

Here we present a geographically extensive compilation of the available sea surface iodide measurements, including data from the literature, archived resources and new, previously unpublished data collected during five research cruises. To the best of our knowledge, this is the largest and most detailed compilation of seawater iodide measurements presented to date. We describe the large-scale distribution of iodine compounds in the surface ocean, with a focus on iodide concentrations at the sea-surface, as it is this that impacts directly on atmospheric chemistry. Relationships between iodide concentration and more easily available oceanographic variables (chlorophyll, nitrate, sea surface temperature, salinity, mixed layer depth) are evaluated as tools to predict iodide concentration.
在这里，我们提供了现有海面碘化物测量数据的地理范围广泛的汇编，包括来自文献、存档资源的数据以及在五次研究航行期间收集的新的、先前未发表的数据。据我们所知，这是迄今为止最大、最详细的海水碘化物测量数据汇编。我们描述了海洋表层碘化合物的大规模分布，重点关注海面的碘化物浓度，因为它直接影响大气化学。碘化物浓度与更容易获得的海洋变量（叶绿素、硝酸盐、海面温度、盐度、混合层深度）之间的关系被评估为预测碘化物浓度的工具。

2. Compilation of the iodide data set
2.碘化物数据集的编译

A large number of studies have examined the distribution of iodine compounds in the oceans over local, regional and basin wide scales. The results of these studies have been digitised where possible and supplemented by data kindly supplied directly by other investigators, data archives, and unpublished measurements made by the authors during five different field campaigns (see Table 1 for a list of data sets). Due to the small total number of measurements, the compiled data set has not been filtered according to season or time of day of sampling. The potential for temporal variation in dissolved iodine speciation is discussed in Section 3.2. A total of 925 surface data points collected from 44 sources have been collated into a single data set. The locations of data points included in the surface compilation are shown in Fig. 1.
大量研究调查了局部、区域和盆地范围内海洋中碘化合物的分布。这些研究的结果已尽可能数字化，并由其他研究人员直接提供的数据、数据档案以及作者在五次不同的实地活动中进行的未发表的测量数据进行补充（数据集列表见表 1 ）。由于测量总数较少，编制的数据集尚未根据季节或采样时间进行过滤。溶解碘形态随时间变化的可能性在 3.2 节中讨论。从 44 个来源收集的总共 925 个表面数据点已整理成一个数据集。表面编译中包含的数据点的位置如图1所示。

Surface is here defined as the upper 20 m of the water column. This depth was selected as a compromise between maximising the number of data points included and attempting to represent concentrations at the actual surface accurately. At the air–sea interface itself, it has been suggested that iodide concentration may be enhanced or depleted compared to the bulk surface seawater immediately below; this is discussed in Section 3.5. Iodide measurements made within a few millimetres of the ocean surface are extremely rare, so it was necessary to use bulk surface water measurements in this compilation. On ship-based campaigns, ‘surface’ water is usually collected from an underway pumped seawater inlet (typically at a depth of around 6 m on a 100 m length research ship), and/or sampling bottles mounted on a CTD rosette and closed within a few metres of the sea surface, but during some field campaigns (e.g. winter samples in the Antarctic⁷³), only data from 15 m depth was available. In most cases, the water column is thought to be sufficiently homogenous between 0 and 20 m that this choice of depth can be assumed to be representative of concentrations in the top few metres of the water column (see Section 3.4 for a description of the changes in iodine speciation with depth).
此处表面定义为水柱上部 20 m。选择该深度是为了最大化所包含的数据点数量和尝试准确表示实际表面的浓度之间的折衷。在空气-海洋界面本身，有人认为与紧邻下方的大量表层海水相比，碘化物浓度可能会增加或减少；这将在 3.5 节中讨论。在海洋表面几毫米内进行的碘化物测量极为罕见，因此在本次汇编中有必要使用大量地表水测量。在基于船的活动中，“地表”水通常从航行中泵送的海水入口（通常在 100 m 长的研究船上位于约 6 m 的深度）和/或安装在 CTD 花环上并封闭在内部的采样瓶收集。数米的海面，但在一些野外活动期间（例如南极洲的冬季样本⁷³ ），只能获得15 m 深度的数据。在大多数情况下，水柱被认为在 0 到 20 m 之间足够均匀，因此可以假设这种深度选择代表了水柱顶部几米的浓度（有关变化的描述，请参见第 3.4 节）碘形态与深度）。

A variety of different methods for the determination of iodine species in seawater have been reported in the literature. Details of the methods used in each study included in our compilation are summarised in Table 1. For all unpublished data included here, iodide was measured using cathodic stripping square wave voltammetry (CSSWV),^69,75 following protocols described in Chance et al., 2010.⁷³ Direct measurements of iodide are most commonly made by CSSWV, which is specific for the iodide ion. Other direct methods of iodide determination include ion chromatography,⁴⁹ capillary electrophoresis⁶³ and flow through electrodes.⁵⁵ Precision estimates for direct methods are 4–10% for CSSWV,^69,73,75 2% for ion chromatography,⁴⁹ 3% for capillary electrophoresis⁶³ and 5% for the flow through electrode method.⁵⁴ Other studies do not measure iodide directly, but infer it as the difference between total dissolved iodine and iodate concentrations, where these parameters have usually been determined by spectrophotometric^47,70 or polarographic^52,68 techniques. The precision of these methods is less than 5% for each species, and sometimes reported as better than 1%;^47,52,68,70 propagation of errors leads to an uncertainty of between <6% to ∼28% for an iodide concentration of 100 nM calculated by difference, and will increase as iodide concentration decreases. Depending on the analytical methods used, the difference approach may result in a small over-estimation of iodide, due to the presence of an unquantified organic iodine fraction with variable reactivity towards the total iodine method. In the open ocean, the dissolved organic iodine fraction is very small (less than 10%)^15,58,76 and only a portion of this may cause analytical interference, so this effect is negligible. However, in coastal waters where organic iodine may be high (40 to 80% e.g.ref. 76–79) it could become significant. Generally, the analytical uncertainties for the iodine species are small compared to the observed environmental gradients. In some campaigns included in our compilation (e.g. Truesdale et al., 2000 (ref. 70)), iodide concentrations were not reported, and so we have calculated them by difference, using total iodine and iodate concentrations taken from the relevant publication.
文献中报道了多种不同的测定海水中碘形态的方法。表 1总结了我们汇编中包含的每项研究中使用的方法的详细信息。对于此处包含的所有未发表的数据，碘化物是使用阴极溶出方波伏安法 (CSSWV) 测量的， ^69,75遵循 Chance等人中描述的方案。 ，2010。 ⁷³碘离子的直接测量最常见的是 CSSWV，它专门针对碘离子。其他直接测定碘化物的方法包括离子色谱法、 ⁴⁹毛细管电泳法⁶³和流过电极法。 ⁵⁵ CSSWV 直接法的精度估计为 4–10%，离子色谱法为^69,73,75 2%，毛细管电泳法为⁴⁹ 3% ⁶³ ，流通电极法为 5%。 ⁵⁴其他研究并不直接测量碘化物，而是将其推断为总溶解碘和碘酸盐浓度之间的差异，其中这些参数通常通过分光光度法^47,70或极谱法^52,68技术确定。对于每个物种，这些方法的精确度低于 5%，有时报告优于 1%； ^47,52,68,70对于通过差值计算的 100 nM 碘化物浓度，误差传播导致不确定度在 <6% 至 ∼28% 之间，并且随着碘化物浓度降低而增加。 根据所使用的分析方法，差异法可能会导致碘化物的估算略有高估，因为存在未定量的有机碘部分，其对总碘方法的反应性不同。在公海中，溶解的有机碘含量非常小（小于 10%） ^15,58,76 ，只有其中一部分可能会造成分析干扰，因此这种影响可以忽略不计。然而，在有机碘含量可能较高的沿海水域（40% 至 80% ，例如参考文献 76-79 ），其含量可能会变得很高。一般来说，与观察到的环境梯度相比，碘物质的分析不确定性很小。在我们的汇编中包含的一些活动中（例如Truesdale等人，2000年（参考文献70 ）），没有报告碘化物浓度，因此我们使用从相关出版物中获取的总碘和碘酸盐浓度通过差值计算它们。

3. The distribution of iodine compounds in seawater
3、海水中碘化合物的分布

3.1. Iodide and iodate concentrations at the sea surface
3.1.海面碘化物和碘酸盐浓度

The 925 surface iodide concentrations in our compilation are shown in Fig. 2A and 3, and the corresponding iodate concentrations are shown in Fig. 2B. Fig. 2 was produced using the DIVA interpolation function in the Ocean Data View software.⁸⁰ The estimated uncertainties for each iodide measurement are shown in Fig. S1 (in the ESI†). Observed iodide concentrations range from undetectable (limits of detection were not always reported, but are typically around 1 nM) to 700 nM, with a median value of 77 nM and interquartile range of 28 to 140 nM (Fig. 4). Although coverage of iodide measurements is sparse compared to parameters such as nutrients and pigments, sufficient data exists to be able to describe the large scale distribution, which shows a clear and systematic spatial gradient. In general, highest iodide concentrations (greater than 100 nM) are observed at low latitudes and lower iodide concentrations (less than 50 nM) at latitudes greater than about 40 degrees north or south (Fig. 2A and 3). Iodide concentrations were significantly correlated with absolute latitude (Tables 2 and 3). The increase in iodide concentrations with decreasing latitude is particularly pronounced between about 50° and 20°, while at tropical latitudes there is a slight indication of a levelling, or even a dip, in iodide concentrations moving toward the equator (Fig. 3). Iodate has an approximately opposite distribution to iodide (Fig. 2B), with highest levels typically observed at high latitudes. This large-scale latitudinal gradient in iodine speciation has been demonstrated during transects of the Atlantic^17,53 and Pacific.⁶⁷
我们编制的925个表面碘化物浓度如图2A和图3所示，相应的碘酸盐浓度如图2B所示。图2是使用Ocean Data View软件中的DIVA插值功能生成的。 ⁸⁰每个碘化物测量的估计不确定度如图 S1 所示（在 ESI †中）。观察到的碘化物浓度范围从不可检测（检测限并不总是报告，但通常在 1 nM 左右）到 700 nM，中值为 77 nM，四分位数范围为 28 至 140 nM（图 4 ）。尽管与营养素和色素等参数相比，碘化物测量的覆盖范围很稀疏，但存在足够的数据能够描述大规模分布，显示出清晰且系统的空间梯度。一般来说，在低纬度观察到最高的碘化物浓度（大于100nM），而在北纬或南纬大于约40度的地区观察到较低的碘化物浓度（小于50nM）（图2A和3 ）。碘化物浓度与绝对纬度显着相关（表2和表3 ）。随着纬度的降低，碘化物浓度的增加在大约 50° 至 20° 之间尤其明显，而在热带纬度，有轻微迹象表明碘化物浓度向赤道移动趋于平稳，甚至下降（图 3 ）。碘酸盐的分布与碘化物大致相反（图2B ），通常在高纬度地区观察到最高水平。 这种大规模的碘形态纬度梯度已在大西洋^17,53和太平洋的横断面中得到证实。⁶⁷

