978-1118741498 Chapter 11 Solution Manual Part 4

11.35 For slightly unstable atmospheric conditions, what are the values the dispersion

coefficients, σy and σz, 3 km downstream in a rural area? Provide your values for (a) the

correct Briggs formula and (b) a graphical method that allows you to estimate the

dispersion coefficients from established figures. (c) How do these values change if the

atmosphere is moderately stable?

Solution:

11.36 Wind is measured at 10 m above the ground surface at 2 m/sec. Estimate the

wind speed at an effective stack height of a 40 m in (a) smooth rural terrain for unstable

atmospheric conditions and (b) for rough urban terrain for the most stable atmospheric

conditions.

Solution:

Use equation 11.32:

11.37 What is the estimated wind speed at a 45 m effective stack height located in the

country side? Assume there are very unstable atmospheric conditions near the stack and

wind measurements made close to the stack location showed the wind speed was 3 m/sec

at a height of 5 m.

Solution:

11.38 What is the ground level concentration of a pollutant (µg/m3) 250, 500, 750, and

1,000 meters downwind for a stack release along the centerline of the plume? The

pollutant is released from a 45-m tall stack at a rate of 8.5 grams per second in an urban

area. The plume rises an additional 10 meters. The wind speed is 3 m/sec and there are

slightly unstable atmospheric stability conditions.

Solution: Note here that y = 0 (we are estimating the concentration along the centerline).

2(145𝑚)2𝑒−(45+10𝑚)2

2(150𝑚)2×106𝜇𝑔

11.39 NOx is emitted from a 75-m high stack at a rate of 65 g/s. Calculate the ground

level concentration of NOx 90 m from the centerline. The plume rises 20 m and the wind

speed is 5 m/sec. Assume σy = 120 m and σz = 47 m and there is reflection from the

ground.

Solution: This problem asked for the concentration at ground level (z = 0) but 90 m in

11.40 Estimate the downwind distance (x) at which the maximum pollutant

concentration would occur at the ground surface for an emission that occurs from a stack

that is 60 m high? Assume the pollutant is SO2, it is emitted at a rate of 3,000 g/sec, the

wind speed is 4 m/s, the plume rises an additional 14 m after being emitted, and there are

slightly unstable atmospheric conditions in this urban area. Calculate your value using

two methods, equations and curves provided in the chapter.

Solution:

11.41 An air pollutant is released at a rate of 2 g/s from the top of a tall stack that is 110

m high. The plume initially rises upward an additional 10 m above the stack exit, after

which it travels with a wind speed of 5 m/s. The atmosphere has moderately stable

conditions in the open country. (a) What is the concentration of the pollutant (µg/m

3

) in

the very center of the plume 750 downwind of the stack and at the effective stack height?

(b) What is the concentration of the pollutant (µg/m3) at ground level 750 downwind of

the stack? (c) At what distance downwind does the maximum ground level

concentration occur? (d) What is the concentration of the pollutant (µg/m3) at this

location you identify in part (c)?

Solution:

2 𝑔/𝑠×106𝜇𝑔

1 𝑔

2(29𝑚)2𝑒−(120𝑚)2

2(9.8𝑚)2=𝟏.𝟐𝑬−𝟑𝟎 𝝁𝒈/𝒎𝟑

11.42 An air pollutant is released at a rate of 0.72 g/s 4 meters above ground level. The

wind speed is 2 m/s. What is the maximum ground level concentration 1 km downwind?

Assume that

σy = 45 m and σz = 26 m.

Solution: we assume this problem is asking for the concentration along the centerline