Background & Summary  背景与总结

There has recently been a resurgence of interest in the marine iodine cycle, reflecting its involvement in a diverse range of processes, from influencing air quality (e.g.1) to recording ocean deoxygenation in sediments (e.g.2). Iodine is a redox active element that is present in seawater in two main forms, iodide (I) and iodate (IO3). Sea-to-air transfer is the dominant source of iodine to the atmosphere, where it is subject to atmospheric processing prior to deposition back to the sea or onto land. It is an essential nutrient for many organisms including humans, and deficiency in humans leads to goitre, cretinism and is the leading cause of preventable mental retardation globally3. Iodine radionuclides are also released to the oceans by anthropogenic activities, where they will be subject to the same processes of biogeochemical cycling and volatilisation as the naturally occurring stable isotope4. Despite the wide ranging impacts of iodine biogeochemistry, the distribution of iodine species in the oceans remains relatively poorly understood. Here we present an updated compilation of all currently available sea surface iodide concentrations. The data set is specifically intended to inform studies of the sea-air exchange of iodine species, but may also be of use in improving understanding of the marine iodine cycle more generally.
最近人们对海洋碘循环的兴趣重新兴起,反映出它参与了各种过程,从影响空气质量(例如1 )到记录沉积物中的海洋脱氧(例如2 )。碘是一种氧化还原活性元素,以两种主要形式存在于海水中:碘化物 (I ) 和碘酸盐 (IO 3 )。海空转移是碘进入大气的主要来源,碘在沉积回海洋或陆地之前要经过大气处理。它是包括人类在内的许多生物体的必需营养素,人类缺乏它会导致甲状腺肿、克汀病,并且是全球可预防的智力低下的主要原因3 。碘放射性核素也通过人类活动释放到海洋,它们将经历与天然存在的稳定同位素相同的生物地球化学循环和挥发过程4 。尽管碘生物地球化学具有广泛的影响,但人们对海洋中碘物种的分布仍然知之甚少。在这里,我们提供了所有当前可用的海面碘化物浓度的更新汇编。该数据集专门用于为碘物质的海-气交换研究提供信息,但也可用于更广泛地增进对海洋碘循环的了解。

The reaction of iodide with ozone at the surface of the ocean has been established as an important sink for ozone, thought to be responsible for around one third of the total ozone loss by dry deposition5. The reaction liberates reactive iodine compounds to the atmosphere, which in turn contribute to further ozone removal processes. Gas phase reactions involving iodine are estimated to account for up to 15% of tropospheric ozone losses6. To incorporate this chemistry, global and regional air quality and atmospheric chemistry models have begun to include predicted sea-surface iodide fields derived from parameterisations (e.g.5,7,8,9). However, current sea surface iodide parameterisations are known to have biases10, are subject to substantial uncertainty6, and do not take advantage of recent and substantial increases in the number of available observations (e.g.11).
碘化物与海洋表面臭氧的反应已被确定为重要的臭氧汇,据认为约三分之一的干沉积臭氧损失是由臭氧汇造成的5 。该反应将活性碘化合物释放到大气中,这反过来又有助于进一步去除臭氧的过程。据估计,涉及碘的气相反应占对流层臭氧损失的 15% 6 。为了纳入这种化学作用,全球和区域空气质量和大气化学模型已开始包括从参数化得出的预测海面碘化物场(例如5789 )。然而,目前的海面碘化物参数化已知存在偏差10 ,存在很大的不确定性6 ,并且没有利用最近可用观测数量的大幅增加(例如11 )。

The observational data underpinning iodide parameterisations is sparse, and has hitherto not been publicly available in a collated form. In many cases, iodide observations are not readily accessible in a digital form (i.e. are only presented in graphical format). To facilitate the development and validation of improved sea surface iodide parameterisations, we have compiled all available sea surface iodide observations. The dataset is an extended version of that used in our earlier publication12, in which we described the large scale sea surface iodide distribution and presented correlations between iodide and other oceanographic variables, but did not publish the observations themselves. The dataset we now present incorporates more than 400 new observations (see Fig. 1), including new, basin scale transects from the Indian Ocean (currently unpublished) and the tropical eastern Pacific11, both of which were previously undersampled12. This new extended dataset is freely available via the British Oceanographic Data Centre (BODC; http://doi.org/czhx)13.
支持碘化物参数化的观测数据很少,并且迄今为止尚未以整理的形式公开提供。在许多情况下,碘化物观测结果不容易以数字形式获得(即仅以图形格式呈现)。为了促进改进的海面碘化物参数化的开发和验证,我们汇编了所有可用的海面碘化物观测结果。该数据集是我们早期出版物12中使用的数据集的扩展版本,其中我们描述了大规模海面碘化物分布,并提出了碘化物与其他海洋学变量之间的相关性,但并未发布观测结果本身。我们现在提供的数据集包含 400 多个新观测数据(见图1 ),包括来自印度洋(目前未发布)和热带东太平洋11 的新盆地规模横断面,这两个区域之前都采样不足12 。这个新的扩展数据集可通过英国海洋学数据中心(BODC;http://doi.org/czhx)免费获取13

