Ozone modeling over Italy: a sensitivity analysis to precursors using BOLCHEM air quality model

Mihaela Mircea1, Massimo D'Isidoro1, Alberto Maurizi1, Maria Gabriella Villani1, Andrea Buzzi1, Sandro Fuzzi1, Francesco Tampieri1

Gabriele Zanini2, Fabio Monforti2, Lina Vitale2

1Istituto di Scienze dell’Atmosfera e del Clima, CNR, Bologna, Italy2ENEA,Italian Agency for New Technologies, Energy and the Environment, Via

Martiri di Monte Sole 4, 40129 Bologna, Italy

Objectives

• to investigate the sensitivity of ozone concentration to the reduction of NOx and VOC for few periods during the years 1999 and 2003 over the whole Italy

• to asses the relative importance of precursors in reducing the ozone levels identifying the regions of Italy where local emissions strategies could not be effective

Photochemical mechanismsCB-IV (Gery et al., 1989) : lumped-structure condensed mechanism-85 reactions and 30 chemical species-organics are grouped according to bond type (for example, as carbon single bonds, carbon

double bounds or carbonyl bounds)-organic species are treated explicitly (e.g. formaldehyde, ethene, isoprene), represented by

carbon bond (PAR – single bonded one carbon atom, OLE –two carbon atoms) or molecular (TOL and XYL aromatic hydrocarbons) surrogates according with their chemistry or importance in the environment.

SAPRC90 (Carter, 1990) : lumped-molecular condensed mechanism-131 reactions with 35 chemical species-calculate the kinetic and mechanistic parameters for lumped species in the mechanism

created for representative emissions profile (mole-weighted approach)-organics species are treated explicitly (e.g. formaldehyde, acetaldehyde, etc) or represented

by molecules as alkane, alkenes, aromatics, etc.

Base case NOx reduced(-35%) VOC reduced(-35%)

Differences in ozone concentrations: ∆O3=O3(65%VOC)-O3(65%NOx)∆O3 > 0 NOx limited area∆O3 <0 VOC limited area

Chemical regimes over Italy

SAPRC90 ppbCB4 ppb

Areas selected for the analysis

Center of the area

Lat Lon Size (km X km)

Milano 45o28’ 9o10’ 160x160

Genova 44o25’ 8o54’ 80x80

Venezia 45o26’ 12o19’ 240x240

Roma 41o54’ 12o28’ 80x80

Napoli 40o51’ 14o16’ 80x80

Taranto 40o25’ 17o14’ 80x80

Pachino 36o15’ 15o05’ 100x100

NOx reduced(-35%) VOC reduced(-35%)

∆O3=local-global reductions

∆O3(ppb)CB4

SAPRC90

Roma: 5 - 8 August 1999

010

20304050

607080

90100

1 7 13 19 25 31 37 43 49 55 61 67 73

Hours

frac

tion

of N

Ox

or V

OC

lim

ited

area

(%)

SA_VOC(-35%)SA_NOx(-35%)CB4_VOC(-35%)CB4_NOx(-35%)

Milano: 5 - 8 August 1999

0102030405060708090

100

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73

Hours

frac

tion

of N

Ox

or V

OC

lim

ited

area

(%)

SA_VOC(-35%)SA_NOx(-35%)CB4_VOC(-35%)CB4_NOx(-35%)

Genova: 5 - 8 August 1999

0102030405060708090

100

1 7 13 19 25 31 37 43 49 55 61 67 73

Hours

frac

tion

of N

Ox

or V

OC

lim

ited

area

(%)

SA_VOC(-35%)SA_NOx(-35%)CB4_VOC(-35%)CB4_NOx(-35%)

Venezia: 5 - 8 August 1999

0102030405060708090

100

1 7 13 19 25 31 37 43 49 55 61 67 73

Hours

frac

tion

of N

Ox

or V

OC

lim

ited

area

(%)

SA_VOC(-35%)SA_NOx(-35%)CB4_VOC(-35%)CB4_NOx(-35%)

Napoli: 5 - 8 August 1999

010

20304050

607080

90100

1 7 13 19 25 31 37 43 49 55 61 67 73

Hours

frac

tion

of N

Ox

or V

OC

lim

ited

area

(%)

SA_VOC(-35%)SA_NOx(-35%)CB4_VOC(-35%)CB4_NOx(-35%)

Taranto: 5 - 8 August 1999

010

2030

4050

6070

8090

100

1 7 13 19 25 31 37 43 49 55 61 67 73

Hoursfr

actio

n of

NO

x or

VO

C li

mite

d ar

ea (%

)

SA_VOC(-35%)SA_NOx(-35%)CB4_VOC(-35%)CB4_NOx(-35%)

Pachino: 5 - 8 August 1999

010

2030

4050

6070

8090

100

1 7 13 19 25 31 37 43 49 55 61 67 73

Hours

frac

tion

of N

Ox

or V

OC

lim

ited

area

(%)

SA_VOC(-35%)SA_NOx(-35%)CB4_VOC(-35%)CB4_NOx(-35%)

Extreme summer 2003Montelibretti: 9-12 August 2003

020406080

100120140160180200220240260

2003080901.00

2003080904.00

2003080907.00

2003080910.00

2003080913.00

2003080916.00

2003080919.00

2003080922.00

2003081001.00

2003081004.00

2003081007.00

2003081010.00

2003081013.00

2003081016.00

2003081019.00

2003081022.00

2003081101.00

2003081104.00

2003081107.00

2003081110.00

2003081113.00

2003081116.00

2003081119.00

2003081122.00

ug/m

3

obsSAPRC90

∆O3=O3(65%VOC)-O3(65%NOx)

Fraction of VOC or NOx limited area

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

VOC

NO

x

VOC

NO

x

VOC

NO

x

VOC

NO

x

VOC

NO

x

VOC

NO

x

VOC

NO

x

Milano Genova Venezia Roma Napoli Taranto

% o

f VO

C o

r NO

x lim

ited

area

99_SAPRC9099_CB403_SAPRC9099_SAPRC90_areas

Pachino

O3 increase due to the increase in isoprene emissionsppb

Preliminary conclusions

The differences in the predicted ozone concentrations due to thephotochemical mechanisms are comparable to those obtained by reducing the emissions of NOx or VOC

The distribution and the “intensity” (differences in ozone concentration) of VOC or NOx limited areas depend on the photochemical mechanism. For example, in the same meteorological and environmental conditions, a region can be VOC or NOx sensitive according with the photochemical mechanism used.

The local reduction of VOC was efficient for Milano and Venice areas. In the other regions, significant increase in ozone concentration was observed by reducing locally both the NOx or VOC emissions.

The increase of isoprene leads to substantial increase in the concentration of ozone at some locations (up to 25%), therefore, the uncertainties in isoprene emissions can bias the air quality design.

ACKNOWLEDGEMENTS

GEMS and ACCENT: EU-projectsICTP Programme for Training and Research in Italian Laboratories”, Trieste, Italy