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AnnouncementsAnnouncements
• Midterm is WED.• Review materials: are posted on
website.
• Review session: in sections this week
* reminder: Bring your books to section.
Announcements:Announcements:
Midterm: • You will need pink scantron & #2 pencil
• You will not need a calculator
• People with accommodations please see me at break
““Biogeochemical Biogeochemical Cycles”?Cycles”?
Biogeochemical cycles: The interlinked cycling of matter
(and energy) between geosphere and biosphere.
““Biogeochemical Biogeochemical Cycles”?Cycles”?
“Only in recent decades have scientists begun to fathom the extremely complex interplay of biological, geological and chemical processes by which materials and energy are exchanged and reused at the Earth's surface. These intermeshed processes, known as biogeochemical cycles, operate on timescales of microseconds to eons and occur within domains that range in size from a living cell to the entire atmosphere-ocean system.”
“ Driven by solar or geothermal energy, these cycles are concentrated at interfaces where living organisms catalyze chemical reactions…”
Sedimentation and burial
0.05
Weathering
0.05
Maybe a better Maybe a better
picturepicture: : understand understand biogeospherbiogeosphere as a e as a
systemsystem
““Biogeochemical Biogeochemical Cycles”?Cycles”?
Three interlocking elements:1) Chemistry 2) Biology3) Geological or atmospheric processes (e.g.
weathering, sedimentation, dust transport etc)
1) The Basics 1) The Basics
Life (biosphere) transforms and recycles carbon
Inorganic matter(oxidized carbon)
CO2
Organic matter(reduced carbon)
CHO
Organic Matter • Based on reduced
carbon (C-H)
• Carbohydrates (sugars and starches - CHO)
• Fats and Oils (CH)• Proteins (contain N
too)
Inorganic Matter
1)Oxidized carbon COx
2) Macro Nutrients– Nitrogen– Phosphorus– Sulfur– Potassium
3) Trace Nutrients– ie, Iron, Cobalt,
Selenium, etc.
Matter: Matter: Building Blocks of Building Blocks of LifeLife
• 1) Autotrophs (plants): Fixation of elements into “organic matter”
• 2) Heterotrophs: return elements to geosphere via breakdown of organic matter
Inorganic matter(oxidized carbon)
CO2
Organic matter(reduced carbon)
CHO
autotrophs
heterotrophs
Carbon & nutrients Captured by Carbon & nutrients Captured by AutotrophsAutotrophs
• Autotrophs get carbon & nutrients from environment in inorganic form
• (ie nitrogen as NO2, Phosphorous as PO4)
Figure 6.1
PRIMARY PRODUCERSPRIMARY PRODUCERS
• autotrophs or green plants
• use energy from the sun to turn nutrients into organic compounds:
PHOTOSYNTHESISCO2 + H2O ==> CH2O +
O2
carbon dioxide + water becomes organic tissue + oxygen
What controls this process? What controls this process?
First: actually, there’s more happening:CO2 + PO4 + NO3 + H2O ==> CH2O,P,N + O2
carbon dioxide + phosphate + nitrate + water becomes organic tissue + oxygen
OrganicMatt
er
• Carbohydrates • Fats and Oils
Proteins • Pigments, etc
Inorganic
Carbon (Co2)
• Macro Nutrients– Nitrogen– Phosphorus– Sulfur– Potassium
• Trace Nutrients
Think of all living things : aThink of all living things : a basic basic “recipe”“recipe”
x
y
z
Typically, it’s the thing you are Typically, it’s the thing you are short of.. short of..
