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Consiglio Nazionale delle Ricerche
ISTITUTO sull’INQUINAMENTO ATMOSFERICO
Via Salaria km 29,300 - C.P. 10
00016 Monterotondo Stazione - ROMA
I. ALLEGRINI and C. PERRINO
Technical tool to evaluate the
effectiveness of control
measures
Reducing the Impact of Vehicles on Air and Environment
Quality in Cities – Mexico City Jan. 22-23, 2004
PRESENTATION OUTLINE
Effectiveness of control measures
Meteorology-Concentration relationship
Evolution of the Boundary layer
Examples
M
C( I ) 
V
Parameters acting on M:
 Emission fluxes
 Physico-chemical transformations
 Deposition
Parameters acting on V:
 Advection (mainly horizontal movements
of the air masses, due to winds)
 Convection (mainly vertical movements
due to the heating of the lower air masses
Concentration variations for a pollutant i
C i
 i ( t )   Ci   Adv  LS   Pi   Li
t
i ( t )
emission flux from the sources
LS
deposition losses on the surfaces
Pi
chemical formation processes
Li
chemical removal processes

stability of the surface layer
 C i
atmospheric mixing
Adv
transport processes
Low-reactivity primary pollutants:
LS ;  Pi ;  Li
are negligible
C
  ( t )   C   Adv
t
Radon:
 ( t ) can be regarded as constant
C R
t
 K   C R  Adv
Low-reactivity primary pollutants:
C
  ( t )   C   Adv
t
Radon:
C R
t
 K   C R  Adv
ATMOSPHERIC
STABILITY
MONITOR
Temporal pattern of natural radioactivity in Rome
The lower atmospheric
layers are well mixed:
the Radon emitted
from the ground
dilutes and its air
concentration is almost
constant.
EMISSIONE DI RADON
The mixing of the
lower atmospheric
layers is reduced:
the dilution of Radon
is hampered and its
air concentration
increases.
EMISSIONE DI RADON
RADIOATTIVITA' NATURALE
2500
2000
CONTEGGI / MINUTO
During warm months
natural radioactivity shows
a well-defined and
modulated temporal
pattern (all days are
similar: nocturnal stability
and convective mixing
during the day)
1500
1000
500
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
VILLA ADA - AGOSTO 2000
RADIOATTIVITA' NATURALE
3000
2500
CONTEGGI / MINUTO
During cold months
high-pressure periods
are sporadic and
advection often occurs.
Diurnal mixing is weak
and of limited duration.
2000
1500
1000
500
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
VILLA ADA - DICEMBRE 1999
The simplest air pollution model
2 maxima at about
6-7 am and 6-7 pm
SUMMER: when the
morning traffic increases
the lower atmopshere is
already well-mixed; night
time stability occurs when
the traffic has already
decreased.
WINTER: when the
morning traffic increases
the mixing layer is still
undeveloped; evening
stability occurs when the
traffic flow is still high.
PRIMARY POLLUTION
EPISODES
December 1st: nocturnal
stability and daytime
mixing - CO shows a
distinct 2-peak shape
December 2nd: weak
daytime mixing – CO
keeps high values during
the whole day
December 3rd:
intermediate conditions
December 4th (from noon)
and 5th: advection – CO
keeps low values during
the whole day
VILLA ADA (ROME)
DOAS JUNE 1996
100
60
O3 ppb
NO2 ppb
90
80
50
70
40
60
30
50
40
20
30
10
20 ratio (ppb)
mixing
10
0
0
Atmospheric
stability and
Oxidants
-10
RADIOACTIVITY
VILLA ADA (ROME)
4000
3500
NO + O3
NO 2
3000
2500
2000
Tot. Ox = Constant
1500
1000
500
0
25/05/96
26/05/96
Ox rome
The Atmospheric Stability
Index (two scalars referring
to morning and to evening
hours) is calculated on the
basis of natural radioactivity
values and of their time
derivatives during significant
periods of the day.
BENZENE
12
3
MIXING RATIO (mg/m )
Primary pollution events
are closely dependent on
the mixing conditions of
the lower atmopsheric
layers, well described by
the ASI
DAY BEFORE THE
EPHIPHANY HOLIDAY
10
8
6
4
2
0
1
3
5
7
9
11
13
15
17
19
21
ROME - JANUARY 2000
23
25
27
29
31
COMBINED ATMOSPHERIC STABILITY INDEX: 1-YEAR RESULTS
A one-to-one correlation is not expected since the ASI takes into
account only one of the two driving forces determining pollutant
concentrations, that is the meteorological factor.
The two data sets should coincide only
if the emission flux of benzene were constant in time
6
R = 0.78
3
BENZENE MIXING RATIO (m g/m )
WEEKDAY
SCATTER PLOT OF THE
MORNING ATMOSPHERIC
STABILITY INDEX
AND THE MORNING
BENZENE AVERAGE
CONCENTRATION:
SATURDAY
5
SUNDAY
R = 0.88
4
3
2
1
0
THE DATA GROUPS
0
1
DURING WEEKDAYS,
SATURDAYS AND SUNDAYS
4
5
6
2500
N° VEHICLES / HOUR (average)
OF THE TRAFFIC
3
TRAFFIC FLOW DURING SUMMER DAYS
OF THE PLANE
THE DIFFERENT INTENSITY
2
MORNING STABILITY INDEX (arbitrary units)
ON THREE DIFFERENT SECTION
ACCORDING TO
R = 0.90
2000
1500
1000
WEEKDAY
SATURDAY
SUNDAY
500
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
TIME OF THE DAY
On August, the benzene air concentration was lower than predictable
on the only basis of the mixing properties of the atmopshere because
the emission flux was distinctly lower than during the rest of the year.
Classification of the days of one year according to the ASI
(probability of a primary pollution event)
and according to the real benzene concentration.
BENZENE
ROME AIR QUALITY NETWORK
14
C3H6 [m g/m3]
12
10
8
6
4
2
0
1999
2000
2001
2002
2003
USE OF THE ATMOSPHERIC STABILITY INDEX FOR THE
EVALUATION OF POLLUTION TRENDS OVER THE YEARS
IN THE PRESENCE OF SIMILAR ATMOSPHERIC CONDITIONS,
WE OBSERVE A DECREASE OF BENZENE AIR CONCENTRATION
WE CAN CONCLUDE THAT THIS IS DUE TO A REAL DECREASE
IN THE EMISSION FLUXES INSIDE THE URBAN AREA
CONCLUSIONS:
 Natural radioactivity is a valuable tool for the interpretation of
atmospheric pollution.
 The Atmospheric Stability Indexes allow the characterisation of
the period under study in terms of meteorological predisposition to a
primary pollution event.
 The ASI allow public Authorities to evaluate, on a scientific
basis, the results of possible strategies or actions undertaken to
reduce urban pollution.
The ASI make it possible to carry our a sound comparison of
pollutant concentration trend over the years.