NAPL-VAPOR PHASE INTERPHASE MASS TRANSFER PROCESSES

气相输送过程对 挥发性有机化合物(VOCs)在大气中的迁移和持久性 地下环境。这样的过程控制着有机物质的释放 蒸气进入大气，有机蒸气溶解到地下水， 以及地下室、下水道和地下设施中的油烟堆积， 这可能会构成最直接和最广泛的健康风险， 挥发性有机碳泄漏。气相传输过程也是 土壤-气体采样方法的发展和解释及其设计 有效的土壤排气修复策略。这项研究将集中于 关于汽相传质的以下两个不好的方面 理解；(A)自然环境中以多组分扩散为主的运输 土壤和(B)被包裹的有机液体在强迫下的挥发。 空气平流。重点将放在实验室的一体化上 和模特研究。子项目0017旨在调查 自然土壤中气相扩散的控制机制。弥漫的 苯和三氯乙烯这两种模型VOCs的行为将是 探索过了。将进行实验来测量汽相 渗透率、努森扩散系数和曲折系数 土壤水分、容重和颗粒大小条件的范围。在……里面 此外，气相吸附对有机蒸气扩散的影响 将对类似的土壤和实验条件进行比率调查。 有机-土壤复合体作为削弱有机污染物的一种手段的应用 还将评估蒸汽的流动性。多组分扩散 模拟器，它结合了几种扩散机制和汽相 吸附作用，将被开发来评估这些 流程。将进行稳态和瞬态柱实验 以验证建模方法。在子项目0006中，实验将是 研究VOCs从不相容体系中的传质速率 稳态和暂态下有机液体相到汽相的转变 条件。一些有机化合物和土壤基质将被 调查过了。结合流量、组成的关联式 发展有机相、土壤含水率和土壤结构 用于气相传质。多相流和输运模型， 在当前NIEHS资助下开发的，将用于探索 限速传质对土壤排气效果的影响 技术。

Vapor-phase transport processes are of fundamental importance to the migration and persistence of volatile organic chemicals (VOCs) in subsurface environments. Such processes control the release of organic vapors into the atmosphere, dissolution of organic vapors into groundwater, and accumulation of fumes in basements, sewers, and underground utilities, which may pose the most immediate and widespread health risks following a VOC spill. Vapor-phase transport processes are also fundamental to the development and interpretation of soil-gas sampling methods and the design of effective soil venting remediation strategies. This research will focus on the following two aspects of vapor-phase transport which are not well understood; (a) multicomponent diffusion-dominated transport in natural soils and (b) the volatilization of entrapped organic liquids under forced- air advection. Emphasis will be placed upon the integration of laboratory and modeling studies. Subproject 0017 is designed to investigate the mechanisms governing vapor-phase diffusion in natural soils. The diffusive behavior of two model VOCs, benzene and trichloroethylene, will be explored. Experiments will be conducted to measure vapor-phase permeabilities, Knudsen diffusion coefficients, and tortuosity factors for a range of soil moisture, bulk density, and particle size conditions. In addition, the effect of vapor-phase sorption on organic vapor diffusion rates will be investigated for similar soils and experimental conditions. The utility of organo-soil complexes as a means of attenuating organic vapor mobility will also be evaluated. A multicomponent diffusion simulator, which incorporates several diffusion mechanisms and vapor-phase sorption, will be developed to assess the relative importance of these processes. Steady-state and transient column experiments will be performed to validate the modeling approach. In subproject 0006, experiments will be conducted to examine the rate of mass transfer of VOCs from the immiscible organic liquid phase to the vapor phase under steady-state and transient conditions. A number of organic compounds and soil matrices will be investigated. Correlations incorporating flow rate, composition of the organic phase, soil moisture content and soil structure will be developed for vapor-phase mass transfer. A multiphase flow and transport model, developed under current NIEHS funding, will be used to explore the implications of rate-limited mass transfer on the efficacy of soil venting technologies.