The final three chapters present the gist of the book through abbreviated, clear tables for the hurried reader. This paradoxical phenomenon comes from the great variety and complexity of the physical properties of geophysical targets.
2 Methods
Geomagnetic Methods
- Aeromagnetic Surveys
The shape of magnetic anomalies further relates to the inclination of the earth's magnetic field, or the geographic latitude of the location. Towing has the advantage that the magnetic influence of the aircraft does not have to be compensated.
Geoelectric Methods
The resistances of the three beds are in the proportions first layer: second layer: third layer. As in seismic work, the depth of the reflector can be determined if the velocity is known.
Seismic Methods
- General
Based on the refraction data, detailed isoline maps of the surface of impermeable layers (aquicludes) can be produced. Seismic waves are produced by a source quite similar to a seismic fracture, which is mostly located on the surface of the earth.
Gravity
The changes in the length of the spring are directly related to changes in the force of gravity. The application of gravity studies to environmental problems is limited due to high costs and small gravity anomalies.
Geothermometry
Such observations should be made only after the temperature distortion caused by probing or drilling has ceased. To eliminate the falsifying influence of sunlight, temperature checks should only be carried out at night, preferably between 4 and 6 am.
Well Logging
The temperature of the well fluid is continuously monitored by an electrical resistance thermometer in relation to the depth. The purpose is to ascertain the deviation of the drilling axis from the vertical and its azimuth towards the north.
Radioactivity
The time dependence of the dose is expressed in units of dose performance (dose wattage). Radon surveys count the a-rays emitted by the decay of the radon isotope.
Isotope Hydrology
The determination of the proportion of hydrogen and oxygen isotopes in the groundwater can be done quickly and cheaply. This effect can only be observed in groundwater that is no older than 4 years. It is, for example, possible to assess whether contaminated groundwater is older than 4 years (Fig. 2.30).
Furthermore, this temperature dependence allows the distinction between groundwater formed during the cold Pliocene period from the more recent groundwater of the warmer Holocene. This means that by measuring the content of radioactive carbon, the age of the groundwater could be calculated. This extra carbon can lead to groundwater ages that may be thousands of years too high.
Today, this tritium is no longer present, and possible age determinations can only be made by qualitative analysis of groundwater that has formed since then. We can decide whether the salinity of the groundwater originates from great depths or from salt mine deposits.
Abandoned Hazardous Sites
3D image of the total magnetic intensity of a hazardous waste repository containing domestic and industrial waste. The boundary of the covered waste deposit can be derived from 3D presentations of both the total intensity and the gradient survey (Figs. 3.1 and 3.2) by connecting all marginal magnetic anomalies. The magnetic survey points to reinforced foundations, steel pipes and iron troughs in the shallow underground, despite the magnetic disturbances created by the industrial buildings nearby.
A separate magnetic anomaly in the southwest corner of the area must belong to another buried magnetic object. The efficiency of a magnetic survey over a landfill in Indiana, USA, was greatly increased by calculating the upward extension of the magnetic field. As in the case of the reinforced air raid shelter, this general structure is caused by the normal inductive magnetization of the.
Perhaps the individual, electrically active components of the debris are too small to create individual anomalies. In the Panoche Fan area of California, groundwater at the fan margins is contaminated with selenium.
Sri 6
- Electromagnetic Methods (EM) Electromagnetic Mapping
- New Disposal Sites
- General
- Horizontal Stratification Vertical Electric Sounding (VES)
Then, the thickness of the landfill was delineated by electrical soundings (VES) (lower, shaded section). Geology and geoelectric profile of the Rhine Valley from the extinct Kaiserstuhl volcano to Strasbourg. A geological interpretation is derived from this model and the calculated apparent resistivity section.
The resistivity contours of the domestic waste zone in the Alpine foreland (Fig. 3.10) show only one center. The leading edge of the plume has migrated up to 350 m from the discharge basins (belt areas D in Fig. 3.36b). 3.9, the EM image is easier to interpret and the extent of the waste dump is more visible.
A calculated increase in density contrast is observed from the north to the south of the landfill. On top of the uranium waste dump (Fig. 3.62), a clay layer 3 meters thick completely hides the gamma radioactivity. An example of the determination of radon by measuring α-radiation in the ground air is given in Fig.
A contaminated plume follows an underground channel, cut into the top of the glacial moraine (arrow).
