Transcript Water Chemistry

Bellwork: 09/05/2012
1) Change 10 to 25% of the water within your
tank.
2) If you are not helping your group change
water, you need to be finishing the fish
morphology questions/activity from the
past two days.
3) If you are done with the fish morphology,
you need to be working on your exam
review.
Analysis of Water Chemistry:
Review
Outline
• Water Chemistry Background
• Chemistry in Urban Streams
Temperature
• Most aquatic organisms are cold-blooded and
have an ideal temperature range, specific to
the organism:
• Diatoms - 15-25 degrees C
• Green algae - 25-35 degrees C
• Blue greens - 30-40 degrees C
• Salmonoids – 5.6 – 14.6 ͦ C (cold water fish)
• Coral reefs – 22 to 28 C
Temperature, continued
• Affects development of invertebrates,
metabolism of organisms
• Affects dissolved oxygen
• Warm water makes some substances more
toxic (cyanide, phenol, xylene, zinc) and, if
combined with low DO, they become even
more toxic
Dissolved Oxygen
• Oxygen that is dissolved in water
• DO increases with cooler water and mixing of
water through riffles, storms, wind
• Nutrient loading can lead to algal blooms which
result in decreased DO
• 5 ppm DO is the minimum that will support large,
diverse fish populations. Ideal DO is 9 ppm.
Below 3 ppm, all fish die.
pH
• pH measures the degree of acidity or alkalinity of
the water (each number is a 10-fold difference)
• 0-6 = acid; 7 = neutral; 8-14 = base
• Ideal for fish = 6.5 –8.6
• Ideal for algae = 7.5 – 8.4
• Acid waters make toxic chemicals (Al, Pb, Hg)
more toxic than normal, and alter trophic structure
(few plants, algae)
Ammonia (NH3)
• During the Nitrogen Cycle Ammonium,
NH4+ (relatively non-toxic) is converted to
ammonia NH3 (toxic at a basic pH).
1) NH4+ + 2O2  NO2- + 2H2O
2) NO2- + O2 + 2H+  NO3- + H2O
Biological
Filtration
If the above biochemical reaction does not take place due to a
lack of nitrifying bacteria ammonium will shift back and forth to
ammonia.
NH4+
NH3 + H+ When solution is
basic and warm
Ammonia (NH3), continued
• Ammonia is excreted by fish and invertebrates
living within the tank.
• This ammonia serves as food for nitrifying
bacteria.
• Without this beneficial bacteria the ammonia will
very quickly kill life within the tank.
• Overcrowding will cause a dangerous level of
ammonia.
• Ideal ammonia level is 0 to 0.05 ppm (mg/L)
Turbidity
• Measures the cloudiness of the water
• Turbidity caused by plankton, chemicals,
silt, etc.
• Most common causes of excess turbidity are
plankton and soil erosion (due to logging,
mining, farming, construction)
Turbidity, continued
• Excess Turbidity can be a problem:
• Light can’t penetrate through the water –
photosynthesis may be reduced or even stop
– algae can die
• Turbidity can clog gills of fish and shellfish
–can be fatal
• Fish cannot see to find food, but can hide
better from predators
• Turbidity levels should be as close to 0
NTUs (Nephelometric Turbidity Units)
Phosphorus (Reactive)
• Is necessary for plant and animal growth
• Natural source = phosphate-containing
rocks
• Anthropogenic source = fertilizer and
pesticide runoff from farming
• Can stimulate algal growth/bloom
• Seawater often only contains around 2 ppt
Phosphate (active phosphorus)
-)
Nitrates (NO3
• Formed by the process of nitrification (addition of
O2 to NH3 by bacteria)
• Used by plants and algae
• Is mildly toxic, fatal at high doses
• Large amounts (leaking sewer pipes, fertilizer
runoff, etc.) can lead to algal blooms, which can
alter community structure, trophic interactions and
DO regimes)
Alkalinity
• A measure of the substances in water that
can neutralize acid and resist changes in pH
• Natural source = rocks
• Ideal water for fish and aquatic organisms
has a total alkalinity of 100-120 mg/L
• Groundwater has higher alkalinity than
surface water
Hardness
• The amount of Calcium and Magnesium in
the water (the two minerals mostly
responsible)
• Natural source = rocks
• Limestone = hard water, granite = not hard
water
Physical Effects of
Urbanization Related to Water
Chemistry
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Riparian (plant biome) Vegetation Removal
Decreased Groundwater Recharge
Heat Island Effect
Increased Surface Runoff / Impervious
Surfaces
• Leaky Storm-water / Sewage Pipes
• Point Source Pollution
Review Questions:
-Get with a partner, get out a sheet of paper and put both of
your names on the paper.
1) Two identical water samples are stored at two different
temperatures, one warm and the other cool. Which sample
will have the highest amount of DO?
2) If the pH of a solution needs to be lowered what must you
do?
3) To neutralize a strong acid, what must you add?