Transcript File

The quantity of chemicals
in the environment can be
monitored.
Lesson Objective: Students will describe and illustrate
the use of biological monitoring as a method of
determining environmental quality.
Check & Reflect.
Page 224, #s 1-10
Due Wednesday, January 20
Ozone Layer
Over the Antarctic
O3(g) shield the Earth from
damaging ultraviolet (UV)
radiation from the Sun.
15 to 50 km above Earth’s
surface.
science
Ozone also exists at ground level…
Ground level ozone can cause health problems.
Monitoring…
Why would you NOT want to swim in this
lake?
Algal Growth
Reduces the oxygen content in the lake which affects
the kinds of organisms that can live there.
Trout- one of first life forms to die when the
concentration of dissolved oxygen decreases.
Clarity
Is NOT a good indicator of water quality.
Water is monitored:
For 5 categories of use.
Both provincial and federal governments set
guidelines.
Human Drinking Water
Recreation (Swimming)
Livestock Drinking Water
Irrigation
Protection of Aquatic Life
Water Monitoring
Scientists use both
biological and chemical
indicators.
Biological Indicators
Organisms that live in water can tell scientists a lot
about water quality.
Fish, plants, worms, insects,
plankton, protozoa, bacteria and
viruses.
Microbiological
Bacteria can cause serious health
problems if they are present in large
enough numbers.
Small samples of water are taken
frequently from water sources that people
use.
E.Coli
Aquatic Invertebrates
Numbers affected by:
Stagnant pond vs higher
concentration of dissolved oxygen.
Water temperature.
pH
pH below 5
Not many fish, especially young fish.
Not many mayflies.
Diversity decreases as acidity increases
and dissolved oxygen decreases
A pond…
With a large variety of organisms
living in it probably has good
water quality.
Would you drink this water?
Chemical Factors:
Water in the environment is
NEVER completely pure.
Will contain many different
organic and inorganic
compounds.
Most commonly monitored:
Dissolved oxygen
Acidity
Heavy metals
Plant nutrients (nitrogen & phosphorus)
Pesticides
Salts (sodium chloride/magnesium sulfate)
Measuring Chemicals in the
Environment
Concentration: usually measured in
parts per million (ppm) or
milligrams per litre (mg/L)
Chlorine: 1 ppm in water
That means…
There is 1 part chlorine for every
million parts of the
chlorine/water solution.
999mL water/1mL food colouring
Stir to make a solution.
You would say: The concentration of
the food colouring in the container is
1mL food colouring per 1000mL of
solution.
Or: 1 part food colouring per 1000 parts
solution.
To make a VERY dilute solution
Take the solution you just made: 1 part food colouring
per 1000 parts solution.
Pour another 999 mL of water into another large
container.
Add 1 mL of the mixture to the first container.
This contains 0.001 mL of food colouring
0.001 mL parts food colouring per 1000 mL
of solution.
How can this be changed
(written) as parts per million?
Solve for X
0.001 parts per 1000 parts = x
parts per 1 000 000 parts.
X = number of parts per million
parts
Ratio
0.001:1000 = x: 1 000 000
Fraction
Multiply each side by 1 000 000
Parts per billion (ppb) and
parts per trillion (ppt)
Only extremely hazardous
substances are measured to this
level of concentration.
For example:
1 drop of food colouring in a half-full
bathtub is about 1 ppm.
1 drop of food colouring in a full
swimming pool is about 1 ppb.
1 drop of food colouring in the amount
of water needed to fill 1000 swimming
pools is about 1 ppt.
PCBs/polychlorinated biphenyls
For example, the average
concentration of polychlorinated
biphenyls (PCBs) in the Great
lakes have been measured at 4
ppt.
Bioaccumulation:
PCBs are manufactured oils which are used in
electrical equipment and which persists/stay in the
environment and accumulate in the body tissues of
animals.
Dissolved Oxygen
Oxygen from the air dissolves into
water.
Is essential for the health of aquatic
life: fish, insects, and microorganisms (bacteria, etc.)
Level of dissolved oxygen is affected by:
Temperature: Cold water has more
dissolved oxygen than warm water.
Level of dissolved oxygen is affected by:
Turbulence: due to wind or the speed of
moving water.
Level of dissolved oxygen is affected by:
Amount of Photosynthesis: By plants &
algae in the water.
Level of dissolved oxygen is affected by:
# of organisms: Using the water.
5 ppm
5 milligrams per litre of dissolved
oxygen will support most
organisms that live in lakes and
streams.
Phosphorus & Nitrogen
High concentrations in water can cause
problems.
Sewage outfalls & runoff from fertilized
fields are two sources.
High concentrations increase the growth
of algae & green plants.
Phosphorus & Nitrogen
More live algae & green plants eventually
means more dead organic matter.
More food for bacteria (decomposers).
Bacteria increase in # and use up all the
oxygen.
Many fish & aquatic insects can’t survive.
Acidity
Normal raid & snow have a pH of 5.6
Carbon dioxide from the air dissolves in
water and forms a weak carbonic acid.
Precipitation with a pH lower than 5.6 is
considered acid rain or snow.
Acidity
Most fish disappear if water pH falls to
4.5.
Acidity
Acid deposition is a major
problem wherever the soil and
water lack natural bases to
neutralize the acidic
precipitation.
Canadian Shield
Spring Acid Shock
When acidic ice and snow melt, the
acid meltwater flows into aquatic
systems which quickly creates a
concentration of acid that can
dramatically lower the pH in a pond,
slough, lake or river.
Pesticides
Can remain in an environment & remain in
the tissues of some organisms.
Pesticide resistance.
Because we use so many pesticides, even a low
concentration of one kind of pesticide can mix
with other pesticides at low concentration in
the water & create a bigger problem.
Toxic
A poisonous substance.
Toxicity describes how poisonous
a substance is.
Measuring Toxicity
LD50
“LD” stands for “lethal dose”
“50” represents “50%”
50% of a test group of animals
will die if given the dose all at
once.
Heavy Metals
Are called heavy metals because they
have a density of 5g/cm3 or more.
Copper, lead, zinc, mercury,
cadmium and nickel.
Occur naturally in rocks, soil and
sometimes in water.
Minimata, Japan
People sick and dying from a mysterious
disease that affects their nervous systems.
Investigators link the disease to eating
fish.
Local fish contain large quantities of
mercury.
Chemical Company
Had been dumping waste into
the ocean.
Mad as a Hatter
Acid water dissolves lead in pipes.
science
Especially harmful to children.
Affects normal
development and can
cause permanent brain
damage and even death.
Once used in gasoline
and pipes for water
systems.
No longer used in
products that might
result in being inhaled
or ingested.