Iron isotope signatures of recent sedimentary pyrite in the Baltic Sea - Contribution to the development of a Paleoceanograpic proxy

波罗的海近期沉积黄铁矿的铁同位素特征 - 对古海洋学代理开发的贡献

• 批准号: NE/J004650/1
• 负责人: Manuela Fehr
• 金额: $ 9.66万
• 依托单位: The Open University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FJ004650%2F1
• 关键词: Iron; isotope; signatures; recent; sedimentary

The marine environment is vulnerable to profound future modification as a result of environmental change. Along with ocean acidification, a widespread increase of oxygen deficient conditions is likely over the coming years. How these modifications will be manifest in the modern oceans is still uncertain. Parts of the bottom waters of the Baltic Sea and the Black Sea are at present deficient in oxygen since very limited exchange with surface waters and inflowing freshwater occurs. Such conditions are rare in the present ocean, but have been more widespread in the Earth's history and may become more widespread in the future as a result of a global temperature increase. Modern oxygen-deficient environments that are present in the Baltic Sea and Black Sea are analogues for ancient oceans and provide important information on how ocean chemistry has changed over time. This project will study two locations in the Baltic Sea, the Gotland Deep and the Landsort Deep, in order to test and calibrate a new tool, iron isotopes, so that it can be applied to past changes in the oxygen content of the ocean.Iron is the fourth most abundant element in the Earth's crust. It is much more soluble during oxygen-deficient conditions than during oxic conditions and therefore, iron concentrations in modern oceans are very low. Iron is also an essential trace element for most living organisms. Marine phytoplankton use CO2 from the atmosphere for growing. The phytoplankton grows faster when more iron is available and therefore, iron is linked to the global climate. Consequently, iron is an important element to study, and recent developments in measuring iron isotopes provide a critical new tool to study the role of iron in the oceans. For iron isotope studies, the relative abundance of iron atoms that have slightly different masses (isotopes) needs to be measured to high precision using a mass spectrometer. Each isotope of iron has slightly different chemical and physical properties due to their different masses and as a result, behaves differently in many processes that involve iron. In particular, iron isotopes give important information about changes in oxygen contents and biological processes.The Baltic Sea is a unique setting where changes from oxygen-rich to oxygen-deficient conditions can be studied, since these occurred repeatedly over the last few hundreds of years. These changes are recorded in the sediments of the Baltic Sea and result in particular in different formation mechanisms of the iron-sulphide mineral pyrite. Pyrite is the most stable iron sulfide mineral and has therefore been intensively studied. The processes that determine the Fe isotopic composition of pyrite are, however, not well understood. This project will investigate how the iron isotope composition of pyrite changes with different formation mechanisms and oxygen contents of the bottom water.The Baltic Sea has problems with heavy-metal pollution and spring algal blooms that are related to redox conditions and iron. Some species of blue-green algae are toxic to humans and the blooms further reduce the oxygen content of the water. The proposed study of iron-redox cycling in the Baltic Sea using Fe isotopes will contribute to a better understanding of the processes that cause the environmental problems in the Baltic Sea.

由于环境变化，海洋环境容易受到深刻的未来修改。随着海洋酸化，在未来几年中可能会广泛增加氧气不足的状况。这些修改将如何在现代海洋中表现出来仍然不确定。目前，波罗的海和黑海的底部水域的一部分缺乏氧气，因为与地表水的交换非常有限，并且出现了淡水流动。在目前的海洋中，这种情况很少见，但在地球的历史上更为普遍，并且由于全球温度的升高，未来可能会变得更加普遍。波罗的海和黑海存在的现代缺氧环境是古代海洋的类似物，并提供了有关海洋化学如何随着时间变化的重要信息。该项目将研究波罗的海，哥特兰深处和兰德索的两个位置，以测试和校准一种新工具，即铁同位素，以便将其应用于海洋氧含量的过去变化。在缺氧条件下，它比在病情条件下更可溶，因此，现代海洋的铁浓度非常低。铁也是大多数生物体的必不可少的痕量元素。海洋浮游植物使用大气中的二氧化碳来生长。浮游植物在有更多的铁时生长更快，因此，铁与全球气候有关。因此，铁是研究的重要元素，测量铁同位素的最新发展为研究铁在海洋中的作用提供了关键的新工具。对于铁同位素研究，需要使用质谱仪将其质量略有不同的铁原子的相对丰度（同位素）测量。铁的每种同位素由于其不同的质量而具有略有不同的化学和物理性能，因此，在涉及铁的许多过程中的行为不同。特别是，铁同位素提供了有关氧含量和生物过程变化的重要信息。波罗的海是一个独特的环境，可以研究从富含氧气到缺氧的条件的变化，因为这些条件在过去几百年中反复发生。这些变化记录在波罗的海的沉积物中，尤其是在铁硫化矿物黄铁矿的不同形成机理中。黄铁矿是最稳定的硫化铁矿物质，因此已被深入研究。但是，确定黄铁矿的Fe同位素组成的过程尚不清楚。该项目将研究黄铁矿的铁同位素组成如何随着底部水的不同形成机制和氧含量而变化。波罗的海存在与氧化还原条件和铁相关的重金属污染和春季藻华的问题。一些蓝绿色藻类对人有毒，而开花进一步降低了水的氧气含量。拟议的使用FE同位素在波罗的海中对铁 - 雷克斯循环的研究将有助于更好地理解引起波罗的海环境问题的过程。