A number of studies have observed a decrease in the proportion of dissolved inorganic iodine present as iodate as the coast is approached,^46,47,52 and it has been suggested that reduction of iodate to iodide may be particularly effective in coastal waters.^50,51,81 We note that the highest iodide concentrations in our compilation often occur near coastlines (Fig. 2). In order to separate the effects of latitude and coastal proximity on iodide distribution, the data set was sub-divided into coastal and open ocean regions, where coastal data points were defined as those falling into coastal biogeochemical provinces,⁸² plus Bermuda inshore waters which fall within an open ocean province (NAST-W) but are on the Bermuda platform.⁴⁷ Exceptions to the latitudinal trend in iodide concentrations occur almost exclusively in coastal waters (Fig. 3). For a given latitude, iodide concentrations appear to have higher variability in coastal waters compared to the open ocean (Fig. 3). This may in part reflect a sampling bias, in that coastal waters may have been sampled at more different times of year (including time series studies) than open ocean locations, which may have only been visited during a single research cruise. Considering all latitudes, there is a modest difference in the spread of data between the open ocean and coastal sub-sets. Coastal waters have a larger range than open ocean waters, but this is due to the occurrence of a very high outlier with an iodide concentration of 700 nM (Fig. 4A). This sample was collected in the Skaggerrak, and had a salinity of 27.7,³⁵ so may be reasonably considered an unusual case. Excluding outliers, the range of coastal samples is 53 nM greater than the open ocean samples and the interquartile range is 20 nM greater (Fig. 4A).
许多研究观察到，随着靠近海岸，以碘酸盐形式存在的溶解无机碘的比例下降， ^46,47,52 ，并且有人建议，将碘酸盐还原为碘化物在沿海水域可能特别有效。 ^50,51,81我们注意到，我们编制的碘化物浓度最高的区域通常出现在海岸线附近（图 2 ）。为了区分纬度和沿海距离对碘化物分布的影响，数据集被细分为沿海和公海区域，其中沿海数据点被定义为属于沿海生物地球化学省的数据点， ⁸²加上百慕大近海水域的数据点。位于开放海洋省（NAST-W）内，但位于百慕大平台上。 ⁴⁷碘化物浓度纬度趋势的例外情况几乎全部发生在沿海水域（图 3 ）。对于给定的纬度，与公海相比，沿海水域的碘化物浓度似乎具有更高的变异性（图3 ）。这可能部分反映了采样偏差，因为与公海地点相比，沿海水域可能在一年中更多的不同时间（包括时间序列研究）进行了采样，而公海地点可能仅在一次研究巡航期间进行了访问。考虑到所有纬度，公海和沿海子集之间的数据分布存在适度差异。沿海水域的范围比公海水域更大，但这是由于出现了碘化物浓度为 700 nM 的非常高的异常值（图 4A ）。该样本是在 Skaggerrak 采集的，盐度为 27。7, ³⁵因此可以合理地视为异常情况。排除异常值，沿海样本的范围比公海样本大53 nM，四分位距大20 nM（图4A ）。

Further sub-division of the open ocean data-set into arbitrary latitudinal bands (0–23.4°; 23.5–35.5°, 36–60° and >60° north or south) also demonstrates the trend for decreasing iodide concentration with increasing latitude (Fig. 4B), although there is overlap between the range of the data, particularly at low latitudes. Interestingly, iodide concentrations at the highest latitudes (>60°) appear to be a little higher than those in more temperate regions (35–60°) with median values of 33 and 18 nM respectively (Fig. 4B).
将公海数据集进一步细分为任意纬度带（0–23.4°；23.5–35.5°、36–60°和>60°北或南）也表明碘化物浓度随着纬度增加而降低的趋势（图 4B ），尽管数据范围之间存在重叠，特别是在低纬度地区。有趣的是，最高纬度（>60°）的碘化物浓度似乎略高于温带地区（35-60°）的碘化物浓度，中值分别为33和18 nM（图4B ）。

3.2. Changes in iodine speciation with time
3.2.碘形态随时间的变化

3.2.1. Rates of iodine redox transformations in seawater
3.2.1.海水中碘氧化还原转化率

The time scales for changes in dissolved iodine speciation in the surface ocean are quite poorly constrained. This is in part due to the scarcity of time series studies, and the need to account for external forcing such as advection and vertical mixing, as well as in situ rates of change in a parcel of water. In general, the reduction of iodate to iodide is considered to occur more rapidly than the reverse reaction.¹⁵Net rates of iodide accumulation (and iodate depletion) of 0.27 to 0.55 nM per day have been observed in the surface ocean over 78 days,⁷³ but other studies have found no discernible net change over similar time periods.³⁷ Under low oxygen conditions, much faster rates have been observed (∼50 nM h⁻¹;⁸³), but these are not relevant to surface open ocean conditions. The oxidation of iodide to iodate in oxygenated seawater is slow;^15,84 this kinetic barrier allows iodide to persist alongside iodate in the surface ocean, despite it being thermodynamically less stable,⁸⁵ and hence it is termed metastable. Estimates of the oceanic lifetime of iodide with respect to oxidation range from 40 years (∼4 nM per year)⁶¹ to six months or less (with rates of 300 nM per year;⁸⁶ 270–560 nM per year;⁴¹ and 670 nM per year;⁸⁷ reported). These latter oxidation rates are too fast to be explained by suggested abiotic pathways,^15,84,88,89 so a biologically mediated route may need to be invoked, for example it has recently been suggested that iodide oxidation is associated with nitrification processes.⁸⁷ Rates of change must be considered when searching for a suitable proxy for iodide concentration – a proxy which changes on an hourly or daily basis is likely to vary too rapidly to reflect significant changes in iodide concentration, while those that vary on a seasonal timescale may be more appropriate, since iodide production and loss processes appear to operate over timescales of weeks to months.
表层海洋中溶解的碘形态变化的时间尺度受到的限制非常少。这部分是由于时间序列研究的缺乏，以及需要考虑平流和垂直混合等外部强迫，以及一块水的原位变化率。一般来说，碘酸盐还原成碘化物被认为比逆反应发生得更快。 ¹⁵在 78 天的时间里，在表层海洋中观察到每天 0.27 至 0.55 nM 的碘化物累积（和碘酸盐消耗）净速率， ⁷³但其他研究发现在相似的时间段内没有明显的净变化。 ³⁷在低氧条件下，观察到更快的速率（∼50 nM h ^-1 ; ⁸³ ），但这些与表面开放海洋条件无关。碘化物在含氧海水中氧化成碘酸盐的速度很慢； ^15,84这种动力势垒允许碘化物与碘酸盐一起存在于海洋表层，尽管它在热力学上不太稳定， ⁸⁵因此被称为亚稳态。碘化物在海洋中的氧化寿命估计范围为 40 年（每年约 4 nM） ⁶¹至 6 个月或更短（每年 300 nM；每年⁸⁶ 270–560 nM；每年⁴¹和 670 nM）。年； ⁸⁷报道）。 后者的氧化速率太快，无法通过建议的非生物途径来解释， ^15,84,88,89因此可能需要调用生物介导的途径，例如最近有人提出碘化物氧化与硝化过程相关。 ⁸⁷在寻找合适的碘化物浓度替代值时，必须考虑变化率——每小时或每天变化的替代值可能变化太快，无法反映碘化物浓度的显着变化，而那些随季节时间尺度变化的替代值可能会变化。更合适，因为碘化物的生产和损失过程似乎需要数周至数月的时间尺度。

3.2.2. Seasonal variation
3.2.2.季节变化

The surface ocean is subject to seasonal cycles in mixing and biological production, which can in turn cause seasonal changes in concentrations of biogeochemically active chemical species.⁹⁰ Very generally, vertical mixing of the water column tends to be deeper in winter, while in summer stratification causes isolation of a surface layer. In spring, increasing light levels and the onset of stratification drive an increase in phytoplankton growth (the ‘spring bloom’), which consumes nutrients and may be associated with an increase in levels of biogenic compounds. Stratification prevents the resupply of nutrients by upward mixing, so eventually nutrients in the surface ocean may become exhausted, causing a decline in phytoplankton growth in the summer.
表层海洋受到混合和生物生产的季节性循环的影响，这反过来又会导致生物地球化学活性化学物质浓度的季节性变化。 ⁹⁰一般来说，冬季水柱的垂直混合往往更深，而夏季分层会导致表层隔离。在春季，光照水平的增加和分层的开始会促进浮游植物的生长（“春季水华”），从而消耗营养，并可能与生物化合物水平的增加有关。分层阻止了通过向上混合来补充营养物质，因此最终海洋表层的营养物质可能会耗尽，导致夏季浮游植物生长下降。

There is evidence both for and against a seasonal cycle in surface iodide (and iodate) concentrations. The spikes in iodide concentrations at 23°N, 32°N, 43°N and 67°S (Fig. 3) are the result of temporal variations observed during time series studies at stations in the tropical Pacific,⁴¹ the Atlantic,^41,47 the Mediterranean^43,44 and the western Antarctic peninsula,⁷³ respectively. Where these changes follow a discernible seasonal cycle, surface iodide concentrations increase (and iodate concentrations decrease) over periods of stratification in summer, while minimum iodide (and maximum iodate) concentrations are observed during winter when vertical mixing is greatest.^43,47,73 Changes in iodine speciation have not necessarily been in step with primary productivity,⁴⁷ but have sometimes indicated a loss of iodate associated with the onset of phytoplankton growth in spring, and a concurrent or delayed increase in iodide concentration.^41,51,73 Meanwhile, other studies have not found any evidence for seasonal changes in iodine speciation.^35,38,46,70
有证据支持和反对表面碘化物（和碘酸盐）浓度的季节性周期。 23°N、32°N、43°N 和 67°S 处的碘化物浓度峰值（图 3 ）是热带太平洋、 ⁴¹大西洋、 ^{41、 47}地中海^43，44和南极半岛西部分别⁷³ 。在这些变化遵循明显的季节周期的情况下，表面碘化物浓度在夏季分层期间增加（而碘酸盐浓度降低），而在垂直混合最大的冬季观察到最低碘化物（和最大碘酸盐）浓度。 ^43,47,73碘形态的变化不一定与初级生产力同步， ⁴⁷但有时表明与春季浮游植物生长开始相关的碘酸盐损失，以及碘化物浓度的同时或延迟增加。 ^41,51,73同时，其他研究尚未发现碘形态季节性变化的任何证据。 ^35,38,46,70

Given the possibility of seasonal variation in iodine speciation, it would be desirable to create a climatology that is filtered by season; unfortunately, insufficient data is available to attempt this at present and the possibility of seasonal iodide variations should be considered as a source of uncertainty when modelling iodine chemistry at the sea surface. Note that the amplitudes of any unaccounted for seasonal variations in iodide concentration in the data compilation are not sufficient to mask the spatial patterns in iodide distribution described in Section 3.1, and the same general trends remain even when the data is divided by season (see Fig. S2a–d in the ESI†). Furthermore, at the time series stations noted above, seasonal maxima and minima are lower at higher latitudes (Fig. 3).
考虑到碘形态存在季节性变化的可能性，建立按季节过滤的气候学是可取的；不幸的是，目前没有足够的数据来尝试这一点，并且在对海面的碘化学进行建模时，应将季节性碘化物变化的可能性视为不确定性的来源。请注意，数据汇编中任何未考虑的碘化物浓度季节性变化的幅度不足以掩盖第 3.1 节中描述的碘化物分布的空间模式，即使数据按季节划分，相同的总体趋势仍然存在（见图 1）。 ESI 中的 S2a–d † )。此外，在上述时间序列站中，季节最大值和最小值在高纬度地区较低（图3 ）。

3.2.3. Diel variation
3.2.3.昼夜变化

As the measurements collated in our iodide data set were taken at many different times of day and night, and we have not attempted to filter the data set according to time of day of sampling, it is pertinent to consider whether iodine speciation in the surface ocean exhibits any diel variation. Though most incubation experiments and time-series measurements report rates of change too low to be detectable on a timescale of hours at typical marine chlorophyll-a levels,^{37,41,73,91–93} consistent with an absence of diel cycling, these rates are based on net changes in iodine speciation observed over timescales of a day or more. A slow net rate of change does not preclude the occurrence of diel cycling in these studies, because the net rates reflect the balance of iodide production and/or loss processes, either or both of which may exhibit a diel cycle. As any such cycles are unlikely to be synchronous, it is possible that daily fluctuations in iodide concentration may occur which are larger than the net change observed over a 24 period or multiple thereof.
由于我们的碘化物数据集中整理的测量值是在白天和晚上的许多不同时间进行的，并且我们没有尝试根据一天中的采样时间过滤数据集，因此有必要考虑表面海洋中的碘形态是否存在表现出任何昼夜变化。尽管大多数孵化实验和时间序列测量报告的变化率太低，无法在典型海洋叶绿素-a 水平^{（37,41,73,91–93）}的小时时间尺度上检测到，与昼夜循环的缺失一致，但这些速率基于一天或更长时间内观察到的碘形态的净变化。在这些研究中，缓慢的净变化率并不排除昼夜循环的发生，因为净速率反映了碘化物产生和/或损失过程的平衡，其中一个或两个可能表现出昼夜循环。由于任何此类循环不太可能同步，因此碘化物浓度的每日波动可能会大于 24 个周期或其倍数内观察到的净变化。

