Quiz2_solution

Quiz2_solution - l I CEE 154 Chemical Fate and Transport in...

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Unformatted text preview: l I CEE 154 Chemical Fate and Transport in Aqueous Environments I ' Quiz 2 ' I ‘ Good luck” Problem 1: (10 points) A lake has been contaminated with chlorobenzene at a concentration of 3 ppb. What concentration of chlorobenzene would you expect to see in Mosquitofish from this lake? For an type 04314314" [03 m: :1 grub \OSKM -—Oa7.3 Fm chlqolmbvm_ .JLGSYM:391 usage =— ma =3 T256?“ CW1 3‘3. 3 PW J53 Conc 'm chk" Celt—‘1' e]: :1 DIETS PQKI “he; “3 Problem 2: (25 points) What is the flux density for each of the following situations: a) Arsenite ion is diffusing from sediments into a lake water column. Diffusion is occurring up through a layer of stagnant porewater 0.5 cm deep, across which the / '_ f D C diffusive gradient exists. Below this layer, the arsenite concentration is 6 ppm, J ’ ‘ (5" and above you can assume it is zero. Let D = 1016 cm2/sec. (10 points) 5- lo "a. ( M3 ,_ M5 I B ’jz—vlo ETIO’LC’ LL: 7 S a 5- gm i ' [0‘0ch ' b) Benzene is difi-‘using from a lake Surface, Where the dissolved benzene concentration in the lake water is 700 ppm and the gas exchange coefiicient for propane ((331-133) has been found to be 1.7 cm/h. (15 points) filgfisum L915“ "Qt/V Jaw: W “New: W 5'1 ' < Problem 3: (20 points) As a results of a boating accident, 5 L of gasoline (you can model it as n—octane) is spilled into a lake. A slick, approximately a rectangle 2 m wide and 10 111 long, forms on the water squace. How long will it take to evaporate? Assume the slick is of uniform thickness, and the gasoline contains 7 mol/L of octane. The wind speed at 10 m above the ground is 2 nil/sec. =' \2l 7 .O‘ ' 4-1 _ KO Ca.” CLOUR deV} , fl "jfjck {M\ causal L ijn 1055K ‘— W‘ i< Problem 4: '1 l :1 An acidic industrial wastestream has pH = 3, and a negative A1]: = -10'3 N. The carbonate system is negligible in the waste. This waste is added to a creek that is at equilibrium with the atmosphere, and has a pH of 7. 8 upstream of the waste influent. 3.) Please find the Alk of the creek. You don’t know the recipe, so you can’t get it from knowing the excess of strong acids and bases. However, you know pH and enough about the carbonate system to calculate what Alk must be for your Alk constraint to be Safigfied' PCOLHOWR"; 0‘) 7 CHLCGSLJ; lo'gm Knocogao PH. 2 Haws“, cm Cale [Macs—3 =- 16% (Hwy) =10 “'55m I'd—q”3 Fit ms PH Alb/[HcoJ-“J 1/0 TB’SN b) Please find the Alk of the creek after the waste input, assuming the wastestream is 10% of the mix and the creek is 90%. MW: 09% (we; +~ mom _ ._._ 10433,“ c) Assuming that a Httle ways downstream, the creek is again at equilibrium with the atmosphere. You can assume you are still at mid-range pH. How much has pH changed? (or; CL—La 653112113: m‘ld-W 9%, 50 [14(03):] : AUG- xo "397 m Problem 5: We’ve learned about the wide variety of electron acceptors thatcan be used by bacteria. . Some organisms can respire mom to M112+ With glucose as an electron donor. a) In what oxidation state is Mn in each of these forms? MILO-Lbs"; X +Z(~Z)=‘—O 5L: Mn” 1 X; it b) Please give AG°for this process. l- Z _.._ a meme «w +e— e vim * was . [51“ iwcu’tth'kzfiHP—O "% ‘I 002% Wt? re“ /0 0) Please give AG for this process, if pH = 7, and Mn2+ and glucose are both present at 104L M. Recall solids have activity = 1. Please report in both kJ/mol electron and keel/moi electron (4.187 J = 1 cal) Ac: are," +£chch matte: 1H5 "Lfirtmst AG; mars JR«S/W 4r H 5km”? 1.3% ‘Hflkj - ml d) Where would you expect this to fall along the ecological redox sequence. Some values we calculated in class: AG" (kcal/mol) AG (kcal/mol electron), typical cond Oxygen —29.9 -29.8 Nitrate -30.3 _ -27. 5 m n. 01. C s) Mmc—H Fe(OH)3 -24 ‘ -12 i 0‘": “(i O CO, n Sulfate _ m P at _ :3 ' Fermentation ‘ -5 .4 bu t [QC/C014); Ca) c) How would a high level of MnOm affect the release of As sorbed to Fe(OH)3 fiom the sediments of a stratified lake? ...
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Quiz2_solution - l I CEE 154 Chemical Fate and Transport in...

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