• “Limiting Nutrient”–Liebig’s law of the minimum: growth rate of plants is determined by the least abundant nutrient relative to the needs of the plant
HeterotrophsHeterotrophs
• Heterotrophs or Consumers: get their energy from their food
• Cannot “fix carbon” = make organic compounds from only inorganic nutrients
DECOMPOSERS DECOMPOSERS (“remineralization”)(“remineralization”)
• Also Heterotrophs - such as fungi and bacteria
• Convert organic molecules to inorganic nutrients, usually using oxygen
RESPIRATION CH2O + O2 ==> CO2 +
H2O Organic tissue + oxygen becomes carbon dioxide
+ water
DECOMPOSERS DECOMPOSERS (“remineralization”)(“remineralization”)
• Heterotrophs such as fungi and bacteria
Again, there’s more happening:CH2O,P,N + O2 ==> CO2 + PO4 + NO3 + H2O
organic tissue + oxygen becomes carbon dioxide + phosphate + nitrate + water
The Basic Carbon Cycle The Basic Carbon Cycle (short (short term)term)
*CO2 from the atmosphere is fixed into organic matter
•Organics Matter (OM) is stored, transported
•Ultimately it is respired- back to CO2…
CO2
OM
OM OM
CO2
Problem: How to be Problem: How to be quantitativequantitative??
Understand biogeochemical system so can make predictions?
(ie, a perturbation will do..what..? )
2) BOX MODELS2) BOX MODELS
• The basic modeling tool used to study biogeochemical systems
• Goal: Parameterize a system as reservoirs and fluxes
• A simple box model of “reservoirs” of carbon- (approximately to scale..)
• What about fluxes?
Terrestrial Marine
Plant
Litter
Biota
Soil
Humus
Biota
DOC
Sedimentary OC
ILKRESVR
ATM CO2
Example:Example: “ “Pools” & Fluxes of Pools” & Fluxes of Carbon in Atmosphere and OceanCarbon in Atmosphere and Ocean
Atmospheric CO = 750 (+3.4/yr)
Land Biota
Soil Humus 1600Marine Biota
3
Soil Litter 70
570
DOC
Kerogen = 15,000,000
50
preservation
60
2
net marineprimary
production
net terrestrialprimary
production
litter
fall
700
organic
particlerain46
0.15uplife and
weathering
Recent Sedimentary OC 1000
river DOC
river POC
Con
tine
nt Oce
an
ILKRSFLX
15
50
0.250.15
Units of 10 gC Fluxes are per year
0.15
DIC: 37,000
Sedimentation and burial
0.05
Weathering
0.05
““Pools and Pools and fluxes”fluxes”
working of the working of the whole system whole system depends on depends on
1) 1) sizesize of of reservoirsreservoirs
2) 2) rates rates of of transfertransfer
Sedimentation and burial
0.05
Weathering
0.05
Key additional Key additional concept: concept:
Is the system in Is the system in equilibrium?equilibrium? =“steady =“steady state”state”
Box Box ModelModel
Box represents a RESERVOIRAmount of substance in reservoir is INVENTORYArrow represents a FLOW or FLUX
IF in STEADY - STATEINVENTORY remains CONSTANTFLUX IN = FLUX OUT
FLUX IN FLUX OUT
Box Box ModelModel
Box represents a RESERVOIRAmount of substance in reservoir is INVENTORYArrow represents a FLOW or FLUX
RESIDENCE TIME = INVENTORY / FLUX= average time one molecule spends in reservoir
WHY IS RESIDENCE TIME IMPORTANT? Tells 1) how long it would take to significantly affect
the INVENTORY if the FLUX IN or OUT is altered 2) how quickly will something can change.
(Start seeing changes in inventory ~half of a residence time)
FLUX IN FLUX OUT
Residence Time ConceptResidence Time Concept
Residence time = Inventory / Flux
“Inventory” = mass (g)“flux” = mass/ time ( g/ yr)
Residence time = (g ) / (g/yr)
= yr (time)
Residence TimeResidence Time
Inventory (total amount in ocean)
Total Fluxes Out
Residence time =
Inventory / Flux
= The average amount of time one atom of constituent spends in ocean
Also = Approx. amount of time it takes for the concentration of a constituent to significantly change
Total Fluxes InAmount / time
=
Residence time ExampleResidence time Example
My assistant will now My assistant will now conceptually demonstrate:conceptually demonstrate:
““Fur Inventory”: (?)Fur Inventory”: (?)
Would you thus estimate the total amount (“inventory”) of Dog-Hair to be on Baxter:
a) relatively LARGE b) Relatively SMALL
(vs other dogs)
What about Bax-Fur “Residence What about Bax-Fur “Residence time”?time”?
