Technical tool to evaluate the effectiveness of control

measures

I. ALLEGRINI and C. PERRINO

Consiglio Nazionale delle Ricerche

ISTITUTO sull’INQUINAMENTO ATMOSFERICOVia Salaria km 29,300 - C.P. 10

00016 Monterotondo Stazione - ROMA

Reducing the Impact of Vehicles on Air and Environment Quality in Cities – Mexico City Jan. 22-23, 2004

PRESENTATION OUTLINE

Effectiveness of control measuresMeteorology-Concentration relationshipEvolution of the Boundary layerExamples

V

MC )I(

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

iiiii LPLAdvC)t(t

CS

)t(i emission fl ux f rom the sources

LS deposition losses on the surf aces

iP chemical f ormation processes

iL chemical removal processes

stability of the surf ace layer

C i atmospheric mixing

Adv transport processes

Concentration variations for a pollutant i

AdvC)t(t

C

Low-reactivity primary pollutants:

ii L;P;LSare negligible

AdvK CRtRC

Radon:

can be regarded as constant )t(

AdvC)t(t

C

Low-reactivity primary pollutants:

AdvK CRtRC

Radon:

ATMOSPHERI

C STABILITY

MONITOR

Temporal pattern of natural radioactivity in Rome

EMISSIONE DI RADON

EMISSIONE DI RADON

The mixing of the lower atmospheric layers is reduced: the dilution of Radon is hampered and its air concentration increases.

The lower atmospheric layers are well mixed: the Radon emitted from the ground dilutes and its air concentration is almost constant.

RADIOATTIVITA' NATURALE

0

500

1000

1500

2000

2500

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 2000C

ON

TE

GG

I /

MIN

UT

O

RADIOATTIVITA' NATURALE

0

500

1000

1500

2000

2500

3000

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

CO

NT

EG

GI / M

INU

TO

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.

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

Atmospheric stability and

Oxidants

VILLA ADA (ROME)DOAS JUNE 1996

0

10

20

30

40

50

60

70

80

90

100

mixing ratio (ppb)

-10

0

10

20

30

40

50

60O3 ppbNO2 ppb

RADIOACTIVITYVILLA ADA (ROME)

0

500

1000

1500

2000

2500

3000

3500

4000

25/05/96 26/05/96

NO + O NO

Tot. Ox = Constant

23

Ox rome

BENZENE

0

2

4

6

8

10

12

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

ROME - JANUARY 2000

MIX

ING

RA

TIO

(

m g/m

3 )

DAY BEFORE THE EPHIPHANY HOLIDAY

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.

Primary pollution events are closely dependent on the mixing conditions of the lower atmopsheric layers, well described by the ASI

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

0

1

2

3

4

5

6

0 1 2 3 4 5 6

MORNING STABILITY INDEX (arbitrary units)

BE

NZ

EN

E M

IXIN

G R

AT

IO (m

g/m

3 )

WEEKDAY

SATURDAY

SUNDAY

R = 0.78

R = 0.90

R = 0.88

TRAFFIC FLOW DURING SUMMER DAYS

0

500

1000

1500

2000

2500

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

N°

VE

HIC

LE

S /

HO

UR

(a

ve

rag

e)

WEEKDAYSATURDAYSUNDAY

SCATTER PLOT OF THE SCATTER PLOT OF THE MORNING MORNING ATMOSPHERIC ATMOSPHERIC STABILITY INDEX STABILITY INDEX AND THE MORNING AND THE MORNING BENZENE AVERAGE BENZENE AVERAGE CONCENTRATION: CONCENTRATION: THE DATA GROUPS THE DATA GROUPS

ON THREE DIFFERENT ON THREE DIFFERENT

SECTION OF THE PLANE SECTION OF THE PLANE

ACCORDING TO ACCORDING TO

THE DIFFERENT INTENSITY THE DIFFERENT INTENSITY

OF THE TRAFFIC OF THE TRAFFIC

DURING WEEKDAYS, DURING WEEKDAYS,

SATURDAYS AND SUNDAYSSATURDAYS AND SUNDAYS

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.

ROME AIR QUALITY NETWORK

0

2

4

6

8

10

12

14

1999 2000 2001 2002 2003

C3H

6 [m

g/m

3]

BENZENE

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.