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GroundwaterSoftware.com - April 2009 Newsletter: LTC Junior Levelogger

 

 

 

 

Vol. 10  No. 2

ELECTRICAL CONDUCTIVITY

&
THE ***NEW*** LTC LEVELOGGER JUNIOR

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Electrical Conductivity

Electrical conductivity is a parameter commonly measured in groundwater studies. This newsletter will outline what electrical conductivity is, and why it is useful in characterising groundwater.

  1. What is electrical conductivity?

  2. What contributes to the electrical conductivity of a solution?

  3. How does the movement of an electrical current differ between a metal and a solution?

  4. Why is electrical conductivity measured in groundwater studies?

  5. What are typical values of electrical conductivity in groundwater?

1.  What is electrical conductivity?

Electrical Conductivity (EC) is a measure of its ability to carry an electrical current, and varies both with the number and type of ions the solution contains. Electrical conductivity is typically reported in units of microsiemens.

2.  What contributes to the electrical conductivity of a solution?

An electrical current is carried by both the anions and cations within a solution; the EC of a groundwater will vary with the number and type of these ions present. Only ions can carry a current; the un-ionized species of weak acids or bases and uncharged soluble organic materials (i.e. ethanol, glucose) cannot carry a current and thus are not measured by conductance.

3.  How does the movement of an electrical current differ between a metal and a solution?

When an electrical current flows through a metal, the chemical properties of the metal are not altered, whereas there is a chemical change in a solution when an electrical current flows through it. In a metal, the electrical current is carried by electrons whereas in a solution it is carried by ions. An increase in temperature causes an increase in electrical resistance in metals, and a decrease in resistance in solutions.  Finally, electrical resistance is typically greater in a solution than in metals.

4.  Why is electrical conductivity measured in groundwater studies?

Electrical conductivity (EC) are frequently used in groundwater studies to obtain a quick estimate of the dissolved solids content of a water sample. The dissolved solids content can be approximated by multiplying the specific conductance by an empirical factor (typically varying from about 0.55 to 0.9). The dissolved solids content of a groundwater can be an indicator of the hardness of the water (the higher the dissolved solids, usually the harder the water), and can also provide some information regarding contamination, depending upon the type of contaminant of interest. As previously mentioned, information regarding weak acids and bases, in addition to uncharged soluble organics, can not be gathered from electrical conductivity measurements.

5.  What are typical values of electrical conductivity in groundwater?

Typical values of electrical conductivity in groundwater can vary from several tens of microsiemens for water nearly as nonsaline as rainwater, to hundreds of thousands of microsiemens for brines in deep sedimentary basins.

There are several tools available to instantly measure electrical conductivity in groundwater.  One of these tools is the new Solinst LTC Levelogger Junior.

References

Domenico P.A. and Schwartz, F.W. (1998). Physical and Chemical Hydrogeology. Published by John Wiley & Sons, Inc. New York, NY.

Fetter, C.W. (1994). Applied Hydrogeology; Third Edition.  Published by Prentice-Hall, Inc., Englewood Cliffs, NJ.

Freeze, R.A. and Cherry, J.A. (1979). Groundwater. Published by Prentice-Hall, Inc., Upper Saddle River, NJ.

Sawyer, C.N., McCarty, P.L. and Parkin, G.F. (1994). Chemistry for Environmental Engineering; Fourth Edition. Published by McGraw-Hill Inc., NY.

 

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***NEW***

The LTC Levelogger Junior logs conductivity, as well as water level and temperature. Like the LT Levelogger Junior, it is easy to transport, program, deploy and retrieve data. It combines a datalogger, 5-year battery, pressure transducer, and temperature and conductivity sensors within a small waterproof housing, 7/8" x 7.5" (22 mm x 190 mm).

The conductivity sensor is a 4-electrode platinum sensor, with auto-ranging capabilities. The minimal maintenance, sealed LTC Levelogger Junior is simple to clean and calibrate, even in the field.

Using standard Levelogger Software, it displays conductivity,temperature, and temperature-compensated water level. Memory is non-volatile and stores up to 16,000 sets of readings. Measurements are linear, in any interval between 5 seconds and 99 hours.

Features

  • Low Cost

  • Three measurements in one probe

  • Compatible with Levelogger Software and accessories

  • Single or multi-point calibration

  • Compact, low maintenance, waterproof design

  • Faraday Cage protection against power surges

  • Real-time viewing and data export to other programs

  • Compatible with STS Gold Telemetry and SDI-12

 

For more info or to purchase click here:  LTC Levelogger Junior



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