Ocean acidification. Suggested reading: Today s journal club and references therein

Transcription

1 Lecture 10 Ocean acidification Suggested reading: Today s journal club and references therein

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3 Zoanthamine: inhibits ear inflammation Norzoanthamine: prevents osteoporosis, cytotoxicity against leukemia cells, inhibits hb human platelet l aggregation

4 Palytoxin: binds to K, Na pump protein, destroying the ion gradient essential for cells. LD 50 ~ 1μg/kg first synthesized dby Prof. Kishi s group at Harvard

5 The synthesis of natural compounds is a vibrant field cuprate Aldol rxn enone keytone Construction of the core by Diels-Alder Functionalization of the core From Behenna, Angew. Chemie 47 (2008)

6 After a series of acid/base and redox reactions Attaching the side chain Final synthesis of norzoanthamine From Behenna, Angew. Chemie 47 (2008)

7 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, 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.

8 800 ppm at (for (99% 2006) confidence interval) 550 ppm at

9 Consequences for Sea Temperature During the 20 th century, increasing atmospheric CO 2 has increased the ocean temperature by 0.74 o C.

10 Consequences for Dissolved CO 2 Since the industrial revolution, the ocean has absorbed ~25% of the CO 2 produced by burning fuels each day, 22 million tons of CO 2 mix with ocean water

11 Consequences for Dissolved carbonate This excess dissolved CO 2 has dramatic consequences for ocean acidity and ocean carbonate ion concentrations Here, change in CO 3 2- from 1700 (pre-industrial era) to 1990 s

12 Ocean Acidification: The Other CO 2 Problem Normal ocean ph~8.2 p Ocean acidity predicted to double by end of century.

13 Critical Thresholds for Coral Communities re peratur ng Temp creasin Inc Decreasing CO 3 2- concentration

14 Coral Reef Scenario A Coral Reef Scenario B Coral Reef Scenario C From Hoegh-Guldberg, Science 318, 1737 (2007)

15 Ωarago onite 1 Changes in aragonite saturation, Ω =[Ca aragonite ][CO 3 ]/K paragonite predicted to occur as atmospheric CO 2 concentrations (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). 0

16 Consequences to Corals 1. Decreased linear extension rate and skeletal density of coral colonies Porites coral: 20.6% drop in growth rate and loss of 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. 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.

17 From WHOI Oceanus Magazine, 418, 1 (2010)

18 From WHOI Oceanus Magazine, 418, 1 (2010)

19 What is the impact of acidification on the ability of individual id species to calcify? J l P i b J h A d d Journal Presentation by John, Andrew, and Alexander

20 Acidifying Seas: Today

21 Acidifying Seas The gradual dissolution i of a pteropod shell, hll a critical ii component of the marine foodchain. Source: A dugong

22 Impact on Biodiversity ) Colla apsed ta axa (% extinction collapse From Worm, Science 314, 787 (2006)

23 ph=8.2 O. Patagonica Coral ph=7.4 ph=8.2 From Fine, Tchernov, Science 315, 1811 (2007)

24 Midterm Exam Review

25 Stellar Nucleosynthesis: H-burning T ~1 7 ~1 3 sun 1.6x10 K, ρ sun 1.4g/cm 1 H 1 H ν 2 H γ 3 He 10 9 years 1 second 4 He ν γ 1 million years Most starts spend their lives burning H in their core 1 H proton neutron positron Because stellar reactions involve mainly charged particles, stellar nucleosynthesis is a slow process.

26 Solutions to Schrodinger s equation in an atom 2 2m m 2 E V 0 V ( r) 2 Ze 4 o r 2 f : ( r,, ) R( r) Y (, ) R: Radial wavefunction depends on two quantum numbers, n and l d w dp d w q b, d Y: Angular wavefunction depends on another quantum number, m l (A fourth quantum number, also in Y, arises from relativity: m s )

27 s p d

28 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 oneelectron problems (and treating the electron-electron interaction term as a small perturbation) The charge experienced by each electron is the effective nuclear charge Z eff e= (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

29 Periodic Table Trends Metallic character Ionization energy Ato omic radius Effective nuclear cha arge Electron affinity & electronegativity Ioni ization ene ergy Effective nuclear charge Atomic radius

30 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 p z or d and d)

31 Benzene (p-orbital MOs) Energy

32 Bond Order & Consequences The bond order b indicates the multiplicity of the bond. b = 1 / 2 (n-n*) n=number of electrons in bonding orbitals n*=number of electrons in antibonding orbitals

33 MO Theory of Extended Molecules & Solids

34 Solid Bonding & Thermo d 0 Born-Haber cycles H L V N z z A A B e2 1 d A 4 0 d 0 d 0 Born-Mayer Equation

35 Cation Exchange to Produce New Lattices Ag + cation exchange: non-selective Ag 2 S nucleation followed by partial phase segregation Ag + /Cd 2+ = 0.2 Ag + /Cd 2+ = 0.8 As Ag 2 S regions grow into the nanorod, ripening occurs to reduce elastic strain Increasing Ag + /Cd 2+ ratio Cu + cation exchange: selective Cu 2 S nucleation of low energy interfaces Cu 2 S nucleates at one or both ends producing a stable configuration 20 nm 2 nm Increasing Ag + /Cd 2+ ratio

36 Acid/Base Theory A Lewis acid acts as an electron pair acceptor. A Lewis base acts as an electron pair donor. vs. Bronsted K a [ H 3 O ][ X [ HX ] ] K b [HB ][OH [B] ] Fluorosulfuric acid O 2 SF(OH)