IF you guessed that the inventory of Baxter-fur is relatively SMALL…
•What would you GUESS the residence time is (short or long)?
•What other information would you need to really find out?
1 Month Yield from Electronic 1 Month Yield from Electronic Hair Isolation/ concentration Hair Isolation/ concentration Device:Device:
* ~ 3lbs total mass !!!
FLUX is HIGH !!FLUX is HIGH !!
Mass: 3 lbs * 90% = 2.7 LB Dog Hair.
2.7 lbs* 0.45 (Kilo/ Lb) = 1.22 Kilos * 1000 (g/Kg)
= 1222 grams Dog Hair!!
if FLUX = mass/timeif FLUX = mass/time
Mass: = 1222 grams Dog Hair Experiment TIME: 30 days
FLUX = 40 grams/Day!!
(That, my friends, is a LOT of dog hair.)
Key Concept:Key Concept:
Inventory and Flux are NOT necessarily related!
Ie: If you know inventory- tells you NOTHING about flux (and vice versa)
*can easily have very small inventory- BUT high flux(or small flux, but Huge inventory..)
So: So: can we get a can we get a real number for real number for Bax-fur residence Bax-fur residence time?time?
What would we need?
1. ASSUME STEADY STATE
Can we get a number for Can we get a number for residence time?residence time?
2. Need a Good estimate for Hair INVENTORY in g’s..but how..
Real Example: Real Example: What is res time of water in ocean?What is res time of water in ocean?
RESERVOIR is the OCEANINVENTORY is 1350 X 106 km3
FLUX IN (river flow from continents into ocean)FLUX OUT (evaporation and transport of water to continents)
FLUX IN FLUX OUT
RESIDENCE TIME OF WATER IN OCEANS: Average t ime it takes for runoff to
replace total ocean volume:
inventory 1350 X 106 km3 = _______ _______________ 34,000 years
flux 0.0 40 X 106 km3/year
What about water in atmosphere?What about water in atmosphere?RESERVOIR is the ATMOSPHEREINVENTORY is 0.013 X 106 km3
FLUX IN (evaporation of water from Earth’s surface)FLUX OUT (precipitation)
FLUX IN FLUX OUT
RESIDENCE TIME OF WATER IN ATMOS PHERE: Average t ime water vapor remains in atmosphere before raining out
inventory 0.01 3 X 106 km3 = _______ = ____ ___________ 11 days
flux 0.425 X 10 6 km3/year
The Atmospheric Carbon Reservoir
In the absence of fossil fuel burning and other human activities,the atmospheric carbon reservoir would be in steady state..
inventory = _______ = ____ ___________ 12 Years
flux
760 Gton
60 Gton/Yr
RESIDENCE TIME in Atmosphere GAS (years)
H2O ~ 0.025 *
CO2 ~ 10 **
O2 ~ 1,000 **
N2 ~ 10,000,000 **
* w.r.t. evaporation/precipitation ** w.r.t. terrestrial biosphere photosynthsis/respiration
RESIDENCE TIME = INVENTORY / FLUX
Fluxes are due to evaporation and precipitationFluxes are due to photosynthesis and respiration
Biogeochem. Cycle where Biogeochem. Cycle where Carbon is Carbon is “currency”“currency”
• Carbon cycle” most commonly studied biogeochemical cycle
• “Currency” (=what you are modeling in fluxes and reservoirs) is CARBON
• Q: Why carbon?
Fig. 6.6
Biota Carbon Balance: Gross primary production (GPP) (carbon flux in)Respiration + Death (carbon flux out)
NET primary production (NPP) = (GPP - Respir) (120 - 60 = 60 Pg/yr)
Biota Balance
Fig. 6.6
ATMOSPHERE (a reservoir NOT in steady-state)Fluxes in: 0.1 + 5.3 + 2.0 + 4 + 60 + 55 + 88 = 7.4 + 207 = 214.4 Pg/yearFluxes out: 120 + 90 = 210 Pg/year (Fluxes in > Fluxes out by ~ 4 Pg/yr)
Atmospheric reservoir of C is growing ~ 4 Pg/year!Human emissions: ~7.4 ± 1.0 Pg/year.
