scholarly journals Environmental And Anthropogenic Gravity Contributions At The Þeistareykir Geothermal Field, North Iceland

2021 ◽  
Author(s):  
Florian Forster ◽  
Andreas Güntner ◽  
Philippe Jousset ◽  
Marvin Reich ◽  
Benjamin Männel ◽  
...  
Keyword(s):  
Surface Displacement ◽  
Environmental Parameters ◽  
Geothermal Field ◽  
Snow Accumulation ◽  
Geothermal System ◽  
Delayed Response ◽  
Local Pressure ◽  
Flow Rates ◽  
Groundwater Levels ◽  
Gravity Signal

Abstract Continuous high resolution gravimetry is increasingly used to monitor mass distribution changes in volcanic, hydrothermal or other complex geosystems. To quantify the often small target signals, gravity contributions from, e.g., atmospheric mass changes, global and local hydrology should be accounted for. We set up three iGrav superconducting gravity meters for continuous monitoring of the Þeistareykir geothermal field in North Island. Additionally, we installed a set of hydrometeorological sensors at each station for continuous observation of local pressure changes, soil moisture, snow and vertical surface displacement. We show that the contribution of these environmental parameters to the gravity signal does not exceed 10 µGal (1 µGal = 10-8 m s-2), mainly resulting from vertical displacement and snow accumulation. The seasonal gravity contributions (global atmosphere, local and global hydrology) are in the order of ±2 µGal at each station. Using the environmental observations together with standard gravity corrections for instrumental drift and tidal effects, we comprehensively reduced the iGrav time series. The gravity residuals were compared to groundwater level changes and geothermal mass flow rates (extraction and injection) of the Þeistareykir power plant. The direct response of the groundwater levels and a time-delayed response of the gravity signal to changes in extraction and injection suggest that the geothermal system is subject to a partially confined aquifer. Our observations indicate that a sustainable “equilibrium” state of the reservoir is reached at extraction flow rates below 240 kg s-1 and injection flow rates below 160 kg s-1.

scholarly journals Environmental and anthropogenic gravity contributions at the Þeistareykir geothermal field, North Iceland

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Florian Forster ◽  
Andreas Güntner ◽  
Philippe Jousset ◽  
Marvin Reich ◽  
Benjamin Männel ◽  
...  
Keyword(s):  
Model Comparison ◽  
Order Approximation ◽  
Geothermal Field ◽  
Snow Accumulation ◽  
Geothermal System ◽  
Delayed Response ◽  
Local Pressure ◽  
Flow Rates ◽  
Groundwater Levels ◽  
Gravity Signal

AbstractContinuous high-resolution gravimetry is increasingly used to monitor mass distribution changes in volcanic, hydrothermal or other complex geosystems. To quantify the often small target signals, gravity contributions from, e.g. atmospheric mass changes, global and local hydrology should be accounted for. We set up three iGrav superconducting gravity meters for continuous monitoring of the Þeistareykir geothermal field in North Island. Additionally, we installed a set of hydrometeorological sensors at each station for continuous observation of local pressure changes, soil moisture, snow and vertical surface displacement. We show that the contribution of these environmental parameters to the gravity signal does not exceed 10 µGal (1 µGal = 10–8 m s−2), mainly resulting from vertical displacement and snow accumulation. The seasonal gravity contributions (global atmosphere, local and global hydrology) are in the order of ± 2 µGal at each station. Using the environmental observations together with standard gravity corrections for instrumental drift and tidal effects, we comprehensively reduced the iGrav time-series. The gravity residuals were compared to groundwater level changes and geothermal mass flow rates (extraction and injection) of the Þeistareykir power plant. The direct response of the groundwater levels and a time-delayed response of the gravity signal to changes in extraction and injection suggest that the geothermal system is subject to a partially confined aquifer. Our observations indicate that a sustainable “equilibrium” state of the reservoir is reached at extraction flow rates below 240 kg s−1 and injection flow rates below 160 kg s−1. For a first-order approximation of the gravity contributions from extracted and injected masses, we applied a simplified forward gravity model. Comparison to the observed gravity signals suggest that most of the reinjected fluid is drained off through the nearby fracture system.

scholarly journals A modeling study of heterogeneity and surface water-groundwater interactions in the Thomas Brook catchment, Annapolis Valley (Nova Scotia, Canada)

2009 ◽  
Vol 6 (2) ◽  
pp. 2751-2793 ◽  
Author(s):  
M. J. Gauthier ◽  
M. Camporese ◽  
C. Rivard ◽  
C. Paniconi ◽  
M. Larocque
Keyword(s):  
Surface Water ◽  
Snow Accumulation ◽  
Return Flow ◽  
Eastern Canada ◽  
Groundwater Levels ◽  
The North ◽  
Spatio Temporal ◽  
Geological Complexity ◽  
Annapolis Valley ◽  
Response Variables