In order to investigate the possibility of a diel cycle in iodine speciation, we conducted Lagrangian sampling of surface seawater over 24 hours at three sites in the tropical east Atlantic. The samples were collected during cruise D325 of the RRS Discovery.⁹⁴ Iodide and iodate concentrations were found to be effectively constant over time (Fig. 5), suggesting iodine species do not undergo diel cycling in the oxygenated surface ocean. This supports our assumption that sampling time does not have a significant effect on iodine speciation. To the best of our knowledge, only three other studies have examined diel variation in iodine speciation specifically, though none under conditions directly relevant to the oxygenated surface ocean. Brandão et al.⁹⁵ reported diurnal changes in iodide and iodate concentrations in nutrient enriched unfiltered seawater incubated under natural light, but not in filtered seawater. The most striking change was an increase in iodide concentration associated with decreasing pH and oxygen levels, during night-time periods of net respiration. The high net primary productivity reported for these experiments (50 to 280 mg C m⁻³ h⁻¹) suggest that phytoplankton density and/or growth rates in the experimental vessel (an 11 L glass vat) were very much greater than in the ocean. Beck and Bruland⁸³ observed diel variations in a shallow (∼1.5 m maximum depth) tidal pool; as noted above, iodate was rapidly converted to iodide following the onset of sub-oxic conditions while the pool was isolated, while tidal flushing replenished the pool with higher iodate/lower iodide waters. Similar factors are likely to be the cause of changes in iodide and iodate concentration observed over periods of hours at a shallow, estuarine site.⁹⁶ While further research is required to confirm whether or not iodine species undergo diel cycles in the surface ocean, the available evidence suggests it is unlikely to be important.
为了研究碘形态中昼夜循环的可能性，我们在热带东大西洋的三个地点对表层海水进行了 24 小时的拉格朗日采样。这些样本是在 RRS Discovery 的 D325 巡航期间采集的。 ⁹⁴碘化物和碘酸盐浓度被发现随着时间的推移实际上保持恒定（图 5 ），这表明碘物质在含氧的表层海洋中不会经历昼夜循环。这支持了我们的假设，即采样时间对碘形态没有显着影响。据我们所知，只有另外三项研究专门研究了碘形态的昼夜变化，尽管没有一项研究是在与氧化表面海洋直接相关的条件下进行的。布兰达奥等人。 ⁹⁵报告了自然光下培养的营养丰富的未过滤海水中碘化物和碘酸盐浓度的日变化，但过滤海水中没有变化。最显着的变化是在夜间净呼吸期间，与 pH 值和氧气水平降低相关的碘化物浓度增加。这些实验报告的高净初级生产力（50 至 280 mg C m ⁻³ h ⁻¹ ）表明实验容器（11 L 玻璃桶）中的浮游植物密度和/或生长速率比海洋中的要大得多。 Beck 和 Bruland ⁸³观察到浅层（最大深度约 1.5 m）潮汐池中的昼夜变化；如上所述，在低氧条件出现后，当水池被隔离时，碘酸盐迅速转化为碘化物，而潮汐冲洗则用较高碘酸盐/较低碘化物的水补充水池。 类似的因素可能是在浅海河口地点数小时内观察到的碘化物和碘酸盐浓度变化的原因。 ⁹⁶虽然需要进一步研究来确认碘物质是否在表层海洋中经历昼夜循环，但现有证据表明这不太重要。

In addition to processes associated with photosynthesis, photochemistry is a potential driver of diel variation. The evidence for a photochemical influence on iodine speciation in seawater is mixed. Some incubations of cell-free seawater under natural sunlight have shown detectable increases in iodide concentration over periods of hours^34,97 but others have not,⁹⁵ and the amount and nature of organic matter present appears to be an important factor.^95,97,98 Spokes and Liss⁹⁷ demonstrated that exposure of seawater to natural light caused an increase in iodide concentration, provided that organic matter was present. Photochemical reduction of iodate to dissolved organic iodine and iodide in the presence of humic acids and has also been demonstrated in salt-water solutions, using a light field replicating the UV-visible solar spectrum.⁹⁹ Conversely, Brandão et al.⁹⁵ found iodate to be reduced by UV light at 254 nm, but not natural light, and further, that the UV photo-reduction was inhibited by the presence of organic matter. As iodate absorbs little light above 280 nm¹⁰⁰ and a delay in the onset of iodide production has been observed in some experiments,⁹⁷ an indirect mechanism of iodate photoreduction has been suggested, whereby dissolved organic iodine compounds are formed from iodate and organic matter, which are then photolysed to yield iodide.^97,99 The iodine species reacting with the organic matter could be HOI or I₂, which may be formed by the reduction of iodate with solvated electrons generated from the irradiation of organic chromophores.⁹⁹ The photolysis of organic iodine compounds to yield iodide has been demonstrated.^78,101,102 In addition to photoreduction of iodate, there is also some evidence to suggest that iodide may also undergo photo-oxidation, particularly at low wavelengths.^89,98 However, it is thought that the rate of iodide photo-oxidation in natural seawater is too slow to have a significant impact on dissolved iodine speciation.⁸⁹ While it is evident that photochemical reactions can alter dissolved iodine speciation, and in particular may cause the reduction of iodate to iodide in the presence of organics, it is not clear whether or not these reactions are significant in the surface ocean. The absence of observable diel variation in the tropical Atlantic (Fig. 5), where the light–dark cycle is pronounced, suggests that photochemical reactions do not cause significant changes in iodine speciation on a daily timescale. Over longer periods, net rates of photochemical iodide production may be sufficient to make a significant contribution to net rates of iodide accumulation.³⁴ The combined influence of light and organic matter on sea surface iodide concentrations requires further investigation.
除了与光合作用相关的过程之外，光化学也是昼夜变化的潜在驱动因素。光化学对海水中碘形态影响的证据是混杂的。一些无细胞海水在自然阳光下的培养显示出在几个小时内碘化物浓度可检测到的增加^34,97但其他的则没有， ⁹⁵并且存在的有机物的数量和性质似乎是一个重要因素。 ^95,97,98 Spokes 和 Liss ⁹⁷证明，如果存在有机物，海水暴露在自然光下会导致碘化物浓度增加。在腐殖酸存在下，碘酸盐光化学还原为溶解的有机碘和碘化物，并且使用复制紫外-可见太阳光谱的光场在盐水溶液中也得到了证明。 ⁹⁹相反，Brandão等人。 ⁹⁵发现碘酸盐会被 254 nm 的紫外光还原，但不会被自然光还原，而且，有机物的存在会抑制紫外光还原。由于碘酸盐几乎不吸收 280 nm 以上的光^100，并且在一些实验中观察到碘化物产生延迟， ⁹⁷有人提出了碘酸盐光还原的间接机制，即由碘酸盐和有机物形成溶解的有机碘化合物，这然后光解产生碘化物。^97,99与有机物反应的碘物质可能是 HOI 或 I ₂ ，它们可能是通过有机发色团照射产生的溶剂化电子还原碘酸盐而形成的。 ⁹⁹有机碘化合物光解产生碘化物已得到证实。 ^78,101,102除了碘酸盐的光还原之外，还有一些证据表明碘化物也可能发生光氧化，特别是在低波长下。 ^89,98然而，人们认为天然海水中碘化物光氧化速率太慢，无法对溶解的碘形态产生重大影响。 ⁸⁹虽然光化学反应显然可以改变溶解的碘形态，特别是在有机物存在的情况下可能导致碘酸盐还原为碘化物，但尚不清楚这些反应在表层海洋中是否重要。光暗循环明显的热带大西洋地区没有可观察到的昼夜变化（图5 ），这表明光化学反应不会在每日时间尺度上引起碘形态的显着变化。在较长时期内，光化学碘化物产生的净速率可能足以对碘化物积累的净速率做出重大贡献。 ³⁴光和有机物对海面碘化物浓度的综合影响需要进一步研究。

3.3. Changes in iodine speciation with depth
3.3.碘形态随深度的变化

This work is concerned with iodine speciation at the sea surface, as it is here that iodide is involved in sea–air exchange processes. However, it should be noted that iodine speciation also varies with depth. Typical depth profiles for oxygenated waters at high and low latitudes are shown in Fig. 6. In surface waters up to half of the iodine present may be found as iodide, while below the ocean mixed layer iodate dominates regardless of location, with only a few nM or less of iodide detectable. At the pH and pE of oxygenated seawater (8.1 and 12.5 respectively), iodate is predicted to be the thermodynamically stable form (based on an equilibrium constant for the interconversion of iodide and iodate of log K = 110.1).^39,85,103 While the preponderance of iodate in deep waters is in accordance with these simple thermodynamic predictions, the surface ocean appears to be in thermodynamic disequilibrium with respect to iodine speciation. This disequilibrium is assumed to be due to biological processes,¹⁵ and is a key feature of the biogeochemical cycling of marine iodine. As exemplified in Fig. 6A, the depth to which the iodide maximum/iodate minimum persists tends to loosely follow the depth of the thermocline.^43,47,49 Under certain conditions, iodide profiles also display sub-surface maxima, which are related to anoxic³⁹ or sub-oxic conditions⁵⁶ or remineralisation processes occurring at depth.^34,64
这项工作涉及海面的碘形态，因为碘化物正是在这里参与海气交换过程。然而，应该指出的是，碘形态也随深度而变化。高纬度和低纬度含氧水域的典型深度剖面如图6所示。在地表水中，多达一半的碘可能以碘化物的形式存在，而在海洋以下，无论位置如何，混合层碘酸盐均占主导地位，仅可检测到几纳摩尔或更少的碘化物。在含氧海水的 pH 值和 pE 值（分别为 8.1 和 12.5）下，碘酸盐预计为热力学稳定形式（基于碘化物和碘酸盐相互转化的平衡常数 log K = 110.1）。 ^39,85,103虽然深水中碘酸盐的优势符合这些简单的热力学预测，但表层海洋在碘形态方面似乎处于热力学不平衡状态。这种不平衡被认为是由于生物过程造成的， ¹⁵并且是海洋碘生物地球化学循环的一个关键特征。如图6A所示，碘化物最大值/碘酸盐最小值持续的深度往往松散地遵循温跃层的深度。 ^43,47,49在某些条件下，碘化物分布还显示地下最大值，这与缺氧³⁹或缺氧条件⁵⁶或发生在深度的再矿化过程有关。 ^34,64

3.4. Iodine speciation in the air–sea interface
3.4.海气界面中的碘形态

When considering air–sea exchange processes, knowing the concentration of reactants at the interface is key, as these are not necessarily the same as in the bulk. This in turn requires consideration of the length scales over which the air–sea interface is defined. In the kinetic model of Carpenter et al.,²⁹ an interfacial layer of a few μm is defined by the reacto-diffusive length over which the ozone–iodide reaction occurs. The thickness of this layer depends on the iodide concentration, for a typical bulk iodide concentration of 100 nM it is 2.6 μm. Within this layer, iodide ions may be enhanced in the immediate vicinity (∼1 nm) of the sea surface.^104,105 Such enhancement is a consequence of the polarisable nature of iodide ions, and has been observed in laboratory studies of salt solutions as well as being predicted in theoretical simulations.^104,105 The partitioning of iodide to the surface can be described as a function of the bulk iodide concentration using the Langmuir isotherm.¹⁰⁶
在考虑空气-海洋交换过程时，了解界面处反应物的浓度是关键，因为这些浓度不一定与本体中的反应物浓度相同。这反过来又需要考虑定义海气界面的长度尺度。在 Carpenter等人的动力学模型中。 , ²⁹几微米的界面层由发生臭氧-碘化物反应的反应扩散长度定义。该层的厚度取决于碘化物浓度，对于 100 nM 的典型碘化物浓度，其厚度为 2.6 μm。在该层内，碘离子可能在海面附近（~1 nm）处增强。 ^104,105这种增强是碘离子的极化性质的结果，并且已在盐溶液的实验室研究中观察到，并在理论模拟中进行了预测。 ^104,105碘化物在表面的分配可以使用 Langmuir 等温线描述为总体碘化物浓度的函数。 ¹⁰⁶

