Reactor 3 Mox a blend of Pu and

Do Japanese Reactor Breakdowns pose a threat to us? • Chernobyl released massive amounts of radioactive material: – 131 I halflife 8 d • Mixed gaseous and particulate phases. • Particles 0. 1 – 1. 0 mm last the longest. • Bioaccumulates in milk and caused thyroid cancer in the Ukraine. • Treatable with 150 mg KI (RDA 150 mg) – 137 Cs halflife 30 yr Copyright © 2010 R. R. Dickerson • Particulate Phase 2

– One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. – Plutonium (239 Pu), an a emitter, and toxic. • Unknown amounts emitted. • Ingestion. bio clearance time: months. – Annual Limit of Intake = 3 E 5 Bq (8 m. Ci) • Inhalation. Small particles stick to the lung alveolae. – Annual Limit of Intake = 300 Bq = 0. 0081 m. Ci = 0. 13 mg 239 Pu. Ultimately, Chernobyl caused only local problems. Copyright © 2011 R. R. Dickerson 3

Gamma Ray Spectrometers. Copyright © 2011 R. R. Dickerson 4

Forward Trajectories from Japanese Nuclear Reactor Fires Copyright © 2011 5

Chernobyl Results • Barely detectable over N. Dakota after 10 d. • 1% of release deposited (wet and dry) onto UK. Not a major health threat. • Local effects serious. • 6000 cases of thyroid cancer in Ukraine. Copyright © 2011 R. R. Dickerson 6

Forward Trajectories today, 17 March. Copyright © 2010 R. R. Dickerson 7

Stratospheric Ozone Lecture AOSC/CHEM 637 Atmospheric Chemistry Russell R. Dickerson Copyright © 2010 R.

Cholesterol photolysis to Vitamin D h → Copyright © 2010 R. R. Dickerson 10

Folate, vitamin B-9 Copyright © 2010 R. R. Dickerson 11

VII. STRATOSPHERIC POLLUTION Without ozone in the atmosphere there could be no life as we know it on the surface of the Earth. All of the atmospheric ozone, that is the “ozone column” is only about 0. 3 atm cm. In other words, if all the air were squeezed out of the atmosphere, and the remaining ozone were brought to STP, it would be only 0. 3 cm thick. – Murphy’s Law is strictly obeyed by NOx pollution in the atmosphere. – Chemistry of the stratosphere different from troposphere. (VIEWGRAPH) See Limb Image Table 15. 1 Solar intensity at the Earth’s surface assuming 0. 30 atm cm (300 D. U. ) ozone. Note that the maximum flux is about 7 x 10¹⁵ (photons/(cm²s)/10 nm). Copyright © 2010 R. R. Dickerson 13

Actual depth of atmospheric layers. Copyright © 2010 R. R. Dickerson 14

λ (nm) σ (atm⁻¹cm⁻¹) I/Io 250 305 1. 0 x 10⁻⁴⁰ 275 162 1. 0 x 10⁻²¹ 300 9. 5 6. 0 x 10⁻² 325 0. 27 9. 2 x 10⁻¹ Where O₃ stops absorbing, sunlight begins to reach the surface of the Earth. Hartley (1880) measured the ozone spectrum. Fabry and Buisson (1913) measured the solar spectrum at the Earth’s surface and concluded that the UV radiation reaching the surface of the Earth must be controlled by ozone in the upper atmosphere, they even made an accurate estimate of the amount of ozone! Today we will examine the various catalytic cycles that control the level of ozone in the stratosphere. We will calculate the O₃ abundance for a highly simplified atmosphere containing only O₂ and N₂. Copyright © 2010 R. R. Dickerson 15

VII. A) OZONE CATALYTIC CYCLES 1) Chapman Reactions (1931) O₂ + h → 2 O O + O₂ + M → O₃ + M† O₃ + h → O₂ + O O + O₃ → 2 O₂ (1) (2) (3) (4) By way of qualitative analysis, Reactions (1) plus (2) produce ozone. O₂ + h → 2 O (1) 2 x ( O + O₂ + M → O₃ + M ) (2) 3 O₂ + h → 2 O₃ NET Copyright © 2010 R. R. Dickerson 17

