Jennifer L. Lewicki

Dynamic coupling of volcanic CO2 flow and wind at the Horseshoe lake tree kill, Mammoth Mountain, California

We investigate spatio-temporal relationships between soil CO2 flux (FCO2), meteorological variables, and topography over a ten-day period (09/12/2006 to 09/21/2006) at the Horseshoe Lake tree kill, Mammoth Mountain, CA. Total CO2 discharge varied from 16 to 52 t d-1, suggesting a decline in CO2 emissions over decadal timescales. We observed systematic changes in FCO2 in space and time in association with a weather front with relatively high wind speeds from the west and low atmospheric pressures. The largest FCO2 changes were observed in relatively high elevation areas. The variations in FCO2 may be due to dynamic coupling of wind-driven airflow through the subsurface and flow of source CO2 at depth. Our results highlight the influence of weather fronts on volcanic gas flow in the near-surface environment and how this influence can vary spatially within a study area.

Near-surface monitoring strategies for geologic carbon dioxide storage verification

Geologic carbon sequestration is the capture of anthropogenic carbon dioxide (CO{sub 2}) and its storage in deep geologic formations. Geologic CO{sub 2} storage verification will be needed to ensure that CO{sub 2} is not leaking from the intended storage formation and seeping out of the ground. Because the ultimate failure of geologic CO{sub 2} storage occurs when CO{sub 2} seeps out of the ground into the atmospheric surface layer, and because elevated concentrations of CO{sub 2} near the ground surface can cause health, safety, and environmental risks, monitoring will need to be carried out in the near-surface environment. The detection of a CO{sub 2} leakage or seepage signal (LOSS) in the near-surface environment is challenging because there are large natural variations in CO{sub 2} concentrations and fluxes arising from soil, plant, and subsurface processes. The term leakage refers to CO{sub 2} migration away from the intended storage site, while seepage is defined as CO{sub 2} passing from one medium to another, for example across the ground surface. The flow and transport of CO{sub 2} at high concentrations in the near-surface environment will be controlled by its high density, low viscosity, and high solubility in water relative to air. Numerical simulations of leakage and seepage show that CO{sub 2} concentrations can reach very high levels in the shallow subsurface even for relatively modest CO{sub 2} leakage fluxes. However, once CO{sub 2} seeps out of the ground into the atmospheric surface layer, surface winds are effective at dispersing CO{sub 2} seepage. In natural ecological systems with no CO{sub 2} LOSS, near-surface CO{sub 2} fluxes and concentrations are controlled by CO{sub 2} uptake by photosynthesis, and production by root respiration, organic carbon biodegradation in soil, deep outgassing of CO{sub 2}, and by exchange of CO{sub 2} with the atmosphere. Existing technologies available for monitoring CO{sub 2} in the near-surface environment include (1) the infrared gas analyzer (IRGA) for measuring point concentrations using IR absorption by the CO{sub 2} molecule, (2) the accumulation chamber (AC) method for measuring soil CO{sub 2} fluxes at discrete points, (3) the eddy correlation (EC) tower that measures net flux over a given area, and (4) light distancing and ranging (LIDAR) that can measure CO{sub 2} concentrations over an integrated path. Novel technologies that could potentially be useful for CO{sub 2} concentration and flux measurement include hyperspectral remote sensing of vegetative stress as an indication of elevated CO{sub 2} concentrations, tunable lasers for long distance integrated concentration measurements, microelectronic mechanical systems (MEMS) that can be dispersed to make widespread point measurements, and trained animals such as dogs as used for landmine detection.

Eddy covariance observations of surface leakage during shallow subsurface CO2 releases

We tested the ability of eddy covariance (EC) to detect, locate, and quantify surface CO{sub 2} flux leakage signals within a background ecosystem. For 10 days starting on 07/09/2007, and for seven days starting on 08/03/2007, 0.1 (Release 1) and 0.3 (Release 2) t CO{sub 2}d{sup -1}, respectively, were released from a horizontal well {approx}100 m in length and {approx}2.5 m in depth located in an agricultural field in Bozeman, MT. An EC station measured net CO{sub 2} flux (F{sub c}) from 06/08/2006 to 09/04/2006 (mean and standard deviation = -12.4 and 28.1 g m{sup -2} d{sup -1}, respectively) and from 05/28/2007 to 09/04/2007 (mean and standard deviation = -12.0 and 28.1 g m{sup -2} d{sup -1}, respectively). The Release 2 leakage signal was visible in the F{sub c} time series, whereas the Release 1 signal was difficult to detect within variability of ecosystem fluxes. To improve detection ability, we calculated residual fluxes (F{sub cr}) by subtracting fluxes corresponding to a model for net ecosystem exchange from F{sub c}. F{sub cr} had reduced variability and lacked the negative bias seen in corresponding F{sub c} distributions. Plotting the upper 90th percentile F{sub cr} versus time enhanced the Release 2 leakage signal. However, values measured during Release 1 fell within the variability assumed to be related to unmodeled natural processes. F{sub cr} measurements and corresponding footprint functions were inverted using a least-squares approach to infer the spatial distribution of surface CO{sub 2} fluxes during Release 2. When combined with flux source area evaluation, inversion results roughly located the CO{sub 2} leak, while resolution was insufficient to quantify leakage rate.

