HW 8 Solutions

# HW 8 Solutions - 53:050 Natural Environmental Systems...

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53:050 Natural Environmental Systems Solutions to Homework No. 8 – Spring 2011 1. Problem 6-2 in Davis and Masten. First we have to convert ppm in gas to mg/m 3 using the ideal gas law (like previous HW!). Assuming 1 atm total pressure (given), 10 ppm = 10 x 10 -6 atm = 10 -5 atm. Also, recall that the MW of H 2 S = 34. The temperature is given as 25 o C (= 298 K). pV = nRT V n = RT p = ) L/m mg/mol)(10 000 , 34 ( K) 298 )( K - mol atm - L (0.0821 atm 10 3 3 -5 = 13.9 mg/m 3 Now we estimate CDI using Eq. 6-15 (a modification of Eq. 6-9) with the following values taken from the problem and from Table 6-8: CA = 13.9 mg/m 3 (from above) IR = 11.3 m 3 /d = 0.471 m 3 /h (Table 6-8) ET = 8 hours per event (from problem statement) EF = 5 d/wk(50 wk/yr) = 250 events/yr (from problem statement) ED = 65 yr old – 18 yr old = 47 yr (from problem statement) BW = 65.4 kg (Table 6-8) AT = 75 yr (EPA assumed lifetime (p. 232) CDI = d/yr) yr)(365 kg)(75 (65.4 yr) (47 events/yr) 50 h/event)(2 /h)(8 m )(0.471 mg/m (13.9 3 3 CDI = 0.344 mg/kg-d 2. Problem 6-5 in Davis and Masten. Compare adult and child CDI for 2,4-D. Using Table 6-8 values for 3-year old child: CDI = yr) wk/yr)(1 d/wk)(20 kg)(1 (16 yr) wk/yr)(1 d/wk)(20 )(1 kg/mg)(0.1 mg/d)(10 mg/kg)(100 (10 -6 CDI child = 6.25 x 10 -6 mg/kg-d Using Table 6-8 for an adult: CDI = yr) wk/yr)(1 d/wk)(20 kg)(1 (78 yr) wk/yr)(1 d/wk)(20 )(1 kg/mg)(0.1 mg/d)(10 mg/kg)(50 (10 -6 CDI adult = 6.41 x 10 -7 mg/kg-d 1

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3. Problem 6-7 in Davis and Masten. Here we will be calculating cumulative CDI from (1)
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HW 8 Solutions - 53:050 Natural Environmental Systems...

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