Collaborative Research: Abiotic Attenuation of Chlorinated Hydrocarbons in the Vapor Intrusion Pathway: Overlooked Nanoscale Chemistry on Soil Mineral Surfaces

摘要/ abstract摘要：项目负责人：nachongzheng提案号：cbet -1033848机构：诺特达大学；项目负责人：李雨松提案号：cbet -1033502机构：内布拉斯加州大学林肯分校标题：合作研究：氯代烃在蒸汽侵入途径中的非生物衰减：土壤矿物表面被忽视的纳米级化学性质氯代烃是土壤和沉积物中普遍存在的污染物，由于处置不当和意外泄漏。人体接触这些污染物的一个重要途径是它们的蒸气通过不饱和渗透带侵入有人居住的建筑物。了解蒸汽侵入（VI）途径的物理、化学和生物调节剂对于评估美国数以万计的污染地点与氯代烃污染物（CHCs）相关的健康风险至关重要。拟议研究的总体目标是调查氯代烃蒸汽侵入途径的一个重要但被忽视的化学调节剂，即纳米尺度。蒸汽化合物与土壤矿物表面之间的非均相反应。本研究采用实验与建模相结合的综合方法。最先进的分析和表面敏感技术，包括气相色谱质谱（GC/MS），原子力显微镜（AFM）和x射线光电子能谱（XPS），将用于鉴定反应产物，量化反应动力学，并阐明反应机制。一个多组分，多阶段模拟器，密歇根土壤环境修复（MISER），将被修改，以纳入新的纳米尺度化学蒸汽入侵的评估。为了支持该项目的目标，将使用三个研究目标来指导假设的制定以及实验的设计和选择：(a)第一个目标是确定使用具有代表性的氯化烃化合物和土壤矿物质（包括老化矿物）进行纳米级表面反应的普遍性。(b)第二个目标是研究湿度和温度等环境参数对反应机理、动力学和产物稳定性的影响。(c)第三个目标是用数学方法评价蒸汽-矿物反应作为蒸汽侵入途径的化学调节剂的意义。拟议的项目有五个任务。首先，将筛选11种具有代表性的CHC化合物、3类土壤矿物和重构方解石，以确定它们在蒸汽侵入途径中相互反应的潜力。CHC化合物的选择是基于它们在不同污染位点的流行程度以及结构多样性。土壤矿物有五种碳酸盐、石英和两种长石。在高湿条件下重建的方解石用于评价老化矿物的反应性。其次，chc -矿物反应的动力学将通过监测AFM流体池中的气相和表面产物来量化。流体电池作为连续搅拌的槽式反应器。反应的演变将通过GC/MS（用于CHC蒸气和气相产物）和AFM（用于表面纳米结构生长）进行量化。第三，利用AFM液池测定不同湿度下反应产物和动力学的变化。潮湿空气中水单分子层的冷凝会对chc -矿物反应产生复杂的后果，包括产生活性羟基、产生活性移动离子和阻断活性表面位点。湿度的变化是季节之间发生的典型环境状况。第四，将利用间歇式反应器在高温下评估挥发性化合物从chc诱导的纳米结构中释放的情况。温度变化是另一个季节变化。在从寒冷季节到温暖季节的过渡过程中，温度的升高可能会破坏chc诱导的纳米结构，并意外释放出有毒的挥发性化合物。最后，建立了具有非生物衰减的蒸汽侵入路径的数值模拟模型。评估将使用从印第安纳州环境管理部获得的具体信息进行。本研究的主要知识价值是为更复杂和准确的氯化烃蒸汽侵入建模提供了知识基础。研究小组还计划通过以下方式在拟议项目中产生更广泛的影响：(1)培训来自代表性不足群体的学生进行环境纳米地球化学研究；(2)将从研究前沿获得的新知识纳入环境科学与工程的本科水平课程；(3)通过外展活动为当地高中生提供研究机会。

AbstractPI: Chongzheng NaProposal Number: CBET-1033848Institution: University of Notre DamePI: Yusong LiProposal Number: CBET-1033502Institution: University of Nebraska-LincolnTitle: Collaborative Research: Abiotic Attenuation of Chlorinated Hydrocarbons in the Vapor Intrusion Pathway: Overlooked Nanoscale Chemistry on Soil Mineral SurfacesChlorinated hydrocarbons are prevalent contaminants in soils and sediments due to improper disposal and accidental spillage. An important pathway for human exposure of these contaminants is the intrusion of their vapors into occupied buildings through the unsaturated vadose zone. Understanding the physical, chemical, and biological regulators of the vapor intrusion (VI) pathway is crucial to assess the health risks associated with chlorinated hydrocarbon contaminants (CHCs) at tens of thousands of pollution sites across the U.S. The overarching goal of the proposed research is to investigate an important, yet overlooked, chemical regulator of the chlorinated hydrocarbon vapor intrusion pathway, namely the nanoscale, heterogeneous reactions between vapor compounds and soil mineral surfaces. The proposed research takes an integrated approach combining experimental and modeling efforts. State-of-the-art analytical and surface-sensitive techniques, including gas chromatography mass spectrometry (GC/MS), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS), will be used to identify reaction products, quantify reaction kinetics, and elucidate reaction mechanisms. A multicomponent, multi-phase simulator, Michigan Soil Environment Remediation (MISER), will be modified to incorporate the new nanoscale chemistry into the assessment of vapor