!!!!class12 global warming - temp ph and algal growth ii - used
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Global Warming:Temperature, pH & Algal Growth
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The model uses Dt=.2, Runge-Kutta4, and time = 1500 hours. Run the
simulation at 18, 27.5, and 33 degrees C by changing the value inside the
TEMP converter. Enter the maximum algae abundances at these
temperatures.
Max Algae Abundance
24.0 C
27.5 C
33.0 C
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Carbon Dioxide
• Algae need CO2 for photosynthesis
• Give off CO2 during respiration
• Drives pH in aquatic ecosystems
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CO2 & Acidity of Aquatic Systems
As CO2 concentrations in the atmosphere increases whathappens to CO2 concentration in water?
More CO2 dissolves into water - Henry’s law
Wil l iam Henry
"At a constant temperature, the amount of a given gas that
dissolves in a given type and volume of liquid is directly
proportional to the part ial press ure of that gas in equilibrium
with that liquid.“ – W. Henry
In a mixture of gases, each gas has a partial pressure which is the
hypothetical pressure of that gas if it alone occupied the volume ofthe mixture at the same temperature.
The total pressure of an ideal gas mixture is the sum of the partial
pressures of each individual gas in the mixture.
[G] = pp(G)/ K
[G] = concentration of gas G in H2O
PpG = partial pressure of gas
K = Henry’s law constant for gas G, a
function of temp. & salinity
Henry’s Law
What is concentration in moles/L and pg/L of CO2 in water with temp = 25 oC?
Percent CO2 in atmosphere = .0397
PpCO2 = .000397 atm
KCO2 = 29.41 L·atm/mol
[CO2] = .000397 atm/29.41 atm/mol = .00001349 mol/L
Mass of 1 mol of CO2 = 12+(16x2) = 12+32 = 44 g
Grams of CO2/L = .00001349*44g = .0005939 g/L = 5.939x10-4 g/L
= 5.939x10 8 pg/L
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[G] = pp(G)/ K
[G] = concentration of gas G in H2O
PpG = partial pressure of gas
K = Henry’s law constant for gas G, a
function of temp. & salinity
Henry’s Law
How many grams of carbon dioxide gas is dissolved in a 1 L bottle of
carbonated water if the manufacturer uses a pressure of 2.4 atm in the bottling
process at 25 °C?
[CO2] = 2.4 atm/29.76 atm/(mol/L) = 0.08 mol/L
Mass of 1 mol of CO2 = 12+(16x2) = 12+32 = 44 g
g of CO2 = 8.06 x 10-2 mol x 44 g/mol
g of CO2 = 3.52 g
CO2 & Acidity of Aquatic Systems
When CO2 dissolves in water it forms carbonic acid H2CO3
which can dissociate into bicarbonate
HCO3- and an H+ ion.
HCO3- can further dissociate into carbonate CO3
2- and an H+
As CO2 concentration increases on the left what happens?
Drives the reaction to the right per - Le Chatelier’s Principle
Causes more H+ ions to be released thus decreasing p H
Le Chatelier
“If a chemical system at equilibrium experiences a change in
concentration, temperature, volume, or partial pressure, then
the equilibrium shifts to counteract the imposed change and a
new equilibrium is established.”
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Calculating pH
[H+]2 = 1.349x10-5 mol/L*4.45x10-7 = 6e-12
SQRT(6e-12) = 2.45x10-6
-LOG10(2.45x10-6) = 5.6
Knowing the concentration of CO2 we can calculate pH
by solving for [H+]2 from the following equilibrium
constant:
Dissolved inorganic carbon
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- ↔ 2H+ + CO3
2-
• These species known as Dissolved Inorganic Cabon (DIC)
– pH < 6 most DIC is H 2CO3
– 6 < pH < 10 most DIC is HCO3-
– pH > 10 most DIC is CO32-
• DIC availability is a potential constraint on productivity
Speciation of CO2 Dependent on pH
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Oceans Acidifying Rapidly
Changes in sea surface pH caused by
anthropogenic CO2 1700-2000
H+ 30%
H+ 70%
Nonl inear – small change in
CO2 causes large change in pH
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Increasing CO2 Levels Drive Acidification
Global warming and ocean acidification will compromise carbonate accretion,
with corals becoming increasingly rare, driving reefs increasingly toward the
tipping point for functional collapse. Future scenarios predict increasingly
serious consequences for reef fisheries, tourism, coastal protection, and people.
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Molluscs, Calcareous Plankton, etc.
Foraminifera
Coccolithophores
Impact on Aquatic Organisms
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Models Inadequate to Predict Ecosystem Impact
Definitions• Standing crop – total amount of producer biomass/carbon
in an ecosystem at a given point in time
• Production:: creation of new organic matter
• Gross Primary Production (GPP): total amount of
energy fixed (or CO2 taken up) by all autotrophs in an ecosystem
• Net Primary Production (NPP): energy remaining
after autotrophs have met their own energetic needs
NPP = GPP – RPP