Light extinction can be divided into the sum of its scattering and absorption components as follows bext = bsg+bag+bsp+b

[answerhappygod]

Light extinction can be divided into the sum of its scattering
and absorption components as
follows
bext =
bsg+bag+bsp+bap
where bext=light extinction coefficient,
bsg= Rayleigh scattering (light scattering by molecules
of
air), bag =light absorption because of gases
(mainly NO2), bsp= light scattering by particles,
and
bap= light absorption by particles. The scattering
and absorption by gases (bsg and bag)
can be
calculated knowing the air pressure (altitude) and temperature,
and the concentration of NO2,
respectively. To deal with the particle-related extinction
(bsp and bag), a standard approach is
to
allocate portions of the extinction to each species of the
mixture and then summarize the
contributions to arrive at the total particle-related
extinction. With this approach, one sums
up the individual contributions
bsp = esulphate(sulphate) +
enitrate(nitrate) + eoc(organic carbon) +
esoil (soil) + ecoarse(coarse)
and, for absorption of light by particles
bap = eBC( black carbon)
where the e values are the extinction
efficiencies. The units of e are M
m-1 per μg m-3; hence
m2g-1. Extinction efficiencies depend on the
size distribution and the molecular composition of the
sulfates, nitrates, and organic carbon. The extinction
efficiencies for hygroscopic substances
(sulfate, nitrate, and organic carbon) are dependent on the
relative humidity. Values are usually
reported for dry particles; the uptake of water can multiply the
given sulfate and nitrate
efficiencies manyfold at high relative humidities. The effect of
water uptake on the organic
carbon efficiency is not as well established as that for the
inorganic salts. Ranges of dry extinction
efficiencies are
esulphate = 1.5 -
4m2 g-1
enitrate = 2.5 -
3m2 g-1
eOC = 1.8 - 4.7
m2 g-1
esoil = 1 - 1.25
m2 g-1
ecoarse = 0.3 - 0.6
m2 g-1
eBC = 8 - 12
m2 g-1
Calculate the visual range of an atmosphere at a 0.02 contrast
ratio for which
esulphate =3m2 g-1
enitrate =3
m2 g-1, eOC =
4m2 g-1,
and eBC =
10m2 g-1, and for which
Sulfate = 20 μg m-3
Nitrate = 5 μg m-3
Organic carbon = 25 μg m-3
Black carbon = 7.5 μg m-3