A Rapid In-Situ Technique for Aerosol Chemical Composition as a Function of the Hygroscopic Growth: Results from Urban, Remote and Polar Field Sites
Abstract
Aerosols, both natural and anthropogenic, are important factors with respect to the radiation budget of the atmosphere. One important property is the ability of an aerosol particle to take up water which can have an impact on aerosol optical properties and cloud formation. To date little is known about how aerosol water uptake depends on the chemical composition of the aerosol. In this study an in-situ measurement setup to determine the chemical composition of atmospheric aerosols as a function of hygroscopicity is presented. This has been done by connecting a custom-built Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) and an Aerosol Time-of-Flight Mass Spectrometers (ATOFMS), commercially available from TSI (Model 3800). Thus, single particle bipolar mass spectra from aerosols leaving the HTDMA could be obtained as a function of hygroscopic growth factor. For these studies the HTDMA was deployed at a relative humidity of 82% and particles with a dry diameter of 260 nm were selected. This novel setup was laboratory-tested with mixed hydrophobic and hygroscopic aerosols. Subsequently, several sets of field experiments were performed during the last year. Two datasets were obtained during wintertime 2007 in Switzerland: One in the urban Zurich environment and the other at the remote high alpine station Jungfraujoch (JFJ). Further data was obtained in July 2007 in Abisko, Sweden. Located 200km north of the Arctic Circle, air masses from different directions were distinguished and examined. In Zurich a large data set was obtained within less than two days of measurements due to a high aerosol loading. At the JFJ, due to low particle concentrations, a longer sampling period was required. At the Abisko station particle concentration (i.e., data acquisition rate) strongly depended on the airmass origin. Both in Zurich and at the JFJ two different growth factor modes were observed. First results from these two locations show that most aerosols were generally internally mixed. A large contribution of organics and biomass combustion was found in the non-hygroscopic growth mode particles for both locations. Refractory material (e.g. metals, mineral dust, fly ash elements) was also highly enhanced in the non-hygroscopic particles. Sulfate was found to be a constituent in almost all particles independent of their growth factor. The Abisko dataset is currently being evaluated.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFM.A51H..04C
- Keywords:
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- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0305 Aerosols and particles (0345;
- 4801;
- 4906);
- 0320 Cloud physics and chemistry