Lecture 10Lecture 10

Ocean acidification

Suggested reading: Today’s journal club and references therein

http://commons.wikimedia.org/wiki/File:Oceans.png

• Zoanthamine: inhibits ear inflammation• Zoanthamine: inhibits ear inflammation• Norzoanthamine: prevents osteoporosis,

cytotoxicity against leukemia cells, h b h l linhibits human platelet aggregation

• Palytoxin: binds to K Na pump protein • Palytoxin: binds to K, Na pump protein, destroying the ion gradient essential for

cells. LD50~ 1μg/kgf h d b P f K h• first synthesized by Prof. Kishi’s group at

Harvard

The synthesis of natural compounds is a vibrant field

t

enone

cuprateAldol rxn

enone

keytonekeytone

From Behenna, Angew. Chemie 47 (2008)

Construction of the core by Diels-Alder Functionalization of the core

After a series of acid/base and redox reactions…

From Behenna, Angew. Chemie 47 (2008)

Attaching the side chain Final synthesis of norzoanthamine

Coral Deterioration: Bleaching & Disease

• Reef-building corals contain plant-like organisms called zooxanthellae that live symbiotically within their tissue. Zooxanthellae provide their coral host with food and oxygen, and in return, the zooxanthellae receive nutrients, carbon dioxide, and an enemy-free shelter When water temperatures are just a degree or two warmer than usual for a few weeks shelter. When water temperatures are just a degree or two warmer than usual for a few weeks, the zooxanthellae are expelled, often leading to the coral’s death.

• “Coral bleaching:” without the coral’s zooxanthellae symbionts, which contain various photosynthetic pigments, corals are nearly transparent and the white, external calcium carbonate skeleton that the coral polyps live on becomes plainly visible.

http://www.eoearth.org/article/Coral_reefs_and_climate_change

800 ppmat 2100 3.4

73.52 (for 1870

550 ppmat 2100 1.8

0.07 +0.223 (99%

confidence interval)

1870-2006)

0.01 +0.0170.7

interval)

Consequences for Sea Temperature

• During the 20th century, increasing atmospheric CO2 has increased the ocean temperature by 0.74oC.

Consequences for Dissolved CO2

• Since the industrial revolution, the ocean has absorbed ~25% of the CO2 produced by burning fuels each day, 22 million tons of CO2 mix with ocean water

Consequences for Dissolved carbonate

•This excess dissolved CO2 has dramatic consequences for ocean acidity and ocean carbonate ion concentrations

• Here, change in CO32- from 1700 (pre-industrial era) to 1990’s

Ocean Acidification: “The Other CO2 Problem”• Normal ocean pH~8.2p• Ocean acidity predicted to double by end of century.

Critical Thresholds for Coral Communities

repe

ratu

rng

Tem

pcr

easi

nIn

c

Decreasing CO32- concentration

Coral Reef Scenario “A”

Coral Reef Scenario “B”

l fCoral Reef Scenario “C”

From Hoegh-Guldberg, Science 318, 1737 (2007)

5

4

3

Ωarago

2

onite

1

Changes in aragonite saturation Ω i =[Ca2+][CO32-]/K i predicted to occur as

0

Changes in aragonite saturation, Ωaragonite [Ca ][CO3 ]/Kp aragonite predicted to occur as atmospheric CO2concentrations (ppm) increase (number at top left of each panel). Pink dots are coral reefs. Before the Industrial Revolution (280 ppm), nearly all shallow-water coral reefs had

Ωaragonite > 3.25 (blue regions in the figure).

Consequences to Corals

1 Decreased linear extension rate and skeletal density of coral colonies1. Decreased linear extension rate and skeletal density of coral colonies

Porites coral: 20.6% drop in growth rate and loss % p gof skeletal density of 0.36%/year over last 16 years

2. If corals maintain their growth rate by reducing skeletal density, erosion could be promoted by grazing animals (i.e., parrotfish),

which prefer to remove carbonates from lower-density substrates. which prefer to remove carbonates from lower density substrates. Also, a loss of structural complexity will affect the ability of reefs to

absorb wave energy, thereby impairing coastal protection

3. If corals maintain both skeletal growth and density under reduced carbonate saturation, they will be investing greater energy in

calcification. Side effect: diversion of resources from other essential processes, like reproduction.