For an interfacial layer of only a few μm, the ‘bulk’ seawater below may be more accurately represented by that in the sea surface micro layer (SML) than surface water at a few metres depth. The SML is a layer of water tens to hundreds of μm thick at the ocean surface, in which many physical, chemical and biological properties are distinctly different to those of the bulk seawater immediately below.¹⁰⁷ Sampling the SML necessarily imposes an operational definition of microlayer thickness, which is dependent on the collection method chosen, and there is still debate as to the ‘true’ thickness of the microlayer.¹⁰⁸ Only one study of inorganic iodine speciation in the SML is described in the literature.¹⁰⁹ Measurements of total dissolved iodine, iodate and iodide (by difference) suggested that none of these species is enriched or depleted in SML samples (∼300 μm) relative to sub-surface water.¹⁰⁹ Unpublished measurements made near Bermuda also found no significant enhancement or depletion of iodide in microlayer samples compared to water collected 1 m below the sea surface (L. Campos, pers. commun.). Conversely, surface foams from marine lakes have been found to be enriched in organic iodine compounds, leading to the suggestion that organic forms of iodine might be enriched in the microlayer.¹¹⁰ It has also been suggested that iodide might be depleted in the SML.³² This idea was proposed to explain why modelled ozone deposition velocities were in better agreement with observations when iodide concentrations approximately one order of magnitude lower than typical oceanic levels were used,³² but is not supported by observations.¹⁰⁹ In summary, the available evidence suggests that iodide concentrations in the SML are similar to those in the bulk seawater below, but more measurements of iodine speciation in the SML are needed to confirm whether enrichment or depletion occurs in this important reaction zone.
对于只有几微米的界面层，海面微层（SML）中的海水可能比几米深度的地表水更准确地代表下面的“大量”海水。 SML是海洋表面数十至数百微米厚的水层，其许多物理、化学和生物特性与紧邻其下的大量海水明显不同。 ¹⁰⁷对 SML 进行采样必然会强加微层厚度的操作定义，这取决于所选择的收集方法，并且对于微层的“真实”厚度仍然存在争议。 ¹⁰⁸文献中仅描述了一项关于 SML 中无机碘形态的研究。 ¹⁰⁹对总溶解碘、碘酸盐和碘化物（差异）的测量表明，相对于地下水，这些物质在 SML 样品 (∼300 μm) 中没有富集或减少。 ¹⁰⁹在百慕大附近进行的未发表的测量也发现，与海面以下 1 m 处采集的水相比，微层样品中的碘化物没有显着增加或减少（L. Campos，个人通讯）。相反，海洋湖泊的表面泡沫被发现富含有机碘化合物，这表明有机形式的碘可能富含在微层中。 ¹¹⁰还有人提出，SML 中的碘化物可能会被耗尽。³²提出这一想法是为了解释为什么当使用比典型海洋水平低约一个数量级的碘化物浓度时，模拟的臭氧沉积速度与观测结果更加一致， ³²但这一想法并未得到观测结果的支持。 ¹⁰⁹总之，现有证据表明，SML 中的碘化物浓度与下方大量海水中的碘化物浓度相似，但需要对 SML 中的碘形态进行更多测量，以确认这一重要反应区是否发生富集或消耗。

4. Predicting iodide concentrations: relationships with other oceanographic variables
4.预测碘化物浓度：与其他海洋变量的关系

Because existing iodide measurements are sparse, and current measurement techniques are time consuming and poorly suited to automation or remote sensing, a means by which to estimate iodide concentrations from some other parameter is desirable. As the controls on dissolved iodine speciation are not yet well understood, a theoretical basis by which to model iodide concentrations is lacking. Instead, we evaluate empirical relationships between iodide concentration and other oceanographic variables in order to find a suitable proxy for iodide levels.
由于现有的碘化物测量很少，并且当前的测量技术非常耗时并且不太适合自动化或遥感，因此需要一种根据一些其他参数来估计碘化物浓度的方法。由于对溶解碘形态的控制尚未得到很好的了解，因此缺乏模拟碘化物浓度的理论基础。相反，我们评估碘化物浓度与其他海洋变量之间的经验关系，以便找到合适的碘化物水平替代指标。

Where available, measurements of salinity, water temperature, chlorophyll-a and nitrate made concurrently with iodide and iodate measurements have been included in our compilation of data. Additionally, climatological values for the same location (one-degree resolution) and the correct month (temperature, salinity, nitrate) or season (chlorophyll-a) have been extracted from the World Ocean Atlas 2009^111–113 for each iodide data point. Mixed layer depth, calculated according to three different criteria (see below for details) for the appropriate month and position (one degree resolution) were also obtained from the World Ocean Atlas.¹¹⁴ Due to some iodide data points falling in grid squares designated as land in the World Ocean Atlas grid, not all iodide points could be associated with World Ocean Atlas parameters.
在可行的情况下，与碘化物和碘酸盐测量同时进行的盐度、水温、叶绿素-a 和硝酸盐的测量已包含在我们的数据汇编中。此外，还从《2009 年世界海洋地图集》 ^111-113中提取了每个碘化物数据点的同一地点的气候值（1 度分辨率）和正确的月份（温度、盐度、硝酸盐）或季节（叶绿素-a）。还从世界海洋地图集中获得了根据适当月份和位置（一级分辨率）的三种不同标准（详细信息见下文）计算的混合层深度。 ¹¹⁴由于一些碘化物数据点落在世界海洋图集网格中指定为陆地的网格方块中，因此并非所有碘化物点都可以与世界海洋图集参数相关联。

Statistical analysis was performed using Microsoft Excel and StatPlus:mac LE software. As the primary objective was to obtain an empirical relationship by which iodide concentration could be estimated from some other parameter, linear regression analysis was conducted. The coefficient of determination (R²; Table 2) obtained by this analysis is the same as the Pearson product–moment correlation coefficient (r²). However, as neither iodide nor the dependent variables (e.g. SST) appeared to have a normal distribution, the non-parametric Spearman's rank correlation was also used to investigate associations between iodide and selected oceanographic parameters (Table 3). Analyses were conducted for a subset of the data (n = 674) for which all independent variables were available, and salinity (observed and/or WOA) was greater than 30 (see Section 4.1). This subset comprised 262 data points classified as ‘Open Ocean’ and 412 classified as ‘coastal’ (see Section 3.1).
使用 Microsoft Excel 和 StatPlus:mac LE 软件进行统计分析。由于主要目标是获得经验关系，通过该关系可以根据一些其他参数估计碘化物浓度，因此进行了线性回归分析。通过该分析获得的决定系数（ R ² ；表2 ）与皮尔逊积矩相关系数（ r ² ）相同。然而，由于碘化物和因变量（例如海温）似乎都不具有正态分布，因此非参数斯皮尔曼等级相关也被用来研究碘化物和选定的海洋学参数之间的关联（表3 ）。对数据子集 ( n = 674) 进行了分析，其中所有自变量均可用，并且盐度（观察到的和/或 WOA）大于 30（参见第 4.1 节）。该子集包含 262 个被分类为“开放海洋”的数据点和 412 个被分类为“沿海”的数据点（参见第 3.1 节）。

As the primary objective of this analysis was to identify robust relationships that could be used in global models without necessarily requiring in situ oceanographic measurements, we present relationships between sea-surface iodide and ancillary parameters from the World Ocean Atlas in Tables 2 and 3. This approach also allows a larger data set to be used. The relationships between observed parameters and sea surface iodide, while not identical, are similar to those obtained using WOA parameters (Fig. 7, 8, 10 and 11, and S3 and Table 1 in the ESI†). Regression analysis was conducted using both [iodide] and the natural logarithm of iodide concentration (ln[iodide]) as the dependent variable. The latter was found to be the more appropriate model as, although both yielded similar coefficients of determination (Table 2), the former gave residuals that changed as a function of the independent variable while the latter gave an approximately random distribution of residuals. Note that due to the existence of some zero values for iodide concentration, for which ln[iodide] cannot be calculated, sample size was smaller (n = 609) for correlations of ln[iodide]. The zero values occur for iodide concentrations calculated as the difference between total iodine and the iodate concentrations, where these parameters were effectively equal⁷⁰ and insufficient information was available to constrain the limit of detection (LoD). Note that for the Spearman's rank correlation analysis, [iodide] and ln[iodide] return identical results, so results are only reported for the former (with n = 674).
由于该分析的主要目标是确定可用于全球模型的稳健关系，而无需进行原位海洋学测量，因此我们在表 2和表 3中列出了海面碘化物与世界海洋地图集中的辅助参数之间的关系。这种方法还允许使用更大的数据集。观测到的参数与海面碘化物之间的关系虽然不相同，但与使用 WOA 参数获得的关系相似（图 7、8、10和11 ，以及 ESI 中的 S3 和表 1 † ）。使用[碘化物]和碘化物浓度的自然对数(ln[碘化物])作为因变量进行回归分析。发现后者是更合适的模型，因为尽管两者都产生相似的决定系数（表 2 ），但前者给出的残差作为自变量的函数而变化，而后者给出了残差的近似随机分布。请注意，由于碘化物浓度存在一些零值，无法计算 ln[碘化物]，因此 ln[碘化物] 相关性的样本量较小 ( n = 609)。碘化物浓度为零，计算为总碘和碘酸盐浓度之间的差值，其中这些参数实际上等于⁷⁰ ，并且没有足够的信息来限制检测限 (LoD)。请注意，对于 Spearman 等级相关分析，[iodide] 和 ln[iodide] 返回相同的结果，因此仅报告前者的结果（ n = 674）。

4.1. Salinity
4.1.盐度

We find a comparatively strong relationship between salinity and iodide concentration at salinity values less than 30 (R² = 0.65; Fig. 7A). This reflects the mixing of coastal seawater (higher iodide, high salinity) and freshwater (lower iodide, negligible salinity) end members. In estuarine environments, iodide concentrations are sometimes strongly correlated with salinity gradients (e.g. Chesapeake Bay, USA⁷⁷). However, in other estuaries iodide levels may be only very loosely related to salinity (e.g. Huon Estuary, Australia¹¹⁵), or more complex relationships involving both positive and negative correlations between iodide and salinity may occur (e.g. Guanabara Bay, Brazil⁹⁶ and the Nile River estuary, Egypt¹¹⁶).
我们发现当盐度值小于30时，盐度和碘化物浓度之间存在相对较强的关系（ R ² = 0.65；图7A ）。这反映了沿海海水（碘化物较高、盐度较高）和淡水（碘化物较低、盐度可忽略不计）末端成员的混合。在河口环境中，碘化物浓度有时与盐度梯度密切相关（例如美国切萨皮克湾⁷⁷ ）。然而，在其他河口，碘化物水平可能仅与盐度非常松散地相关（例如澳大利亚休恩河口¹¹⁵ ），或更复杂的关系，涉及碘化物和盐度之间的正相关和负相关（例如巴西瓜纳巴拉湾⁹⁶和尼罗河）河口，埃及¹¹⁶ )。