While Reactions (3) plus (4) destroy ozone. O₃ + h → O₂ + O O + O₃ → 2 O₂ 2 O₃ + h → 3 O₂ NET (3) (4) Reactions (3) plus (2) add up to a null cycle, but they are responsible for converting solar UV radiation into transnational kinetic energy and thus heat. This cycle causes the temperature in the stratosphere to increase with altitude. Thus is the stratosphere stratified. O₃ + h → O₂ + O (3) O + O₂ + M → O₃ + M* (2) NULL NET By way of quantitative analysis, we want [O₃]ss and [Ox]ss where “Ox” is defined as odd oxygen or O + O₃. The rate equations are as follows. Copyright © 2010 R. R. Dickerson 18

(a) (b) (a+b) From the representation for O atom chemistry: In the middle of the stratosphere, however, R₃ >>2 R₁ and R₂ >> R₄ thus: (I) This does not mean that R₄ is unimportant, but it can be ignored in an approximation of [O]ss at the altitude of the ozone layer. The ratio of [O] to [O₃] can also be useful: Copyright © 2010 R. R. Dickerson 19

(II) Reactions 2 and 3 set the ratio of O to O₃, while Reactions 1 and 4 set the absolute concentrations. Now we will derive the steady state ozone concentration fro the stratosphere. From the assumption that Ox is in ready state we know: R₁ = R₄ Thus j(O₂)[O₂] = k₄[O][O₃] Substituting from (I), the steady state O atom concentration: or Copyright © 2010 R. R. Dickerson 20

SAMPLE CALCULATION At 30 km (VIEWGRAPH) Copyright © 2010 R. R. Dickerson 21

• In any good experiment you check ratios of variables first, to avoid errors or bias. Lets look at the O/O 3 ratio. Then we’ll consider the absolute concentration of ozone. Copyright © 2010 R. R. Dickerson 22

Copyright © 2010 R. R. Dickerson & Z. Q. Li 23

Copyright © 2010 R. R. Dickerson & Z. Q. Li 24

O/O 3 = j(O 3)/(k 2 M O 2) Beautiful agreement! Copyright © 2010

What is the observed O 3 mixing ratio? 2 x 1012 molecules cm-3/2. 7 x 1019 (P 30/P 0*298/T) P 30 ~ P 0 exp(-30/7) = 0. 014 atm [O 3] = (2 E 12/3 E 19)/0. 014 ~ 5 E-6 = 5 ppm Copyright © 2010 R. R. Dickerson & Z. Q. Li 26

We calculated almost a factor of ten above the true concentration! What is wrong? There must be ozone sinks missing. 2) Bates and Nicolet (1950) “HOx” Odd hydrogen “HOx” is the sum of OH and HO₂ (sometimes H and H₂O₂ are included as well). HO₂ + O₃ → OH + 2 O₂ OH + O₃ → HO₂ + O₂ 2 O₃ → 3 O₂ The following catalytic also destroys ozone. OH + O₃ → HO₂ + O₂ HO₂ + O → OH + O₂ O + O₃ → 2 O₂ Copyright © 2010 R. R. Dickerson (5) (6) NET (6) (7) NET 27

The second catalytic cycle speeds up Reaction 4, that is it effectively increases k₄. Note that any loss of odd oxygen is the same as loss of ozone. These catalytic losses are still insufficient to explain the observed ozone concentration. 3) Crutzen (1970); Johnston (1971) “NOx” Odd nitrogen or “NOx” is the sum of NO and NO₂. Often “NOx” is used as “odd nitrogen” which includes NO₃, HNO₃, 2 N₂O₅, HONO, PAN and other species. This total of “odd nitrogen” is better called “NOy” or “total reactive nitrogen. ” N₂ and N₂O are unreactive. NO + O₃ → NO₂ + O₂ O + NO₂ → NO + O₂ O + O₃ → 2 O₂ NET This is the major means of destruction of stratospheric ozone. The NOx cycle accounts for about 70% of the ozone loss at 30 km. We will calculate the implied steady ozone concentration later. Copyright © 2010 R. R. Dickerson 28

