Water Chemistry pgs 305 - 311 text
Water quality of ecosystems is dependent on chemical, physical, and
biological factors.
 organisms are the best indicators of water quality
When substances in water are harmful to the organisms that live there,
the water is considered polluted.
Chemical and physical factors
Dissolved oxygen (D.O.) (chemical)
- This is the most important chemical requirement for aquatic
organisms.
- Water mixes with air when it falls over rocks and waterfalls increasing
the level of D.O.
- Standing or slow moving bodies of water have less D.O. than fast
moving water bodies.
- Photosynthesis increases D.O. as respiration by aquatic animals
decreases it. (remember the carbon-oxygen cycle?)
- Water polluted with organic matter has less D.O. than clean water
because decomposers of the organic matter use up the D.O.
- Most fish cannot live with D.O. less than 5 ppm.
0-5 ppm low
6-10 ppm medium 11-15 ppm high
Temperature (physical)
- As temperature increases less D.O can be held in the water.
- Trout require high levels of D.O. which is why they live in coldwater
streams.
- Thermal pollution occurs when industries (power plants) use water for
cooling. The hot water is dumped into aquatic systems raising the temp.
Turbidity (physical)
- It is the measure of the amount of light scattered or absorbed by
particles in water (cloudiness).
- eroded soil in water increases turbidity, clog fish gills, and
smothers aquatic insects.
pH (chemical)
Few aquatic organisms can live in water with pH lower than 4 or higher
than 9.
- Best range: fish 6.7 - 8.6
- CO2 produced from decaying organisms forms carbonic acid
decreasing pH.
- sulfuric acid in water comes from acid mine drainage and acid rain
(burning fossil fuels) decreasing pH.
- alkaline industrial waste (bleaching plant) can increase pH.
Hardness (chemical)
- Water with many minerals is considered hard.
- Water containing calcium and magnesium is said to be hard.
- The minerals in hard water can buffer acidic rain water.
- Calcium is needed for clams, snails, and other shelled organisms.
- 0 - 60 ppm soft
60 - 120 med. 120 - 180 hard
Nitrates and Nitrites (chemical)
- Runoff of fertilizers, animal wastes, and sewage are the major sources.
- Excessive nitrogen causes algae population to explode (algae bloom).
Eutrophication – when algae dies- bacteria takes out D.O.
- Most nitrogen is constantly used up in the system. More than 1 ppm.
indicates excess.
- When the algae dies it decomposes using up the D.O.
- high nitrogen harms animals - causes methemoglobinemia (blue
babies) (look it up pg. 311 in text).
Phosphates (chemical)
- Comes from the same sources as nitrogen as well as some industrial
processes.
- also causes algae blooms. eutrophication
- not as harmful to humans or animals as nitrogen.
- More than 0.5 ppm. indicates excess.
Water Chemistry pgs 305 - 311 text
Water quality of ecosystems is dependent on ________, _______, and
__________ factors.
When substances in water are harmful to the organisms that live there,
the water is considered polluted.
Chemical and physical factors
Dissolved oxygen (D.O.) (chemical)
- This is the most important chemical requirement for aquatic
organisms.
- Water mixes with air when it falls over rocks and waterfalls increasing
the level of D.O.
- Standing or slow moving bodies of water have less D.O. than fast
moving water bodies.
- ________ increases D.O. as _______ by aquatic animals decreases it.
(remember the carbon-oxygen cycle?)
- Water polluted with organic matter has less D.O. than clean water
because __________ of the organic matter use up the D.O.
- Most fish cannot live with D.O. less than__ ppm.
____ ppm low
_____ ppm medium _____ ppm high
Temperature (physical)
- As temperature increases ______ D.O can be held in the water.
- Trout require high levels of D.O. which is why they live in coldwater
streams.
- _________pollution occurs when industries (power plants) use water
for cooling. The hot water is dumped into aquatic systems raising the
temp.
Turbidity (physical)
- It is the measure of the amount of ______ scattered or absorbed by
particles in water (cloudiness).
- eroded soil in water increases turbidity, clogs __________, and
smothers aquatic insects.
pH (chemical)
Few aquatic organisms can live in water with pH lower than _ or higher
than _.
- Best range: fish 6.7 - 8.6
- CO2 produced from decaying organisms forms ______ _____
decreasing pH.
- ________ acid in water comes from ______________ and acid rain
(burning fossil fuels) decreasing pH.
- alkaline industrial waste (bleaching plant) can increase pH.
Hardness (chemical)
- Water with many minerals is considered hard.
- Water containing ________ and ________ is said to be hard.
- The minerals in hard water can _______ acidic rain water.
- Calcium is needed for ______, _____, and other shelled organisms.
- ______ ppm soft
__________ med.
________ hard
Nitrates and Nitrites (chemical)
- Runoff of _________, ___________, and _________ are the major
sources.
- Excessive nitrogen causes algae population to explode
(________________)
- Most nitrogen is constantly used up in the system. More than ___
ppm. indicates excess.
- When the algae dies it decomposes using up the D.O.
- high nitrogen harms animals - causes _________________ (blue
babies) (look it up pg. 311 in text).
Phosphates (chemical)
- Comes from the same sources as nitrogen as well as some industrial
processes.
- also causes algae blooms.
- not as harmful to humans or animals as nitrogen.
- More than 0.5 ppm. indicates excess.