Abstract. A modelling study of the impacts of subsurface heterogeneity on the hydrologic response of an 8 km2 catchment in the Annapolis Valley (Eastern Canada) is reported. The study is focused in particular on the hydraulic connection and interactions between surface water and groundwater. A coupled (1-D surface/3-D subsurface) numerical model is used to investigate, for a range of scenarios, the spatio-temporal patterns of response variables such as return flow, recharge, groundwater levels, surface saturation, and streamflow. Eight scenarios of increasing geological complexity are simulated, introducing at each step more realistic representations of the geological strata and corresponding hydraulic properties. In a ninth scenario the effects of snow accumulation and snowmelt are also considered. The results show that response variables and significant features of the catchment (e.g., springs) can be adequately reproduced using a representation of the geology and model parameter values that are based on targeted fieldwork and existing databases, and that reflect to a sufficient degree the geological and hydrological complexity of the study area. The hydraulic conductivity values of the thin surficial sediment cover (especially till) and of the North Mountain basalts emerge as key elements of the basin's heterogeneity for properly capturing the overall catchment response.

scholarly journals Hydrogeochemical Characteristics and Genesis of Geothermal Water from the Ganzi Geothermal Field, Eastern Tibetan Plateau

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1631
Author(s):  
Fan ◽  
Pang ◽  
Liao ◽  
Tian ◽  
Hao ◽  
...  
Keyword(s):  
High Temperature ◽  
Tibetan Plateau ◽  
Heat Source ◽  
Chloride Concentration ◽  
Geothermal Field ◽  
Geothermal Water ◽  
Helium Isotope ◽  
Geothermal System ◽  
The Tibetan Plateau ◽  
Geothermal Waters

The Ganzi geothermal field, located in the eastern sector of the Himalayan geothermal belt, is full of high-temperature surface manifestations. However, the geothermal potential has not been assessed so far. The hydrochemical and gas isotopic characteristics have been investigated in this study to determine the geochemical processes involved in the formation of the geothermal water. On the basis of δ18O and δD values, the geothermal waters originate from snow and glacier melt water. The water chemistry type is dominated by HCO3-Na, which is mainly derived from water-CO2-silicate interactions, as also indicated by the 87Sr/86Sr ratios (0.714098–0.716888). Based on Cl-enthalpy mixing model, the chloride concentration of the deep geothermal fluid is 37 mg/L, which is lower than that of the existing magmatic heat source area. The estimated reservoir temperature ranges from 180–210 °C. Carbon isotope data demonstrate that the CO2 mainly originates from marine limestone metamorphism, with a fraction of 74–86%. The helium isotope ratio is 0.17–0.39 Ra, indicating that the He mainly comes from atmospheric and crustal sources, and no more than 5% comes from a mantle source. According to this evidence, we propose that there is no magmatic heat source below the Ganzi geothermal field, making it a distinctive type of high-temperature geothermal system on the Tibetan Plateau.

scholarly journals Geochemical response of deep geothermal processes in the Litang region, Western Sichuan

2018 ◽  
Vol 37 (2) ◽  
pp. 626-645
Author(s):  
Wei Zhang ◽  
Guiling Wang ◽  
Linxiao Xing ◽  
Tingxin Li ◽  
Jiayi Zhao
Keyword(s):  
Groundwater Recharge ◽  
Hot Springs ◽  
Cold Water ◽  
Isotope Analysis ◽  
Geothermal Field ◽  
Geothermal System ◽  
Calcite Dissolution ◽  
Western Sichuan ◽  
Geothermal Fields ◽  
Positive Correlations

The geochemical characteristics of geothermically heated water can reveal deep geothermal processes, leading to a better understanding of geothermal system genesis and providing guidance for improved development and utilization of such resources. Hydrochemical and hydrogen oxygen isotope analysis of two geothermal field (district) hot springs based on regional geothermal conditions revealed that the thermal water in the Litang region is primarily of the HCO3Na type. The positive correlations found between F−, Li2+, As+, and Cl− indicated a common origin, and the relatively high Na+ and metaboric acid concentrations suggested a relatively long groundwater recharge time and a slow flow rate. The values of δD and δ18O were well distributed along the local meteoric line, indicating a groundwater recharge essentially driven by precipitation. The thermal reservoir temperature (152°C–195°C) and thermal cycle depth (3156–4070 m) were calculated, and the cold water mixing ratio (60%–68%) was obtained using the silica-enthalpy model. Finally, hydrogeochemical pathway simulation was used to analyze the evolution of geothermal water in the region. The results were further supported by the high metasilicate content in the region. Of the geothermal fields in the region, it was found that the Kahui is primarily affected by albite, calcite precipitation, and silicate, while the Gezha field is primarily affected by calcite dissolution, dolomite precipitation, and silicate.