intrusion. In support of the goal of this project, three research objectives will be used to guide the formulation of hypotheses and the design and selection of experiments: (a) The first objective is to determine the prevalence of nanoscale surface reactions using representative chlorinated hydrocarbon compounds and soil minerals (including aged minerals). (b) The second objective is to investigate the effects of environmental parameters such as humidity and temperature on the reaction mechanisms, kinetics, and product stability. (c) The third objective is to mathematically evaluate the significance of vapor-mineral reactions as a chemical regulator of the vapor intrusion pathway.The proposed project has five tasks. First, eleven representative CHC compounds, three classes of soil minerals, and reconstructed calcite will be screened for their potentials to react with one another in the vapor intrusion pathway. The CHC compounds are selected based on their prevalence at various contamination sites as well as structural diversity. The soil minerals are five carbonates, quartz, and two feldspars. Calcite reconstructed under high humid conditions is used to evaluate the reactivity of aged minerals. Second, the kinetics of CHC-mineral reactions will be quantified by monitoring both gas-phase and surface products in an AFM fluid cell. The fluid cell serves as a continuously stirred tank reactor. The evolution of the reactions will be quantified by GC/MS (for CHC vapor and gas-phase products) and AFM (for surface nanostructure growth). Third, the changes of reaction products and kinetics under varying humidity will be determined using the AFM fluid cell. The condensation of water monolayers from humid air can have complicated consequences for CHC-mineral reactions, including generating reactive hydroxyl groups, creating reactive mobile ions, and blocking reactive surface sites. The variation of humidity is a typical environmental condition that happens between seasons. Forth, the release of volatile compounds from CHC-induced nanostructures will be evaluated using batch reactors at elevated temperatures. Temperature change is another seasonal variation. The increase of temperature that occurs during the transition from a cold season to a warm one may destabilize the CHC-induced nanostructures and release toxic volatile compounds unexpectedly. Last, a numerical model will be developed to simulate the vapor intrusion pathway with the abiotic attenuation. The evaluation will be performed usingsite specific information acquired from the Indiana Department of Environmental Management. The main intellectual merit of the proposed research is to provide a knowledge base for more sophisticated and accurate modeling of chlorinated hydrocarbon vapor intrusion. The research team also plans to make broader impacts in the proposed project by (1) training students from underrepresented groups on environmental nanogeochemistry research, (2) incorporating new knowledge obtained from the research frontier to the undergraduate-level courses for environmental science and engineering, and (3) providing local high-school students with research opportunities through outreach activities.