GEOG 1220 Midterm: Human Impact Post Midterm Summary

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lavenderbat874

23 Nov 2011

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All are rather extensive and reading through this once and simplifying it in the process would be more than enough review for all!!! Pages 249 252, 265 278, and chapter 13: Chapter 12: the hydrologic environment: precipitation, land use, and water resources. All water frozen is in polar ice caps. Hydrologic condition of earth essential to understand life and support system. Most important factor of life = water. Water delivered by atmosphere to land as part of weather. Five natural reservoirs of water: 1) oceans 2) glacial ice caps 3) Glacial ice = largest reservoir for freshwater. The rest are sources that humans and organisms depend on for water supplies. Hydrologic cycle: flow-system characterized by exchanges of water among five major reservoirs. Driven by heat of earth"s absorption of solar radiation. Transpiration also returns water into the atmosphere, when coupled with evaporation. Groundwater released from land through stream and river discharge. Atmosphere exchanges on average every nine days.

Related Questions

When carbon dioxide dissolves in water, essentially all of itreacts to form carbonic acid, H2CO3.

CO2(g) + H2O(l) <---> H2CO3(aq)

The carbonic acid can then dissociate into H+ and bicarbonateions,

H2CO3(aq) <----> H+(aq) + HCO-3(aq).

Consider a body of otherwise pure water that is in equilibrium withthe atmosphere near sea level, where the partial pressure of carbondioxide is 3.4x10^-4 bar (or 340 ppm). Calculate the molality ofcarbonic acid and of bicarbonate ions in the water, and determinethe pH of the solution. Note that even "natural" precipitation issomewhat acidic.

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Here is some data from the back of the book that I think isimportant, anything else that is needed let me know.
G(CO2)(g) = -394.36kJ
G(H2O)(l) = -237.13kJ
G(H2CO3)(aq) = -623.08kJ
G(H+)(aq) = 0kJ
G(HCO3-)(aq) = -586.77kJ

If anybody has any idea how to do this problem, any input isappreciated.

A huge intestinal parasitic roundworm called Ascaris maintainsinternal pressures
0.3 atm above the atmospheric pressure! Consider a cylindrical worm2 cm long and
0.2 cm in diameter, and essentially water.

i) A worm at constant temperature that is initially flaccid (atequal pressure with the environment)becomes turgid (at fullpressure). What is the change in Gibbs Free Energy?

ii) The wormâs high pressure makes eating challenging. Thewormâs digestive tract has aone-way valve to prevent vomiting. Whatis the force on a circular valve 0.02 cm in diameter?

iii) The wormâs high pressure produces explosive defecation intoair. The expulsion of a volumeof feces at a pressure of 0.3atmcreates a pressure-volume work that shoots the feces upward.To whatheight will the feces rise? (This has actually been measured!) Youmay assume thatworm feces are essentially water and that theprocess is isothermal.

3. 3 Stratosphere-troposphere exchange

The rate of exchange of air between the troposphere and thestratosphere is critical for determining the potential of variouspollutants emitted from the surface to reach the stratosphere andaffect the stratospheric ozone layer. One of the first estimates ofthis rate was made in the 1960s using measurements of strontium-90(90Sr) in the stratosphere. Strontium-90 is a radioactive isotope(half-life 28 years) produced in nuclear explosions. It has nonatural sources. Large amounts of 90Sr were injected into thestratosphere in the 1950s by above-ground nuclear tests. Thesetests were banned by international treaty in 1962. Following thetest ban the stratospheric concentrations of 90Sr began to decreaseas 90Sr was transferred to the troposphere. In the troposphere,90Sr is removed by wet deposition with a lifetime of 10 days (bycontrast there is no rain, and hence no wet deposition, in thestratosphere). An intensive stratospheric measurement network wasoperated in the 1960s to monitor the decay of 90Sr in thestratosphere. We interpret these observations here using a 2-boxmodel for stratosphere-troposphere exchange with transfer rateconstants kTS and kST (yr-1) between the tropospheric andstratospheric reservoirs. The reservoirs are assumed to beindividually well-mixed.

Let mS and mT represent the masses of 90Sr in the stratosphere andin the troposphere respectively. Observations of the decrease inthe stratospheric inventory for the period 1963-1967 can be fittedto an exponential mS(t) = mS(0)exp(-kt) where k = 0.77 yr-1.

1. Write mass balance equations for mS and mT in the 1963-1967period.

2. Assuming that transfer of 90Sr from the troposphere to thestratosphere is negligible (we will verify this assumption later),show that the residence time of air in the stratosphere is tS =1/kST = 1.3 years.

3. Let m'T and m'S represent the total masses of air in thetroposphere and the stratosphere, respectively. Show that theresidence time of air in the troposphere is tT = tS (m'T/m'S) = 7.4years. Conclude as to the validity of your assumption in question2.

4. Hydrochlorofluorocarbons (HCFCs) have been adopted asreplacement products for the chlorofluorocarbons (CFCs), which werebanned by the Montreal protocol because of their harmful effect onthe ozone layer. In contrast to the CFCs, the HCFCs can be oxidizedin the troposphere, and the oxidation products washed out byprecipitation, so that most of the HCFCs do not penetrate into thestratosphere to destroy ozone. Two common HCFCs have trade namesHCFC-123 and HCFC-124; their lifetimes against oxidation in thetroposphere are 1.4 years and 5.9 years, respectively. There are noother sinks for these species in the troposphere. Using our 2-boxmodel, determine what fractions of the emitted HCFC-123 andHCFC-124 penetrate the stratosphere.

GEOG 1220 Midterm: Human Impact Post Midterm Summary

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