Eddy covariance mapping and quantification of surface CO2 leakage fluxes

We present eddy covariance measurements of net CO{sub 2} flux (F{sub c}) made during a controlled release of CO{sub 2} (0.3 t d{sup -1} from 9 July to 7 August 2008) from a horizontal well {approx}100 m in length and {approx}2.5 m in depth located in an agricultural field in Bozeman, MT. We isolated fluxes arising from the release (F{sub cr}) by subtracting fluxes corresponding to a model for net ecosystem exchange from F{sub c}. A least-squares inversion of 611 F{sub cr} and corresponding modeled footprint functions recovered the location, length, and magnitude of the surface CO{sub 2} flux leakage signal, although high wavenumber details of the signal were poorly resolved. The estimated total surface CO{sub 2} leakage rate (0.32 t d{sup ?1}) was within 7% of the release rate.

New insights into Kawah Ijen's volcanic system from the wet volcano workshop experiment

Abstract Volcanoes with crater lakes and/or extensive hydrothermal systems pose significant challenges with respect to monitoring and forecasting eruptions, but they also provide new opportunities to enhance our understanding of magmatic–hydrothermal processes. Their lakes and hydrothermal systems serve as reservoirs for magmatic heat and fluid emissions, filtering and delaying the surface expressions of magmatic unrest and eruption, yet they also enable sampling and monitoring of geochemical tracers. Here, we describe the outcomes of a highly focused international experimental campaign and workshop carried out at Kawah Ijen volcano, Indonesia, in September 2014, designed to answer fundamental questions about how to improve monitoring and eruption forecasting at wet volcanoes.

Detection of Leaking CO

Multispectral vegetation reflectance measurements were used as an indirect method of sensing CO2 gas leaking from underground in a controlled release experiment in Bozeman, Montana, USA. The leak location is identified through time-series analysis of the reflectances and the normalized difference vegetation index (NDVI), evaluated at a test location and a control location. Vegetation reflectance changes that correlated with root-level CO2 exposure were distinguishable from changes attributed to seasonal factors including precipitation, wind, air temperature variation, etc. The NDVI of the vegetation became steadily smaller until saturating approximately twenty days after the beginning of the release. However, before reaching the threshold values, both reflectance and NDVI values changed more rapidly when exposed to elevated CO2 fluxes.

