| 1. |
- Choularton, T. W., et al.
(författare)
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The Great Dun Fell Cloud Experiment 1993 : An overview
- 1997
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Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2393-2405
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Tidskriftsartikel (refereegranskat)abstract
- The 1993 Ground-based Cloud Experiment on Great Dun Fell used a wide range of measurements of trace gases, aerosol particles and cloud droplets at five sites to study their sources and sinks especially those in cloud. These measurements have been interpreted using a variety of models. The conclusions add to our knowledge of air pollution, acidification of the atmosphere and the ground, eutrophication and climate change. The experiment is designed to use the hill cap cloud as a flow-through reactor, and was conducted in varying levels of pollution typical of much of the rural temperate continental northern hemisphere in spring-time.
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| 2. |
- Gieray, R., et al.
(författare)
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Phase partitioning of aerosol constituents in cloud based on single-particle and bulk analysis
- 1997
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Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2491-2502
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Tidskriftsartikel (refereegranskat)abstract
- Single-particle analysis, performed by laser microprobe mass spectrometry and bulk analytical techniques were used to study aerosol-cloud interactions within the third field campaign of the EUROTRAC subproject 'ground-based cloud experiments' at the Great Dun Fell, Cumbria, U.K. in spring 1993. The shape of the ridge made it possible for ground-based instrumentation to sample similar parcels of air before, during and after their transit through the cloud. A single jet five-stage minicascade impactor was used for sampling particles of the interstitial aerosol. A second impactor worked in tandem with a counter-flow virtual impactor and collected residues of cloud droplets. Considering marine conditions largest droplets nucleated on sea-salt particles, whereas smaller droplets were formed on sulphate and methane sulphonate containing particles. This clearly indicates chemical inhomogeneities in the droplet phase. Particles, which were disfavoured by droplet formation, often contained the highest amounts of water-insoluble carbonaceous matter. For the submicron size range we found that the carbonaceous matter was always internally mixed with sulphate. The fraction of carbonaceous matter increased with decreasing size. A detectable fraction of particles remained in the cloud interstitial air, although they were in size as well as in composition suitable to form cloud droplets. The findings confirm that nucleation is the most important process affecting phase partitioning in cloud, but that spatial and temporal variations of water vapour supersaturation have also an influence on the observed phase partitioning. Proton induced X-ray emission analysis and light absorption measurements of filter samples showed that the average scavenged fraction was 0.77 for sulphur and 0.57 for soot in clouds formed by continental influenced air and 0.62 and 0.44, respectively, for marine influenced clouds.
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| 3. |
- Mentes, B., et al.
(författare)
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Vaporisation characteristics and detection limits of ion beam thermography
- 1999
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 150:1-4, s. 136-143
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Tidskriftsartikel (refereegranskat)abstract
- Analytical properties of the chemical speciation method, Ion beam thermography (IBT), have been investigated. IBT combines the multi-elemental ion beam techniques PIXE, PESA, pNRA and cPESA with thermography. During thermography the sample temperature is gradually increased, causing vaporisation of chemical compounds at specific temperatures and the sample at the same time undergoes analysis by the above-mentioned techniques. The characteristic vaporisation temperature (CVT) and the stoichiometric relations between the elements vaporised at that temperature, identify the chemical compounds. This work describes the reproducibility of the method, the dependence of the rate of temperature increase, the dependence of the sample thickness and the influence from aerosol particle size on the CVT. In addition the minimum detectable mass changes for IBT analysis of marine and continental aerosols were estimated by calculation for major and minor elements.
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| 4. |
- Papaspiropoulos, G., et al.
(författare)
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High sensitivity elemental analysis methodology for upper tropospheric aerosol
- 1999
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 150:1-4, s. 356-362
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a sampling and analysis tool for aerosol particles has been developed. Its purpose is to characterize upper tropospheric aerosols, where concentrations are low. Since measurements will be made from an airplane, a time resolution of one hour is desirable. These conditions require efficient sampling and analysis with low detection limits. To accomplish this, our sampler uses impaction, concentrating the aerosol deposit on a small area. The impactor has 14 parallel sampling lines which are used sequentially to achieve the time resolution. The elemental analysis is done with Particle-Induced X-ray Emission (PIXE), profiting from its high absolute sensitivity. The aerosol is expected to contains primarily sulphur (S) and emphasis is placed on this element, however the multi-elemental nature of PIXE is of course used. Several substrates have been investigated regarding minimum detection limits. Scanning Transmission Ion Macroscopy (STIM) analysis has been conducted on two outdoor aerosol samples, rendering three-dimensional images and mass distribution profiles. The setup was tested at ground level with high time resolution (5 min). Results show that the detection capabilities are excellent.
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