HLEM
Cost Structures
Comparison of Geophysical Expenditures
Comparison of costs per borehole meter with expenses for the application of geophysical methods. This enabled the complete exploration of the contaminated area of 30,000 m2 to a depth of 20 m. Furthermore, a distinction could be made between industrial and domestic waste and isolated concentrations of scrap metal, building material and industrial sludge were detected.
These tables should only be considered as a rough guide to estimate the cost of an environmental investigation before consulting a geophysical expert. Comments rectangular grid rectangular grid along roads and roads rectangular grid rectangular grid rectangular grid geophone separation geophone separation.
5 Briefing for Geophysical Surveys
Areas of Application
The successful and cost-effective application of geophysics strongly depends on the physical properties of the location and on the skill of the responsible geophysicist to combine the right methods to obtain optimal information. There is no point in applying geophysics if the differences between the physical properties are too small. Their presence may limit any geophysical activities or require the application of methods that remain undisturbed by installations.
It is therefore recommended that you first go through the area with a cable or pipe detector.
Objectives and Limitations
Objectives of Environmental Geophysics Methods Objectives Location of domestic abandoned industrial waste Magnetic + + + Geoelectrical mapping + + + Geoelectrical + + Induced polarization + + * Self-potential * + Electromagnetic: EM, VLF, Ground radar + * + + Seismic refraction * * Seismic reflection Suitability: + = good, * = limited, -= not possible. Even in soil and excavated landfills, magnetics can be successful if the magnetic properties of the deposited material differ sufficiently from the bedrock. Magnetic measurements are prone to the magnetic influence of iron installations such as cast pipes, fences or well casings, and above all, of the operator's iron buttons or buttons; care must be taken to avoid them.
In most cases, only statements about the location and depth of objects can be made. Geoelectrical measurements are limited if there are buildings, metal pipes and cables in the ground, or if railroad tracks or guardrails cross the investigation area. The results of self-potential investigations are difficult to interpret because the redox potential and flow potential overlap, and the spatial position of the plus and minus poles or the exact location of the SP sources can rarely be determined.
Electromagnetic measurements are disturbed by all metal installations, and especially by power lines running near the study area. The VLF profiles should run perpendicular to a straight line between the object of investigation and the very distant transmitting station.
Planning and Execution of Investigations
Consideration should be given to whether combinations of methods should be applied simultaneously or sequentially. The sequence of geophysical measurements should be arranged based on the specific results of each method, the geological background, preliminary investigation analyzes and drilling data. Therefore, the interpretation of geophysical field observations should be based on long-term experience and reviewed by environmental engineers, geologists or geohydrologists.
Evaluation and interpretation must be carried out with the same caution and care as the geophysical fieldwork. The formal and generalized computer results must be corrected according to the specifications of the order and to the known properties of the object. Records and reports on the time and nature of material dumped and installation of seals must be studied.
Distances between points and lines should be selected according to vertical and lateral penetration requirements. As these are very expensive, the responsible geophysicist should exercise great caution in recommending such developments only after careful consideration of the geophysical results.
Combination of Geophysical Methods
Research and Development
One of the many research goals is to differentiate between substances by means of complex resistance measurements or induced polarization measurements, using the mathematical tool of the fractal dimension. This new geophysical approach should be used to distinguish between clay and unconsolidated rock filled with saline groundwater. Research work should be aimed at finding a way to tell the difference between the two effects.
If a leak occurs, it can only be detected much later, after its seepage has reached one of the monitoring wells outside the landfill. The water seeped under the plastic liner and collected on top of the clay barrier. To avoid this crucial delay, it is proposed to implant stainless steel electrodes in the clay barrier, directly under the plastic liner.
Their connectors must be riveted to non-corrodible cables leading to a constant current source and a digital voltmeter with automatic memory functions. With the growing application of geophysics to shallow environmental targets, new problems will need to be solved, necessitating more research and development.
Procedures
To achieve this, the measurement points of all methods must be entered on the maps at the same scale.
Call for Tenders
3D image of the total magnetic strength of a hazardous waste landfill containing domestic and industrial waste [47]. 61 Figure 3.6. Contours of the total magnetic strength of a buried shelter with a reinforced concrete roof and walls [53]. Contours of EM conductivity data at a hazardous waste landfill with two plumes and monitoring wells (triangles) [16].
List of Tables
8 References
Frischknecht, EC., 1990: Application of geophysical methods to the study of contamination associated with abandoned and injection wells. D., 1990: Seismic reflection methods applied to engineering, environmental and groundwater.- In Ward, Geotechnical and Environmental Geophysics (Publ.), ISBN I, 1-31; Tulsa.
9 Index
Spri nger-Verlag and the Environment
