Chemistry Reference
In-Depth Information
1.E+01
1.E+00
1.E-01
Friction velocity (m/s)
1.E-02
0.003
0.01
0.03
0.1
1.E-03
0.01
0.1
1
10
Particle diameter, Dp (µm)
Fig. 4 Dependency of the deposition rate (
k
) on the particle diameter and friction velocity
where
b
is the first-order loss coefficient for deposition in a rectangular space
V
,
u
dv
,
u
du
, and
u
dd
, are the deposition velocities for vertical, upward and downward facing
surfaces, respectively, and
A
v
,
A
u
, and
A
d
are the corresponding deposition surface
areas.
As a result of the particle size-dependent properties the accumulation mode
particles having highest penetration efficiencies and lowest deposition rates tend to
enter indoors most efficiently and remain suspended there, thus substantially
contributing to indoor exposures. Another implication is that the particle size
distribution indoors differs significantly from that outdoors, even in the absence
of indoor sources. Finally particle infiltration varies from home to home, resulting
in higher variability across homes in indoor particle concentrations compared to
outdoor concentrations.
4 Empirical Studies on Indoor-Outdoor Relationships
of Particles
4.1 Methodological Issues
For assessment of exposure in epidemiological studies, the
correlation
between
indoor and outdoor concentration is of importance in addition to the quantitative
contribution of outdoor air to indoor air quality. Figure
5
presents the median of the