If 4 Pg/year is accumulating in the atmosphere, where are the other 3.4 ± 1.0 Pg/year going?
Atmosphere: not in balance!
•We emit about 7.4 ± 1.0 Pg/yr
• We measure atmosphere gaining 4.0 Pg/yr
• Calculation 3.4 ± 1.0 Pg/yr missing from the atmosphere
Fig. 6.6
BIOTA & SOILSReservoir size: 2000Flux in: 120Flux out: 4+60+55 = 119120 - 119 = 1 Pg/yr BIOTA & SOILS are gaining ~ 1 Pg/yr
Is it going into Biota? Some..
Fig. 6.6
OCEANReservoir size: 38000Flux in: 90Flux out: 88+0.2=88.290 - 88.2 = 1.8 Pg/yrOCEAN is gaining 1.8 Pg/yr
Is it going into Ocean?.. A lot more!
Sources & Sinks of Anthropogenic Sources & Sinks of Anthropogenic carboncarbon
BIOTA & SOILSFlux in: 120Flux out: 4+60+55 = 119Net SINK: 1 Pg/yr
OCEANFlux in: 90Flux out: 88+0.2 = 88.2Net SINK: 1.8 Pg/yr
Human SOURCES: 7.4 ± 1.0 Pg/yrMeasured Atmospheric increase: 4.0 Pg/yrCALCULTED Carbon SINKS: 3.4 ± 1.0 Pg/yrMeasured carbon SINKS: 2.8 Pg/yr
Calculated and Measured SINKS are equal within error
SOURCE: where atmospheric carbon is coming fromSINK: where atmospheric carbon is going
Ocean currently taking up ~ 2x more Ocean currently taking up ~ 2x more than land..than land..
• Ocean currently takes up ~ 2x more than land.. But also..
• Ocean uptake each year is 50% what’s going into the atmosphere.
our problems would be MUCH MUCH worse if ocean uptake slowed down.. Much better if speeded up..
Key to understand ocean C uptake mechanisms!
1. CO2 fertilization: higher CO2 1. CO2 fertilization: higher CO2 causes faster plant growth, more causes faster plant growth, more carbon uptake carbon uptake
Fossil Fuel use increase
CO2 increases
Plant growth increases
CO2 decreases
(-)
2. warming also causes faster 2. warming also causes faster plant growth, more carbon uptake plant growth, more carbon uptake
Fossil Fuel use
CO2 increases
Global warming
Plant growth increases
CO2 decreases
Fixed Nitrogen*
Plant growth increases
CO2 decreases
3. Nitrogen fertilization: faster 3. Nitrogen fertilization: faster plant growth, more carbon uptake plant growth, more carbon uptake
* Via fertilizer production
Fossil Fuel use
CO2 increases
Global warming
Decay increases
CO2 increases
5. BUT: warming causes faster 5. BUT: warming causes faster decay, decay, carbon releasecarbon release
Fossil Fuel use
CO2 increases
Global warming
Decay increases
Nutrients increase
Plant growth increases
CO2 decreases
4. BUT faster decay, also means 4. BUT faster decay, also means more nutrients for plant growth, more nutrients for plant growth, carbon uptakecarbon uptake
Overall: to understand Overall: to understand system- must explore, system- must explore,
parameterize & parameterize & test test all all feedbacks.. feedbacks..
Create enormous super-Create enormous super-
computer models..computer models..
EndEnd
Next : Next : Focus on Ocean’s Focus on Ocean’s Role in Atm CO2 Role in Atm CO2 regulationregulation
Sources & Sinks of Anthropogenic Sources & Sinks of Anthropogenic carboncarbon
BIOTA & SOILSFlux in: 120Flux out: 4+60+55 = 119Net SINK: 1 Pg/yr
OCEANFlux in: 90Flux out: 88+0.3 = 88.3Net SINK: 1.7 Pg/yr
Human SOURCES: 7.4 ± 1.0 Pg/yearAtmospheric increase: 4.0 Pg/yearCarbon SINKS: 3.4 ± 1.0 Pg/year
SOURCE: where carbon is coming fromSINK: where carbon is going
Two Mechanisms for ocean to take up carbon:1. Increase in ‘biological pump’2. Increase in carbon dissolving in ocean (“buffering”), causes ocean
acidification!
