NATURAL AND ARTIFICIAL TRACERS IN GROUND WATER

Submitted By:-1. Amrit singh Choudhary2. Amit Kumar Garg.3. Aman Khandelwal

Overview of presentation

• Introduction• Groundwater tracing-overview• Why is tracing imp.?• Types of tracers• Tracer tests• Applications• Conclusion

Introduction

• The fundamental idea of the tracer technique is simple and clear. • water is “marked” with the aid of a tracer and its propagation is

followed.• it has useful means in almost all fields of applied hydrology and

hydrogeology.(groundwater, rivers, lakes, glaciers, etc.)

• The most frequently treated questions are the following:

Where does the water flow? Where does the water come from? Is there a hydraulic connection between two points? How do substances migrate in water?

Groundwater tracing - an overview

• Groundwater tracers include any substance that can become dissolved or suspended in water, or attached to the water molecule, and recovered or measured from a water sample that can be used to trace the source of groundwater in terms of its specific or relative location and time of recharge.

• Groundwater tracers can include both artificially introduced and naturally occurring substances.

• Groundwater tracing as a science has been in practice for more than a century.

Why is tracing important?

• Tracing techniques can be used in all types of hydrological and hydro geological environments to obtain information about water movement and contaminant transport.

• water tracing was initially developed for the investigation of karst aquifers.

• Tracer tests in caves are mostly used to identify active conduit networks.

Cont….

• Example:- Florida boasts the highest concentration of springs on the planet. People drank the water without treatment. But Florida's spring water quality has been declining markedly for more than 10 years, with the most notable problem being increasing nitrates.

Type of Tracers

1. Natural Tracers• it involves the use of naturally occurring

components of a water sample to determine information about the source and age of the sample.

• Used in case of age-dating.

• Environmental isotopes are now used to trace not only groundwater provenance, but also recharge processes, subsurface processes, geochemical reactions and reaction rates.

Cont…

• The most commonly used natural tracers are isotopes. Some are:-

–Oxygen Isotopes.–Isotopes of Hydrogen–Nitrogen–Carbonate, organic carbon and

hydrocarbon

Input outputaquifier

2. Artificial Tracers• they can be used to evaluate the extent to which

aquifers interact with surface water features, providing information on groundwater flow paths, travel times, velocities, dispersion, flow rates and the degree of hydraulic connection.

• they should have low toxicological impact.

• This differs from natural tracers methods which rely on the measurement and interpretation of background concentrations of the chemical constituents of water, such as major ions, stable or radioactive isotopes.

Cont…

The purpose of using artificial tracers is to answer three basic questions.

1. Where does the water go (say from a sinkhole) or where does the water come from (say from a spring)?

2. How long does it take to get there?

3. What happens to the water along the way?

ARTIFICIAL TRACERS

• Fluorescent Dyes• Carbonate, organic carbon and hydrocarbon

Sulphur Nitrogen Chlorine Bromine, lithium and boron Strontium

• Tritium• Carbon-14 • Chlorine-36 and iodine-129 • Argon-39 • Krypton • Uranium series isotopes

Radioisotopes

Dye tracer technique for assessing groundwater and surface water interaction in the field

Tracer tests

There are two basic types of dye tracer tests:-

1.Qualitative Tracer Tests.

2. Quantitative Tracer Tests.

ApplicationsPossible applications of the tracer technique in different aquifer types

Karstic aquifers • Regional surveys of groundwater flow• Establishment of conceptual models of karst systems• Detection of karstic networks

Alluvial aquifers • Regional investigations of groundwater flow• Delimitation of catchments (containment areas)• Delimitation of contaminant leakage zones

Hillslope groundwater and fractured aquifers• Detection of flow paths in hard rocks• Investigation of water bearing structures (e.g. joints, fractures and

layering)

Main focuses of tracer investigations in hydrogeology

• Catch works (wells, springs) • Groundwater protection zones • Recharge area• Risk assessments, simulation of hazards• Ancient waste deposits, contaminated sites• Interaction between ground and surface water• Evidence of “foreign water”• Determination of aquifer parameters/ groundwater modelling• Expertise in case of damage• Boreholes, groundwater observation network

Tritium-Helium age Dating

Ground water Tracing using Redon

Advantages and DisadvantagesAdvantages Disadvantages

Application and monitoring can be designed in a controlled way.

Tracer tests can have overheads in terms of cost and time, particularly when investigating longer or slower groundwater flow paths.

Tracers can be used to assess the significance of local geological features on stream-aquifer connectivity.

Requires careful planning and design with some pre-test knowledge of hydrogeology.

Seepage can be assessed either qualitatively or quantitatively .

Unanticipated short travel times can lead to high tracer concentrations being released to watercourses and potentially into public water supplies.

Tracers can provide direct evidence for the movement of water from one point to another.

Dyes can have complex chemical interactions which tend to be pH-dependent or can be selectively sorbed with geological material.

Tracers can be used to track pollutants such as human pathogens, where the movement and fate of these pollutants may not match water flow.

Conclusion

• Groundwater, in its natural state, contains environmental isotopes and conclusions may be drawn from the distribution variations.

• The distribution of the stable isotopes, deuterium and oxygen-18, of groundwater correlated with average isotopic data of precipitation define the origin and movement of subsurface waters.

• Radioisotopes, such as tritium, provide valuable information on recent recharge whereas carbon-14 data show slow-moving groundwater.

• The use of isotope techniques which complement hydrochemical and hydrogeological studies should be encouraged in both surface water and groundwater resource development.

References• Clark, I.D., and Fritz, P., 1997, Environmental Isotopes in Hydrogeology, Lewis, New York,  328p. • Jablonski, J.M., 2002, personal communication; Global Underwater Explorers, 15 south Main St.,

High Springs, Florida; phone (386) 454-0811.• Käss, W., 1998, Tracing Technique in Geohydrology, Balkema, Rotterdam, 581 p.• Smith, R. L., J. K. Böhlke, S. P. Garabedian, K. M. Revesz, and T. Yoshinari (2004), Assessing

denitrification in groundwater using natural gradient tracer tests with 15N: In situ measurement of a sequential multistep reaction, Water Resour. Res., 40, W07101, doi:10.1029/2003WR002919. Received 1 December 2003; accepted 12 May 2004; published 28 July 2004.

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• McClelland, J.W., I. Valiela, and R.H. Michener. 1997. Nitrogen-stable isotope signatures in food webs: A record of increasing urbanization in coastal watershed. Limnology and Oceanography 42, p. 930-937.

Thank you