ENV 1101 Lecture : Class 10 - Air Pollution & Global Climate Change.docx

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skytoad178

16 Mar 2012

School

University of Ottawa

Department

Environmental Studies

Course

ENV 1101

Professor

Sonia Wesche

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Document Summary

Is the highest elevation on earth (8. 85km above sea level) Name in tibetan is chomolungma, in nepalese sagarmantha. Wind blows at about 250km/h for much of the year die to the jet stream. There is only 1/3 the concentration of oxygen per unit air at sea level. The temperature is virtually always well below freezing, can go to -75c. First successful climb to summit and return: 1953, hillary and norgay. First clime without oxygen: 1978, habeler and messner. Most summits: 10, ang rita sherpa (all without oxygen) Where we live (and everything else on earth) Temperature gets colder the higher you go (dry air cools at ~loc/100m; moist air at a typically lower rate. Means that airborne pollution can make its way up to the tropopause fairly quickly. Air is thin, does not move around much. Contains ozone (o3) which absorbs some radiation, causing the stratosphere to warm. Higher up are the mesosphere, thermosphere and transition to outer space.

Related Questions

The motion of air masses through atmosphere can be approximated as adiabatic and reversible. Air can be treated as an ideal gas with average molar mass 29 g mol^-1â and average heat capacity 29 J K^-1 mol^-1.

b. Suppose the average atmospheric pressure near the earth's surface is P₀ and the temperature is T₀â. The air is displaced upward until the temperature is T and the pressure is P. Determine the relationship between P and T. (Hint: consider the process as occuring in two steps, equate the sum of the two entropy changes to (delta S total=0))

c. In the lower atmosphere, the dependence of pressure on height, h, above the Earth's surface can be approximated as ln(P/P₀â)= -Mgh/RT

Where M is the molar mass, g the acceleration due to gravity, and R the gas constant. If the air temperature near the equator is 38 degrees C (roughly 100degrees F) calculate the air temperature at the summit of Mount Kilimanjaro, roughly 5.9km above sea level.

ceruleanwallaby719

Nitrogen Oxide is a pollutant in the lower atmosphere thatirritates the eyes and lungs and leads to the formation of acidrain. Nitrogen oxide forms naturally in the atmosphere according tothe following endothermic reaction:
N2(g) + 02(g) <---> 2 NO(g)
Kp= 4.1 x 10-31 at 298K
Use the ideal gas law to calculate the concentration of nitrogenand oxygen present in air at a pressure of 1.0atm and a temperatureof 298K. Assume that nitrogen composes 78% of air by volume andthat oxygen composes 21% of air. Find the "natural" equilibriumconcentration of NO in air in units of molecules/cm^3. Ho would youexpect this concentration to change in an automobile engine inwhich combustion is occuring?

cyanlizard197

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.

ENV 1101 Lecture : Class 10 - Air Pollution & Global Climate Change.docx

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