“BIOLOGICAL PUMP”:-primary producers use inorganic nutrients and carbon to form organic matter-organic matter is exported out of surface ocean into deep ocean -carbon is stored in deep ocean for 100’s of years
“OCEAN BUFFERING”CO2 + CO3
2- + H2O ==> 2 HCO3--
Surface versus Deep Dissolved Surface versus Deep Dissolved NutrientsNutrients
• Surface Ocean (light in upper ~100 m)– Photosynthesis dominates– carbon/nutrient concentrations are LOW
• Organic particles formed in surface ocean fall into deep ocean (exporting nutrients out of surface)
• Deep Ocean (dark below ~100 m)– Respiration of organic particles– carbon/nutrient concentrations are HIGH
CO2 + PO4 + NO3 + H2O CH2O,P,N + O2
photosynthesis
respiration
0
500
1000
1500
2000
2500
3000
350050 100 150 200 250 300 350
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Depth
(mbs
f)
PO4 (µmol/kg)
O2 (µmol/kg)
O2
PO4
1 mole = 6.023 X 1023 molecules molecular mass = grams/moleµmol/kg = 1 x 10-6 moles per kg
O2 PO4
At surface: Photosynthesis
Uses PO4 Produces O2
Photosynthesis
Falling Particles of Dead Organic Matter
Respiration
Uses O
2
Prod
uces
PO
4
Dissolved Inorganic Carbon in the Ocean
High dissolved Carbon in the Surface
Higher dissolved Carbon in the Sub-surface
WHY ISN’T CARBONIN THE SURFACE USED UP?
Two Mechanisms for ocean to take up carbon:1. Increase in ‘biological pump’2. Increase in carbon dissolving in ocean (“buffering”), causes ocean
acidification!
“BIOLOGICAL PUMP”:-primary producers use inorganic nutrients and carbon to form organic matter-organic matter is exported out of surface ocean into deep ocean -carbon is stored in deep ocean for 100’s of years
“OCEAN BUFFERING”CO2 + CO3
2- + H2O ==> 2 HCO3--
Regions with HIGH Nitrogen, but LOW biological production(where biological growth is limited by IRON)IRON FERTILIZATION: An idea for increasing the biological pump in regions that are iron-limited.
Box model review Box model review
OCEAN
Land (via rivers)
hydrothermal
atmosphere Ocean Salt is in “Steady State”
Chemistry of ocean is not changing
Input fluxes = Output fluxesOR
Sources = Sinks
Sediments
Question #1Question #1
• Autotrophs– A. only need sunlight to grow– B. get their nutrients from eating
complex organic molecules– C. get their nutrients from inorganic
compounds – D. need all the elements found on
earth
Question #2Question #2
• Heterotrophs– A. only need sunlight to grow– B. get their nutrients from eating
complex organic molecules– C. get their nutrients from inorganic
compounds – D. need all the elements found on
earth
Question #3Question #3
The residence time of a constituent in a reservoir is approximately equal to the amount of time:
A. it takes to fill the reservoir with input fluxesB. it takes to empty the reservoir with output fluxesC. it takes to significantly alter the inventory of the
reservoirD. all of the aboveToday’s fluxes of carbon into and out of various
reservoirs indicates that the Global Carbon Cycle is:A.Well-balanced and in steady-stateB.Imbalanced and not in steady-stateC.About to achieve steady-state soon
Question #5Question #5
Which of these are currently causing the flux of carbon INTO the biosphere to increase:
A. more CO2 is slowing plant growthB. more nitrogen is increasing plant growthC. global warming causes more respiration and
release of CO2 from soilsD. global warming is slowing plant growth