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Consiglio Nazionale delle Ricerche ISTITUTO
sullINQUINAMENTO 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
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PRESENTATION OUTLINE

• Effectiveness of control measures
• Meteorology-Concentration relationship
• Evolution of the Boundary layer
• Examples

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Parameters acting on M

• Emission fluxes
• Physico-chemical transformations
• Deposition

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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

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Concentration variations for a pollutant i
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Low-reactivity primary pollutants
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Radon
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Low-reactivity primary pollutants
Radon
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• ATMOSPHERIC STABILITY MONITOR

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Temporal pattern of natural radioactivity in Rome
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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
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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)
During cold months high-pressure periods are
sporadic and advection often occurs. Diurnal
mixing is weak and of limited duration.
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The simplest air pollution model
2 maxima at about 6-7 am and 6-7 pm
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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
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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
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Atmospheric stability and Oxidants
NO O NO Tot. Ox Constant
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Ox rome
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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.
DAY BEFORE THE EPHIPHANY HOLIDAY
Primary pollution events are closely dependent on
the mixing conditions of the lower atmopsheric
layers, well described by the ASI
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COMBINED ATMOSPHERIC STABILITY INDEX 1-YEAR
RESULTS
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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
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SCATTER PLOT OF THE MORNING ATMOSPHERIC STABILITY
INDEX AND THE MORNING BENZENE AVERAGE
CONCENTRATION THE DATA GROUPS ON THREE
DIFFERENT SECTION OF THE PLANE ACCORDING TO THE
DIFFERENT INTENSITY OF THE TRAFFIC DURING
WEEKDAYS, SATURDAYS AND SUNDAYS
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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.
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Classification of the days of one year according
to the ASI (probability of a primary pollution
event) and according to the real benzene
concentration.
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BENZENE
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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
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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.