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Hidden geothermal systems are those systems above which hydrothermal surface features (e.g., hot springs, fumaroles, elevated ground temperatures, hydrothermal alteration) are lacking. Emissions of moderate to low solubility gases (e.g., CO2, CH4, He) may be one of the primary near-surface signals from these systems. Detection of anomalous gas emissions related to hidden geothermal systems may therefore be an important tool to discover new geothermal resources. This study investigates the potential for CO2 detection and monitoring in the subsurface and above ground in the near-surface environment to serve as a tool to discover hidden geothermal systems. We focus the investigation on CO2 due to (1) its abundance in geothermal systems, (2) its moderate solubility in water, and (3) the wide range of technologies available to monitor CO2 in the near-surface environment. However, monitoring in the near-surface environment for CO2 derived from hidden geothermal reservoirs is complicated by the large variation in CO2 fluxes and concentrations arising from natural biological and hydrologic processes. In the near-surface environment, the flow and transport of CO2 at high concentrations will be controlled by its high density, low viscosity, and high solubility in water relative to air. Numerical simulations of CO2 migration show that CO2 concentrations can reach very high levels in the shallow subsurface even for relatively low geothermal source CO2 fluxes. However, once CO2 seeps out of the ground into the atmospheric surface layer, surface winds are effective at dispersing CO2 seepage. In natural ecological systems in the absence of geothermal gas emissions, near-surface CO2 fluxes and concentrations are primarily controlled by CO2 uptake by photosynthesis, production by root respiration, and microbial decomposition of soil/subsoil organic matter, groundwater degassing, and exchange with the atmosphere. Available technologies for monitoring CO2 in the near-surface environment include (1) the infrared gas analyzer (IRGA) for measurement of concentrations at point locations, (2) the accumulation chamber (AC) method for measuring soil CO2 fluxes at point locations, (3) the eddy covariance (EC) method for measuring net CO2 flux over a given area, (4) hyperspectral imaging of vegetative stress resulting from elevated CO2 concentrations, and (5) light detection and ranging (LIDAR) that can measure CO2 concentrations over an integrated path. Technologies currently in developmental stages that have the potential to be used for CO2 monitoring include tunable lasers for long distance integrated concentration measurements and micro-electronic mechanical systems (MEMS) that can make widespread point measurements. To address the challenge of detecting potentially small-magnitude geothermal CO2 emissions within the natural background variability of CO2, we propose an approach that integrates available detection and monitoring methodologies with statistical analysis and modeling strategies. Within the area targeted for geothermal exploration, point measurements of soil CO2 fluxes and concentrations using the AC method and a portable IRGA, respectively, and measurements of net surface flux using EC should be made. Also, the natural spatial and temporal variability of surface CO2 fluxes and subsurface CO2 concentrations should be quantified within a background area with similar geologic, climatic, and ecosystem characteristics to the area targeted for geothermal exploration. Statistical analyses of data collected from both areas should be used to guide sampling strategy, discern spatial patterns that may be indicative of geothermal CO2 emissions, and assess the presence (or absence) of geothermal CO2 within the natural background variability with a desired confidence level. Once measured CO2 concentrations and fluxes have been determined to be of anomalous geothermal origin with high confidence, more expensive vertical subsurface gas sampling and chemical and isotopic analyses can be undertaken. Integrated analysis of all measurements will determine definitively if CO2 derived from a deep geothermal source is present, and if so, the spatial extent of the anomaly. The appropriateness of further geophysical measurements, installation of deep wells, and geochemical analyses of deep fluids can then be decided based on the results of the near surface CO2 monitoring program.

Gas With Vegetation Reflectances Measured By a Low-Cost Multispectral Imager

LBNL-56623 GEO-SEQ Best Practices Manual Geologic Carbon Dioxide Sequestration: Site Evaluation to Implementation GEO-SEQ Project Team Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, Oak Ridge National Laboratory, Stanford University, University of Texas Bureau of Economic Geology, Alberta Research Council September 30, 2004 Earth Sciences Division Ernest Orlando Lawrence Berkeley National Laboratory Berkeley, CA 94720 This work was supported by the Assistant Secretary for Fossil Energy, Office of Coal and Power Systems, of the U.S. Department of Energy (DOE) under Contract No. DE-AC03-76SF00098.

Strategies for Detecting Hidden Geothermal Systems by Near-Surface Gas Monitoring

The concurrent measurement of self-potential (SP) and soil CO{sub 2} flux (F{sub s}{sup CO2}) in volcanic systems may be an important tool to monitor intrusive activity and understand interaction between magmatic and groundwater systems. However, quantitative relationships between these parameters must be established to apply them toward understanding processes operating at depth. Power-law scaling exponents calculated for SP and F{sub s}{sup CO2} measured along a fault on the flanks of Masaya volcano, Nicaragua indicate a nonlinear relationship between these parameters. Scaling exponents suggest that there is a declining increase in SP with a given increase in F{sub s}{sup CO2}, until a threshold (log F{sub s}{sup CO2} {approx} 2.5 g m{sup -2}d{sup -1}) above which SP remains constant with increasing F{sub s}{sup CO2}. Implications for subsurface processes that may influence SP at Masaya are discussed.

GEO-SEQ Best Practices Manual. Geologic Carbon Dioxide Sequestration: Site Evaluation to Implementation

From 14 May to 6 October 2016 measurements of gas and heat emissions were made at Bison Flat, an acid-sulfate, vapor-dominated area (0.04-km2) of Norris Geyser Basin, Yellowstone National Park, WY. An eddy covariance system measured half-hourly CO2, H2O and sensible and latent heat fluxes, air temperature and pressure, wind speed and direction, soil moisture and rainfall. A Multi-GAS instrument measured (1 Hz frequency) atmospheric H2O, CO2 and H2S volumetric mixing ratios, air pressure, temperature and relative humidity and wind speed and direction. Soil CO2 fluxes and temperature profiles were also measured on a grid using the accumulation chamber method and thermocouple probes, respectively. These data were used to derive hydrothermal CO2 and heat emission rates and characterize the chemical compositions of fumarole and soil-gas emissions. The eddy covariance, Multi-GAS and soil CO2 flux and temperature data sets are saved in spreadsheets in the *.csv format.