Erste atmosphärische Untersuchungen der Wechselwirkung von Mineralstaub mit den Spurengasen HNO₃ und SO₂: Einsatz einer hochempfindlichen CIMS-Sonde

Mineral dust is the single most abundant atmospheric aerosol by mass. In the presence of pollutants it could have a lasting effect on the earth's climate. This work deals with the interaction of mineral dust and the tropospheric trace gases sulfur dioxide, SO2, and nitric acid, HNO3. For this purpose, the CIMS technique (Chemical Ionization Mass Spectrometry) has been refined: A new inlet and filter system has been developed and employed successfully to perform calibrations and background measurements of the CIMS apparatus during the field campaign. Field measurements on the Monte Cimone in northern Italy showed a continuous decrease of HNO3 in dust loaded air masses, however HNO3 depletion was not com- plete. The atmospheric HNO3 mixing ratio decreased from 2 to 0.15 ppbv whereas the average concentration of HNO3 measured on Monte Cimone was about 1 ppbv or more. In contrast, there was no correlation between SO2 and mineral dust. The SO2 uptake depends strongly on the pH value of the mineral dust. Presumably the dust was suciently acidic to prevent SO2 uptak

Atmosphärische Untersuchungen der Wechselwirkung von Mineralstaub mit den Spurengasen HNO ₃ und SO ₂

The trace gases HNO3 and SO2 have an influence on various atmospheric processes concerning the earths climate. Mineral dust, one of the most abundant aerosols in the atmosphere, may have a lasting but almost unexplored effect on their concentrations. Within the scope of this work the interaction of mineral dust with these trace gases was studied in Izana, 2367m asl, Tenerife. During six periods of high atmospheric dustload the HNO3 concentration decreased below the detection limit, allowing a first calculation of the uptake coefficient based on in-situ measurements: γ HNO3 = 0.033. In contrast and in contradiction with the results of laboratory experiments from other research teams, a mineral dust-SO2-anti-correlation was not observed. A lack of information regarding the dust composition and alkalinity which have a decisive influence on the SO2 uptake allows no profound interpretation of this result yet. The detection of the above trace gases was performed using the highly sensitive CIMStechnique (CIMS = Chemical Ionization Mass Spectrometry). This work included the improvement of calibration, diagnostic measurements and the deployment of a newly designed blower inlet to prevent volatile aerosols from entering the CIMS probe. Finally, a successful comparison of the CIMS technique with several techniques of other research teams regarding the measurement of HNO3, SO2 and H2O2 was performed during various measurement campaigns

Atmospheric measurements of gas-phase HNO₃ and SO₂ using chemical ionization mass spectrometry during the MINATROC field campaign 2000 on Monte Cimone

International audienceThe EU-project MINATROC (MINeral dust And TROpospheric Chemistry) aims at enabling an estimation of the influence of mineral dust, a major, but to date largely ignored component of tropospheric aerosol, on tropospheric oxidant cycles. Within the scope of this project continuous atmospheric measurements of gas-phase HNO3 and SO2 were conducted in June and July 2000 at the CNR WMO station, situated on Monte Cimone (MTC) (44° 11' N -- 10° 42' E, 2165 m asl), Italy. African air transporting dust is occasionally advected over the Mediterranean Sea to the site, thus mineral aerosol emitted from Africa will encounter polluted air masses and provide ideal conditions to study their interactions. HNO3 and SO2 were measured with an improved CIMS (chemical ionization mass spectrometry) system for ground-based measurements that was developed and built at MPI-K Heidelberg. Since HNO3 is a very sticky compound special care was paid for the air-sampling and background-measurement system. Complete data sets could be obtained before, during and after major dust intrusions. For the first time these measurements might provide a strong observational indication of efficient uptake of gas-phase HNO3 by atmospheric mineral-dust aerosol particles