In some estuaries, exceptionally high iodide (and as a consequence, total iodine) levels are occasionally encountered (e.g. the Skagerrak³⁵). These diverse findings likely arise from the large range of estuarine processes with potential to affect iodine speciation, most of which are not salinity dependent. For example, sediment interactions will be more important than in the open ocean, and low oxygen conditions may occur.^77,116 Such processes will cause deviations from conservative behaviour, and probably contribute to the scatter about the best-fit line for the low salinity samples (Fig. 7A). As low salinity samples represent a special case of iodine chemistry distinct from the open ocean, they have been excluded from further correlation analyses (Section 4.2–4.6). Removal of these samples from the data set reduced the overall range of iodide concentrations to undetectable to 450 nM, but the distribution was otherwise little changed (median 74 nM, interquartile range 27 to 135 nM; see Fig. 4).
在一些河口，偶尔会遇到异常高的碘化物（因此总碘）水平（例如斯卡格拉克河³⁵ ）。这些不同的发现可能来自于可能影响碘形态的大范围河口过程，其中大多数不依赖于盐度。例如，沉积物相互作用将比公海中更重要，并且可能会出现低氧条件。 ^77,116此类过程将导致保守行为的偏差，并可能导致低盐度样本最佳拟合线的分散（图 7A ）。由于低盐度样品代表了与公海不同的碘化学的特殊情况，因此它们已被排除在进一步的相关分析之外（第 4.2-4.6 节）。从数据集中除去这些样品将碘化物浓度的总体范围降低至无法检测到的 450 nM，但分布在其他方面几乎没有变化（中位数 74 nM，四分位数范围 27 至 135 nM；见图4 ）。

At salinities more typical of ‘true’ seawater (30–40; shaded area in Fig. 7A), we find iodide concentrations to be only very weakly associated with salinity (R² = 0.15, Table 2). This is consistent with the view that, while total dissolved iodine is approximately conservative, individual iodine species are biogeochemically reactive and so do not behave conservatively. The lack of a strong correlation between iodide and salinity on a large scale (Table 2 and Fig. 7B) suggests that biogeochemical processes exert greater control on iodide speciation in the oceans than precipitation, evaporation and mixing. Although it is true that precipitation and evaporation will cause co-variation in total salinity and the concentrations of individual salt components such as iodide (via simple dilution and concentration), in the open ocean, the magnitude of these effects is very small. For example, a change in salinity from 34 to 35 due to evaporation would only cause a 3% increase in iodide concentration. The mixing of water masses with different iodide and salinity signatures can also result in a relationship between the two on a regional or local scale, where mixing of water masses is the dominant control on their properties (e.g. the British Isles shelf seas⁷⁰). Positive correlations between atmospheric iodine (IO and IOx) and salinity have been observed and attributed to variation in iodide concentrations;^21,117 despite the lack of a significant relationship in our large scale data set, regional scale correlations between iodide and salinity may have existed in these study areas. Alternatively, the relationship may arise because of the salinity dependence of iodine volatilisation,^29,30 though the small change in salinity is estimated to cause only a 1% change in I₂ flux as a result of enhanced volatilisation rates.³⁰ Concentrations of iodine species are sometimes reported as values normalised to salinity (rationalisation^118,119) to account for any dilution or concentration effects (see above). However, when attempting to quantify processes with a rate dependence on the iodide (or iodate) concentration, absolute concentrations are more appropriate and so have been used in the data compilation and regression analyses presented here. We have repeated the regression analyses using rationalised iodide concentrations, and find the linear relationships (R², slope and intercept) obtained are almost identical to those for absolute iodide concentration (data not shown).
在更典型的“真实”海水盐度（30-40；图 7A中的阴影区域）下，我们发现碘化物浓度与盐度的相关性非常弱（ R ² = 0.15，表 2 ）。这与这样的观点是一致的：虽然总溶解碘近似保守，但单个碘种类具有生物地球化学反应性，因此表现不保守。碘化物和盐度之间在大范围内缺乏强相关性（表2和图7B ）表明生物地球化学过程对海洋中碘化物形态的控制比降水、蒸发和混合更大。尽管降水和蒸发确实会导致总盐度和碘化物等单个盐成分的浓度共同变化（通过简单的稀释和浓缩），但在公海中，这些影响的幅度非常小。例如，由于蒸发而导致盐度从 34 变为 35，只会导致碘化物浓度增加 3%。具有不同碘化物和盐度特征的水团的混合也可以导致两者在区域或局部尺度上的关系，其中水团的混合是对其性质的主要控制（例如不列颠群岛陆架海⁷⁰ ）。已观察到大气碘（IO 和 IOx）与盐度之间呈正相关，并将其归因于碘化物浓度的变化； ^21,117尽管我们的大规模数据集中缺乏显着关系，但这些研究区域中碘化物和盐度之间可能存在区域尺度相关性。 或者，这种关系可能是由于碘挥发的盐度依赖性而出现的， ^29,30尽管盐度的微小变化估计由于挥发率增加而仅导致 I ₂通量变化 1%。 ³⁰碘物质的浓度有时报告为盐度标准化值（合理化^118,119 ），以考虑任何稀释或浓度效应（见上文）。然而，当尝试量化依赖于碘化物（或碘酸盐）浓度的速率的过程时，绝对浓度更合适，因此已用于此处介绍的数据编译和回归分析中。我们使用合理化的碘化物浓度重复了回归分析，发现所获得的线性关系（ R ² 、斜率和截距）与绝对碘化物浓度的线性关系几乎相同（数据未显示）。

4.2. Sea-surface temperature
4.2.海面温度

Of the variables tested, the strongest parametric correlations (Table 2), and second strongest non-parametric correlations (Table 3) were between iodide concentration and sea-surface temperature (SST). This association between iodide and temperature is consistent with the observed latitudinal trends in iodide distribution (as, with the exception of upwelling waters, low latitude waters are warmer than high latitude waters). Where temperature is measured in degrees Celsius, rather than Kelvin, SST² is a stronger predictor of iodide than SST (Table 2). This is because there are some relatively high iodide values at negative sea surface temperatures (Fig. 8) that are effectively shifted to the right, and hence closer to the line of best fit, when the square function is applied. Conversely, for the case of SST⁻¹, the association with iodide is much stronger where temperature is measured in Kelvin rather than degrees Celsius (R² of 0.51 and 0.0006 respectively). MacDonald et al.³⁰ report an Arrhenius style dependency of ln[iodide] on SST⁻¹ (K⁻¹) for a sub-set of the data presented here. Using our larger data set, a significant Arrhenius style relationship is also found (R² = 0.47; Table 2), but the slope and intercept fall outside the error bounds of the MacDonald et al. relationship and vice versa.
在测试的变量中，碘化物浓度和海面温度 (SST) 之间的参数相关性最强（表​​ 2 ），非参数相关性次强（表 3 ）。碘化物与温度之间的这种关联与观察到的碘化物分布的纬度趋势一致（因为除了上升流水域外，低纬度水域比高纬度水域温暖）。当温度以摄氏度而不是开尔文测量时，SST ²比 SST 更能预测碘化物（表 2 ）。这是因为在负海面温度下存在一些相对较高的碘化物值（图 8 ），这些碘化物值实际上向右移动，因此在应用平方函数时更接近最佳拟合线。相反，对于 SST ^-1的情况，当温度以开尔文而不是摄氏度测量时，与碘化物的关联性更强（ R ²分别为 0.51 和 0.0006）。麦克唐纳等人。 ³⁰报告了此处提供的数据子集的 ln[碘化物] 对 SST ^-1 (K ^-1 ) 的阿伦尼乌斯风格依赖性。使用我们更大的数据集，还发现了显着的阿伦尼乌斯式关系（ R ² = 0.47；表 2 ），但斜率和截距超出了 MacDonald等人的误差范围。关系，反之亦然。

There are a number of hypotheses that may explain the positive dependency of iodide concentration on SST. Firstly, SST may be positively correlated with iodide concentration because both are related to mixed layer depth (MLD). Vertical mixing is expected to affect iodide concentration, as it effectively determines the volume of seawater within which iodide is diluted. In warmer waters, stratification leads to a shallow mixed layer in which iodide could accumulate, while in cooler waters, deeper winter mixing would result in the dilution of iodide produced in surface waters with lower iodide, deep water (see Section 3.4). Relationships between iodide and MLD are considered further in Section 4.3. A second, related, explanation is that upwelling of cold, low iodide/high iodate deep waters could sometimes result in co-variation of iodide and temperature on a regional scale. Upwelling has sometimes been observed to have this effect on surface water iodine speciation.^17,81 However, in many cases the low iodide signal of upwelled water may be altered, because upwelling regions are associated with high productivity, and the formation of iodide has been linked to productivity.^43,73,120 Indeed, the impact of high productivity in upwelling zones could have the opposite effect on iodine speciation, leading to higher iodide concentrations in the colder, upwellling waters. Finally, a positive correlation between iodide and sea surface temperature could occur if either the rate of iodide production has a positive temperature dependency and/or the rate of iodide removal has a negative temperature dependency. As both these processes may be biologically mediated,¹⁵ any such dependency could be caused by an indirect link with temperature, rather than the direct effect of temperature on reaction kinetics. For example, plankton community composition varies with temperature, and these different communities may produce iodide at varying rates.^92,121 Alternatively, as SST reflects the amount of solar irradiation reaching the ocean surface, photochemical reactions may influence the dissolved iodine distribution (see Section 3.2.3).
有许多假设可以解释碘浓度对海表温度的正相关性。首先，SST 可能与碘化物浓度正相关，因为两者都与混合层深度（MLD）相关。垂直混合预计会影响碘化物浓度，因为它有效地确定了稀释碘化物的海水体积。在较温暖的水域中，分层会形成浅混合层，碘化物可以在其中积聚，而在较冷的水域中，较深的冬季混合会导致地表水产生的碘化物被碘化物较低的深水稀释（见第 3.4 节）。第 4.3 节进一步考虑了碘化物和 MLD 之间的关系。第二个相关的解释是，寒冷、低碘/高碘深水的上涌有时可能导致区域范围内碘化物和温度的共同变化。有时观察到上升流对地表水碘形态有这种影响。 ^17,81然而，在许多情况下，上升流水的低碘化物信号可能会改变，因为上升流区域与高生产力相关，并且碘化物的形成与生产力相关。 ^43,73,120事实上，上升流区高生产力的影响可能会对碘形态产生相反的影响，导致较冷的上升流水域中碘化物浓度更高。最后，如果碘化物产生速率具有正温度依赖性和/或碘化物去除速率具有负温度依赖性，则碘化物和海面温度之间可能出现正相关。 由于这两个过程都可能是生物介导的， ¹⁵任何此类依赖性都可能是由与温度的间接联系引起的，而不是温度对反应动力学的直接影响。例如，浮游生物群落组成随温度变化，这些不同的群落可能以不同的速率产生碘化物。 ^92,121另外，由于 SST 反映了到达海洋表面的太阳辐射量，光化学反应可能会影响溶解的碘分布（见第 3.2.3 节）。

The apparent relationship between iodide and SST may explain, at least in part, observed relationships between SST and both atmospheric iodine above the oceans, and ozone deposition to the oceans. Positive correlations between atmospheric iodine species (IO and IOx) and SST have been observed in the eastern Pacific.^21,22,117 These could be partially a consequence of the correlation between iodide and SST in the surface ocean, given that iodide concentration affects the flux of reactive iodine from the sea surface.³⁰ Our findings support the suggestion that observed correlations between atmospheric IOx and SST are due to higher concentrations of reactive iodine precursors in warmer waters.^21,22,117 Helmig et al.³² found measured rates of oceanic ozone uptake to have a positive temperature dependency, while model predictions made assuming a fixed rate constant for chemical destruction of ozone displayed a negative or neutral temperature dependency, suggesting that reactivity may be weaker in regions with colder water. The lower levels of iodide present in colder waters may contribute to this reduced reactivity. Ozone deposition velocity increased up to threefold over an SST range of 0 to 33 °C³² while our results suggest at least a 12-fold increase in iodide concentration over the same temperature range (Table 2). Note a 12-fold increase in concentration equates to an approximately threefold increase in √[concentration] and ozone deposition velocity is reported to be a function of √[iodide].²⁹
碘化物和海表温度之间的明显关系可以至少部分解释观察到的海表温度与海洋上方大气碘以及海洋臭氧沉积之间的关系。在东太平洋观察到大气碘形态（IO 和 IOx）与海温呈正相关。 ^21,22,117考虑到碘化物浓度影响来自海面的活性碘通量，这可能部分是由于碘化物与表层海洋海温之间的相关性造成的。 ³⁰我们的研究结果支持这样的观点，即观察到的大气 IOx 和海表温度之间的相关性是由于较温暖的水域中活性碘前体浓度较高所致。 ^21,22,117 Helmig等人。 ³²发现测量的海洋臭氧吸收率具有正温度依赖性，而假设臭氧化学破坏固定速率常数的模型预测显示负或中性温度依赖性，这表明在水冷地区反应性可能较弱。较冷水域中碘化物含量较低可能导致反应活性降低。在 0 至 33 °C 的海温范围内，臭氧沉积速度增加了三倍^32，而我们的结果表明，在相同温度范围内，碘化物浓度至少增加了 12 倍（表 2 ）。请注意，浓度增加 12 倍相当于 √[浓度] 增加约三倍，据报道臭氧沉积速度是 √[碘化物] 的函数。 ²⁹

