(1) the production of the organic aerosol compound from the reaction of parent organic gases,
(2) the partitioning of the organic compound
between the gas and particulate phases forming
SOA [5]. Secondary organic aerosol concentrations tend to be higher during periods of greater
photochemical reactivity (e.g., summer months),
but can be significant year-round depending on
the location, meteorology (e.g., humidity and temperature), solar radiation, the existing aerosols and
availability, abundance, and reactivity of gasphase precursors and oxidants [44–47]. The
0
1
2
4
6
9
12 36
30
20
40
50
60
–30
–20
–10
0
10
20
30
40
50
60
–30
–20
–10
0
10
20
30
40
50
60
60
60
60
50
50
50
40
40
40
10
30
20
10
1500 km
1000
500
0
1500 km
1000
500
0
No data
Months
Estimated losses in life expectancy attributable to exposure to fine particulate matter (PM 2.5 ) from anthropogenic
emissions for 2000 (left) and 2020 (right)
Outside study area
Regional Air Quality, Fig. 7 Health impact of particulate matter (PM) mass concentrations (mg m
À3
). Loss in
statistical life expectancy (months) that can be attributed to
anthropogenic contributions to PM 2.5 for the year 2000
(left) and for 2020 (right) for the Clean Air for Europe
(CAFE) baseline scenario, which takes into account
changes in air quality standards and reductions in emissions (IIASA; EEA [39])
BC/EC
SO 4
2–
NO 3
–
NH 4
+
Others
Organic
compounds
SO 4
2–
Organics
& BC/EC
Others
Regional Air Quality, Fig. 8 Relative contribution of
aerosol components to the total aerosol burden (28.9 Tg)
for the present atmosphere, based on a model simulation
from 1990 using emission estimates from 1990 and later.
Secondary organic aerosol (SOA) produced from
anthropogenic sources (SOAa), secondary organic aerosol
from biogenic VOC oxidation (SOAb), primary organic
aerosol (POA), black carbon (BC), and methane sulfonic
acid (MSA) (Tsigaridis et al. [40])
Regional Air Quality
357