Water Quality Indicators

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Water Quality Indicators

• Physical Indication of Water Pollution

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To a great extent, the success or failure of an
aquatic ecosystem is determined by water quality
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Water Quality Variables

• Temperature
• Dissolved oxygen
• Total ammonia-nitrogen, NH3, NO-2
• Alkalinity Hardness
• pH
• Turbidity
• Salinity

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How water quality values are expressed as
Parameter Value
Dissolved oxygen mg/L or ppm
Water temperature Degrees C or F
pH
Total ammonia nitrogen mg/L or ppm
Nitrite mg/L or ppm
Alkalinity/Hardness mg/L or ppm CaC03
Salinity g/L or ppt salt
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Temperature

• Normal temperature 22 degrees CSources
  sunlight, thermal pollutionEffects amount of
  oxygen that can dissolve, photosynthetic rate,
  metabolic rates change, sensitivity to toxic
  wastes
• Water temperature fluctuates seasonally,
  resulting in thermal stratification in deeper
  water.

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Dissolved oxygen and water temperature
dissolved oxygen and water temperature usually
vary over a 24 hour cycle.
Surface dissolved oxygen, mg/L
Surface water temperature, C
31
15
29
10
27
summer
5
25
0
6 a.m.
6 a.m.
midnight
6 p.m.
noon
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Dissolved oxygen and water temperature
Stratification can cause dissolved oxygen and
temperature to vary at different depths in the
same pond.

• In general the minimum DO should be 60 of
  saturation or 5 ppm (mg/L)

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Turbidity

• Measures the amount of suspended particles in
  water
• Too turbid, then what are the effects?
• Temperature rises
• Fish may have difficult finding a mate
• Clogs fish gills

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pH
pH is a measure of acidity (hydrogen ion
concentration) in water or soil.
pH - log H
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
neutral
acid
alkaline
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Total Ammonia Nitrogen
Total ammonia nitrogen ( TAN ) is a measure of
the unionized-ammonia (NH3) and ammonium levels
(NH4) in the water
The ratio of ammonia and ammonium varies in an
equilibrium determined by pH and water
temperature.
Ammonia as a of total ammonia nitrogen
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Nitrite/Nitrate
feces
Bacterial decomposition
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Alkalinity and Hardness
Alkalinity buffers against variations in pH.
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Salinity
Fresh water is less than 2 g/L
Brackish water is 2 g/L to 34 g/L
NaCl
Sea water is more than 34 g/L