Post on 22-Aug-2020
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)