Mapping groundwater salinization using transient electromagnetic and direct current resistivity methods in Azraq Basin, Jordan

Geophysics ◽  
2013 ◽  
Vol 78 (2) ◽  
pp. B89-B101 ◽  
Author(s):  
Jafar Sadi Abu Rajab ◽  
Ali Ramadan El-Naqa
Keyword(s):  
Spatial Distribution ◽  
Salt Content ◽  
Chloride Concentration ◽  
Groundwater Salinization ◽  
Near Surface ◽  
Saline Groundwater ◽  
Transient Electromagnetic ◽  
Aquifer Systems ◽  
Mud Flat ◽  
Azraq Basin

Hydrogeophysical characterization using the transient electromagnetic method (TEM) and the DC resistivity sounding (VES) method was implemented in the central part of Azraq Basin (Qa Basin), Jordan, to identify and map the spatial distribution of shallow fresh and saline groundwater in the upper aquifer systems. The alluvium (Al) and chert limestone (URC) shallow aquifers show different degrees of groundwater salinization. The range of groundwater resistivity varies from 0.06 to 10.8 ohm-m. Saline groundwater was detected at depths between 5 to 30 m where the aquifers have a wide spectrum of resistivity values from 0.14 to 120 ohm-m. The integrated geophysical and hydrogeologic models are significantly correlated in chloride concentration, groundwater resistivity, and aquifer resistivity. Using 1D inversion results from the TEM and VES soundings in addition to quasi-3D modeling (1D spatially constrained inversion) at selected TEM sites, groundwater resistivity variation was attributed to two different salinization mechanisms. First, the spatial distribution of the salt content in mud flat deposits had a significant effect on the groundwater salinity. Second, in situ dissolution of near-surface rock-forming salts occurred at areas away from the mud flat deposits. The proposed hydrogeophysical models revealed the potential effect of both mechanisms in the study area.

Physical properties and spatial distribution of the sea ice surface layer (SSL/snow) during the autumn phase of the MOSAiC expedition

2021 ◽  
Author(s):  
Ruzica Dadic ◽  
Martin Schneebeli ◽  
Henna-Reeta Hannula ◽  
Amy Macfarlane ◽  
Roberta Pirazzini
Keyword(s):  
Surface Layer ◽  
Spatial Distribution ◽  
Sea Ice ◽  
Physical Properties ◽  
Surface Scattering ◽  
Climate Feedback ◽  
Energy Fluxes ◽  
Scattering Layer ◽  
Near Surface ◽  
Ice Surface

<p>Snow cover dominates the thermal and optical properties of sea ice and the energy fluxes between the ocean and the atmosphere, yet data on the physical properties of snow and its effects on sea ice are limited. This lack of data leads to two significant problems: 1) significant biases in model representations of the sea ice cover and the processes that drive it, and 2) large uncertainties in how sea ice influences the global energy budget and the coupling of climate feedback. The  MOSAiC research initiative enabled the most extensive data collection of snow and surface scattering layer (SSL) properties over sea ice to date. During leg 5 of the MOSAiC expedition, we collected multi-scale (microscale to 100-m scale) measurements of the surface layer (snow/SSL) over first year ice (FYI) and MYI on a daily basis. The ultimate goal of our measurements is to determine the spatial distribution of physical properties of the surface layer. During leg 5 of the MOSAiC expedition, that surface layer changed from the  surface scattering layer (SSL),   characteristic for the melt season, to an early autumn snow pack. Here,  we will present data showing both a) the physical properties and the spatial distribution of the SSL during the late melt season and b) the transition of the sea ice surface from the SSL to the fresh autumn snowpack. The structural properties of this transition period are poorly documented, and this season is critical  for the initialization of sea ice and snow models. Furthermore, these data are crucial to interpret simultaneous observations of surface energy fluxes, surface optical and remote sensing data (microwave signals in particular), near-surface biochemical activity, and to understand the sea ice  processes that occur as the sea ice transitions from melting to freezing.</p>

Shallow Magnetic Induction Measurements for Delineating Near-Surface Hot Groundwater Sources in Alaskan Geothermal Areas

1983 ◽  
Vol 105 (2) ◽  
pp. 156-161 ◽  
Author(s):  
T. E. Osterkamp ◽  
K. Kawasaki ◽  
J. P. Gosink
Keyword(s):  
Electrical Conductivity ◽  
Magnetic Induction ◽  
Hot Springs ◽  
Measured Temperature ◽  
Conductivity Data ◽  
Induction Method ◽  
Near Surface ◽  
Saline Groundwater ◽  
Geophysical Surveys ◽  
Conductivity Anomalies

