Environmental Geophysics

7/30/2019 Environmental Geophysics

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Sundus Ghaida Noor Azizah

Journal by : Dr.Robert J. Whiteley



Mankind is now at risk from natural geophysical events andfrom industries whose accumulated wastes release toxicsubstances into the environment.

There are two majors challenges for environmentalgeophysicist. First, to understand socio-economic which

govern the demand for their service. Second, to use improvedmethods which more effectively address environmentalproblems.

The process about salinisation of agricultural lands by electromagnetic responses of soils can be expressed forproducing appropriate plant species.

Conventional geophysical methods have had limited successin delineating hydrocarbon LNAPL (Light Non-AqueousPhase Liquids) and DNAPL (Dense Non-Aqueous PhaseLiquids) contamination, both major pollutants.



Natural hazards and disasters are not simply geophysical events, but result from the interaction of physical and social forces.

Paradoxically, while science and technology have mademany people’s lives safer and healthier, their by products have superimposed significant man-made ortechnological hazards on these natural hazards.

Prime importance is now given to minimising andaverting environmental risk.



Considering figur (1) from today’s perspectivethere is little doubt that environmental

hazards are increasingly manmade,increasingly voluntary and diffuse in theirimpact.



In its broadest sense, environmental geophysics isconcerned with the location, delineation andmonitoring of subsurface hazards, regardless of theircauses.

The U.S Environmental Protection Authority (EPA)has recognised that not all available geophysicalmethods for subsurface characterisation areapplicable to studies at waste disposal sites, a major

environmental problem.



There are two principal challenges for geophysicists wishing to be involved withenvironmental problems :

- To better understand socio-economic and environmental factors and theirinter-relationships.

- To develop improved geophysical methods and practices.

1. Socio-economic factorsSocial and economic activity is geared to the complex interaction of environmental factors in which each factor operates over time within anacceptable range and close to its average value.

2. Natural hazards

Significant socio-economic factors and patterns are not always easy to identify

in the case of natural hazards.3. Technological hazards

The socio-economic factors associated with technological hazards aresomewhat easier to predict than for natural hazard as there is a worldwidetrend of decreasing tolerance.



4. Current methods and practice

Available geophysical methods and practices for environmentalstudies of contaminated lands derive from related applications such as

groundwater and engineering geophysics.5. Field examples

The following examples illustrate the application of environmentalgeophysics to major technological hazards that is salinisation of agricultural land and hydrocarbon pollution of urban environments.

6. Land degradation and dryland salinity Salt contamination of soils and salinisation of agricultural land affectsproductivity and the financial viability of many farmers.

Traditional direct methods : salt concentration or salinity isdetermined on the extract by Electrical Conductivity (EC)

measurements.Laboratory methods: determining salinity are costly and timeconsuming . They are essential for calibration of apparentconductivity (Eca) measurements made with resistivity or EMgeophysical methods.



In order to determine the salinity status of an area allconductivity measurements on extracts must be related tosoil salinity classes.

Where a and b are constant which

depend essentially on soil textureand clay content respectively .

Over the selected depth interval (0 to z cm)

the averaged Eca (0 – z cm) is then regressed

againts the averaged ECe (0 – z cm)



Actual hydrocarbon contaminants are found in many differents forms, concentrations and densities. They can bepresent as light (LNAPL) such as toluene and benzeneabove or at the water table, or dense (DNAPL) such astrichloroethane.

The detection of hydrocarbon contaminants by conventional electrical; EM induction (50Hz to 25 kHz respond in electrical conductivity) and Ground ProbingRadar much higher frequencies (13 to 1000 MHz respond

in dielectric permitivity) are very difficult. Radiowave methods (R-EM) operating in range 30 kHz to 5

MHz respond to both properties.



The interaction of socio-economic and environmental factors governs the demand for environmental geophysics. The challenges forgeophysicists, if they wish to address the expanding spectrum of environmental problems, are to better understand these factors and todevelop improved methods and practices. If geophysicist wereprepared to meet these challenges environmental geophysics, has a

bright future. If not, other non specialists will increasingly enter thefield. A major environmental problem of salinisation of agricultural land can

be effectively addressed by careful calibration of electromagneticinduction measurements which allow results to be provided to farmers,land managers and agronomists in terms of likely crop productivitiesfor appropriating plant species which are of direct use. Another majorenvironmental problem of groundwater contamination by LNAPL andDNAPL hydrocarbon spills may be addressed with a new method of radiowave electromagnetic profiling which responds mainly to thelarge dielectric contrasts caused by the introduction of thesecontaminants into soils and groundwater.



TERIMAKASIH

Environmental Geophysics

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