4) Stolarski & Cicerone (1974) “Cl. Ox” Cl + O₃ → Cl. O + O₂ Cl. O + O → Cl + O₂ O + O₃ → 2 O₂ NET This reaction scheme is very fast, but there is not much Cl. Ox in the stratosphere … yet. Today Cl. Ox accounts for about 8% of the ozone loss at 30 km. If all these catalytic destruction cycles are added together, they are still insufficient to explain the present stratosphere O₃ level. The general for of a catalytic ozone destruction cycle is: X + O₃ → XO + O₂ XO + O → X + O₂ O + O₃ → 2 O₂ NET Copyright © 2010 R. R. Dickerson 29

Molina, M. J. , and Rowland F. S. , Stratospheric sink for chloroflurormethanes – chlorine atomic-catalyzed destruction of ozone, Nature, 249 (5460): 810 -812 1974. CClx. Fy + h → CClx-1 Fy + Cl CFC’s do not decompose in the troposphere. Copyright © 2010 R. R. Dickerson 30

Table 15. 2 Stratospheric ozone destruction cycles Cycle Sources Sinks Reservoirs HOx H₂O, CH₄, H₂ HNO₃ · n. H₂O, H₂O₂ H₂SO₄ · n. H₂O NOx N₂O + O(¹D) HNO₃ HO₂NO₂, Cl. O NO₂ Cl. Ox CH₃Cl, CFC HCl, HOCl The sinks involve downward transport to the troposphere and rainout or other local loss. Note that some sinks are also reservoirs: HCl + OH → H₂O + Cl Copyright © 2010 R. R. Dickerson 31

Antarctic Ozone Hole In the Antarctic winter there is no sunlight and even in the spring there is too little UV to generate enough O atoms to destroy ozone. The annual loss of ozone over Antarctica is driven by heterogeneous chemistry and visible radiation. A good current review Is provided by Solomon Nature, 1990, and “Scientific Assessment of Ozone Depeation : 1991” (WMO). The destruction of ozone is usually moderated by the production of chlorine nitrate, an important reservoir species. NO₂ + Cl. O + M → Cl. ONO₂ + M In the Antarctic winter, heterogeneous reactions “denitrify” the stratosphere (Molina et al. , Science, 1987). Molecular chlorine is only weakly bound, and can be dissociated by visible radiation. Copyright © 2010 R. R. Dickerson 32

Cl + O₃ → O₂ + Cl. O + M → (Cl. O)₂ + M (Cl. O)₂ + hv → Cl + Cl. OO + M → Cl + O₂ + M 2 O₃ → 3 O₂ NET Two types of Polar Stratospheric Clouds (PSC’s) exist. Type I = HNO₃ · 3 H₂O Nitric acid trihydrate, formed at T ≤ 195 K Type II = H₂O Ice formed at T ≤ 190 K • They move NOy species from the vapor phase to the condensed phase as HNO₃. • The are involved in catalytic cycles with chlorine and bromine compounds that speed the reaction of ozone with itself to form oxygen. • They move chlorine from the reservoir species HCl and Cl. ONO₂ to Cl. Ox. Copyright © 2010 R. R. Dickerson 33

OTHER STUFF Mc. Elroy et al. (1986) Cl + O₃ → Cl. O + O₂ Br + O₃ → Br. O + O₂ Cl. O + Br. O → Cl + Br + O₂ 2 O₃ → 3 O₂ NET twice (Cl + O₃ → O₂ + Cl. O) Cl. O + M → (Cl. O)₂ + M (Cl. O)₂ + hv → Cl + Cl. OO + M → Cl + O₂ + M 2 O₃ → 3 O₂ NET Copyright © 2010 R. R. Dickerson 34

Cl. O + M → Cl₂O₂ + M → Cl₂ + O₂ + M Cl₂ + hv → 2 Cl etc. Note HCl is a reservoir, not a stable sink: HCl + OH → H₂O + Cl Solomon et al. (1986) OH + O₃ → HO₂ + O₂ Cl + O₃ → Cl. O + O₂ HO₂ + Cl. O → HOCl + O₂ HOCl + hv → OH + Cl 2 O₃ → 3 O₂ NET (6) Crutzen and Arnold (1986) Copyright © 2010 R. R. Dickerson 35

1. 2. 3. 4. Remove NOx via reactions on particles Condensation of HNO₃ 3 H₂O at higher temperatures than pure H₂O. Cosmic ray induced OH – not a big deal. HCl + OH → Cl. Ox HBr + OH → Br. Ox Copyright © 2010 R. R. Dickerson 36