Variations in the electrical conductivity of a soil and water system with temperature and salt concentration suggest that a soil containing hot and/or saline groundwater may be expected to have a higher conductivity compared to a cooler and/or less saline system. Temperature and conductivity surveys were carried out at Pilgrim Springs, on the Seward Peninsula, and at Chena Hot Springs, near Fairbanks, to test the use of a magnetic induction method (which measures electrical conductivity) for delineating near-surface hot groundwater sources in geothermal areas surrounded by permafrost. Comparison of the temperature data and conductivity data from these surveys demonstrates that the conductivity anomalies, as measured by the magnetic induction method, can be used to define the precise location of hot groundwater sources in these geothermal areas with the higher temperatures correlating with higher values of conductivity. Magnetic induction measurements of conductivity can also be used to define the lateral extent of the thawed geothermal areas (used for calculating the stored energy) in permafrost terrain. The utility of these magnetic induction measurements of conductivity for reconnaissance geophysical surveys of geothermal areas is that a much greater density of data can be obtained in a shorter time in comparison with shallow temperature measurements. In addition, it is simpler, cheaper and easier (physically) to obtain the data. While conductivity anomalies can result from other than hot and/or saline groundwater, these conductivity data, when coupled with a few measured temperature profiles and groundwater samples, should result in reliable reconnaissance level geophysical surveys in Alaskan geothermal areas.

scholarly journals Effects of climate and spawning stock structure on the spatial distribution of Northeast Arctic cod larvae

2020 ◽  
Author(s):  
Clarissa Akemi Kajiya Endo ◽  
Frode B Vikebø ◽  
Natalia A Yaragina ◽  
Solfrid Sætre Hjøllo ◽  
Leif Christian Stige
Keyword(s):  
Spatial Distribution ◽  
Environmental Variables ◽  
Barents Sea ◽  
Condition Index ◽  
Ocean Current ◽  
Larval Abundance ◽  
Near Surface ◽  
Spawning Stock ◽  
Long Time ◽  
Abundance And Distribution

Abstract The spatial distribution of fish early life stages can impact recruitment at later stages and affect population size and resilience. Northeast Arctic (NEA) cod spawning occurs along the Norwegian coast. Eggs, larvae, and pelagic juveniles drift near-surface towards the Barents Sea nursery area. In this study, a 35-year long time series of NEA cod larvae data was analysed in combination with factors that potentially may affect the distribution of eggs and larvae. These factors included biological aspects of the spawning stock, and environmental variables, such as water temperature, wind, ocean current, and prey abundance. Our aim was to shed light on how these factors influence larval abundance and distribution and how larval abundance and distribution influenced recruitment at age 3. We found that biomass and mean weight of the spawners were positively associated with larval abundance and that a high liver condition index of the spawners was associated with a north-easterly distribution of the larvae. The environmental variables showed generally weak or no correlations with abundance or distribution of larvae. Lastly, we found significant association between larval abundance and year-class abundance at age 3, while the spatial distribution metrics of the larvae, i.e. distribution extent, mean longitude, and mean latitude, showed no significant association with future year-class abundance.

Interpretation of 3-D effects in long‐offset transient electromagnetic (LOTEM) soundings in the Münsterland area/Germany

Geophysics ◽  
1992 ◽  
Vol 57 (9) ◽  
pp. 1127-1137 ◽  
Author(s):  
Andreas Hördt ◽  
Vladimir L. Druskin ◽  
Leonid A. Knizhnerman ◽  
Kurt‐Martin Strack
Keyword(s):  
Integral Equation ◽  
Thin Sheet ◽  
Three Dimensional ◽  
Equation Modeling ◽  
Data Sets ◽  
Sign Reversal ◽  
Near Surface ◽  
Transient Electromagnetic ◽  
Long Offset ◽  
Geological Situation

The interpretation of long‐offset transient electromagnetic (LOTEM) data is usually based on layered earth models. Effects of lateral conductivity variations are commonly explained qualitatively, because three‐dimensional (3-D) numerical modeling is not readily available for complex geology. One of the first quantitative 3-D interpretations of LOTEM data is carried out using measurements from the Münsterland basin in northern Germany. In this survey area, four data sets show effects of lateral variations including a sign reversal in the measured voltage curve at one site. This sign reversal is a clear indicator of two‐dimensional (2-D) or 3-D conductivity structure, and can be caused by current channeling in a near‐surface conductive body. Our interpretation strategy involves three different 3-D forward modeling programs. A thin‐sheet integral equation modeling routine used with inversion gives a first guess about the location and strike of the anomaly. A volume integral equation program allows models that may be considered possible geological explanations for the conductivity anomaly. A new finite‐difference algorithm permits modeling of much more complex conductivity structures for simulating a realistic geological situation. The final model has the zone of anomalous conductivity aligned below a creek system at the surface. Since the creeks flow along weak zones in this area, the interpretation seems geologically reasonable. The interpreted model also yields a good fit to the data.

