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**Unformatted text preview: **02/20/2001 TUE 12:05 FAX 6434330 MOFFITT LIBRARY 001 Energy and Resources 102 QUANTITATIVE ASPECTS OF GLOBAL ENVIRONMENTAL PROBLEMS Professors John Harte and Marc Fischer with TAs
Sid Dietz, James Fine, and Edgar Hertwich FINAL EXANHNATION
May 19, 1998 This is a closed book, closed notes, exam. You may use a one-page, 2-sided review sheet and
calculators are also permitted. Each problem is worth the number of points indicated; There are a total of 180 points, which is
also the number of minutes you have for the entire exam. So allocate your time wisely. The problems are not tricky; don’t make them harder than necessary and look for the simplest
possible way to answer them. Always show your work so that credit can be given for valiant attempts. Ifyou write neatly, the
grader won’t get angry reading your paper and will be more likely to be generous! Ifyou need a number and can’t ﬁnd it, please guess the value and state clearly what your guess is.
Even if the guess is wrong, you can get a lot of partial credit for working consistently with a
guessed value. Of course a good guess will get more credit than a bad one. Have a good summer! 02/20/2001 TUE 12:05 1. FAX 6434330 MOFFITT LIBRARY 002 State whether each of the following is true or false and give a 1 sentence justiﬁcation for your
answer. (20 pts.) a.
b. In the absence of human activity on the planet, the pH of rain would be about 7.0 In any region of the world where the pH of rain has been 4 or lower for decades, you can
be sure that no trout are living in the lakes there. All the oxides of nitrogen produced in coal combustion come ﬁom the oxidation of
atmospheric nitrogen in the combustion process. I If, starting today, the everyone in the world adhered to a mo-children-per-family policy,
the human population would neither drop nor rise. Ifyou have just been told that the thin-walled container you were carrying around in your
shirt pocket for the last four hours holds 2 milligrams of a pure sample of a radioactive
isotope that has a mean life of 6 minutes and that emits a 1 MeV gamma ray, then you
would prefer that the isotope had a small atomic weight. 2. Explain qualitatively how each of the following variables can affect the rate at which lake
acidiﬁcation will occur in a watershed located 500 km downwind from a huge smelter or coal- fired electric generating plant. (20 pts.) 5. 1.
ii. iv. V. the height of the smoke stack at the source, the concentration of H202 in the atmosphere downwind of the source,
the thickness of the soil in the watershed draining into the lake, the hydraulic residence time of the lake, the net difference between nitriﬁcation and nitrate uptake by vegetation in the lake. . Explain why an increase in atmospheric aerosol in the Polar regions can result in a warming of the surface below, whereas elsewhere aerosol tends to cool earth’s surface.
(8 pts.)
4. Brieﬂy describe two mechanisms by which CFC emissions can lead to a cooling of the stratosphere. (6 pts.)
Endocrine disrupter questions: a) Explain in simple terms what endocrine disrupting chemicals do. (4 pts) b) Identify two types of compounds that are known to aﬁ'ect the endocrine system. (4 pts)
c) Suggest ﬁve possible scientiﬁc and/or policy responses to the threat posed by endocrine disrupters. (5 pts) 6. Past observations of stratospheric ozone concentrations reveal that global ozone was
signiﬁcantly depressed following the June 1991 eruption of Mt. Pinatubo. Explain two ways
in which the sulﬁir and nitrogen oxides and particulate matter emitted in a large volcanic
eruption could be expected to aggravate stratospheric ozone depletion. (6 pts) Fuelwood can boil about 3 times its (dry) weight of water. Ifeveryone living today had
access only to polluted water and had to meet their drinking and cooldng water needs by
boiling water using fuelwood, what ﬁaction of the world’s net annual terrestrial primary
production would be required? (6 pts.) '7. 02/20/2001 TUE 12:06 FAX 6434330 8. 10. 11. i. MOFFITT LIBRARY The carcinogenic potential of dimethyl nitrosamine can be represented as a lifetime cancer probability of 0.5 from a continuous intake of 75 mg per day. The carcinogenic potential of beryllium metal can be represented as a lifetime cancer probability of 0.5 per gram of Be inhaled. Put these ﬁgures on a common-unit basis to determine which is the more pOWCI‘ﬁll carcinogen. (8 pts) Benzene (MW = 84 g/ mol) is used as a component of gasoline and has a carcinogenic potency of 30 cancers per million persons exposed to a concentration of 1 ug/m3 for their lifetime. Assume that a gas station attendant spends 40 years of work, 40 hours per week, exposed to an average workplace concentration of 10 ppm benzene. a) Express the benzene concentration in 143/1113. You may assume that ambient air has a
density of l mol/24 liters. (3 pts) b) Estimate the lifetime cancer risk associated with this benzene exposure assuming the
average lifetime is 70 years. (8 pts) The slab model for atmospheric dispersion assumes that a pollutant is emitted uniformly from
the ground surface area, and mixes rapidly and uniformly into the overlying air up to the
mixing height (so that you can treat all the air in the box as having the same pollutant
concentration). The pollutant outﬂow ﬁom the box is caused by the wind. Let the air space
be bounded by a square ground area of L2 square meters and mixing height H meters, let the
ground source of pollutant be R kilograms per square meter per second, and let the wind be
blowing perpendicular to one of the sides of the square with a speed of U meters per second.
