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Class objectives:

Class objectives:. Cover some of the major topics in Environmental Chemistry Energy Atmospheric Compartment Water compartment Soil. 1. Some examples of environmental chemicals. Polynuclear Aromatic HC (PAHs) Dioxins Ketones PCBs CFCs DDT O 3 , NO 2 , aerosols, SO 2.

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Class objectives:

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  1. Class objectives: • Cover some of the major topics in Environmental Chemistry • Energy • Atmospheric Compartment • Water compartment • Soil

  2. 1. Some examples of environmental chemicals Polynuclear Aromatic HC (PAHs) Dioxins Ketones PCBs CFCs DDT O3, NO2, aerosols, SO2

  3. Toxic loads • Scientists have hypothesized that the fetus is sharingthe mother’s toxic load, and may actually provide some protection to the mother by reducing her internal exposure.

  4. Children get 12% of their lifetime exposure to dioxins during the 1st year. • Their exposure is 50 times greater than an adult during a very critical developmental period.

  5. Firstborns from dolphins off the coast of Florida usually die before they separate from their mothers

  6. Mother’s milk • Human babies nursed by mothers with the highest PCB contamination levels in their milk are afflicted with more acute ear infections than bottle fed Inuit babies. • Many of these children don’t seem to produce enough antibodies for childhood vaccinations to take.

  7. PCBs and lower intelligence • There is evidence of lower intelligence in babies exposed to PCBs. • In adults, a blood-brain barrier insulates the brain from many potentially harmful chemicals circulating through the body • In a human child this barrier is not fully developed until 6 months after birth.

  8. 2. Energy

  9. SO what is a joule?? Force = mass x acceleration; f = m x a a = D velocity / D time = dv/dt velocity = D distance / D time; a= D distance / D time2 Work = force x distance W = f x d W= m x a x d and W = m x d2 /t2 Work and energy have the same units a joule is defined as accelerating 1 kg of mass at 1 meter/sec2 for a distance of 1 meter A watt is a unit of power= 1 joule/second or energy/time D

  10. how long will the oil last?? 1980 estimate of reserves Oil 1x1022 J 1980 estimate of oil usage /year1.35x1020 J/year Estimate the # years of oil left if we used at the above rate from 1980 to 1990 and 2x’s the 1980 rate after 1990= 3x; we estimated ~50 to 80 years We used more recent data in class.

  11. Fuel energy • When we burn a fuel where does the energy reside? • Let s take hydrogen in water as an example. If we were to react H2 with O2 to form water, we would 1st have to break the hydrogen bonds and the oxygen bonds • This takes energy; in the case of H2 it takes 432 kJ/mole (~100,000 calories/mole) for H2 2H. • How many days of food will supply you with 100,000 calories? • To break O2 to O. (O2  2O.) requires494 kJ/mol • When when water forms, however, we get energy back from the formation of H2O because new bonds are formed. Which ones??

  12. Combustion energies from different fuels (kJ) react. per per per moles heat mole mole gram CO2 per kJ O2 fuel fuel 1000kJ hydrogen 482 482 241 120 02H2+O2 2H2O Gas 810 405 810 52 1.2CH4 + 2O2CO2 +2H2O Petroleum 1220 407 610 44 1.62 (-CH2-)+ 3O22CO2 +2H2O Coal 2046 409 512 39 2.04 (-CH-)+ 5O24CO2 +2H2O Ethanol 1257 419 1257 27 1.6C2H5OH + 3O22CO2 +3H2O wood 447 447 447 15 2.2(-CHOH-) + O2CO2 +2H2O

  13. 3. Basic concepts • Where does pV=nRT come from? • At standard state can you calculate R? • A+B C+Dln Keq =-DH/R x 1/T + const.

  14. 4. The atmospheric compartment

  15. Two important features the atmosphericCompartment aretemperature and pressure

  16. Why does the temperature normally decrease with height in the troposphere and increase with height in the stratosphere??

  17. The pressure or force per unit area • decreases with increasing altitude • The decline in pressure (P) with altitude is approximately = to log P= - 0.06 (z); where z is the altitude in km and P is bars

  18. How thin is the air at the top of Mt. Everest? • Mt. Everest is 8882 meters high or 8.88 km high • log P = -0.06 x 8.88 • P = 10-0.06x 8.88 = 0. 293 bars • Assume there are 1.01bars/atm. • This means there is < 1/3 of the air

  19. The quantity dis called the dry the dry adiabatic lapse rate • Air that contains water is not as heavy and has a smaller lapse rate and this will vary with the amount of water • If the air is saturated with water the lapse rate is often called s • Near the surface sis ~ 4 oK/km and at 6 km and –5oC it is ~6-7 oK/km

  20. How does air circulate • At the equator air is heated and rises and water is evaporated. • As the air rises it cools producing large amounts of precipitation in equatorial regions. • Having lost its moisture the air mass moves north and south. • It then sinks and compresses (~30oN and S latitude) causing deserts

  21. The mean residence time (MRT) can be expressed as: MRT = mass / flux where flux is mass/time • If 75% of the mass/year in the stratosphere comes from the troposphere • 1 MRT = ----------------- = 1.3 years • 0.75/year

  22. Mt. Pinatubo in the Philippines erupted in June 1991, and added a huge amount of SO2 and particulate matter the stratosphere. After one year how much SO2 was left? • For a 1st order process C= Coe-1 year/ MRT • C/Co= e -1 year/ MRT = e -1/1.3= 0.47 or ~ 50% • in 4 years, C/Co= e -4 years/1.3 years = ~5%

  23. What happened to global temperatures after the Pinatubo eruption? • A lot of SO2 was injected into the atmosphere • SO2 forms fine sulfate particles that reflect light back into the atmosphere and this cools the upper troposphere

  24. 5. What is Global Warming and how can it Change the Climate?