4.3. Mixed layer depth
4.3.混合层深度

As mixed layer depth (MLD) estimates vary according to the definition chosen,^114,122 relationships between iodide concentration and all three of the mixed layer depth fields available in Monterey and Levitus¹¹⁴ were investigated. The three MLD criteria used in Monterey and Levitus¹¹⁴ are as follows: (i) a potential temperature change from the ocean surface of 0.5 °C, here referred to as MLD_pt (ii) a potential density change from the ocean surface of 0.125 (sigma units), here referred to as MLD_pd (iii) a variable density change from the ocean surface equivalent to a temperature change of 0.5 °C, taking account of the temperature dependence of the thermal expansion coefficient of seawater, here referred to as MLD_vd. For each MLD criteria, the relationship between iodide concentration and MLD was evaluated using climatological monthly mean MLD at the time of sampling (‘monthly MLD’), the deepest climatological monthly mean MLD over the course of a year (‘maximum MLD’) and the sum of climatological monthly mean MLDs for a year (‘summed MLD’). The latter parameter was selected as a simplistic indicator of the extent and duration of vertical mixing/stratification i.e. small values of summed MLD reflect prolonged periods of stratification, while large values indicate deep mixing and/or deep mixing over many months.
由于混合层深度 (MLD) 估计值根据所选的定义而变化，因此对碘化物浓度与蒙特利和利维图斯中可用的所有三个混合层深度场之间的关系进行了研究^{114,122 114} 。 Monterey 和 Levitus ¹¹⁴使用的三个 MLD 标准如下： (i) 与海洋表面相比的潜在温度变化为 0.5 °C，此处称为 MLD _pt (ii) 与海洋表面相比的潜在密度变化为 0.125 ( sigma 单位），这里称为 MLD _pd (iii) 海洋表面的可变密度变化，相当于 0.5 °C 的温度变化，考虑到热膨胀系数的温度依赖性海水，这里简称MLD _vd 。对于每个 MLD 标准，使用采样时的气候月平均 MLD（“月 MLD”）、一年中最深的气候月平均 MLD（“最大 MLD”）和一年中气候月平均 MLD 的总和（“MLD 总和”）。后一个参数被选择作为垂直混合/分层的程度和持续时间的简单指标，即MLD总和的小值反映长期的分层，而大值表示深度混合和/或数月的深度混合。

Summed and maximum MLD_pt were relatively strongly inversely associated with iodide (R² ≥ 0.34; |ρ| ≥ 0.63), while monthly MLD_pt, and all MLD_pd and MLD_vd parameters were only weakly associated with iodide and not all relationships were significant (Tables 2 and 3). For all MLD variables, the potential temperature criterion (i) yielded the strongest correlations (Tables 2 and 3). MLD definitions vary in their ability to capture different structures in the water column in both space and time.^114,122 For example, compared to MLD definitions based on a smaller change in potential temperature, the MLD_pt definition is thought to sometimes detect deeper thermocline gradients, rather than weaker restratification events at shallower depths, and place the maximum MLD later in the season.¹²² Of the three criteria used here, the potential temperature criterion appears to yield MLD values most relevant to iodide speciation. These findings are consistent with the a priori assumption that vertical mixing must have some effect on the concentration of relatively long-lived moieties such as iodide that are produced in surface waters. The results suggest that the deepest extent of the winter mixed layer, and the duration of stratification over the course of a year are more important than mixed layer depth at the time of sampling. Long periods of stratification are expected to allow iodide to accumulate at the ocean surface, while deep winter mixing will dilute the iodide signal, effectively resetting the iodide signal to a low winter value. The impact of changes in mixed layer depth on surface iodide (and iodate) concentrations was considered by Chance et al. (2010),⁷³ who found that observed changes in surface concentration over 100 days were similar to those calculated from the known deepening of the mixed layer in Antarctic coastal waters.⁷³ Further investigation using more refined estimates of MLD may yield more insights into the relationship between iodine speciation and vertical mixing.
总 MLD _{pt 和最大 MLD pt}与碘离子呈相对较强的负相关 ( R ² ≥ 0.34; | ρ | ≥ 0.63)，而月 MLD _pt以及所有 MLD _pd和 MLD _vd参数仅与碘离子呈弱相关，且并非所有关系均显着（表 2和表3 ）。对于所有 MLD 变量，潜在温度标准 (i) 产生最强的相关性（表 2和表 3 ）。 MLD 的定义因捕获水柱中空间和时间上不同结构的能力而异。 ^114,122例如，与基于较小位温变化的 MLD 定义相比，MLD _pt定义有时被认为可以检测到更深的温跃层梯度，而不是较浅深度的较弱的重层化事件，并将最大 MLD 放置在季节后期。 ¹²²在此处使用的三个标准中，位温标准似乎产生与碘化物形态最相关的 MLD 值。这些发现与先验假设一致，即垂直混合必定对地表水中产生的相对寿命较长的部分（例如碘化物）的浓度有一定影响。结果表明，冬季混合层的最深范围和一年中分层的持续时间比采样时的混合层深度更重要。长时间的分层预计会使碘化物在海洋表面积聚，而深冬混合将稀释碘化物信号，有效地将碘化物信号重置为冬季的低值。 Chance等人考虑了混合层深度变化对表面碘化物（和碘酸盐）浓度的影响。 (2010)， ⁷³他们发现 100 天内观察到的表面浓度变化与根据已知的南极沿海水域混合层加深计算出的变化相似。 ⁷³使用更精确的 MLD 估计进行进一步研究可能会更深入地了解碘形态与垂直混合之间的关系。

In Section 4.2 it was hypothesised that the observed link between iodide and SST was the result of higher SST being associated with shallower mixed layer depths. An exploration of the links between mixed layer depth and sea surface temperature is beyond the scope of this work. However, we note that within our data set, maximum and summed MLD_pt were relatively strongly correlated with SST² (r² of 0.33 and 0.35 respectively), while maximum and summed MLD_pd and MLD_vd were not (r² ≤ 0.08). Furthermore, none of the three monthly MLD parameters correlated strongly with SST² (r² of 0.13, 0.003 and 0.01 for MLD_pt, MLD_pd and MLD_vd respectively). Our results are broadly consistent with the view that iodide is related to SST because of the influence of SST on vertical mixing, where the potential density criterion identifies the most relevant mixing features. Of course a significant correlation cannot be taken as proof of cause and effect, so the possibility remains that iodide concentration is related to MLD_pt only because both are related to temperature. As the relationship between iodide concentration and SST is stronger than either that between iodide concentration and MLD_pt (see Table 2), or SST and MLD_pt (see above), it is also possible that other factors in addition to mixing contribute to the link between iodide concentration and SST. Possible additional factors are suggested in Section 4.2.
在第 4.2 节中，假设观察到的碘化物和海表温度之间的联系是较高的海表温度与较浅的混合层深度相关的结果。探索混合层深度与海面温度之间的联系超出了本工作的范围。然而，我们注意到，在我们的数据集中，最大和总和 MLD _pt与 SST ²相关性相对较强（ r ²分别为 0.33 和 0.35），而最大和总和 MLD _pd和 MLD _vd则不然（ r ² ≤ 0.08）。此外，三个月的 MLD 参数均与 SST ²没有很强的相关性（MLD _pt 、MLD _pd和 MLD _vd的r ²分别为 0.13、0.003 和 0.01）。我们的结果与碘化物与海表温度相关的观点大致一致，因为海表温度对垂直混合的影响，其中潜在密度标准识别了最相关的混合特征。当然，显着的相关性不能作为因果关系的证据，因此碘化物浓度与 MLD _pt相关的可能性仍然存在，只是因为两者都与温度相关。由于碘化物浓度与 SST 之间的关系比碘化物浓度与 MLD _pt （见表2 ）或 SST 与 MLD _pt （见上文）之间的关系更强，因此除了混合之外的其他因素也可能有助于这种联系碘化物浓度和 SST 之间的关系。第 4.2 节中建议了可能的其他因素。

4.4. Chlorophyll-a
4.4.叶绿素a

Regression analysis suggests that there is not a statistically significant relationship between iodide and chlorophyll-a concentrations on a large scale (Fig. 10 and Table 2), while Spearman's rank correlation finds a weak but significant negative association between the two (ρ = −0.24; Table 3). The majority of regional and basin scale studies included in our compilation (see Table 1 for references) make no mention of a correlation, or lack thereof, between iodine speciation and chlorophyll-a. Only very rarely has a significant relationship between chlorophyll-a and iodide concentration been reported, and this has generally been in environments unrepresentative of the open ocean.^47,96 Rebello et al.⁹⁶ report a positive correlation between iodide and chlorophyll-a (slope of 0.231 mM iodide per mg L⁻¹ chl-a, r = 0.79) for a 5 m deep sampling site in Guanabara Bay, a polluted estuarine (average salinity 29) bay in southeastern Brazil. The observed relationship was derived from the average iodide and chlorophyll-a concentrations for each of four different depths, which were sampled at four time points over the course of one day only, and was not replicated on other sampling days. This relationship was extrapolated to estimate iodide concentration in the Gulf of Mexico in two modelling studies examining ozone deposition.^32,33 Helmig et al.³² found that inferring iodide from chlorophyll-a (after Oh et al.³³) gave better agreement between modelled and observed values of ozone deposition velocity (Vd) than inferring iodide from nitrate concentrations (after Ganzeveld et al.²⁷), as the use of nitrate as an iodide proxy led to an over-estimate of Vd. However, as Helmig et al.³² note, the iodide concentrations obtained using chlorophyll-a were probably not realistic, as they were an order of magnitude lower than typical oceanic levels. Interestingly, anti-correlations between chlorophyll-a concentration and atmospheric iodine species (IO and IOx) have been observed.^21,22,117 Given that we find sea surface iodide and chlorophyll-a are not related, an inverse relationship between atmospheric iodine and chlorophyll-a does not preclude the role of iodide as a precursor of IOx.
回归分析表明，大范围内碘化物和叶绿素-a 浓度之间不存在统计显着关系（图 10和表 2 ），而 Spearman 等级相关发现两者之间存在微弱但显着的负相关关系（ ρ = -0.24）表3 ）。我们的汇编中包含的大多数区域和流域规模的研究（参考文献见表 1 ）没有提及碘形态和叶绿素-a 之间的相关性或缺乏相关性。叶绿素a和碘化物浓度之间存在显着关系的报道非常罕见，而且这种情况通常发生在不能代表公海的环境中。 ^47,96雷贝洛等人。 ⁹⁶报道了瓜纳巴拉湾（污染河口（平均盐度 29）海湾）5 m 深采样点的碘化物和叶绿素-a 之间的正相关性（斜率为 0.231 mM 碘化物/mg L ⁻¹ chl-a， r = 0.79）在巴西东南部。观察到的关系源自四个不同深度的平均碘化物和叶绿素-a 浓度，这些深度仅在一天内的四个时间点采样，并且在其他采样日没有重复。在两项检查臭氧沉积的模型研究中，通过推断这种关系来估计墨西哥湾的碘化物浓度。 ^32,33赫尔米格等人。 ³²发现从叶绿素-a 推断碘化物（Oh等人之后，³³ ）比从硝酸盐浓度推断碘化物（遵循 Ganzeveld等人²⁷ ）的臭氧沉降速度（Vd）模型值和观测值之间的一致性更好，因为使用硝酸盐作为碘化物替代物导致 Vd 的高估。然而，正如 Helmig等人。 ³²请注意，使用叶绿素-a 获得的碘化物浓度可能不现实，因为它们比典型海洋水平低一个数量级。有趣的是，已经观察到叶绿素-a 浓度与大气中碘形态（IO 和 IOx）之间的反相关性。 ^21,22,117鉴于我们发现海面碘化物和叶绿素-a 不相关，大气碘和叶绿素-a 之间的反比关系并不排除碘化物作为 IOx 前体的作用。

