Aerosol iron solubility over the Southern and Atlantic Oceans

本项目旨在研究环境中铁化学对海洋中微观植物（浮游植物）生长影响的一些重要方面。海洋中的铁含量极低，这给浮游植物带来了一个问题，因为铁是它们许多酶系统的重要组成部分。大量的铁从世界各地的沙漠中被吹入海洋，但离沙漠很远的海洋地区吸收的铁很少。南极洲周围的南大洋就是这样一个地区，那里的铁含量非常低，以至于在大片地区，浮游植物种群无法消耗大量的营养物质，如氮和磷，因为它们有足够的铁（它们是铁有限的）。矛盾的是，尽管南大洋作为一个铁含量有限的区域具有重要意义，但我们所掌握的关于从大气中输入的铁的可靠资料可能是最不可靠的。因此，我们项目的目标之一是在两次研究巡航中收集雨水和气溶胶的样本，这两次巡航将从非洲南端到南极洲，然后向西穿越南大洋的威德尔海，最后向北到达南美洲的尖端。研究进入海洋的铁元素的一个复杂因素是，以灰尘形式进入海洋的铁元素中有很大一部分留在了灰尘中，只是落到了海底。只有溶解在海水中的那部分铁可供浮游植物利用。了解可溶部分是什么，以及什么环境因素控制它，是一个主要的挑战。我们的第二个目标是测量在两次南大洋巡航中收集的气溶胶样本中铁的可溶性部分，以及我们在大西洋其他地区的11次其他研究巡航中收集的样本。这个庞大的数据库将使我们更好地了解地球系统的这个关键组成部分是如何运作的，以及铁沉积到海洋中如何影响浮游植物的生长和气候。

This project aims to study some important aspects of the influence of iron chemistry in the environment on the growth of microscopic plants (phytoplankton) in the ocean. Levels of iron in the ocean are extremely low and this poses a problem for phytoplankton, because iron is an essential component of many of their enzyme systems. Large amounts of iron get blown into the oceans from deserts around the world, but ocean areas a great distance from deserts receive very little of this iron. The Southern Ocean around Antarctica is one such area, where iron levels are so low that in vast areas the phytoplankton population is unable to use up large stores of nutrients such as nitrogen and phosphorus because they do have enough iron (they are iron-limited). Paradoxically, despite the importance of the Southern Ocean as an iron-limited region, it is probably the ocean region for which we have the least reliable information on iron inputs from the atmosphere. One of the goals of our project is therefore to collect samples of rain and aerosol during two research cruises that together will track from the southern tip of Africa to Antarctica, then west across a region of the Southern Ocean known as the Weddell Sea, and finally north to the tip of South America. A complicating factor in studying iron inputs to the ocean is that a large proportion of the iron that falls into the ocean in dust remains in the dust and simply falls to the seabed. Only the proportion of iron that dissolves in seawater is available for use by phytoplankton. Understanding what that soluble portion is, and what environmental factors control it, is a major challenge. Our second goal is to measure the soluble portion of iron in aerosol samples collected during the two Southern Ocean cruises and also in samples we have already collected during 11 other research cruises in other regions of the Atlantic Ocean. This large database will allow us to better understand how this key component of the Earth System functions and how iron deposited into the oceans can affect phytoplankton growth and climate.