Atmosphärische Untersuchungen der Wechselwirkung von Mineralstaub mit den Spurengasen HNO3 und SO2

Die Spurengase HNO3 und SO2 haben Anteil an vielen klimarelevanten Prozessen in der Erdatmosphäre. Einen bislang weitgehend unerforschten Einfluss auf ihre Konzentrationen kann Mineralstaub, eines der häufigsten atmosphärischen Aerosole, haben. Im Rahmen der vorliegenden Arbeit wurde in Izana, 2367 m üdM, Teneriffa, die Wechselwirkung von Mineralstaub mit diesen Spurengasen untersucht. In insgesamt sechs Perioden hohen Staubaufkommens wurde jeweils ein HNO3-Rückgang bis auf die Nachweisgrenze gemessen. Aufgrund dieser Antikorrelationen konnte erstmals eine Berechnung der die HNO3-Aufnahme charakterisierende Größe (uptake coefficient gamma), basierend auf in-situ-Messungen vorgenommen werden: gamma(HNO3) = 0.033. Im Gegensatz dazu konnte eine Mineralstaub-SO2-Antikorrelation, wie sie in Labormessungen anderer Gruppen festgestellt wurde, nicht gemessen werden. Informationen über die Staubzusammensetzung und dessen Alkalinität, die entscheidenden Einfluss auf die SO2-Aufnahme haben, liegen derzeit noch nicht vor. Der Nachweis obiger Spurengase erfolgte mittels einer hochempfindlichen CIMS-Sonde (CIMS = Chemische-Ionisations-MassenSpektrometrie). Die Weiterentwicklung der Kalibriertechnik sowie umfangreiche diagnostische Messungen zur Optimierung der CIMS-Technik waren Bestandteil dieser Arbeit. Sie beinhaltete die Entwicklung eines neuen Einlasssystems, das einen (unerwünschten) HNO3-Beitrag aus volatilen Aerosolen verhinderte. Schließlich konnte die CIMS-Methode im Rahmen diverser Messkampagnen erfolgreich mit den Messmethoden anderer Forschungsgruppen bezüglich HNO3, SO2 und H2O2 verglichen werden

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

Deployment of a ground-based CIMS apparatus for the detection of organic gases in the boreal forest during the QUEST campaign

Measurements of atmospheric volatile organic compounds were performed in the Finnish Boreal forest atmosphere during spring 2003, as part of the project QUEST (Quantification of Aerosol Nucleation in the European Boundary Layer), using a ground-based Chemical Ionization Mass Spectrometer (CIMS) instrument. Based on the study of their hydrate istribution, methanol, acetonitrile, acetaldehyde, dimethyl amine (DMA), ethanol/formic acid, acetone, trimethyl amine (TMA), propanol/acetic acid, isoprene, methyl vinyl ketone (MVK) and metacrolein (MaCR), monoterpenes and monoterpene oxidation product (MTOP) are proposed as candidates for masses 32, 41, 44, 45, 46, 58, 59, 60, 68, 70, 136, and 168 amu, respectively. It would be, to our knowledge, the first time DMA, TMA and MTOP are measured with this method. Most compounds show a clear diurnal variation with a maximum in the early night, corresponding to the onset of the noctural inversion and in agreement with independant measurements of CO. Biogenic compounds are highly correlated with each other and the ratio monoterpene/oxidation product shows a typical daily pattern of nightime maxima. However, because isoprene mixing ratios are also maximum during the early night, it is likely that it suffers of the interference from another unidentified biogenic compound. Hence mass 68 amu is identified as isoprene + compound X

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

The 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

The Interaction of Mineral Dust with Gas-Phase HMO3 and SO2 during the MINATROC II Field Campaign: First Estimate of the Uptake Coefficient yHNO3 from Atmospheric Data

Within the second part of the MINATROC project (MINeral dust And TROpospheric Chemistry) we investigated the interaction of mineral dust with gaseous HNO3 and SO2. The measurements were performed at Izana, Tenerife, 2367 m asl) using the highly sensitive Chemical Ionization Mass Spectrometry technique. During six periods of high atmospheric dust load, the HNO3 concentration decreased with increasing dust concentrations. From the HNO3 decrease, the uptake coefficient for HNO3 was calculated and found to vary between 0.017 and 0.054. Moreover, during the dust events a significant decrease of ozone (O3) was detected. We conclude that this decrease is only due to the HNO3 depletion and that no significant uptake of O3 on dust occurred. A general interaction between SO2 and mineral dust were detected.JRC.H.2-Climate chang

Interaction of mineral dust with gas phase nitric acid and sulfur dioxide during the MINATROC II field campaign: First estimate of the uptake coefficient γHNO3 from atmospheric data

Mineral dust, one of the most abundant aerosols by mass in the atmosphere, may have a lasting but to date almost unexplored effect on the trace gases nitric acid (HNO3) and sulfur dioxide (SO2). These gases have an important influence on, for example, the tropospheric ozone cycle, aerosol formation or acid rain. Within the second part of the MINATROC project (Mineral Dust and Tropospheric Chemistry) we investigated the interaction of mineral dust with gaseous HNO3 and SO2. The measurements were performed on a high mountain plateau (Izaña, Tenerife, 2367 m asl) using the highly sensitive CIMS (Chemical Ionization Mass Spectrometry) technique. During five periods of medium and one period of high atmospheric dust load, the HNO3 concentration decreased with increasing dust concentrations, and in all cases the HNO3 detection limit was reached. From the HNO3 decrease the uptake coefficient γHNO3 was calculated for the first time on the basis of in situ measurements. For the observed events, γHNO3 varied between 0.017 and 0.054. Moreover, during the dust events a significant decrease of ozone (O3) of the order of 30% was detected. The measurements and the analyses made in this paper show that the direct uptake of O3 on dust is a minor pathway for O3 depletion compared to the indirect effect, i.e., HNO3 depletion on dust which takes away a source of the O3 precursors nitrogen oxides. In contrast, a general interaction between SO2 and mineral dust was not observed. Positive as well as negative and no correlations between SO2 and mineral dust were detected.JRC.H.2-Climate chang