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Water Quality IndicatorsWater Quality Indicators
Physical Indication of Water Physical Indication of Water PollutionPollution
To a great extent, the To a great extent, the success or failure of an success or failure of an
aquatic ecosystem is aquatic ecosystem is determined by water determined by water
qualityquality
• TemperatureTemperature
• Dissolved oxygenDissolved oxygen
• Total ammonia-nitrogen, NHTotal ammonia-nitrogen, NH33, NO, NO--22
• Alkalinity & HardnessAlkalinity & Hardness
• pHpH
• TurbidityTurbidity
• SalinitySalinity
Water Quality VariablesWater Quality Variables
How water quality values How water quality values are expressed as:are expressed as:
ParameterParameter ValueValue
Dissolved oxygenDissolved oxygen mg/L or ppmmg/L or ppm
Water temperatureWater temperature Degrees C or F Degrees C or F
pHpH
Total ammonia nitrogenTotal ammonia nitrogen mg/L or ppmmg/L or ppm
NitriteNitrite mg/L or ppmmg/L or ppm
Alkalinity/HardnessAlkalinity/Hardness mg/L or ppm CaC0mg/L or ppm CaC033
SalinitySalinity g/L or ppt saltg/L or ppt salt
TemperatureTemperature• Normal temperature: 22 Normal temperature: 22
degrees Cdegrees CSources: sunlight, thermal Sources: sunlight, thermal pollutionpollutionEffects: amount of oxygen Effects: amount of oxygen that can dissolve, that can dissolve, photosynthetic rate, photosynthetic rate, metabolic rates change, metabolic rates change, sensitivity to toxic wastessensitivity to toxic wastes
• Water temperature Water temperature fluctuates seasonally, fluctuates seasonally, resulting in thermal resulting in thermal stratification in deeper stratification in deeper water. water.
Dissolved oxygen and water Dissolved oxygen and water temperaturetemperature
dissolved oxygen and dissolved oxygen and water temperature usually water temperature usually vary over a 24 hour cycle.vary over a 24 hour cycle.
6 a.m.6 a.m. 6 a.m.6 a.m.midnightmidnight6 p.m.6 p.m.noonnoon
00
1515
1010
55
Surface dissolved oxygen, mg/LSurface dissolved oxygen, mg/L
2525
2727
2929
3131
Surface water temperature, °CSurface water temperature, °C
summersummer
Stratification can cause dissolved oxygen Stratification can cause dissolved oxygen and temperature to vary at different depths and temperature to vary at different depths in the same pondin the same pond..
Dissolved oxygen and water Dissolved oxygen and water temperaturetemperature
Epilimnion
Thermocline
Hypolimnion
High temperature
High dissolved oxygen
Low dissolved oxygen
Low temperature
•In general the minimum DO should be ≥ 60% of saturation or ≥ 5 ppm (mg/L)
TurbidityTurbidity
• Measures the amount Measures the amount of suspended particles of suspended particles in waterin water
• Too turbid, then what Too turbid, then what are the effects?are the effects?– Temperature risesTemperature rises– Fish may have difficult Fish may have difficult
finding a matefinding a mate– Clogs fish gillsClogs fish gills
pH = - log [ HpH = - log [ H+ + ]]
00 11 22 33 44 55 66 77 88 99 1010 1111 1212 1313 1414
acidacid alkalinealkaline
pHpH
pH is a measure of acidity pH is a measure of acidity (hydrogen ion concentration) in (hydrogen ion concentration) in water or soil.water or soil.
neutralneutral
Total Ammonia Nitrogen Total ammonia nitrogen ( TAN ) is a measure Total ammonia nitrogen ( TAN ) is a measure of the unionized-ammonia (NHof the unionized-ammonia (NH33) and ) and
ammonium levels (NHammonium levels (NH44++) in the water) in the water
The ratio of ammonia and ammonium varies in an The ratio of ammonia and ammonium varies in an equilibrium determined by pH and water temperature.equilibrium determined by pH and water temperature.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
7
7.4
7.8
8.2
8.6 9
9.4
9.8
pH of water
NH 3 a
s %
of T
AN
at 20C
at30C
Ammonia as a % of Ammonia as a % of total ammonia total ammonia nitrogennitrogen
Nitrite/Nitrate
fecesfeces
BacterialBacterialdecompositiondecomposition
NHNH44++ +1.5 O+1.5 O22 + Nitrosomonas + Nitrosomonas NONO22
-- + 0.5 O + 0.5 O2 2 + Nitrobacter + Nitrobacter
NONO33-- nitritenitrite nitratenitrate
Alkalinity and HardnessAlkalinity and HardnessAlkalinity buffers against variations in pH.Alkalinity buffers against variations in pH.