Geochemical Switches

地球化学开关

• 批准号: 9980532
• 负责人: George Helz
• 金额: $ 32.43万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-01-01 至 2002-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9980532&HistoricalAwards=false
• 关键词: Geochemical; Switches

Helz9980532Biogenic sulfide profoundly affects geochemical behavior of many elements. This study focuses on interactions between HS- and oxyanions of the elements Mo, Re, Ge, As and Sb. In some cases soluble thioanions are formed by replacement of O atoms by S atoms around the core element in the presence of HS-. A dramatic switch in the geochemical properties of the core element ensues. The best studied example, the transformation of MoO42- to MoS42-, occurs abruptly at H2S(aq) = 11 3 ?M under near-equilibrium conditions. The abrupt character of the transformation and marked difference in geochemical properties of the thioanion vs. the oxyanion have led us to describe this transformation as a geochemical switch (Helz et al. 1996). Sulfide-actuated switches affect important geochemical properties of core elements: mobility, bioavailability, and chemical interactions with other solutes. Because thioanions are multidentate, sulfur-donating ligands, they are expected to interact particularly strongly with soft metals, which include many hazardous metals. The environmental and biogeochemical implications of such interactions are still unknown. Calibrating the action points of switches will enhance the use of trace elements as paleoredox indicators. The chief goal is production of the kinds of fundamental data needed in geochemical models to predict behavior of elements in reducing environments.

生物成因硫化物深刻地影响着许多元素的地球化学行为。本文主要研究了Mo、Re、Ge、As、Sb等元素的HS-离子与氧阴离子的相互作用。在某些情况下，在HS-存在的情况下，核心元素周围的S原子取代了O原子，形成了可溶的硫代阴离子。随后，核心元素的地球化学性质发生了戏剧性的变化。研究得最好的一个例子是MoO42-向MoS42-的转变，在近平衡条件下，当H_2S(Aq)=11.3M时发生突变。这种转变的突发性和硫代阴离子与氧阴离子在地球化学性质上的显著差异使我们将这种转变描述为一种地球化学开关(Helz等人)。1996年)。硫化物驱动的开关影响核心元素的重要地球化学性质：流动性、生物利用度以及与其他溶质的化学相互作用。由于硫代阴离子是多齿的供硫型配体，它们有望与软金属发生特别强烈的相互作用，其中包括许多危险金属。这种相互作用对环境和生物地球化学的影响尚不清楚。校准开关的作用点将加强微量元素作为古氧化还原指示剂的使用。主要目标是产生在地化模型中所需的各种基本数据，以预测元素在还原环境中的行为。