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Turbidity

Turbidity. What is Turbidity?. A measure of water clarity The murkier the water, the higher the turbidity. Turbidity reduces the transmission of light into water. Turbidity increases as a result of suspended solids in the water. Sources of Turbidity. Phytoplankton blooms Soil erosion

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Turbidity

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  1. Turbidity

  2. What is Turbidity? • A measure of water clarity • The murkier the water, the higher the turbidity. • Turbidity reduces the transmission of light into water. • Turbidity increases as a result of suspended solids in the water.

  3. Sources of Turbidity • Phytoplankton blooms • Soil erosion • Waste discharge • Urban runoff • Abundant bottom feeders

  4. Why is Turbidity Important? • Suspended particles diffuse sunlight and absorb heat. • As temperature increases, DO decreases. • Suspended solids can clog fish gills • Less light is available for photosynthesis. • As sediment settles, gravel beds become fouled.

  5. How is Turbidity Measured? Secchi disk • Measures water transparency • Measures depth at which disk is no longer visible • Useful for deep water

  6. Turbidimeter optical device that measures scattering of light (most accurate) Measure in NTU (nephelometric turbidity units) or JTU (Jackson turbidity units) Turbidity in the lab and field

  7. What is the Turbidity of our Water? • 5 NTU’s = maximum contamination level allowed (MCL) • 0.45 NTU = highest average turbidity from a local well • 0.15 NTU = highest level found at Del Valle Water Treatment Plant

  8. Typical Turbidity Data Water Quality Testing and Monitoring Program for Middle Schools and High Schools. San Diego County Water Authority.

  9. So what? • Increase in turbidity in reservoirs in southwestern U.S. • Increase in turbidity in Delta waters during dry years • Degrades drinking water quality. • Water treatment costs increase. • Decreases light penetration in water. • Can clog gills of fish.

  10. Conductivity

  11. What is Conductivity? • Conductivity is the measure of water’s ability to conduct an electric current. • Estimates amount of total dissolved minerals (ions).

  12. Conductivity in water • Dissolved salts (ions) conduct electrical current in water. • Absolutely pure water is a poor electrical conductor. http://www.humboldt.edu/~dp6/chem110/cond/cond.html

  13. How do we measure Conductivity? • Test with a Conductivity meter • Measured in Siemens or mhos/cm

  14. Conductivity Units • Mhos is ohms backwards! (Mhos is the reciprocal of ohms –if you have to know) • So….ohms is a measure of the resistance to a current. • The less the resistance, the greater the conductivity. • Conductivity in drinking water is low, so we use µmhos/cm or 1 x 10-6 mhos/cm! • Units are sometimes expressed as microsiemens (µS).

  15. Conductivity and Turbidity Demo SEE HANDOUT • Use of lightbulb as class demo • Use of conductivity meter • Use of probeware • Kit Secchi disk

  16. Some Conductivity Data http://www.swrcb.ca.gov/nps/docs/Cond_sal.doc

  17. So What? • Increased concentration of salts increases the conductivity • Salts cannot be filtered out • Higher conductivity can.… • Foul irrigation water (leads to high salinity soils) • Kill wildlife • Create water shortages

  18. Salt water and cells • Salt water is hypertonic to the cells of some plants • This causes plants to wilt and possibly die http://www.cofc.edu/~zaninm/packet_two_files/image024.jpg http://www.encyclopedia.com/html/section/osmosis_BiologicalImportanceofOsmosis.asp

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