Assessment of near-surface mapping capabilities by airborne transient electromagnetic data — An extensive comparison to conventional borehole data

Geophysics ◽  
2014 ◽  
Vol 79 (4) ◽  
pp. B187-B199 ◽  
Author(s):  
Cyril Schamper ◽  
Flemming Jørgensen ◽  
Esben Auken ◽  
Flemming Effersø
Keyword(s):  
Raw Materials ◽  
Sedimentary Environment ◽  
Poor Quality ◽  
Aquifer Vulnerability ◽  
Data Types ◽  
Borehole Data ◽  
Surface Mapping ◽  
Near Surface ◽  
Transient Electromagnetic

A newly developed helicopter transient electromagnetic (TEM) system has the ability to measure very early times within just a few μs after the turn off of the primary current. For such a system, careful calibration and accurate modeling of the electromagnetic (EM) response is critical to get true resistivities of the very shallow geologic layers. We discovered that this leads to resolution of the same level or in some cases even better than what can be obtained from airborne frequency EM systems. This allowed a range of important applications where high and accurate resolution is mandatory, e.g., geotechnical applications such as urban planning, railroad and road investigations, landslides or distribution of raw materials, and assessing aquifer vulnerability. We evaluated the results of a pilot survey covering the Norsminde catchment south of Aarhus, Denmark, where we found that near-surface layers (top 30 m) can be mapped with an accuracy of a few meters in a complicated glacial sedimentary environment. The mapping of the geologic layers was assessed by a detailed analysis in which we developed a general methodology for crosschecking the EM and borehole data. This methodology is general and can easily be adapted to other data types and surveys. After rating the quality of the boreholes based on a list of predefined criteria, we concluded that the EM data matched with about three-quarters of the boreholes located within less than 15 m from the closest EM soundings. The remaining quarter of the boreholes fell into two groups in which half of the boreholes were of very poor quality or had inaccurate coordinates. Only eight of all the boreholes could not be reproduced by the data, and we attributed this to be caused by very strong lateral or vertical geologic variations not resolvable by the TEM technique.

Modelling of the Waste Form Behaviour in a Wet Near-Surface Repository Site Over Extended Time Periods

2001 ◽  
Author(s):  
Michael I. Ojovan ◽  
Natalia V. Ojóvan ◽  
Irene V. Startceva ◽  
Zoja I. Golubeva ◽  
Alexander S. Barinov
Keyword(s):  
Experimental Data ◽  
Surface Area ◽  
Salt Content ◽  
Volume Ratio ◽  
Waste Glass ◽  
Near Surface ◽  
Waste Forms ◽  
Time Periods ◽  
Radionuclide Release

Abstract A mathematical model was used to predict radionuclide release from bitumen and glass waste forms over extended time periods. To calculate some model parameters, we used experimental data derived from 12yr field tests with six borosilicate waste glass blocks (each ∼30 kg in weight) and a bitumen block (310 kg), containing real intermediate-level NPP operational waste (NaNO3, 86 wt.% of a dry salt content; 137Cs, 82% of the radioactive inventory). Specific radioactivities of the glass material containing 35 wt.% waste oxides were βtot(90Sr+90Y), 3.74×106 Bq/kg, and αtot(239Pu), 1.3×104Bq/kg. The bitumen block with ∼31 wt.% salt content and βtot(90Sr+90Y), 4.0·106 Bq/kg, and αtot(239Pu), 3.0×103 Bq/kg was manufactured on base of a hard bitumen BN-IV. Tests with the waste forms were performed under saturated conditions of an experimental near-surface repository with a free access of groundwater to the waste blocks through a covering of host loamy soil and backfill of coarse sand. The way used to quantify the amount of leached radioactivity was to measure the volume and radioactivity concentrations of contacting groundwater. In the model, radionuclide release from the waste glass is assumed to be controlled by the processes of diffusion limited ion exchange and glass network dissolution. The mechanism of radionuclide release from the bitumen matrix is believed to remain the same throughout the long-term storage period, except for the initial stage when an enhanced leaching from the surface layer occurs. This long-term release is assumed to be controlled by diffusion of radionuclides through the bitumen matrix. So, identical formulae were applied to calculate the values of leached radioactivity fractions for two waste forms. Radioactivity release curves were plotted for field data and calculation results. For both waste forms, there was good agreement between the modelled and available experimental data. According to the modelling results, fmax = 2.3×10−3% of the initial radioactivity will release from the waste glass into the environment within a proposed institutional control period of 300 years under conditions of the near-surface repository and in the absence of additional engineered barriers. For the bitumen block and the same 300-yr period, the total (maximum) leached radioactivity fraction will be fmax = 4.2×10−3%. The main result of the modelling and experimental studies concerning the leaching behaviour of the bituminised and vitrified waste materials is that the fractional radioactivity release for two waste forms is on the same order of magnitude. Numerical release values per a unit of a surface area to volume ratio are also rather close for two waste forms (exposed surface area to volume ratio for the bitumen block is 2 to 4 times greater then for the glass).

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