Supply of soluble Fe to ocean surface waters - quantitative approaches from ICDP site Hawaii by determining interface driven Fe transfer from subsurface volcanic rocks

铁作为海洋表层浮游植物生长的关键限制性微量营养元素，对全球碳循环具有重要影响。人们认为火山岩对海洋某些部分的铁收支有显著贡献，但正如最近的一篇综述（Ayris & Delmelle, 2012）所述，对于这种影响的量化，对铁释放/溶解的复杂界面驱动机制的了解过于有限。特别是对微生物活动如何释放铁的了解很少。在夏威夷和其他火山岛附近，海洋表层可溶性铁的含量明显增加。来自ICDP站点HSDP2的样品是不同的几乎新鲜到蚀变的地下火山岩的档案，包括透明质碎屑岩、熔岩流和枕状玄武岩。因此，这些样品非常适合于检测铁在固液界面释放的相关机制、铁的溶解度模式和该过程的定量方法。在第一年，根据不同的标准选择合适的样品，如岩石类型、年龄、蚀变程度、淡水或海水的影响以及温度。定量四种不同的次级铁结合形式的核心样品是通过顺序提取程序完成的。采用比色湿化学法测定铁（II）和总铁（Fe）。在微生物学实验中，研究了真菌伯克霍尔德菌诱导铁从岩心样品转移到可溶性形式。用新鲜合成玄武岩玻璃进行定殖实验，结果表明菌株和亚铁对生物活性有较强的促进作用。离子对玄武岩玻璃在蚀变过程中固液界面化学的影响，通过zeta电位的测量和实验室实验样品以及岩心样品的比表面积（SSA）的测定来追踪，计划在第一提案的第二年进行。在申请资金的第三年，我们希望通过t依赖水释放、Woods金属侵入和渗透来研究岩石样品的孔隙度和孔隙连通性。层析研究和拉曼光谱将提供孔隙分布和相丰度的额外信息。此外，测量温度对放水量的影响将得到次生矿物含量的数据。各种参数（溶液组成、玻璃中的菌株、铁的氧化还原状态）对细菌定植的影响将通过XPS、ESEM和激光显微镜进行研究。将不同的发现与文献数据相结合，将提高我们对矿物组成、溶液组成、生化因素和可溶性铁释放变化率的相互依赖性的理解。

Fe as a key limiting micro-nutrient for phytoplankton growth in the surface ocean has impact on the global C cycle. Volcanic rocks are thought to have a marked contribution to the Fe budget in some parts of the oceans, but for quantification of the effect, as stated in a recent review (Ayris & Delmelle, 2012), knowledge on the complex interface driven mechanisms of Fe release/solubility is too limited. In particular the understanding how microbial activity works to release Fe is poor. Inventories on soluble Fe in the surface ocean show marked increases in the vicinity of Hawaii and other volcanic islands. Samples from ICDP site HSDP2 are an archive for different almost fresh to altered subsurface volcanic rocks from hyaloclastites, lava flows and pillow basalts. Thus, these samples are excellently suited for the detection of relevant mechanisms of Fe release at the solid-liquid interface, modes of Fe solubility and quantitative approaches on this process. In the first year suitable samples were selected based on different criteria such as type of rock, age, degree of alteration, fresh- or seawater influenced and temperature. Quantification of four different secondary Fe binding forms in core samples was done using a sequential extraction procedure. A colorimetric wet-chemistry method was used to quantify Fe(II) and total Fe. Fe transfer from core samples to a soluble form induced by the bacterium Burkholderia fungorum was investigated in microbiological experiments. Colonization experiments with fresh synthetic basaltic glasses were performed which show a strong promoting effect of strain and ferrous iron on biological activity. Ionic effects on the chemistry of the solid-liquid interface of basaltic glass during alteration traced by measurements of the zeta potential and determination of the specific surface area (SSA) of samples from laboratory experiments as well as core samples are planned for the second year of the first proposal.In the third year, for which funding is requested here, we want to study porosity and pore connectivity in the rock samples by T-dependent water-release, Woods metal intrusion and penetration. Tomographic studies and Raman spectroscopy will provide additional information on pore distribution and phase abundance. Additionally, the measurement of water-release in function of temperature will yield data about contents of secondary minerals. Influence of various parameters (solution composition, strain in glasses, redox state of iron) on bacterical colonization will be studied using XPS, ESEM and Laser microscopy. Combining the different findings with literature data will improve our understanding of interdependencies of mineralogical composition, solution composition, biochemical factors and alteration rates on release of soluble Fe.