assignment 2 soln - CEE 2300 Environmental Engineering...

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CEE 2300 – Environmental Engineering Principles S08 1 Assignment 2 Solution Due Date: Friday, February 1 Total Points: 100 Instructions (20 pts) : You may work alone or in groups to complete the homework assignments, but you should solve each problem yourself and turn in individual solutions. If you do work in groups, write the names of the people you worked with at the top of the homework set. Homework solutions are due at the start of class. Problem 1 (10 pts) . Precipitation in the north Georgia mountains is collected and analyzed. The annual mean concentrations of major ions, other than H + , are as follows: [SO 4 2- ] = 2.4x10 -4 M; [NO 3 - ] = 1.0x10 -4 M; [NH 4 + ] = 5.0x10 -4 M. (a) Estimate the annual mean pH of precipitation. charge balance: [H + ] + [NH 4 + ] = 2 [SO 4 2- ] + [NO 3 - ] [H + ] = 2 [SO 4 2- ] + [NO 3 - ] – [NH 4 + ] = 2 x 2.4x10 -4 + 1.0x10 -4 – 5.0x10 -4 = 8.0x10 -5 pH = - log [H + ] = 4.1 (b) If a power plant influences an area of 500 km x 500 km and the amount of precipitation over this region is 500 mm, estimate the emissions of SO 2 from the power plant over a year (kg/yr) that results in the measured SO 4 2- concentration. volume of rain = 500x10 3 m x 500x10 3 m x 500x10 -3 m = 1.25x10 11 m 3 = 1.25x10 14 L/yr moles of SO 4 = [SO 4 2- ] x volume = 2.4x10 -4 M x 1.25x10 14 L/yr = 3.0x10 10 mol/yr 1 mole SO 2 per mole SO 4 MW of SO 2 = 64 g/mol mass SO 2 emission rate = 3.0x10 10 mol/yr x 64 g/mol = 1.92x10 12 g/yr = 1.92x10 9 kg/yr = 1.92x10 6 tonnes/yr Problem 2 (15 pts) . Short answer. (a) Why is there a peak in the ozone concentration in the stratosphere? O 2 photolysis by high energy photons O combines with O 2 to produce ozone (b) Why is the ozone hole worst over Antarctica in spring? Cl converted to inactive forms in late spring Inactive forms converted to Cl 2 in winter on ice crystals in coldest regions (at poles) Photolysis of Cl 2 when sun rises in spring (c) Why does the hole continue to develop each spring despite the fact that CFC’s were phased out in 1990’s?
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This note was uploaded on 09/15/2008 for the course CEE 2300 taught by Professor Spain during the Spring '08 term at Georgia Institute of Technology.

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assignment 2 soln - CEE 2300 Environmental Engineering...

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