Fig. 1  图1
figure 1

Locations of iodide observations included in our dataset. New data reported here is in red and existing data from Chance et al.12 is blue. Figure produced with Python Matplotlib79.
我们的数据集中包含碘化物观测位置。此处报告的新数据以红色显示,现有数据来自 Chance等人12是蓝色的。使用 Python Matplotlib 79生成的图。

We anticipate that the primary use of the dataset will be modelling of ozone deposition to the sea surface and/or associated trace gas emissions to the atmosphere. It has been used to generate new monthly parameterised sea-surface iodide fields (12 × 12 km resolution) using a machine learning approach, described in our accompanying partner publication10. The dataset may also be of interest in other areas of iodine research. In particular, improved understanding of the marine iodine cycle is needed to refine the use of iodine speciation as a paleo-oceanographic tracer of past ocean oxygenation (e.g.2), and to better predict the impacts of iodine radionuclides released to the environment by anthropogenic activities (e.g.4).
我们预计该数据集的主要用途将是对海面臭氧沉积和/或相关的大气痕量气体排放进行建模。它已被用于使用机器学习方法生成新的每月参数化海面碘化物场(12 × 12 km 分辨率),如我们随附的合作伙伴出版物10中所述。该数据集也可能对碘研究的其他领域感兴趣。特别是,需要加深对海洋碘循环的了解,以完善碘形态作为过去海洋氧化作用的古海洋示踪剂的使用(例如2 ),并更好地预测人类活动释放到环境中的碘放射性核素的影响(例如4 )。

Methods  方法

Data compilation  资料整理

The data set includes iodide measurements made by a number of different research groups (Online-only Table 1). These were collated from the following sources:
该数据集包括由多个不同研究小组进行的碘化物测量(仅在线表1 )。这些内容是从以下来源整理的:

  1. A.  一个。

    Published manuscripts. Data was digitised from tables and graphics, either by hand or using the free online tool WebPlotDigitizer (https://automeris.io/WebPlotDigitizer).
    发表手稿。数据通过手工或使用免费在线工具 WebPlotDigitizer ( https://automeris.io/WebPlotDigitizer ) 从表格和图形中数字化。

  2. B.

    Data originators. Data (both published and unpublished) was provided directly by the owners.
    数据发起者。数据(已发布和未发布)由所有者直接提供。

  3. C.

    Data repositories. Data was obtained by request or on-demand download from hosting repositories (e.g. BODC, PANGAEA, the US JGOFS Data System).
    数据存储库。数据是通过请求或从托管存储库(例如 BODC、PANGAEA、美国 JGOFS 数据系统)按需下载获得的。

Following the approach adopted previously12, ‘surface’ concentrations are considered to be those from depths of less than 20 m. As discussed in Chance et al.12, the ocean is usually considered well mixed to this depth, and to restrict ‘surface data’ to shallower depths would substantially reduce the number of observations included. We examined a sub-set of data (n = 93) where observations were available from multiple depths within the upper 20 m of the water column. While significant differences were occasionally found between individual pairs of samples collected from depths of ~1-2 m and ~10 m at a given station, concentrations were within 10 nM in almost 50% of pairs (49.5%), and 80% were within 26 nM. Statistical analysis (using a paired students t-test) found no significant difference between samples from different depths within the upper 20 m. The exact depth of near surface samples can itself have high relative uncertainty, as factors such as sea swell can lead to metre scale fluctuations to the exact depth of e.g. a ship seawater inlet. Furthermore, the exact depths of such inlets, or the ‘surface’ sample bottle, was not always stated in the original data sources. Therefore, we have not included depth as a parameter in our compiled data set and no distinction has been made between samples obtained using a CTD rosette fitted with Niskin bottles (or similar), a pumped underway seawater supply or a manual method (such as bucket sampling).
按照之前采用的方法12 ,“表面”浓度被认为是来自深度小于 20 m 的浓度。正如 Chance等人所讨论的。如图12所示,海洋