RUI: Quantitative XRD-Sequential Extraction Analysis of Trace Metal Speciation in Ultramafic-Derived Soils and Waters

0126018瑞安为了了解自然系统的微量金属预算的人为改变，首先重要的是要了解这些系统的矿物学和化学特征。富含微量金属的一种类型的系统是与超镁铁岩有关的自然环境。以前的研究记录了与超镁铁岩有关的土壤、植物和沃茨中铬、镍和钴等微量金属的浓度升高-在某些情况下，其浓度被认为对生态和人类健康有害。这些研究还没有做的是定量分析微量含金属相的形态，这是理解流动性的关键组成部分。我们将应用最近开发的定量XRD方法结合连续化学萃取（SCE）来评估痕量金属分配。SCE通常用于顺序溶解土壤中的矿物质和有机质。然而，只有当与先进的粉末XRD技术相结合时，才能使用连续提取来准确地确定土壤中的矿物成分，结构和丰度。这类数据特别重要，因为它提供了以下信息：（1）土壤中固相的溶解度，以及（2）矿物成分和结构对元素浓度、形态和流动性的影响。 除了XRD和SCE（使用ICP-AES），还将进行C-N分析以帮助确定土壤有机质含量，透射光和SEM分析将用于评估原生-次生矿物空间关系，激光衍射将用于评估各种土壤和矿物相的粒度。实地分析将包括测量Eh、pH值、Cr和Ni，本项目的目的是确定水圈表层中自然存在的微量金属的形态和浓度，包括超镁铁岩（新鲜和化学蚀变）、土壤（无机固体、有机物、土壤水）、地表水和河流沉积物。为了评估对这些岩石的风化和微量金属释放的主要控制，我们将从广泛的风化状态中取样和分析岩石、土壤和水标本，包括（1）冷温带、最近冰川化的北方阿巴拉契亚山脉（佛蒙特州），（2）冷温带、未冰川化的英格兰康沃尔，（3）半干旱和半湿润的北方加州，湿润热带哥斯达黎加。 这种比较分析的结果将被应用到一个预测模型的痕量金属形态在广泛的环境。

0126018 RyanIn order to understand anthropogenic alterations to the trace metal budget of natural systems, it is first important to understand the mineralogical and chemical features of such systems. One type of system enriched in trace metals is the natural environment found in association with ultramafic rocks. Previous studies have documented elevated concentrations of trace metals such as Cr, Ni and Co in soils, plants and waters associated with ultramafic rocks-- in some cases, at levels considered to be detrimental to ecological and human health. What these studies have not done is quantitatively analyze speciation of trace metal-bearing phases, which is a crucial component of understanding mobility. We will apply a recently developed quantitative XRD method in conjunction with sequential chemical extractions (SCE) to assess trace metal partitioning. SCE is often used to sequentially dissolve minerals and organic matter in soil. However, it is only when combined with advanced powder XRD techniques that sequential extractions can be used to accurately determine mineral composition, structure, and abundance in the soil. This type of data is especially important because it provides information on (1) the solubility of solid phases in the soil, and (2) the influence of mineral composition and structure on elemental concentration, speciation and mobility. In addition to XRD and SCE (using ICP-AES), C-N analyses will be performed to aid in determinations of soil organic matter content, transmitted light and SEM analyses will be used to assess primary-secondary mineral spatial relationships, and laser diffraction will be used to assess particle size of various soils and mineral phases. Field analyses will include measurements of Eh, pH, Cr and Ni.The intent of this project is to characterize the speciation and concentration of naturally-occurring trace metals in surficial aspects of the hydrosphere, including ultramafic rock (fresh and chemically altered), soil (inorganic solids, organic matter, soil water), surface water, and stream sediment. In order to assess the main controls on weathering and release of trace metals from these rocks, we will sample and analyze rock, soil and water specimens from a wide range of weathering regimes, including (1) the cool temperate, recently glaciated northern Appalachians (Vermont), (2) cool, temperate, unglaciated Cornwall, England, (3) semiarid and subhumid northern California, and (4) humid tropical Costa Rica. Results of this comparative analysis will be applied to a predictive model of trace metal speciation in a wide range of environments.