Slide1 : Heterogeneous chemistry on mineral aerosol : Influence on tropospheric ozone
Y. Balkanski, M. Schulz, C. Textor, D. Hauglustaine, S. E. Bauer*
LSCE Laboratoire des Sciences du Climat et de l'Environnement
Gif-sur Yvette, France
*Now at Goddard Institute for Space Studies, New York, USA.
R. Van Dingenen, F. Dentener JRC, Ispra, Italy
M. Hanke, B. Umann MPIK, Heidelberg,Germany
J. Crowley, M. De Reus, H. Fischer MPIC, Mainz, Germany
P. Bonasoni CNR – ISAO, Bologna, Italy
M. Rossi EPFL Lausanne, Switzerland
Slide2 : DUST O3 NO3 N2O5 HNO3 How does mineral dust effect atmospheric chemistry ? OH HO2 NO2 SO2 NO
Reaction of HNO3 with bulk dust substrates (Knudsen reactor) - Reaction of HNO3 with airborne dust particles (Aerosol flow reactor) 0.11 Lifetime (dust 5 mg/m3) is 4 hours Hanisch and Crowley, J. Phys. Chem., 2001. Hanisch and Crowley, Phys. Chem. Chem. Phys.,, 2001. : Reaction of HNO3 with bulk dust substrates (Knudsen reactor) - Reaction of HNO3 with airborne dust particles (Aerosol flow reactor) 0.11 Lifetime (dust 5 mg/m3) is 4 hours Hanisch and Crowley, J. Phys. Chem., 2001. Hanisch and Crowley, Phys. Chem. Chem. Phys.,, 2001. Reaction of N2O5 with bulk dust substrates (Knudsen reactor)
2-5 10-2, reaction is water dependant
- Reaction of O3 (Knudsen reactor)
(7 3) x 10-6 depends on the initial ozone concentration.
With very high O3 concentration, saturation occurs.
.
Hanisch F. and J. N. Crowley, Atmos. Chem. Phys. , 2003.
Slide4 : HNO3
O3
N2O5
NO3 0.05
3 e-6
0.05
- 0.1
1 e-5
0.02
0.003 0.25
3 e-5
0.003
- min best guess max g
Slide5 : LMDz INCA:
LMDz (Laboratoire de Météorologie Dynamique) general circulation model
INCA (Interaction with Chemistry and Aerosols) is a chemistry-aerosol-emission-deposition module that is coupled online to the GCM
CHEMISTRY: Tropospheric chemistry including methane oxidation
(45 chemical tracers and 100 reactions)
AEROSOLS: Mineral dust, sea salt,sulfate and carbonaceous aerosols
MODEL SET UP:
Simulation of the year 2000 (nudged towards ECMWF reanalysis)
With 19 vertical layers and on two different horizontal resolutions:
96 x 72 3.75°x 2.5 ° and 160 x 98 2.25° x 1.8°
Slide6 :
Slide7 : Control Simulation CTL:
No interaction between mineral dust and gas phase species
Simulation with Heterogeneous Chemistry HC:
Loss of O3, HNO3, NO3 and N2O5 on the surface of mineral dust
Removal rate: Rx = Kd (r,T,p,rH, gx)· n(r) dr
Do we see a signal due to heterogeneous chemistry in the observations ?
Slide8 : Mt. Cimone (44°12'N, 10°42' E, 2165 m) is the highest peak of the Northern Apennines: Mediterranean free tropospheric air June July Aug Sep Oct DUST June July Aug Sep Oct DUST Observations: P. Bonasoni et al. in preparation [mm3/cm3] Volume concentration
for the size bin: 1-2 mm
Slide9 :
Slide10 :
Changes in NOy (tropospheric mean for the year 2000) : Changes in NOy (tropospheric mean for the year 2000) HNO3 [ppbv] : HC – CTL N2O5 [pptv] : HC – CTL HNO3 [ppbv] : CTL N2O5 [pptv]: CTL
Change in the ozone concentrations [%] HC - CTR: : Change in the ozone concentrations [%] HC - CTR: Vertical mean over the troposphere Year 2000
Slide13 : - - - - - - - - HNO3
O3
N2O5
NO3 0.05
3 e-6
0.05
- 0.1
1 e-5
0.02
0.003 0.25
3 e-5
0.003
- g min best guess max Test of the uptake coefficients
Summary : Summary The accomodation coefficients of HNO3, N2O5 and O3 on mineral dust surfaces have been measured through lab. studies that used both Knudsen and aerosol flow reactors.
The rapid drop to less than 10pptV of HNO3 measured in both Mt Cimone 2000 and Izana 2002 field campaigns indicates that the reaction of HNO3 on dust is environmentally significant. HNO3 uptake acts as the driving mechanism to limit O3 during dust episodes.
Chemical reactions on the surface of mineral aerosols lower tropospheric ozone concentrations by about 6 % globally. Locally (e.g. Northern Africa) ozone can be reduced by as much as 40 %.
Slide15 : a) On going work to confront model runs with Izana measurements by sorting out upslope vs. Downslope wind conditions.
b) Uptake of OH and HO2 on mineral dust
c) Heterogeneous reactions on other aerosol surfaces On going and Future work