TRANSPORT AND BIODEGRADATION OF VOLATILE ORGANIC COMPOUNDS IN THE VADOSE ZONE

受污染的地下水是接触有毒物质的最重要途径 为许多依赖水井饮水的人类人口提供化学品 和其他家庭用途。地下水含水层极易受到 来自超级基金和其他公司的污染物迁移造成的污染 危险废物场地。不幸的是，很难预测 地下水含水层受污染的可能性和 污染物从危险废物场地向地下水位的移动。这个 非饱和地下(包气)环境极为不均一， 它的物理、化学和生物过程还没有得到 注意这类过程在饱和的地下水含水层中产生的影响。这个 将包气带中的局地过程放大到 系统规模阻碍了预测模型的发展 对描述地下运输和评估潜力是必不可少的 暴露在人类群体中。 挥发性有机化学品(VOC)，如三氯乙烯、甲苯和 萘是地下水中普遍存在的常见污染物。全 有三种化学物质是环保局的优先污染物，有可能成为 在环境中转化为不受欢迎的代谢物 对人类人口的健康风险。 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 生物降解--影响VOCs在土壤和土壤中的去向和迁移 地质沉积物。生物降解率将与 原住民的种群大小、酶特性和遗传特性 污染与未污染包气带微生物群落 样本。挥发性有机化合物有毒代谢物形成的可能性 它们的生物降解过程将在不同的条件下进行测定。 实验室规模的柱状研究将使用土壤和 确定地质沉积物对多种环境的影响 影响VOC浓度的过程和VOCs迁移到 地下水和大气。挥发性有机化合物运输之间的关系 包气带的过程和野外规模的地质属性，如 沉积相、粒度、有机碳、分选和矿物学 将会被确定。对这些关系的定量描述将 被合并到确定性和随机性的交通模型中 包气地带。这些模型将使用受污染的 在劳伦斯·利弗莫尔国家实验室进行灵敏度测定 VOCs和VOCs的迁移率和气相和溶液相浓度 它们的代谢物具有运输特性的空间变异性。

Polluted groundwater is the most significant route of exposure to toxic chemicals for many human populations who rely on wells for drinking water and other domestic use. Groundwater aquifers are extremely vulnerable to contamination due to migration of pollutants from Superfund and other hazardous waste sites. Unfortunately, it is very difficult to predict the potential for contamination of a groundwater aquifer and the rate of movement of pollutants from hazardous waste sites to the water table. The unsaturated subsurface (vadose) environment is extremely heterogeneous and its physical, chemical, and biological processes have not received the attention that such processes have in saturated, groundwater aquifers. The uncertainties in scaling up local processes in the vadose zone to the system scale impedes the development of the predictive models that are essential for describing subsurface transport and assessing the potential exposure of human populations. Volatile organic chemicals (VOCs), such as trichloroethylene, toluene, and naphthalene, are ubiquitous and common contaminants of groundwater. All three chemicals are E.P.A. priority pollutants and have the potential to be transformed in the environment into undesirable metabolites that pose a health risk to human populations. Studies will be conducted to investigate the fundamental processes-- including diffusive and convective transport, sorption/desorption, and biodegradation--affecting the fate and transport of VOCs in soil and geological sediments. Rates of biodegradation will be related to population size and the enzymatic and genetic properties of indigenous microbial communities in contaminated and uncontaminated vadose zone samples. The potential for formation of toxic metabolites of the VOCs during their biodegradation will be determined under various conditions. Laboratory-scale, column studies will be conducted using soil and geological sediments to determine the effect of multiple environmental processes on VOC concentrations and the potential for movement of VOCs to the groundwater and atmosphere. 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. These models will be run with data from a contaminated site at Lawrence Livermore National Laboratory to determine the sensitivity of migration rates and vapor and solution phase concentrations of VOCs and their metabolites to spatial variability in transport characteristics.