Environmental Engineering Reference
In-Depth Information
Appendix4
Concentration Units
for Compartments in
Environmental
Engineering
Concentrations of pollutants can be expressed in several units. The following is a
summary of some of the common ones in air, water, and soil matrices that also appear
in the text:
COMPARTMENT: AIR
The following are the common units to represent air concentration of a pollutant:
(i) A volumetric ratio (ppmv)
V
i
V
T
10
6
,
(
ppmv
)
=
×
where
V
i
is the volume of pollutant
i
and
V
T
is the total volume
(air
pollutant). The advantage of the volume unit is that gaseous con-
centrations reported in these units do not change upon gas compression or
expansion.
(ii) Amixedunit
C
ia
(
+
gof
i
/m
3
ofair),whichisrelatedtoppmv(attemperature
T
degrees K and
P
T
total pressure),
μ
RT
P
T
1
M
i
(
g
/
m
3
)
10
3
μ
(
ppmv
)
=
,
where
M
i
is the molecular weight of pollutant
i
,
R
is the gas constant
0.08205 P atm/K/mol,and1000isaconversionfactor(1000 L
1m
3
).Note
that at 1 atm total pressure and standard ambient temperature of 298 K, the
conversion factor
RT
/1000
P
T
is 0.0245.
=
435
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