RPG: Nonionic Organic Pollutant Sorption Mechanisms in Natural Clay-Rich Aquitards

摘要EAR-9506403富含艾伦-金粘土的含水层和人造粘土衬垫为污染物的迁移提供了低渗透性屏障，并因其对地下地下水资源的保护范围而被用于危险废物处理。含水层基质中的吸附阻碍了运输，并随着时间的推移为有机污染物的吸收和释放提供了一个汇。然而，富含粘土的含水层中的吸附机理还不是很清楚。例如，最近的观察表明，现有方法严重低估了四氯乙烯(PCE)在几个粘土丰富且碳含量相对较低的天然含水层中的吸附。假设在天然、低组分有机含量(FOC)和富含粘土的含水层中，有机质是PCE等非离子有机化合物(NIOCs)的主要吸附介质。拟议研究的目的是：(1)确定有机碳和/或对粘土矿物的直接吸附的相对重要性；(2)确定有机质的氧化和分布的差异对吸附的大小和形式的影响；(3)测试相似溶质之间的竞争吸附。利用规划拨款，将使用两个具有相似粘土矿物学和FOC但明显不同的PCE吸附行为的对比天然含水层样本来验证这一假设。这些结果将为建立更全面的研究的最佳方法提供对吸附机理的洞察和基础。其目的是提高对天然低碳地质样品中NIOC吸附的机械理解，从而为地下水资源保护和修复提供更准确的污染物迁移评估。

ABSTRACT EAR-9506403 Allen-King Clay-rich aquitards and constructed clay-liners provide low permeability barriers to contaminant migration and are used for hazardous waste disposal because of the margin of protection provided to underlying groundwater resources. Sorption in the aquitard matrix retards transport and provides a sink for uptake and release of organic contaminant mass over time. However, the mechanisms of sorption in clay-rich aquitards are not well understood. Recent observations, for example, have shown that perchloroethene (PCE) sorption in several natural clay-rich and relatively low carbon aquitards is significantly under-predicted by existing methods. It is hypothesized that in natural, low-fraction organic content (foc) and clay-rich aquitards, organic matter is the primary sorbing medium for nonionic organic compounds (NIOCs) such as PCE. The objectives of the proposed research are: (1) to determine the relative importance of organic carbon and/or direct sorption to clay minerals; (2) to determine the effects of differences in oxidation and distribution of organic matter on the magnitude and form of sorptionO and (3) to test for competitive sorption between similar solutes. Using the Planning Grant, the hypothesis will be tested using two contrasting natural aquitard samples with similar clay mineralogy and foc, but markedly different PCE sorption behavior. The results will provide insights into sorption mechanisms and bases for establishing the best methodologies for a more comprehensive study. The objective is to improve mechanistic understanding of NIOC sorption in natural low-carbon geologic samples, thereby allowing more accurate assessments of contaminant transport for groundwater resource protection and remediation.