Time resolved spatially-averaged set up for in situ CO2 monitoring in soil

Most studies in the past focus on the measurement of CO2 release from the soil surface, which is the parameter of interest for balancing carbon fluxes. However, for advancing our mechanistic understanding measurement of CO2 concentration within the soil are required. Soil CO2 concentrations do not only relate directly to local production of CO2 by plants and soil biota, but are also a key for understanding soil solution chemistry (in particular pH dynamics). The relationship between soil CO2 concentration and CO2 flux at the soil surface will depend on the chemical gradients, the size and connectivity of air filled pore space (related to soil structure and actual water content), and temperature gradients in the system. CO2 production as well as soil water content and temperature show temporal variation directly or indirectly related to day night cycle and related plant growth. It was the aim of the present study to test a recently developed linear membrane-based gas sensor (line sensor) for in situ measurement of soil respiration at high temporal resolution. Data from two soil depths were related to measurement of CO2 flux at the soil surface. Simultaneously, soil temperature, soil water content, and soil matric potential were measured at high temporal resolution in the respective depths. The measurements were conducted in 50 x 50 x 50 cm boxes filled with topsoil material from a Chernozem. To evaluate the sensitivity of the measurement system we compared a treatment planted with barley (Hordeum vulgare) to one without plants (three replications each). Besides a detailed description of the experimental set-up we will present and discuss first results from this new system

Multifunctional Sensor for Monitoring of CO2 Underground Storage by Comprehensive and Spatially Resolved Measuring of Gas Concentrations, Temperature and Structural Changes

AbstractOne of the main unsolved issues of CCS is the comprehensive surveillance of CO2 storage areas with reasonable effort and costs. This study presents an approach for distributed subsurface monitoring of gas storage areas. The concept combines different measurement technologies to one multifunctional sensor: membrane based measurement technology for in situ monitoring of gases in soil and fibre optical sensing of temperature and strain (as a measure for structural change). A test field of application-relevant dimensions is built up to validate and optimize the technology

Leak detection with linear soil gas sensors under field conditions - First experiences running a new measurement technique

A 400 m² soil test field with gas injection system was built up, which enables an experimental validation of linear gas sensors for specific applications and gases in an application-relevant scale. Several injection and soil watering experiments with carbon dioxide (CO2) at different days with varying boundary conditions were performed indicating the potential of the method for, e.g., rapid leakage detection with respect to Carbon Capture and Storage (CCS) issues

Tomographic reconstruction of soil gas distribution from multiple gas sources based on sparse sampling

A monitoring method is introduced that creates twodimensional (2D) maps of the soil gas distribution. The method combines linear gas sensing technology for in-situ monitoring of gases in soil with the mapping capabilities of Computed Tomography (CT) to reconstruct spatial and temporal resolved gas distribution maps. A weighted iterative algebraic reconstruction method based on Maximum Likelihood with Expectation Maximization (MLEM) in combination with a source-by-source reconstruction approach is introduced that works with a sparse setup of orthogonally-aligned linear gas sensors. The reconstruction method successfully reduces artifact production, especially when multiple gas sources are present, allowing the discrimination between true and non-existing so-called ghost source locations. Experimental validation by controlled field experiments indicates the high potential of the proposed method for rapid gas leak localization and quantification with respect to Pipeline or underground gas storage issues

P2.2 - Test Field for the Validation of a Multifunctional Sensor for Distributed Subsurface Monitoring of Gas Storage Areas

BAM Federal Institute for Materials Research and Testing, in cooperation with the company MeGaSen UG carries out a research project to enhance and validate an innovative approach for distributed subsurface monitoring of gas storage areas. The concept combines different measurement technologies to one multifunctional sensor: membrane-based gas measurement technology for in-situ monitoring of gases in soil and fiber optical sensing of temperature and strain (as a measure for structural change). Key aspect of the research project is the first-time validation of the system in an application relevant dimension. For this purpose a 20 x 20 m2 test field is build. A comprehensive validation of the system is carried out by systematic variation of different parameters like position-dependent gasinjection, temperature and mechanical impact