Development of gallium-aluminum ratios as a tracer of the Critical Zone behavior of Al

铝（Al）是常见的原生和次生造岩矿物的主要成分，并形成主要土壤矿物和粘土的“骨架”。涉及铝的矿物转化是风化和土壤形成过程的基础。已知铝在生物体中没有任何有益作用，并且在高浓度下可能对水生生物有毒。 铝能抑制植物对土壤中养分的吸收，土壤中高铝有效性已被证明限制作物生产力。铝在环境中的化学行为很复杂，很难研究。 地球化学家用来研究许多其他元素行为的工具之一是使用天然存在的同位素的变化作为示踪剂，但铝只有一种同位素。 相反，研究人员建议开发镓（Ga）与铝的比例作为Al行为的示踪剂。 Ga具有与Al类似的化学性质，并且显示出整体相干行为。 他可以使用Ga/Al比率来确定环境中Al的关键矿物来源和反应途径。 此外，镓本身是一种具有关键技术应用的微量元素，用于普通消费产品（如蜂窝电话）的关键电子元件。 因此，镓被美国能源部列为“战略金属”。 例如，计划中的研究应该为可以将Ga富集到铝土矿中经济可回收水平的过程提供更多的见解。 拟议的研究将与临界区观测站国家办公室（CZO-NO）合作，创建与临界区科学相关的宣传和教育材料。铝的毒性和镓作为一个关键资源的应用方面提供了一个很好的机会，开发课程资源连接基础研究和社会影响。研究人员将与CZO-NO合作，为中学和本科科学课程开发课程资源，以支持下一代科学标准（NGSS，2013）。他将继续通过工程和生物学部门促进对HBCU的推广，以展示关键区科学的智力兴奋和社会影响。在HBCUs建立连接是特别重要的建设地球科学的多样性，因为大多数没有地球科学系，因此没有传统的管道地球科学研究生programmes.The调查员建议开发镓铝比（Ga/Al）作为一种有效的地球化学示踪剂的行为铝在关键区。 总体目标是发展必要的基本理解，以支持使用镓/铝作为一种有效的工具，质量平衡和示踪剂研究的铝在临界区和超越; a？伪同位素他将重点讨论控制Al在临界带中分布并可能导致Ga/Al分馏的四个过程，以回答以下问题：1）粘土矿物和羟基氧化物的新形成是否是风化过程中Ga/Al分馏的原因？2)Ga和Al在临界区中的分馏是否由溶液化学（即水解或配体络合物形成）驱动？3)Ga和Al在胶体中的结合差异是否会导致Ga在流输出过程中从Al中分馏？他将使用现场和实验室为基础的研究相结合的材料从花岗岩集水区在四个关键区观测站（卡尔霍恩，博尔德溪，卡塔利娜-赫梅兹，和卢基略）。他将分析岩石，土壤，植物和水样品，以表征Ga/Al比在不同气候，风化和生物活动条件下的行为。矿物合成和土壤柱淋溶实验在实验室中将提供理解的Ga在羟基氧化物中的分配和有机配体对Ga和Al在土壤中的影响，地球化学模拟的支持。开发一种有效的环境中铝的示踪剂，将受到环境和地球科学界的广泛关注。铝在许多地球化学过程中起着核心作用，并与人类健康，水质和作物生产力等多个问题有关。作为一种战略金属，提高对镓地球化学的认识对社会也具有广泛的重要性。拟议的工作将提供深入了解镓地球化学，将感兴趣的矿产勘探界，特别是考虑到CZ过程是负责形成的主要经济来源的镓，铝土矿。

Aluminum (Al) is a major component of common primary and secondary rock-forming minerals, and forms the "backbone" of major soil minerals and clays. Mineral transformations involving aluminum are fundamental to weathering and soil formation processes. Aluminum is not known to perform any beneficial role in organisms, and can be toxic to aquatic life at elevated concentrations. Aluminum can inhibit plant uptake of nutrients in soils, and high Al availability in soils has been shown to limit crop productivity. The chemical behavior of aluminum in the environment is complex, making it difficult to investigate. One of the tools that geochemists have used to study the behavior of many other elements is to use variations in naturally occurring isotopes as tracers, but aluminum only has one isotope. Instead, the investigator proposes to develop the ratio of gallium (Ga) to aluminum as a tracer for Al behavior. Ga has similar chemistry to Al, and shows overall coherent behavior. He can use Ga/Al ratios to identify key mineral sources and reaction pathways for Al in the environment. Further, gallium itself is a trace element with critical technological applications, used in key electronic components in common consumer products such as cellular telephones. As such, gallium is classified as a "strategic metal" by the US Department of Energy. The planned research should provide additional insight into processes that can enrich Ga to levels that are economically recoverable in bauxite ores, for example. Proposed research will work in conjunction with the Critical Zone Observatories National Office (CZO-NO) to create outreach and educational materials related to Critical Zone science. The applied aspects of Al toxicity and Ga as a critical resource provide an excellent opportunity to develop curricular resources linking basic research and societal impacts. The investigator will work with the CZO-NO to develop curricular resources for secondary school and undergraduate science programs in support of Next Generation Science Standards (NGSS, 2013). He will continue fostering outreach to HBCUs via engineering and biology departments to demonstrate intellectual excitement and societal impacts of Critical Zone science. Building connections at HBCUs is especially important for building geoscience diversity since most do not have geoscience departments and thus do not have a traditional pipeline to Earth science graduate programs.The investigator proposes to develop gallium-aluminum ratios (Ga/Al) as an effective geochemical tracer for the behavior of Al in the Critical Zone. The overarching goal is to develop the necessary fundamental understanding to support the use of Ga/Al as an effective tool for mass balance and tracer studies of Al in the Critical Zone and beyond; a ?pseudo-isotope? for Al. He will focus on four of the processes that control the distribution of Al in the Critical Zone and may cause fractionation of Ga/Al in order to answer the following questions: 1) Is the neoformation of clay minerals and oxyhydroxides responsible for Ga/Al fractionation during weathering? 2) Is the fractionation of Ga and Al in the Critical Zone driven by solution chemistry (i.e. hydrolysis or ligand complex formation)? 3) Do differences in the incorporation of Ga and Al in colloids result in fractionation of Ga from Al during stream export? He will use a combination of field and laboratory-based studies on materials from granitoid catchments across four Critical Zone Observatories (Calhoun, Boulder Creek, Catalina-Jemez, and Luquillo). He will analyze rock, soil, plant, and water samples from each to characterize the behavior of Ga/Al ratio under different conditions of climate, weathering and biological activity. Mineral synthesis and soil column leaching experiments in the laboratory will provide understand partitioning of Ga in oxyhydroxides and the impact of organic ligands on Ga and Al in soils, supported by geochemical modeling. Development of an effective tracer for Al in the environment should be of broad interested to the environmental and geoscience community. Aluminum plays a central role in many geochemical processes and is associated with multiple issues in human health, water quality, and crop productivity. As a strategic metal, an improved understanding of gallium geochemistry is also of broad importance for society. The proposed work will provide insight into Ga geochemistry that will be of interest to the mineral exploration community, especially given that CZ processes are responsible for the formation of the main economic source of Ga, bauxites.