The results presented here suggest that chlorophyll-a concentration is a poor proxy for iodide concentration. However, the absence of a correlation between iodide and chlorophyll does not necessarily controvert a link between iodide production and biological activity. Although commonly used as an easily quantifiable indicator of biological activity, chlorophyll-a concentrations are a measure of the standing stock of phytoplankton biomass at a given point in time. Concentrations of metastable biogenic species (such as iodide is thought to be) are more likely to reflect integrated biological activity over a period of time than the net biomass. Links between iodine speciation and biological activity are discussed further in Section 4.5.
这里给出的结果表明叶绿素-a 浓度不能很好地代表碘化物浓度。然而，碘化物和叶绿素之间不存在相关性并不一定会质疑碘化物产生和生物活性之间的联系。虽然叶绿素-a 浓度通常用作生物活性的易于量化的指标，但它是衡量给定时间点浮游植物生物量的常量的指标。亚稳态生物物质（例如碘化物）的浓度比净生物量更能反映一段时间内的综合生物活性。碘形态和生物活性之间的联系将在 4.5 节中进一步讨论。

4.5. Nitrate
4.5.硝酸盐

Iodide is inversely related to nitrate, with a relatively large coefficient of determination (R² = 0.36; Fig. 10 and Table 2) and the strongest non-parametric correlation coefficient (ρ = −0.73; Table 3). Negative correlations between iodide and nitrate have previously been identified in the southern Atlantic and Southern Ocean, with the exact relationship differing according to hydrographic region.⁵³ Given that iodide exhibits an approximately inverse relationship to iodate (Fig. 2 and 6), these results are also in broad agreement with observations of tight coupling between iodate and nitrate in individual vertical profiles.^17,48,63 However, correlations between iodine species and nutrients are not ubiquitously observed,^42,70 and Bluhm et al.⁶⁴ did not find a relationship between iodide and nitrate in the Atlantic sector of the Southern Ocean. Though an inverse relationship between iodide and nutrient concentrations could arise as the result of hydrographic coupling,¹⁷ it is also consistent with the view that iodide formation may be biologically mediated, as discussed in Section 4.4. Both the biologically mediated production of iodide in association with nutrient uptake in the euphotic zone, and the upwelling of deep, low iodide/high nutrient waters, may contribute to an inverse relationship in surface waters.
碘化物与硝酸盐呈反比，具有较大的决定系数（ R ² = 0.36；图10和表2 ）和最强的非参数相关系数（ ρ = -0.73；表3 ）。先前已在南大西洋和南大洋发现了碘化物和硝酸盐之间的负相关性，具体关系因水文区域而异。 ⁵³鉴于碘化物与碘酸盐表现出近似反比关系（图 2和6 ），这些结果也与各个垂直剖面中碘酸盐和硝酸盐之间紧密耦合的观察结果大致一致。 ^17,48,63然而，碘形态与营养素之间的相关性并未普遍观察到， ^42,70和 Bluhm等人。 ⁶⁴没有发现南大洋大西洋部分的碘化物和硝酸盐之间存在关系。尽管水文耦合的结果可能会导致碘化物和营养物浓度之间出现反比关系， ^17，但这也与碘化物形成可能是生物介导的观点一致，如第 4.4 节所述。生物介导的碘化物产生与富光带养分吸收相关，以及深层、低碘/高营养水体的上涌，都可能导致地表水中的反比关系。

Although it is generally accepted that there is a link between iodine speciation and biological activity,¹⁵ this has not yet been unequivocally established and the mechanism remains unknown. The occurrence of iodide in the surface ocean (e.g.Fig. 6), where the majority of marine primary production also occurs, strongly suggests that iodide production might be biologically mediated. A number of laboratory studies have demonstrated iodate uptake and the conversion of iodate to iodide in phytoplankton cultures,^{91–93,121,123,124} but in other cases no link has been found.^93,98 Similarly, a time series study in Antarctic waters found iodide accumulation to be correlated with primary productivity,⁷³ while a mesocosm study at a similar location found no change in iodine speciation associated with phytoplankton growth.³⁷ Elsewhere, associations between iodide concentrations and both new^120,125 and regenerated primary production⁴³ have been inferred from field measurements. It has been suggested that iodate could be reduced by nitrate reductase enzymes,^120,125,126 which are widespread in marine micro-organisms,¹²⁷ and an association between nitrate reductase activity and iodate reduction has been shown in cellular extracts^126,128 and the East China Sea.¹²⁰ However, deactivation of nitrate reductase activity in micro-algal cultures did not prevent the production of iodide,⁹³ and conversely, bacterial cultures only reduced iodate under certain conditions, despite always displaying nitrate reductase activity,¹²⁹ suggesting nitrate reductases are not involved in iodate reduction, or at least are not the sole control. More recently, it has been suggested that the reduction of iodate to iodide may be brought about sulphides or thiols,^87,91,130 which may be released from leaking senescent cells.⁹¹
尽管人们普遍认为碘形态与生物活性之间存在联系， ¹⁵但这一点尚未明确确立，其机制仍不清楚。碘化物在表层海洋中的出现（例如图6 ），大部分海洋初级生产也发生在表层海洋中，强烈表明碘化物的产生可能是生物介导的。许多实验室研究已经证明了浮游植物培养物中碘酸盐的吸收以及碘酸盐向碘化物的转化， ^{91-93,121,123,124} ，但在其他情况下没有发现任何联系。 ^93,98同样，南极水域的一项时间序列研究发现碘化物积累与初级生产力相关， ⁷³而类似地点的中生态研究发现与浮游植物生长相关的碘形态没有变化。 ³⁷在其他地方，碘化物浓度与新^120,125和再生初级生产⁴³之间的关联是通过现场测量推断的。有人提出，碘酸盐可以被硝酸还原酶还原， ^120,125,126广泛存在于海洋微生物中， ¹²⁷并且硝酸盐还原酶活性与碘酸盐还原之间的关联已在细胞提取物^126,128和东海中得到证实。¹²⁰然而，微藻培养物中硝酸盐还原酶活性的失活并不能阻止碘化物的产生， ⁹³相反，细菌培养物仅在某些条件下还原碘酸盐，尽管始终表现出硝酸盐还原酶活性， ¹²⁹表明硝酸盐还原酶不参与碘酸盐减少，或者至少不是唯一的控制。最近，有人提出，碘酸盐还原成碘化物可能会产生硫化物或硫醇， ^87,91,130 ，它们可能从泄漏的衰老细胞中释放出来。⁹¹

Considering the full water column, the existence of correlations between dissolved iodine species and nutrients has prompted an extension of the Redfield ratio approach to consider iodine.^16,48 As dissolved iodine is present in multiple oxidation states, which may themselves be interconverted by biological uptake and remineralisation, as well as additional extracellular processes, the Redfield approach is most appropriate for total dissolved iodine (i.e. iodide plus iodate).^16,131 Total iodine is coupled to phosphate, suggesting it is subject to similar processes of assimilation and regeneration,¹⁶ though the coupling breaks down at depth, indicating a greater proportion of iodine is recycled in shallower waters, compared to nitrogen and phosphorus.¹³¹
考虑到整个水体，溶解的碘种类和营养物之间存在相关性，促使雷德菲尔德比率方法的扩展以考虑碘。 ^16,48由于溶解的碘以多种氧化态存在，这些氧化态本身可能通过生物吸收和再矿化以及其他细胞外过程相互转化，因此 Redfield 方法最适合总溶解碘（即碘化物加碘酸盐）。 ^16,131总碘与磷酸盐偶联，表明它经历了类似的同化和再生过程， ¹⁶尽管这种偶联在深度处分解，表明与氮和磷相比，更大比例的碘在较浅水域中循环利用。 ¹³¹

The relationships between iodide and nitrate in the south Atlantic reported by Campos et al.⁵³ were adapted by Ganzeveld et al.²⁷ to estimate iodide concentrations under ‘in gyre’ and ‘out of gyre’ conditions (defined as waters with surface concentrations less than and greater than 2 μM nitrate respectively), and hence model ozone deposition to the sea surface. Ganzeveld et al.²⁷ demonstrated that the equations of Campos et al.⁵³ yielded a latitudinal iodide distribution in reasonable agreement with observations made during meridional transects of the Atlantic,¹⁷ but underpredicted iodide levels near Hawaii and Bermuda.⁴¹ They attributed the latter discrepancy to the nitrate climatology used not resolving high biological activity in the coastal waters near these islands.²⁷ Considering our data compilation, the relationship between iodide and nitrate at nitrate concentrations greater than 2 μM is very similar to that used by Ganzeveld et al.,²⁷ with overlap between the error bounds of the gradient and slope (Fig. 11C and Table 3). Visual inspection also suggests reasonable agreement between the relationships for nitrate concentrations less than 2 μM (Fig. 11B), but in this case there is no overlap between the error bounds of the gradient and intercepts (Table 4).
Campos等人报道了南大西洋碘化物和硝酸盐之间的关系。 ⁵³由 Ganzeveld等人改编。 ²⁷估计“环流内”和“环流外”条件下的碘化物浓度（定义为表面硝酸盐浓度分别小于和大于 2 μM 的水域），从而模拟海面臭氧沉积。甘泽维尔德等人。 ²⁷证明了 Campos等人的方程。 ⁵³得出的纬度碘化物分布与大西洋经向横断面的观测结果相当一致， ¹⁷但夏威夷和百慕大附近的碘化物水平预测不足。 ⁴¹他们将后一个差异归因于所使用的硝酸盐气候学未能解决这些岛屿附近沿海水域的高生物活性问题。 ²⁷考虑到我们的数据汇编，硝酸盐浓度大于 2 μM 时碘化物和硝酸盐之间的关系与 Ganzeveld等人使用的关系非常相似。 ， ^27，梯度和斜率的误差界限之间有重叠（图11C和表3 ）。目视检查还表明硝酸盐浓度小于 2 μM 的关系之间存在合理的一致性（图 11B ），但在这种情况下，梯度和截距的误差范围之间没有重叠（表 4 ）。

4.6. Multiple linear regression
4.6.多元线性回归

Multiple linear regression analysis of iodide against SST², absolute latitude, MLD (summed MLD_pt, as this had strongest individual relationship, see Table 2), nitrate concentration, salinity and chlorophyll-a concentration was carried out using StatPlus software as an add on to Microsoft Excel. Analysis was carried out for different combinations and functions of the key variables, in order to find the combination that accounted for the greatest amount of variability in the dataset i.e. returned the largest value of R².
使用 StatPlus 软件作为附加软件，对碘化物对 SST ² 、绝对纬度、MLD（MLD _pt求和，因为这具有最强的个体关系，参见表2 ）、硝酸盐浓度、盐度和叶绿素-a 浓度进行多元线性回归分析到 Microsoft Excel。对关键变量的不同组合和函数进行分析，以找到数据集中变异性最大的组合，即返回R ²的最大值。

