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

PI：崇正NaProposal编号：CBET-1033848机构：圣母大学PI：玉松Liposal编号：CBET-1033502机构：内布拉斯加大学林肯分校标题：合作研究：气相入侵途径中氯代烃的非生物衰减：土壤矿物表面被忽视的纳米级化学由于处置不当和意外溢出，氯代烃是土壤和沉积物中普遍存在的污染物。人类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的包气带侵入被占领的建筑物。了解蒸气入侵(VI)途径的物理、化学和生物调节因素对于评估美国各地数万个污染地点氯代烃污染物(CHC)的健康风险至关重要。拟议研究的总体目标是调查氯化碳氢化合物蒸气侵入途径的一个重要但被忽视的化学调节因素，即蒸气化合物和土壤矿物表面之间的纳米级非均相反应。拟议的研究采取了实验和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/质谱仪(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、量化反应动力学和阐明反应机理。将对密歇根土壤环境修复(MISER)多组分、多相模拟器进行修改，以将新的纳米级化学物质纳入对蒸汽入侵的评估中。为支持该项目的目标，将使用三个研究目标来指导假设的提出以及实验的设计和选择：(A)第一个目标是确定使用典型的氯代烃化合物和土壤矿物(包括陈年矿物)进行纳米尺度表面反应的普遍性。(B)第二个目标是研究环境参数，如湿度和温度对反应机理、动力学和产品稳定性的影响。(C)第三个目标是从数学上评估蒸汽-矿物反应作为蒸汽侵入路径的化学调节器的重要性。首先，将筛选11种具有代表性的CHC化合物、三类土壤矿物和重建的方解石，以确定它们在蒸汽入侵途径中相互反应的潜力。根据CHC化合物在不同污染部位的流行程度以及结构多样性来选择CHC化合物。土壤矿物是五种碳酸盐、石英和两种长石。用高湿条件下重构的方解石来评价老化矿物的反应活性。其次，将通过监测AFM流体池中的气相和表面产物来量化CHC-矿物反应的动力学。流体槽起到连续搅拌釜式反应器的作用。反应的演变将用GC/MS(对于CHC蒸气和气相产物)和AFM(对于表面纳米结构生长)进行量化。第三，利用原子力显微镜流体池测定不同湿度下反应产物和反应动力学的变化。湿空气中的水单分子层的冷凝可能会对CHC-矿物反应产生复杂的后果，包括产生反应性羟基，产生反应性可移动离子，以及阻断反应性表面位置。湿度的变化是一种典型的季节间发生的环境状况。第四，将使用间歇反应器在高温下评估CHC诱导的纳米结构中挥发性化合物的释放。温度变化是另一个季节性变化。在从冷季到暖季的过渡过程中，温度的升高可能会破坏CHC诱导的纳米结构的稳定性，并意外释放有毒的挥发性化合物。最后，开发了一个数值模型来模拟具有非生物衰减的水蒸气入侵路径。评估将使用从印第安纳州环境管理部获得的现场特定信息进行。该研究的主要智力价值在于为氯代烃蒸汽侵入的更复杂、更准确的建模提供了知识库。研究小组还计划通过以下方式在拟议的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和工程本科课程；以及(3)通过外联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.