!!!!class12 global warming - temp ph and algal growth ii - used

8/11/2019 !!!!Class12 Global Warming - Temp PH and Algal Growth II - USED

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04/03/201

Global Warming:Temperature, pH & Algal Growth



04/03/201

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



04/03/201

Carbon Dioxide

• Algae need CO2 for photosynthesis

• Give off CO2 during respiration

• Drives pH in aquatic ecosystems



04/03/201

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



04/03/201

[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.”

http://en.wikipedia.org/wiki/Concentration

http://en.wikipedia.org/wiki/Temperature

http://en.wikipedia.org/wiki/Volume

http://en.wikipedia.org/wiki/Pressure

http://en.wikipedia.org/wiki/Pressure

http://en.wikipedia.org/wiki/Volume

http://en.wikipedia.org/wiki/Temperature

http://en.wikipedia.org/wiki/Concentration



04/03/201

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



04/03/201

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



04/03/201

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.



04/03/201

Molluscs, Calcareous Plankton, etc.

Foraminifera

Coccolithophores

Impact on Aquatic Organisms



04/03/201

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

!!!!class12 global warming - temp ph and algal growth ii - used

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