Collaborative Research: Integrated Geophysical and Hydrogeologic Study of a Large Maine Peatland

0106074 ReeveSolute运输控制泥炭地的植被和水化学梯度。 分散混合和平流输送泥炭将在实验室柱实验和自然梯度示踪剂测试泥炭地，以确定这些过程的相对重要性。 我们将评估基质扩散和双域模型的适用性溶质的阻滞。 通过直接测量验证的电地球物理方法将用于跟踪示踪剂迁移，泥炭地的广泛地球物理和水文地质特征将绘制整个盆地泥炭深度的变化图，并确定地层。 将采用探地雷达和电阻率/激发极化成像。 压力计测试将提供一个测量的空间变异性在驯鹿沼泽，一个大的泥炭地在中央缅因州的水力传导性。 将评估水文地质参数和地球物理参数之间的相关性，并用于为地下水流动和物质输运建模提供参数约束。将收集泥炭芯进行实验室测试，以测量水力传导率、分散度、有效孔隙度、比表面和复电阻率。 泥炭特性随深度的变化将通过实验室测试来确定。 将评估泥炭电特性与水文地质参数之间的关系。将向泥炭地注入NaBr示踪剂并监测12个月。 将使用地面和井眼电成像来跟踪示踪剂。 地球物理图像上的像素将取代广泛的直接水采样点，允许快速和几乎连续的溶质分布跟踪。从示踪剂试验中收集的地球物理和地下水化学数据将用于计算溶质羽流随时间的空间矩。 将根据地球化学和地球物理数据校准三维水文地质和物质迁移模型，以进一步评估物质迁移参数。 基质扩散，溶质迁移到水力隔离孔隙中，将被纳入数值模型以评估这一重要过程。该项目将评估：（1）分散混合的性质，（2）水文地质和地球物理参数的相关性，以及（3）泥炭地中质量迁移的作用。泥炭地是一个巨大的碳库，也是甲烷气体的重要来源。 地下水流和物质迁移在调节有利于甲烷产生和泥炭积累的地球化学条件方面很重要。 这项工作将增加对影响泥炭地碳和养分动态的过程的理解。 对示踪剂的地球物理监测将提供关于这种追踪溶质羽流运动的非侵入性方法的效用的重要信息。 该项目将展示在水文地质评估和湿地特征描述中包括电地球物理学的潜在好处。

0106074ReeveSolute transport controls vegetation and water chemistry gradients in peatlands. Dispersive mixing and advective transport in peat will be measured in laboratory column experiments and in a natural gradient tracer test in a peatland to determine the relative importance of these processes. We will assess the retardation of solutes by matrix diffusion and the applicability of a dual-domain model. Electrical geophysical methods, verified through direct measurements, will be used to track tracer migration.An extensive geophysical and hydrogeologic characterization of the peatland will map variability in peat depth across the basin and identify stratigraphy. Ground-penetrating radar and resistivity/induced polarization imaging will be employed. Piezometer tests will provide a measure of the spatial variability in hydraulic conductivity within Caribou Bog, a large peatland in Central Maine. Correlations between hydrogeologic and geophysical parameters will be assessed and used to provide constraints on parameters for ground-water flow and mass transport modeling.Peat cores will be collected for laboratory tests to measure hydraulic conductivity, dispersion, effective porosity, specific surface and complex resistivity. The variability of peat properties with depth will be determined through laboratory testing. Relationships between peat electrical properties and hydrogeologic parameters will be evaluated.An NaBr tracer will be injected into the peatland and monitored for 12 months. The tracer will be tracked using surface and borehole electrical imaging. The pixels on the geophysical images will be a substitute for extensive direct water sampling points, allowing rapid and nearly continuous tracking of solute distribution. Geophysical and ground-water chemistry data collected from the tracer test will be used to calculate the spatial moments of the solute plume through time. Three-dimensional hydrogeologic and mass transport models will be calibrated to the geochemical and geophysical data to further evaluate mass transport parameters. Matrix diffusion, the migration of solutes into hydraulically isolated pores, will be incorporated into the numerical models to evaluate this important process.The project will evaluate: (1) the nature of dispersive mixing, (2) the correlation of hydrogeologic and geophysical parameters, and (3) the role of mass transporft in peatlands. Peatlands are a large carbon reservoir and a significant source of methane gas. Ground-water flow and mass transport are important in regulating geochemical conditions favorable for methane production and peat accumulation. The work will add to the understanding of processes that impact carbon and nutrient dynamics for peatlands. Geophysical monitoring of a tracer will provide important information on the utility of this non-invasive method for tracking the movement of solute plumes. This project will demonstrate the potential benefits of including electrical geophysics in hydrogeologic assessments and wetland characterization.,