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.

SalinitySalinityFresh water is less than 2 g/LFresh water is less than 2 g/L Brackish water is 2 g/L to 34 g/LBrackish water is 2 g/L to 34 g/L

Sea water is more than 34 g/LSea water is more than 34 g/L

NaClNaCl