RESISTIVITY, SELF‐POTENTIAL, AND INDUCED‐POLARIZATION SURVEYS OF A VAPOR‐DOMINATED GEOTHERMAL SYSTEM

Geophysics ◽  
1973 ◽  
Vol 38 (6) ◽  
pp. 1130-1144 ◽  
Author(s):  
A. A. R. Zohdy ◽  
L. A. Anderson ◽  
L. J. P. Muffler
Keyword(s):  
Geothermal Field ◽  
Induced Polarization ◽  
Hot Water ◽  
Thermal Waters ◽  
Geothermal System ◽  
Electrical Soundings ◽  
Lateral Extent ◽  
High Concentrations ◽  
Lake Deposits ◽  
Self Potential

The Mud Volcano area in Yellowstone National Park provides an example of a vapor‐dominated geothermal system. A test well drilled to a depth of about 347 ft penetrated the vapor‐dominated reservoir at a depth of less than 300 ft. Subsequently, 16 vertical electrical soundings (VES) of the Schlumberger type were made along a 3.7‐mile traverse to evaluate the electrical resistivity distribution within this geothermal field. Interpretation of the VES curves by computer modeling indicates that the vapor‐dominated layer has a resistivity of about 75–130 ohm‐m and that its lateral extent is about 1 mile. It is characteristically overlain by a low‐resistivity layer of about 2–6.5 ohm‐m, and it is laterally confined by a layer of about 30 ohm‐m. This 30‐ohm‐m layer, which probably represents hot water circulating in low‐porosity rocks, also underlies most of the survey at an average depth of about 1000 ft. Horizontal resistivity profiles, measured with two electrode spacings of an AMN array, qualitatively corroborate the sounding interpretation. The profiling data delineate the southeast boundary of the geothermal field as a distinct transition from low to high apparent resistivities. The northwest boundary is less distinctly defined because of the presence of thick lake deposits of low resistivities. A broad positive self‐potential anomaly is observed over the geothermal field, and it is interpretable in terms of the circulation of the thermal waters. Induced‐polarization anomalies were obtained at the northwest boundary and near the southeast boundary of the vapor‐dominated field. These anomalies probably are caused by relatively high concentrations of pyrite.

Understanding the past-climate history from Antarctica

2005 ◽  
Vol 17 (4) ◽  
pp. 487-495 ◽  
Author(s):  
ERIC W. WOLFF
Keyword(s):  
Greenhouse Gas ◽  
Ice Core ◽  
Ice Cores ◽  
Environmental Parameters ◽  
Snow Accumulation ◽  
Climate History ◽  
Past Climate ◽  
Carbon Dioxide Concentrations ◽  
The Antarctic ◽  
Climate Events

Antarctic ice cores have become a unique and powerful resource for studies of climate change. They contain information on past climate, on forcing factors such as greenhouse gas concentrations, and on numerous other environmental parameters. For recent centuries, sites with high snow accumulation are chosen. They have, for example, provided the only direct evidence that carbon dioxide concentrations have increased by over 30% over the last two centuries. They have provided key datasets for other greenhouse gases, and for other forcings such as solar and volcanic. Over longer timescales, the Vostok ice core has shown how greenhouse gas concentrations and climate have closely tracked one another over the last 400 000 years. Other cores have shown detailed spatial and temporal detail of climate transitions, including the Antarctic response during rapid climate events such as Dansgaard-Oeschger events. The new core from Dome C has extended the range of ice cores back beyond 800 000 years, and even older ice could be obtained in future projects.

scholarly journals Simultaneous leaf-level measurement of trace gas emissions and photosynthesis with a portable photosynthesis system

2020 ◽  
Author(s):  
Mj Riches ◽  
Daniel Lee ◽  
Delphine K. Farmer
Keyword(s):  
Environmental Parameters ◽  
Co2 Assimilation ◽  
Trace Gas ◽  
Ionization Mass ◽  
Gas Emissions ◽  
Flow Rates ◽  
Trace Gas Emissions ◽  
Level Measurement ◽  
Online Measurements ◽  
Leaf Level

Abstract. Plants emit considerable quantities of volatile organic compounds (VOCs), the identity and amount of which vary with temperature, light and other environmental factors. Portable photosynthesis systems are a useful method for simultaneously quantifying in situ leaf-level emissions of VOCs and plant physiology. We present a comprehensive characterization of the LI-6800 portable photosynthesis system's ability to be coupled to trace gas detectors and measure leaf-level trace gas emissions, including limits in flow rates, environmental parameters, and VOC backgrounds. Instrument contaminants from the LI-6800 can be substantial, but are dominantly complex molecules such as siloxanes that are structurally dissimilar to biogenic VOCs and thus unlikely to interfere with most leaf-level emissions measurements. We validate the method by comparing CO2 assimilation calculated internally by the portable photosynthesis system to measurements taken with an external CO2 gas analyzer; these assimilation measurements agree within 1 %. We also demonstrate both online and offline measurements of plant trace gas exchange using the LI-6800. Offline measurements by pre-concentration on adsorbent cartridges enable detection of a broad suite of VOCs, including monoterpenes (e.g., limonene) and aldehydes (e.g., decanal). Online measurements can be more challenging if flow rates require dilution with ultra-pure zero air. We use high resolution time-of-flight chemical ionization mass spectrometry coupled to the LI-6800 to measure direct plant emission of formic acid.

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