(EGB) Understanding and Modeling Hydrogeological, Microbiological, and Geochemical Processes that Control Groundwater Redox Zonation

小行星9708487 含水层地球化学中最基本的问题之一是溶质运移和地球化学过程与微生物活动联合收割机结合影响氧化还原分带时空变化的机制。 我们将研究这些机制，在一个浅的桑迪含水层污染的石油烃，表现出氧化还原分带的季节性时间尺度上的变化。 在这个网站的氧化还原分带的动态性质，使我们能够检查水文地质，地球化学和微生物过程之间的相互作用，并测试假设（1）控制地下水从一个区域到另一个区域的演变和（2）控制氧化还原带的空间和时间维度的因素。 通过耦合从三个学科获得的信息，通过现场和实验室研究，一个三维的，瞬态反应流和输运模式的氧化还原分带的演变将被构建。 这一跨学科研究的目标是：（1）定量评估水文地质学、地球化学和微生物对某一区域内氧化还原过程的影响;（2）利用这些限制来确定描述地下水从一个区域到另一个区域演化的反应集;以及（3）将反应集与动态流动和传输模型集成，以模拟过去关于该地点各种氧化还原区尺寸的观察结果，以及比较地下水水文事件的预测结果和观测结果，如长时间的高水位或低水位。 这些目标将通过实地采样（季节性和事件）、实验室分析和实验、现场水文地质、微生物和地球化学分析以及水文地球化学建模来实现。 这些方法的独特之处在于：（1）结合地球物理和水文地质资料来估计含水层的性质;（2）利用16 SrRNA核酸探针杂交来确定微生物丰度，利用脂肪酸甲酯谱和16 SrDNA限制性分析（ARP-PCR）来确定群落结构;（4）使用现场取样器和实验评估矿物-微生物相互作用;（5）在反应性流动和传输模型中结合地球化学和微生物反应集，以定量解释研究现场观察到的水化学。 这一方法将使每一学科受益，因为它能更好地理解导致原始和受污染含水层氧化还原地带化的物理、化学和生物过程之间的相互作用，并将为设计适当的取样、监测和补救方法提供宝贵的基本信息。 该提案是应NSF 96-152环境地球化学和生物地球化学招标而提交的，并由地球科学和环境生物学部门共同资助。

9708487 Long One of the most fundamental issues in aquifer biogeochemistry concerns the mechanisms by which solute transport and geochemical processes combine with microbiological activity to influence spatial and temporal variations in redox zonation. We will examine these mechanisms in a shallow sandy aquifer contaminated with petroleum hydrocarbons, which has exhibited redox zonation that varies on seasonal time scales. The dynamic nature of redox zonation at this site allows us to examine the interaction among hydrogeological, geochemical, and microbiological processes, and test hypotheses regarding the (1) reactions that govern groundwater evolution from zone to zone and (2) factors which control the spatial and temporal dimensions of redox zones. By coupling information gained from the three disciplines, through field and laboratory research, a three-dimensional, transient reactive flow and transport model for the evolution of redox zonation will be constructed. The goals of this interdisciplinary study are to (1) quantitatively assess hydrogeologic, geochemical and microbiological constraints that influence redox processes within a given zone; (2) use these constraints to identify sets of reactions that describe the evolution of groundwater from one zone to another; and (3) integrate the reaction sets with a dynamic flow and transport model to simulate past observations regarding the dimensions of various redox zones at the site, as well as compare the predicted and observed outcome of groundwater hydrologic events such as prolonged periods of high or low water table. These goals will be achieved through field sampling (seasonal and event), laboratory analysis and experimentation, in-situ hydrolgeological, microbiological, and geochemical analyses, and hydrogeochemical modeling. Unique aspects of the methods include: (1) combining geophysical and hydrolgeological data to estimate aquifer properties; (2) using 16S rRNA nucleic acid probe hybridization to determine microbial abu ndance, fatty acid methyl ester profiles and 16S rDNA restriction analysis (ARDRA) to determine community structure; (3) estimating redox state from H2 gas concentrations; (4) assessing minerals-microbial interactions using in-situ samplers and experiments; and (5) combing geochemical and microbiological reaction sets in a reactive flow and transport model to quantitatively account for observed water chemistry at the study site. This approach will benefit each discipline through improved understanding of the interaction among physical, chemical and biological processes that lead to redox zonation in both pristine and contaminated aquifers, and will provide fundamental information valuable to the design of appropriate sampling, monitoring and remediation methodologies. This proposal was submitted in response to the Environmental Geochemistry and Biogeochemistry solicitation NSF 96-152, and is being funded jointly by the Divisions of Earth Sciences and Environmental Biology.