From WHOI Oceanus Magazine, 418, 1 (2010)

From WHOI Oceanus Magazine, 418, 1 (2010)

What is the impact of acidification on the bili f i di id l i l ifability of individual species to calcify?

J l P i b J h A d d Journal Presentation by John, Andrew, and Alexander

Acidifying Seas: Today

Acidifying Seas

Th d l di l i f d h ll i i l f h i The gradual dissolution of a pteropod shell, a critical component of the marine foodchain. Source: http://pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F.

A dugong

Impact on Biodiversity) extinction

axa

(%ap

sed

ta

ll

Col

la collapse

From Worm, Science 314, 787 (2006)

pH=8.2O. Patagonica Coral

pH=7.4

pH=8.2

From Fine, Tchernov, Science 315, 1811 (2007)

Midterm Exam Review

Stellar Nucleosynthesis: H-burning

T ~1 6x107 K ρ ~1 4g/cm3

γν 2H1H3He

Tsun 1.6x10 K, ρsun 1.4g/cm

109 years 1 second

1H3He

1 million years

4He

protonneutronγ

ν 1H

Most starts spend their lives burning H in their core

positronγ

Because stellar reactions involve mainly charged particles, stellar nucleosynthesis is a slow process.

2m

Solutions to Schrodinger’s equation in an atom

022

2 VEm

rZerV4

)(2

ro4

:2 f

)()()( ),()(),,( YrRr

R: Radial wavefunction – depends on two quantum numbers, “n” and “l”d w d p d w q b , dY: Angular wavefunction – depends on another quantum number, “ml”

(A fourth quantum number, also in Y, arises from relativity: “ms”)

s

pp

dd

http://www.orbitals.com/orb/index.html

Multielectron atoms: The Orbital Approximation

•Assume each electron in a multi-electron atom occupies an atomic orbital that resembles those found in hydrogenic atoms.

•Basically, reducing a many-electron problem to many “one-electron” problems (and treating the electron-electron

interaction term as a small perturbation)

•The charge experienced by each electron is the “effective nuclear The charge experienced by each electron is the effective nuclear charge” Zeffe = (Z-σ)e: Shielding constant σ

•S l i f th i f th l t i lti l t t •Solving for the energies of the electrons in multielectron atoms yields a dependence on n and

Periodic Table Trends

M t lli h t

Ionization energy

Metallic character

s

Electron affinity & electronegativity

Ioniarge

omic

rad

ius ization enenu

clea

r ch

a

Ato

ergyE

ffec

tive

n

Effective nuclear chargeEffective nuclear charge

Atomic radius

MO Theory and SALCs

σ Orbitals δ Orbital

Molecular orbitals arise from atomic orbitals of the same symmetry (i.e., overlap of s and s or s and pz or d and d)

Benzene (p-orbital MOs)

Ene

rgy

E

http://user.mc.net/~buckeroo/ARSY.html

The bond order b indicates the multiplicity of the

Bond Order & ConsequencesThe bond order b indicates the multiplicity of the

bond.

b 1/ ( *)

n=number of electrons in bonding orbitals

b = 1/2(n-n*)

gn*=number of electrons in antibonding orbitals

MO Theory of Extended Molecules & Solids

Solid Bonding & Thermo

++ ‐‐ ++ ‐‐ ++ ‐‐ ++ ‐‐ ++ ‐‐ ++ ‐‐d0

HL V NA zAzB e2

4 d1 d

d

A

Born-Haber cycles40d0 d0

Born-Mayer Equation

Cation Exchange to Produce New Lattices

Ag+/Cd2+ = 0.2 Ag+/Cd2+ = 0.8

Ag+ cation exchange: non-selective Ag2S nucleation followed by partial phase segregation

As Ag2S regions grow into the nanorod, ripening occurs to

Increasing Ag+/Cd2+ ratio

reduce elastic strain

Ag /Cd2 ratio

Cu+ cation exchange: selective Cu2S nucleation of low energy interfaces

Cu2S nucleates at one or both ends producing a stable configuration

Increasing Ag+/Cd2+ ratio

20 nm 2 nm

configuration

Acid/Base Theory

A Lewis acid acts as an electron pair acceptor. A Lewis base acts as an electron pair donor.

vs. Bronsted

]][[ 3 XOHK ]][OH[HB

K][]][[ 3

HXXOHKa [B]

]][[bK

Fluorosulfuric acid O2SF(OH)