  25. How fast are green house gases increasing??? • time trace for the concentration of carbon dioxide from 1958-1992 at Mt. Mauna lowa Hawaii • Why does it oscillate up and down as it generally goes up??

  26. How fast is Global Warming Occurring? • The rate of global warming over the next century may be more rapid than any temperature change that has occurred over the past 100,000 years!!! • This will cause major geographical shifts in forests, vegetation, and cause significant ecological disruption

  27. 1979 perennial Ice coverage Nat. Geographic, Sept 2004)

  28. 2003 perennial Ice coverage

  29. Doubling Emissions of CO2 • Often discussed are the effects of doubling CO2 concentrations from pre-industrial times (2xpre-Ind. CO2=550 ppm) • Some times predications are made with the assumption of CO2 doubling or even quadrupling. • On the next slide you will see world wide emissions using different assumptions.

  30. Including Particles in Global Models • Fine particles, especially sulfate particles resulting from SO2 emissions from coal, combustion can reflect light from the sun and actually cause a negative temp. effect • The next 2 picture from a global circulation model (GCM by Bob Charleston, UW-Wash, USA), shows a cooling effect in the industrialized world.First without considering particles then with • red= +2oC, yellow =+3oC, blue = +10C

  31. red= +2oC, yellow=+3 oC, blue = +10C

  32. red= +2oC, yellow=+3 oC, blue = +10C

  33. 6. Kinetics: 1st order reactions A ---> B -d [A] /dt = krate [A] - d [A]/[A] = kratedt [A]t= [A]0 e-kt

  34. Hr Conc [A] Ln[A] 0 2.718 1 0.3 2.117 0.75 0.6 1.649 0.50 0.9 1.284 0.25 1.2 1.000 0.00 1.5 0.779 -0.25 Some time vs conc. data

  35. A plot of the ln[conc] vs. time for a 1st order reaction gives a straight line with a slope of the 1st order rate constant.

  36. ln [A]/[A]o=-k t1/2 ; ln2 /k =t1/2 2nd order reactions A + B  products dA/dt = k2nd [A][B] If B is constant kpseudo1st = k2nd [B]

  37. kpseudo1st = k2nd [B] ln2 /k =t1/2 1. constant OH radicals in the atmosphere kpseudo1st = k2nd [OH.]

  38. 7. Stratospheric o3 The Stratosphere begins about 10k above the surface of the earth and goes up to 50k The main gases in the stratosphere, as at the surface, are oxygen and nitrogen uv light of low wave lengths ( high energy) split molecular oxygen (O2 ) to split oxygen O2  O. + O.  requires 495 kJ mole-1 of heat (enthalpy)  What wave length of light can do this?? Let’s start with hn = E, where h is Planck’s constant and n is the frequency of light and E is the energy associated with one photon.

  39. And, nl = c where c is the speed of light and l is the wave length of light Combining we can solve for the wave length that will break apart oxygen at an enthalpy of 495,000 J mole-1 l= h c/ E If the value of Planck’s constant is 6.62  10-34 joules sec c = 2.9979 x108 m sec-1 l= h c/ E = 241 nm can you verify this calculation? Hint energy E is for one photon??

  40. Paul Crutzenin 1970 showed that NO and NO2 react catalytically with O3 and can potentially remove it from the stratosphere.(he get’s a nobel prize for this in 1995) NO + O3 NO2 + O2 NO2 + O. -> NO + 2O2 So where would NO come from?? SST’s

  41. CCl3F + uv  Cl. + .CCl2F but the free chlorine atom can react with O3 Cl. + O3  ClO. (chlorine oxides) + O2 what is really bad is that ClO. + O.  Cl. + O2 Remember that: O.+ O2  O3 (Ozone) It is estimated that one molecule of chlorine can degrade over 100,000 molecules of ozone before it is removed from the stratosphere or becomes part of an inactive compound.

  42. Molina found in 1985 that HCl could be stored on the surface of small nitric acid particles in polar stratospheric clouds (PSC). The HCl then just had to wait for a ClO-NO2 to hit the particle particle Cl2 Cl2 + uv Cl. + Cl.These nitric acid particles form under extremely low temperatures in polar stratospheric clouds ClO-NO2 HCl Cl2

  43. 8. What are aerosols? • Aerosols are simply airborne particles • They can be solids or liquids or both • They can be generated from some of the following sources: 1. combustion emissions 2. atmospheric reactions 3. re-entrainment

  44. Cooking stir-fried vegetables: Kamens house, 1987, EAA data

  45. Anthropogenic sources • Primary aerosolIndustrial particles 100x 1012 g/yearsoot 20forest fires 80 • Secondary aerosolssulfates from SO2 140organic condensates 10nitrates from NOx 36 • sum of Anthropogenic 390 x1012g/year • sum of natural sources 3070 x1012g/year

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