TRANSPORT AND BIODEGRADATION OF VOLATILE ORGANIC COMPOUNDS IN THE VADOSE ZONE

暴露评估，环境风险的一个重要组成部分 分析，需要定量的方法来估计 环境介质中污染物的分布和持久性。 挥发性化合物(VOC)，如TCE、DCE、甲苯、对硝基苯酚和 萘在美国环保局的优先污染物名单上，通常 在超级基金废品场发现的。扑热息痛是一种熏蒸剂，广泛用于 农业中的数量。从最初放置在包气带中开始， 这些挥发性污染物进入地下水和空气中， 是人类最重要的两条接触途径。而在土壤中， 它们可能会被微生物新陈代谢转化为 比原始污染物更危险或更小的危险。 将进行研究，以调查基本过程 包括扩散和对流输送、吸附/解吸以及 影响液体和液体的去向和运输的生物降解 土壤和地质沉积物中挥发性有机化合物的气相。研究将会 重点关注耦合和相互依赖的物理、化学和 生物过程决定了污染物的运输和分配 化学混合物。将进行实验室规模的专栏研究 利用土壤和地质沉积物确定多次复盖效果 环境过程对VOCs向 地下水和大气。由以下物质引起的持久性代谢物 生物降解性的鉴定将在 免疫化学项目和分析核心。水蒸气的估算 浓度。可能会为各种废品场地提供场景 给热修复项目的调查人员。尘埃样本将 提供给肺部暴露项目，以评估 吸附在灰尘中的化学物质对健康的潜在危害。化学品和 来自土壤的渗滤液中的代谢物将使用 青竹和基于细胞的生物检测。 挥发性有机化合物运移过程与野外地质尺度的关系 包气带的属性，如沉积相、粒度、 将确定有机碳、分类和矿物学。量化 对这些关系的描述将合并到 包气带中输运的确定性和随机性模型 包括二维和三维流动数值模拟实验 和单一液体相(溶解于水的挥发性有机化合物)和 气相。包气带热水输运模型 可在白天地面供暖较强的条件下使用， 通过实验室和现场试验进行开发和测试。这款车 将与化学挥发模型相结合，以获得 进入大气层。大气成分的验证 将基于100米以上边界层的激光雷达测量 比例尺最高可达几公里的区域比例尺。这些型号将 用于评估现场范围内潜在的人体接触水平。

Exposure assessment, an essential component of environmental risk analysis, requires quantitative approaches for estimating the distribution and persistence of pollutants in environmental media. Volatile compounds (VOCs), such as TCE, DCE, toluene, p-nitrophenol, and naphthalene are on the EPA Priority Pollutants List and are commonly found at Superfund waste sites. Metam sodium is a fumigant used in large quantities in agriculture. From initial placement in the vadose zone, these volatile contaminants move into the groundwater and the air which are the two most important exposure routes for humans. While in the soil, they may be transformed by microbial metabolism into compounds which are either more or less hazardous than the original contaminants. Studies will be conducted to investigate the fundamental processes including diffusive and convective transport, sorption/desorption, and biodegradation that affect the fate and transport of both the liquid and vapor phases of VOCs in soil and geological sediments. Research will focus on the coupled and interdependent physical, chemical, and biological processes determining the transport and distribution of chemical mixtures. Laboratory-scale, column studies will be conducted using soil and geological sediments to determine the effect of multiple environmental processes on the potential for movement of VOCs to the groundwater and atmosphere. Persistent metabolites resulting from biodegradation will be identified with the assistance of the Immunochemical project and the Analytical Core. Estimates of vapor concentrations. likely for various waste site scenarios will be provided to investigators in the thermal remediation project. Samples of dust will be provided to the pulmonary exposure project in order to assess the potential health hazard of chemicals sorbed to dust. Chemicals and metabolites in leachate from soil will be tested for toxicity using the medaka and cell based bioassays. Relationships between VOC transport processes and field-scale geological attributes of the vadose zone such as depositional facies, grain size, organic carbon, sorting and mineralogy will be determined. Quantitative descriptions of these relationships will be incorporated into deterministic and stochastic models of transport in the vadose zone which include two and three-dimensional numerical modeling experiments of flow and transport of a single liquid phase (VOC dissolved in water) and a gaseous phase. A heat-water transport model for the vadose zone, which can be used under conditions of strong diurnal land surface heating, will be developed and tested with laboratory and field experiments. This model will be coupled with the models of chemical volatilization to obtain the flux into the atmosphere. The validation of the atmospheric component will be based on lidar measurements of the boundary layer over 100 m scale plots up to regional scales of a few kilometers. These models will be used to evaluate potential human exposure levels at the field scale.