Transcript Impact of Humans on Ecosystems

Impact of Humans on Ecosystems
Carry-over from O3, UV radiation, the
Greenhouse Effect and Global
Warming
Sewage and Rivers –
• 1st and foremost: you must be able to interpret
the graph on page 22 of the Option G packet
Sewage and Rivers
• Untreated rivers = pathogenic orgs = water
system = 
• Untreated discharge = high nutrient and
organic matter = “food” for bacteria = elevated
oxygen consumption.
• THE B.O.D. rises and the amount of DO2 falls

Biological Oxygen Demand
(B.O.D.)
B.O.D.
• Fish and other orgs that use DO2 may die
from the low levels of DO2 = mass death =
mass decomposition = release of nitrates,
phosphates and other minerals =
EUTROPHICATION
Eutrophication
• A eutrophic body of water, commonly a lake or
pond has high primary productivity due to
excessive nutrients and is subject to algal
blooms resulting in poor water quality.
• Downstream = nutrient levels decrease = algal
bloom recedes = aquatic system recovers
Fertilizers and Rivers
• Applied to improve crop growth
• Rainwater dissolves and takes inorganic ions
not taken up by plants and transports them to
rivers
• Another way to get EUTROPHICATION
Acid Precipitation
• Rain normally weakly acidic 5.2 – 5.6
• Acid a normal byproduct of several
processes – volcanic activity – electrical
storms – marine plankton physiology
• Acids from human activities = vehicle
exhausts, factories, power stations
• Acid rain pH = 4.5
Acid Rain
Acid Rain Flow Chart – With Your own
Drawings
• Wind ;
• Oxides of Nitrogen from Motor Vehicles;
• Oxides of Sulfur from Factories and Power
Station
• Conversion to Nitric Acid & Sulfuric Acid in
Clouds
• Lakes in shallow soil and low in limestone
become acidic
• Droplets in acid dissolve in rain and snow
• Lakes in deep soil and high in limestone are
buffered
Flowchart Page
Key Effects of Acid Rain
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Fish get screwed – eggs fail to hatch
Causes increased Na+ loss through gills
Increases gill mucus layer = lower O2 uptake
Reduces Hb ability to take up O2
Causes calcium deficiency in shell fish and
birds that eat them
• Leaches aluminum into lakes and rivs = dead
fish
• Removes phosphate from solution = no P = no
algae growth = crystal clear DEAD lakes
Biogas
• CH4 produced by anaerobic breakdown by
of
and human
Fuel produced used for:
• A mixture of methane, carbon dioxide, and
hydrogen sulfide. CO2 and HSO2 will be
removed for final product
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Cooking
Generating electricity
Compressed and used for vehicle fuel
Heating fuel for houses
So how do we make biogas?
• Process must be sealed
• Temp 35-55o C
• Organic residue – set upon by methane-forming
bacteria
• Methanobacterium
• Methanobacillus
• Methanococcus
• = Methane Production
Key reactions
hydrolysing
bacteria
• Organic matter ------ organic acids & alcohols
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acetate forming bacteria
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CO2 + H + acetate
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methane forming bacteria
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Methane (CH4)