As reported in Table 2, SST², latitude, summed MLD_pt and nitrate concentration are the strongest individual predictors of iodide concentration, accounting for about ∼40 to ∼60% of the observed variability. Combining these four variables increased R² for each variable added, to a maximum increase of ∼10% for all four variables compared to SST² alone. The increases in R² caused by adding these variables were not cumulative because of the high interdependency of the variables e.g. latitude and SST. The inclusion of salinity caused an increase in R² of between ∼1 to ∼5%. Chlorophyll-a was not found to be a significant contributor (5% significance level) in any of the multivariate combinations tested and its inclusion did not increase R². For the dependent variables [iodide] and ln[iodide], maximum R² values of 0.676 and 0.642 respectively were achieved and relationships (1) and (2) identified:
如表 2所示，SST ² 、纬度、MLD _pt总和和硝酸盐浓度是碘化物浓度最强的个体预测因子，占观察到的变异性的约 40% 至 60%。结合这四个变量增加了每个添加变量的R ² ，与单独的 SST ²相比，所有四个变量的最大增加约为 10%。由于纬度和海温等变量的高度相互依赖性，添加这些变量引起的R ²增加不是累积的。盐度的加入导致R ²增加约 1% 至约 5%。未发现叶绿素-a 在任何测试的多变量组合中具有显着贡献（5% 显着性水平），并且其包含不会增加R ² 。对于因变量 [碘化物] 和 ln[碘化物]，分别实现了最大R ²值 0.676 和 0.642，并确定了关系(1)和(2) ： [iodide] = 0.28(±0.0.02) × SST² + 1.7(±0.2) × |latitude| + 0.9(±0.4) × [NO₃⁻] − 0.020(±0.002) × sumMLD_pt+ 7(±2) × salinity − 309(±75)
[碘化物] = 0.28(±0.0.02) × SST ² + 1.7(±0.2) × |纬度| + 0.9(±0.4) × [NO ₃ ⁻ ] − 0.020(±0.002) × sumMLD _pt + 7(±2) × 盐度 − 309(±75) (1) ln[iodide] = 0.0026(±0.0003) × SST² + 0.016(±0.003) × |latitude| − 0.009(±0.006) × [NO₃⁻] − 0.00044(±0.00004) × sumMLD_pt+ 0.05(±0.03) × salinity + 2(±1)
ln[碘化物] = 0.0026(±0.0003) × SST ² + 0.016(±0.003) × |纬度| − 0.009(±0.006) × [NO ₃ ⁻ ] − 0.00044(±0.00004) × sumMLD _pt + 0.05(±0.03) × 盐度 + 2(±1) (2) where [iodide] is in nmol L⁻¹, SST is in °C, [NO₃⁻] is in μmol L⁻¹ and sumMLD_pt is the annual sum of monthly average mean mixed layer depths taken from Monterey and Levitus¹¹⁴ (potential temperature criterion). As for the individual correlations, the use of ln[iodide] rather than [iodide] as the dependent variable gave a more uniform distribution of residuals, suggesting eqn (2) is the more appropriate model despite the lower R² value. In eqn (1) all variables were significant (at p = 5%). In eqn (2) neither nitrate concentration or salinity were significant, but each became significant when the other was excluded from the regression, and the inclusion of both increased the R² value slightly.
其中，[碘化物] 的单位为 nmol L ⁻¹ ，SST 的单位为 °C，[NO ₃ ⁻ ] 的单位为 µmol L ⁻¹ ，sumMLD _pt是取自 Monterey 和 Levitus ^{114 的}月平均混合层深度的年度总和（潜在）温度标准）。至于个体相关性，使用 ln[iodide] 而不是 [iodide] 作为因变量给出了更均匀的残差分布，表明尽管R ²值较低，但方程 (2)是更合适的模型。在等式 (1)中，所有变量均显着（ p = 5%）。在方程（2）中，硝酸盐浓度或盐度都不显着，但当将另一个排除在回归之外时，两者都变得显着，并且两者的包含都会略微增加R ²值。

5. Concluding remarks
五、结束语

Knowledge of sea surface iodide concentrations is required in order to accurately predict both ozone deposition to the sea surface and the sea-to-air flux of reactive iodine arising from this reaction. Sea surface iodide concentrations from the literature and unpublished data sets have been compiled as a first step towards a global iodide climatology. Despite only patchy coverage of the world's oceans, the 925 data points reveal clear trends in the iodide distribution. Observed iodide concentrations in waters with salinities greater than 30 range from effectively zero to 450 nM, with 50% of measurements falling between 26 and 135 nM. There is a strong trend of increasing concentration with decreasing latitude, evident in both the Atlantic and the Pacific. Very large gaps in the data set remain, particularly in the eastern Pacific, Indian and Arctic Oceans, where further field measurements are required. For the purposes of studying air–sea exchange, it is important to consider concentrations in the sea surface microlayer; current evidence is limited but suggests iodide is neither enhanced nor depleted in the sea surface microlayer.
为了准确预测海面的臭氧沉积以及由该反应产生的活性碘从海到空的通量，需要了解海面碘化物浓度。来自文献和未发表的数据集的海面碘化物浓度已被汇编，作为全球碘化物气候学的第一步。尽管对世界海洋的覆盖范围很分散，但 925 个数据点揭示了碘化物分布的明显趋势。在盐度大于 30 的水中观察到的碘化物浓度范围从 0 到 450 nM，其中 50% 的测量值落在 26 到 135 nM 之间。随着纬度的降低，浓度增加的强烈趋势在大西洋和太平洋都很明显。数据集仍然存在很大差距，特别是在东太平洋、印度洋和北冰洋，需要进一步的现场测量。为了研究海气交换，重要的是要考虑海面微层中的浓度；目前的证据有限，但表明海面微层中的碘化物既没有增加也没有减少。

Relationships between iodide concentration and other, more widely measured oceanographic variables have been explored. Of the variables tested, SST² appears to be the strongest predictor of iodide surface concentration, and nitrate concentration the second best, and these variables are recommended for use where proxies of iodide concentration are required. Atmospheric iodine oxides (IO and IOx) are also positively correlated with SST;^21,22,117 that both sea surface iodide and atmospheric IOx are related to SST suggests that the former may be an important predictor of the latter. Observed iodide concentrations in surface waters vary across approximately an order of magnitude, which would equate to an approximately three-fold variation in the reactive iodine flux, assuming that this is proportional to √[iodide]²⁹ and that all other factors are equal, with highest fluxes expected at lowest latitudes. No relationship between iodide and chlorophyll-a was found. Inclusion of additional variables in a multivariate linear regression gave only a slight increase in the amount of iodide variability accounted for, compared to SST alone. Given that the reasons for the link between iodide concentration and SST are not established, this relationship should be used with caution and any iodide fields generated should be checked against actual measurements to ensure they are realistic. For example, in highly productive upwelling regions, or situations where surface waters become hypoxic, higher iodide concentrations than predicted from SST may occur.
碘化物浓度与其他更广泛测量的海洋变量之间的关系已经得到探索。在测试的变量中，SST ²似乎是碘化物表面浓度的最强预测因子，硝酸盐浓度次之，建议在需要碘化物浓度代理的情况下使用这些变量。大气中的碘氧化物（IO 和 IOx）也与海温呈正相关； ^21,22,117海面碘化物和大气 IOx 都与 SST 有关，这表明前者可能是后者的重要预测因子。观察到的地表水中的碘化物浓度变化大约一个数量级，这相当于活性碘通量的大约三倍变化，假设这与 √[碘化物] ²⁹成正比并且所有其他因素都相同，其中预计最低纬度地区的最高通量。没有发现碘化物和叶绿素-a 之间存在任何关系。与单独的 SST 相比，在多元线性回归中包含其他变量仅导致碘化物变异量略有增加。鉴于碘化物浓度与海温之间联系的原因尚未确定，应谨慎使用这种关系，并且应根据实际测量结果检查生成的任何碘化物场，以确保其真实性。例如，在高产上升流区域或地表水缺氧的情况下，可能会出现比海表温度预测更高的碘化物浓度。

The controls on iodide concentration are still not fully understood, and further work is needed to provide a theoretical framework with which to explain and predict iodide concentrations. The observed link between iodide and nitrate concentration is in agreement with individual studies, and consistent with a biological role in determining iodine speciation. Meanwhile, the strong associations between SST and latitude and iodide remain somewhat enigmatic, particularly given that MLD was less strongly associated with iodide concentration. Annual patterns of vertical mixing can account for some of the variation in iodide concentration, but other factors related to temperature and/or latitude may also be important. The sea surface distribution of iodide is strikingly similar to that of dissolved organic carbon (DOC).¹³² Both show elevated levels in the tropics and lower levels at higher latitudes in the southern hemisphere. The same large scale physical and biogeochemical processes that determine the global DOC distribution may also control iodide concentrations, and indeed create the broader differences between oligotrophic warm water gyres and seasonally well mixed mid- and high latitude systems. The potential for shared drivers of both iodide and DOC distributions merits further investigation. It is hoped that the nascent compilation of iodine speciation measurements presented here may be a useful tool for probing iodine dynamics in seawater in future.
对碘化物浓度的控制仍不完全清楚，需要进一步的工作来提供解释和预测碘化物浓度的理论框架。观察到的碘化物和硝酸盐浓度之间的联系与个别研究一致，并且与确定碘形态的生物学作用一致。与此同时，海温与纬度和碘化物之间的强关联仍然有些神秘，特别是考虑到 MLD 与碘化物浓度的相关性不太强。垂直混合的年度模式可以解释碘化物浓度的一些变化，但与温度和/或纬度相关的其他因素也可能很重要。碘化物的海面分布与溶解有机碳（DOC）的分布惊人相似。 ¹³²两者都显示热带地区的水平较高，而南半球高纬度地区的水平较低。决定全球 DOC 分布的大规模物理和生物地球化学过程也可能控制碘化物浓度，并确实在贫营养温水环流和季节性混合的中高纬度系统之间产生更广泛的差异。碘化物和 DOC 分布的共同驱动因素的潜力值得进一步研究。希望这里介绍的碘形态测量的新汇编可能成为未来探测海水中碘动态的有用工具。

Acknowledgements  致谢

We would like to thank the British Oceanographic Data Centre (BODC) for providing data used in the compilation, and the following for providing data sets retrieved from BODC or online archives: G. W. Luther, III (University of Delaware), V. Truesdale (Oxford Brookes University), R.C. Tian (University of Maryland). We would particularly like to thank to Lucia Campos (Universidade de São Paulo, Brazil) for providing unpublished iodide measurements in the sea surface microlayer and iodide measurements from the South Atlantic (via BODC), and John Brindle (University of East Anglia) for many patient hours of iodide analysis. Roberto Fernández Bilbao (now at University of Reading) helped in handling an earlier version of the dataset. We are also grateful to the officers, crew and scientific parties of the RRS James Clark Ross, RRS Discovery and RV Polarstern for support during cruises JR124, D325, D361 and ANT 18-1, and to Hugh Ducklow (Lamont Doherty Earth Observatory, US) for the collection of samples during cruise LMG1201 of the RV Laurence M. Gould. RC was supported to work on marine iodine chemistry by the Natural Environment Research Council (NERC) studentship NER/S/A/2003/11224 and NERC UK-SOLAS grant NE/D006538/1.
我们要感谢英国海洋学数据中心 (BODC) 提供编译中使用的数据，并感谢以下提供从 BODC 或在线档案检索的数据集：GW Luther, III（特拉华大学）、V. Truesdale（牛津）布鲁克斯大学）、RC Tian（马里兰大学）。我们要特别感谢 Lucia Campos（巴西圣保罗大学）提供了未发表的海面微层碘化物测量值和南大西洋碘化物测量值（通过BODC），以及 John Brindle（东安格利亚大学）为许多人提供了信息。患者进行碘化物分析的时间。 Roberto Fernández Bilbao（现就职于雷丁大学）帮助处理了该数据集的早期版本。我们还感谢 RRS James Clark Ross、RRS Discovery 和 RV Polarstern 的官员、船员和科学团队在 JR124、D325、D361 和 ANT 18-1 巡航期间提供的支持，并感谢 Hugh Ducklow（美国拉蒙特·多尔蒂地球观测站） ）用于在 RV Laurence M. Gould 的 LMG1201 巡航期间收集样本。 RC 的海洋碘化学工作得到了自然环境研究委员会 (NERC) 学生奖学金 NER/S/A/2003/11224 和 NERC UK-SOLAS 赠款 NE/D006538/1 的支持。

References  参考

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