Environmental Engineering Reference
In-Depth Information
Table 4.1 Physical properties of particulate matter depending on the amount of oxygen in the
combustion system
Relation to carbon,
in reaction (% mass)
Structure properties
Average particle
diameter measured
with the electron
microscope (nm)
Apparent
specific
volume for
50 kg cm 3 g 1
Specific surface
area by the BET
method (m 2 g 1 )
DBP index
(cm 3 g 1 )
Hydrogen Oxygen
175-275
95-135
0.20-0.32
0.75-1.45
1.25-1.45
1.45-1.75
140-270
120-145
0.28-0.34
1.00-2.00
1.30--1.70
1.55-1.75
290-350
95-125
0.60-0.75
2.90-3.50
1.04--1.20
1.49-1.64
240-300
100-135
0.50-0.60
2.70-3.60
1.04-1.25
1.49-1.60
230-260
130-160
0.40-0.52
2.70-3.60
1.03-1.20
1.50-1.65
175-275
175-420
0.33-0.45
2.60-4.00
1.15-1.65
1.50-1.75
In general, free radicals have a short life in the atmosphere, but three types of
radicals are abundant especially in industrial areas or heavy traffic areas around
major urban agglomerations: HO (x) ,NO (x) and XO (x) ,(X
¼
Cl, Br) [ 4 - 6 ]. Section 2.1
describes in detail the formation mechanism of XO (x) -type of oxygenated acids of
halogens in the atmosphere.
Consequently, the reaction of ozone or its above-mentioned radicals with the
gaseous compounds produced by pollution leads to gas oxidation: SO 2 to SO 3 ,NO x
to NO 2 . Through the action of the fine water drops contained in clouds, these
anhydrides become H 2 SO 4 and HNO 3 respectively (Fig. 4.2 )[ 7 ].
The two acids are most commonly seen both in low pH (below 6.5) precipita-
tions, and reactions with metal compounds present under the form of nanoparticles
in flying ash or with salts lifted by hurricanes from the planetary ocean, converting
them into nanoparticles of different nature [ 8 ].
HX halogenated acids (HCl in particular) appear in the atmosphere following the
incineration of chloride-containing waste or the reactions that chlorides contained
in wind-carried aerosols from the planetary ocean produce in contact with H 2 SO4
and HNO 3 [ 9 ]:
CH 3
CH 2
Cl
þ
3O 2 !
2CO 2 þ
HCl
þ
2H 2 O
ð
4
:
9
Þ
2NaCl
þ
H 2 SO 4 !
Na 2 SO 4 þ
2HCl
ð
4
:
10
Þ
NaCl
þ
HNO 3 !
NaNO 3 þ
HCl
ð
4
:
11
Þ
The stratospheric reactions between ozone or any other forms of active oxygen
with compounds of the chlorofluorocarbons class (also known as freon) can gener-
ate both organic radicals and significant amounts of hydrochloric or hydrofluoric
acid [ 10 ].
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