Page 350 - Fundamentals of Air Pollution 3E

III. Estimating Concentrations from Point Sources 305

TABLE 19-6
Urban Dispersion Parameters by Briggs (for Distances between
100 and 10000 m)
Pasquill type cr v, m ar z, m

A-B 0.32x(l + 0.0004x)-°- 5 0.24x(l + O.OOlx) 05
C 0.22x(l + 0.0004x)-° 5 0.20*
D 0.16x(l + 0.0004xr 05 0.14x(l + 0.0003x)-° 5
0 5
E-F O.llx(l + 0.0004*)- - 0.08x(l + 0.0015x)-° 5
Source: From Gifford (12).

cr y = 49.0 m (from Table 19- 4). First, the maximum can be estimated by
Eq. (19-5):

To see if this is approximately the distance of the maximum, the equation

which results from Eq. (19-2) with y and z equal to 0, is evaluated at three
distances: 0.26, 0.28, and 0.30 km. The parameter values and the resulting
concentrations are given in the following table:

x,km <r z,m cr v/m x,g m 3
0.26 26.2 45.9 1.53 x 10~ 5
0.28 28.2 49.0 1.56 x 10~ 5
0.30 30.1 52.2 1.55 x 10~ 5
o- 2 is obtained from equations in Table 19-5.
tr v is obtained from equations in Table 19-4.

TABLE 19-7
Rural Dispersion Parameters by Briggs (for Distances between
100 and 10000 m)
Pasquill type <r y, m ar z, m
A 0.22x(l + 0.0001*r 05 0.20x
0 5
B 0.16*(1 + O.OOOlx)- - 0.12*
C O.lbr(l + O.OOOlx)- 05 0.08x(l + 0.0002x)-° 5
D 0.08x(l + O.OOOlx)- 05 0.06x(l + 0.0015x)-° 5
E 0.0fct(l + O.OOOlx)- 05 0.03x(l + O.OOOSx)- 1
F 0.04x(l + O.OOOlx)- 05 0.016x(l + O.OOOSx)- 1
Source: From Gifford (12).