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Investigation of reductive chromium removal and associated stable isotope fractionation within the Oxygen Minimum Zone offshore Peru

秘鲁近海最低氧区内还原铬去除和相关稳定同位素分馏的调查

基本信息

批准号：
395901092
负责人：
Dr. Philipp Nasemann
金额：
--
依托单位：
Department of Physics and Earth Sciences
依托单位国家：
德国
项目类别：
Research Fellowships
财政年份：
2018
资助国家：
德国
起止时间：
2017-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/395901092?language=en
关键词：
Investigation reductive chromium removal associated

项目摘要

Chromium (Cr) is a transition metal that occurs only at trace levels in seawater (~80 to 550 ng/kg). The distribution of stable Cr isotopes is thereby highly susceptible to redox changes, which has promoted development of stable Cr isotopes as a proxy for the evaluation of redox conditions and oxygenation in the water column. First investigations have revealed an unexpected heterogeneity of seawater Cr isotopes hypothesized to derive from surface water removal of reduced Cr species and associated isotope fractionation in Oxygen Minimum Zones (OMZs), possibly utilizing phytoplankton as removal vector. In order to test this hypothesis and better disclose the extend of surface and deep water Cr isotope variability, a two-year project investigating Cr isotopes in seawater and sediment samples collected along the Peru Margin is proposed for a DFG research fellowship. The Peru Margin hosts the most prevalent OMZ found in the modern-day oceans and covers major gradients in coastal upwelling and benthic flux intensities, producing variations in nutrient supply that affect primary production. It thus provides a unique setting to conduct a detailed study assessing the influence of changing biogeochemical and redox conditions on Cr isotope behaviour in the marine environment and across the seawater-sediment boundary. Gaining an enhanced understanding of the factors controlling Cr isotope fractionation is a prerequisite for establishing Cr isotopes as a novel isotope proxy, and is greatly assisted by the wealth of information already available for the selected samples and the entire Peruvian upwelling region.The required analytical methods facilitating Cr isotope analysis of seawater and sediment samples including chemical pre-concentration and purification techniques as well as advanced methods in isotope ratio mass spectrometry, are routinely applied at the Institute of Geological Sciences, University of Bern, allowing for prompt first results. The output of the proposed research project will provide critically needed insights into Cr isotope effects internal to the oceans with far-reaching implications for the interpretation of sedimentary Cr isotope records and our understanding of the marine carbon cycle and nutrient biogeochemistry.

铬（Cr）是一种过渡金属，仅在海水中以痕量水平存在（约80至550 ng/kg）。因此，稳定的铬同位素的分布对氧化还原变化非常敏感，这促进了稳定的铬同位素作为水柱中氧化还原条件和氧化作用的评价的代表的发展。第一次调查发现了一个意想不到的海水铬同位素的异质性，假设来自地表水去除减少铬物种和相关的同位素分馏氧最低区（OMZs），可能利用浮游植物作为去除载体。为了检验这一假设，并更好地揭示表层和深层水铬同位素变异的程度，提出了一个为期两年的项目，调查沿着秘鲁边缘收集的海水和沉积物样品中的铬同位素DFG研究金。秘鲁陆缘是现代海洋中最普遍的有机物隔离区，覆盖了沿海涌升和海底通量强度的主要梯度，造成影响初级生产的营养供应变化。因此，它提供了一个独特的设置进行详细的研究，评估不断变化的海洋地球化学和氧化还原条件对铬同位素行为在海洋环境中的影响，并跨越海水沉积物边界。提高对控制Cr同位素分馏的因素的认识是建立Cr同位素作为一种新的同位素代用指标的先决条件，所需的分析方法有助于海水和沉积物样品的铬同位素分析，包括化学预处理，伯尔尼大学地质科学研究所定期应用浓缩和纯化技术以及同位素比质谱法中的先进方法，从而迅速获得第一批结果。拟议研究项目的产出将提供急需的深入了解海洋内部的铬同位素效应，对沉积铬同位素记录的解释以及我们对海洋碳循环和营养物地球化学的理解产生深远影响。