a) Draw a picture of this situation label all relevant dimensions and flows. (4 pts.) b) Assume the air on the up wind side of the square contains no pollutant. Calculate the rate
at which pollutant is entering the air volume from the ground, and the rate at which
pollutant is leaving the volume from the downwind side of the square. You may assume
the concentration in the box is C kilograms per cubic meter. Now assume the system is in
steady state and calculate the pollutant concentration, C. (8 pts) c) If in addition to removal by wind, the pollutant is removed by dry deposition with a
deposition velocity V, derive a new expression for the steady state concentration in the
square region. (6 pts) Consider the following simpliﬁed global carbon model: X2 = atmosphere
. 0X3 X3 = dead orgamc matter What are the approximate current numerical values for X1. X2, and X3 in units of GT(C)? (3
pts.) dXﬁXﬁ X1 = living
vegetation le 003 02/20/2001 TUE 12:06 FAX 6434330 ii. iv. MOFFITT LIBRARY 004 Ignoring fossil the] burning and other processes that unbalance the ﬂows (that is, that lead to
net accumulation or loss in one or more boxes) what is the approximate current numerical
value of the intercompartmental ﬂow in units of GT(C)/year? (2 pts.) Given your answers above, what are the numerical values of a, b, and 0 (state the units
careﬁilly)? (6 pts.) Suppose global wannng speeds up the rate of decomposition of dead organic matter so that
the coefﬁcient c is increased by 30%, but that the coefﬁcients a and b are unchanged. Using
your answers above, calculate the values of the X; (in GT(C)) when a new steady state is
eventually reached. You may assume that the sum of the three X’s remains unchanged even
though the carbon will be distlibuted differently among the boxes due to the change in the
constant c. (16 pts.) v. Explain why it is reasonable to assume that the ﬂwo ﬁom 2 to 1 depends on a product of two X’s, whereas the other two ﬂows each depend on only one of the X;. (3 pts.) 12. Plutonium-239 has a half-life of 24,000 years and a speciﬁc gravity of 20 (when the plutonium is in metallic form). Inhalation of plutOnium oxide yields a lung-dose commitment of 300 rem per microcurie inhaled. Assume a linear dose-response relation for irradiation of the lung of 8e—5 excess deaths per rem. a) Calculate how many curies there are in 1 gram of plutonium—23 9. [6 pts] b) The US and Russia each ﬁnd themselves with roughly 10,000 nuclear weapons as their bonus prizes for participating in the cold war. Having taken ERl 02, you are asked by Certain Interested Authorities (CIA) to estimate the potential threat of poisoning from the 239 Pu in those weapons. Assume that each weapon contains about 5 kg of 23 9Pu. Estimate the mass of the world supply of 239Pu and, if inhaled, the total number of lung cancer deaths that could be caused by breathing it. (Don’t be surprised if your answer exceeds the human population today!) (8 pts) Assume terrorists managed to burn a cubic centimeter of plutonium metal, converting it all into plutonium oxide smoke, in the ventilating system of a US ofﬁce building with 100,000 square meters of ﬂoor space and ceilings 3 meters high. Assume that the plutonium oxide smoke mixes rapidly and uniformly into the air in the office building, and that the
subsequent concentration of the plutonium in the air in the building is governed by the
ventilation rate of 2 air changes per hour. Assume that the occupants are unaware of what has happened, so that they remain in the building breathing air at a rate of 1 m3 . i) What is the concentration of plutonium oxide (in Curies) in the building air
immediately after the initial mixing has taken place? (4 pts) ii) Write an expression for the Pu concentration as a ﬁmction of time in the indoor air. (4 pts) iii) Estimate the quantity of plutonium inhaled by an occupant of the building who remains
inside for several hours following the initial contamination. State your assumptions
clearly. (8 pts) iv) If 5,000 such occupants work in the building, how many lung-cancer deaths would be
expected to result from this terrorist act? (4 pts) ...

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