Zeolites--A Potential New Tool for Environmental Studies? Isotope and Elemental Studies of Zeolites

沸石——环境研究的潜在新工具？

• 批准号: 9628402
• 负责人: Xiahong Feng
• 金额: $ 13.99万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-08-01 至 2000-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9628402&HistoricalAwards=false
• 关键词: Zeolites; Potential; New; Tool; Environmental

Feng 9628402 This proposal describes a three year project that studies natural zeolites and their relationship to environmental change. Since the exchange rate between zeolite and the environment is affected by many factors, our approach includes collecting samples from a number of different environments and using chemical and isotope tracers that respond to various environmental factors with different sensitivity. These tracers are oxygen, hydrogen and nitrogen isotopic compositions, K/Ar dating, and major and trace elements. Our initial efforts will be focused on Yucca Mountain drill core samples for two reasons. First, preliminary results on oxygen isotopic compositions of zeolites and clay minerals and the K/Ar dates have provided very affirmed indication for the feasibility of the project. Oxygen isotope compositions show that clinoptilolite from Yucca Mountains is out of equilibrium with the current temperature and fluid conditions. The results also imply a possibility to determine groundwater level variations since zeolite formation. The second and an obvious reason is that there has been a great amount of interdisciplinary research done for the site as a result of the site characterization efforts of the nation's first high-level nuclear wastes repository. A number of other zeolite-containing units will also be sampled to do a comparative study. These units will include the John Day Formation of Oregon, The Barstow Formation, Mud Hills and Lake Tecopa of Inyo County, California, and few zeolite ore deposits in Northeast China. These sites vary in age, diagenetic history and hydrological environments, and can be compared to the Yucca Mountain site. For each tracer, we will study mineral separates of zeolites and other authigenic minerals that are much less exchangeable, such as feldspars and clay minerals. These less exchangeable minerals can be considered to have preserved the formational information, and can be used to derive the conditions and environments (temperat ure and chemical and isotopic compositions of fluid) at the time of zeolite formation. If we assume that all the authigenic minerals formed at the same time and from the same fluid, the current compositions of zeolites may be related to the environmental changes occurred after their formation. For zeolites, we will also study, if possible, the chemical and isotopic compositions of different size fractions. This would help us understand the mechanisms (diffusion versus recrystallization) of exchange between zeolite and fluid, and determine whether zeolite has reached equilibrium with the current pore fluid and at the current temperature. Experimental studies will be conducted to understand the mechanism for chemical and isotopic exchange between zeolites and the environmental fluid, and to determine the physical constants (such as diffusivity and rate constants) necessary for quantifying the rate of exchange from the analytical data of natural zeoliltes.

丰9628402 该提案描述了一个为期三年的项目，研究天然沸石及其与环境变化的关系。 由于沸石与环境之间的交换率受许多因素的影响，我们的方法包括从许多不同的环境中收集样品，并使用化学和同位素示踪剂，以不同的灵敏度响应各种环境因素。 这些示踪剂是氧、氢和氮同位素组成、K/Ar定年以及常量和微量元素。 我们最初的努力将集中在尤卡山钻芯样品有两个原因。 首先，沸石和粘土矿物的氧同位素组成和K/Ar年龄的初步结果为项目的可行性提供了非常肯定的指示。 氧同位素组成表明，尤卡山斜发沸石与当时的温度和流体条件不平衡。 结果还意味着一种可能性，以确定自沸石形成地下水位的变化。 第二个也是一个明显的原因是，由于国家第一个高放核废料处置库的场地特征化工作，对该场地进行了大量的跨学科研究。 还将对一些其他含沸石的单元进行取样以进行比较研究。 这些单元将包括俄勒冈州的约翰戴组、加州因约县的巴斯托组、泥山和特科帕湖，以及中国东北的一些沸石矿床。 这些遗址在年龄、成岩历史和水文环境方面各不相同，可以与尤卡山遗址相比较。 对于每一种示踪剂，我们将研究沸石和其他自生矿物的矿物分离，这些自生矿物的可交换性要低得多，如长石和粘土矿物。 这些可交换性较低的矿物可被认为保存了地层信息，并可用于推导沸石形成时的条件和环境（温度、流体的化学和同位素组成）。 如果我们假设所有自生矿物都是在同一时间、同一流体中形成的，那么沸石的现今组成可能与它们形成后所经历的环境变化有关。 对于沸石，如果可能的话，我们还将研究不同粒度级分的化学和同位素组成。 这将有助于我们理解沸石和流体之间的交换机制（扩散与重结晶），并确定沸石是否与当前孔隙流体和当前温度下达到平衡。 将进行实验研究，以了解沸石和环境流体之间的化学和同位素交换机制，并确定从天然沸石的分析数据中量化交换速率所需的物理常数（如扩散率和速率常数）。