A Comprehensive Combined ICP-MS/XAFS Study of Transition Metal Sorption on a Natural Organic Substrate

人们早就知道，天然水体中的大多数金属吸附涉及有机表面和无处不在的无机表面上的有机涂层。不幸的是，有机表面没有显示出在无机表面研究中如此有利的性质。例如，它们拥有令人眼花缭乱的各种官能团，其优势随着环境pH值的复杂变化而变化，从而产生很大的金属亲和力动态范围。此外，除了被动化学过程外，金属在生物体上的吸附还可能受到主动生理过程的驱动。在这个项目中，马里兰大学环境科学中心切萨ake生物实验室的研究人员将进行一种新颖的溶液（ICP-MS）和表面（XAFS）实验的结合，研究绿色大藻Ulva lactuca对过渡金属的吸附。Ulva lactuca是一种具有许多“原型”属性的生物。有机基质。初步研究表明，与已发表的将单一金属与简单生物（如浮游植物）或相当复杂的生物（如维管植物）配对的研究相比，最初选择U. lactuca和化学上连贯的钇和稀土元素（YREE）系列可以更直接地解决尚未解决的问题。特别是，可以根据相对稀土分布系数的模式进行表面位置识别，并使用EXAFS技术独立验证。实验策略是专门设计来回答这样的基本问题：(A)在溶液中与金属相互作用的主要官能团是哪些？(B)分布系数如何随pH和其他关键参数变化？(C)三元配合物能在有机表面形成吗？(D)金属吸附是否受到外聚物鞘层和有机配体渗出物的影响？(E)金属吸附的主动生理途径和被动化学途径之间有什么相互作用？该项目预计将对水生和海洋系统中过渡金属与有机表面相互作用的各种研究领域产生重大而广泛的影响。这些包括生物体的表面以及其他具有复杂有机涂层的固体表面。该项目将作为一名或两名研究生的硕士论文研究。

It has long been known that most metal sorption in natural waters involves organic surfaces and the organic coatings ubiquitously present on all inorganic surfaces. Unfortunately, organic surfaces display none of the properties that are so advantageous in studies of inorganic surfaces. For instance, they boast a bewildering variety of functional groups whose dominance shifts intricately with ambient pH, yielding a large dynamic range of metal affinities. Moreover, metal sorption on living organisms may be driven by active physiological in addition to passive chemical processes. In this project, researchers at the Chesapeake Biological Laboratory of the University of Maryland Center for Environmental Sciences will conduct a novel combination of solution (ICP-MS) and surface (XAFS) experiments to study the sorption of transition metals on the green macroalga Ulva lactuca, an organism possessing many attributes of a ?prototype? organic substrate. Preliminary work has demonstrated that the initial choice of U. lactuca and the chemically coherent yttrium and rare earth element (YREE) series allows unresolved problems to be addressed in a more straightforward manner than published studies that paired single metals with simple organisms (e.g., phytoplankton) or fairly elaborate ones (e.g., vascular plants). In particular, surface site identifications can be made from patterns of relative YREE distribution coefficients and verified independently with EXAFS techniques. The experimental strategy is specifically designed to answer such fundamental questions as: (A) Which are the dominant functional groups interacting with metals in solution? (B) How do distribution coefficients vary as a function of pH and other key parameters? (C) Do ternary complexes form on organic surfaces? (D) Is metal sorption affected by exopolymer sheaths and organic ligand exudates? (E) What interplay occurs between active physiological and passive chemical pathways of metal sorption? The project is expected to have significant broader impacts in a variety of research areas related to transition metal interactions with organic surfaces in aquatic and marine systems. These include the surfaces of living organisms as well as other solid surfaces with complex organic coatings. The project will serve as the M.Sc. thesis research of one or, if possible, two graduate students.