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- 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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| 7. |
- Martinsson, L., et al.
(författare)
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Oxygen concentration and temperature measurements in N2-O2 mixtures using rotational coherent anti-Stokes Raman spectroscopy
- 1996
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Ingår i: Applied Physics B. - 0946-2171. ; 62:1, s. 29-37
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Tidskriftsartikel (refereegranskat)abstract
- The accuracy and precision of oxygen concentration and temperature measured by dual-broadband rotational Coherent Anti-Stokes Raman Spectroscopy (CARS) were investigated in nitrogen-oxygen mixtures at atmospheric pressure and temperatures between 290 and 1410 K. The relative standard deviation of temperatures evaluated from pure oxygen rotational CARS spectra was found to be around 5%, and the mean temperature was the same as for nitrogen CARS spectra, except for temperatures above 1000 K, where the temperature was 120 K below the correct value. The in situ calibrated oxygen concentrations were within 10% of the correct value, with a standard deviation of around 1.2% for the mixtures of 12 and 20% oxygen in nitrogen. For the lowest oxygen concentrations considered in this study (2 and 4%), the systematic errors in the evaluated concentrations were very large, and the standard deviation of repeated single-shot measurements was above 2%. However, employing weighting in the spectral fitting routine reduced the errors in the concentration and the single-shot standard deviation was lowered to 0.5%. Finally, it was shown that spectral interference (from oxygen) in a rotational CARS spectrum of nitrogen generally had little impact on the temperature evaluated from fitting the spectra to theoretical nitrogen spectra.
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| 8. |
- Romer, Rolf L., et al.
(författare)
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Scapolite: a tracer for the initial lead isotopic composition in sulfide deposits with later additions of radiogenic lead
- 1996
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Ingår i: Mineralium Deposita. - 0026-4598 .- 1432-1866. ; 31:1-2, s. 134-139
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Tidskriftsartikel (refereegranskat)abstract
- The initial lead isotopic composition of metamorphosed and tectonically reworked sulfide deposits is not always preserved, as sulfides easily change their lead isotopic composition through incorporation of lead derived from external fluids or redistribution and recrystallization of the deposit. Sulfide trace-lead and in cases even galena-lead from such deposits may show exceedingly radiogenic lead isotopic compositions. Thus, the initial lead isotopic composition has to be estimated from other minerals. Scapolite, which is a common phase in alteration haloes associated with epigenetic sulfide deposits in northern Sweden, has very low uranium-contents. Therefore, its trace-lead contents could preserve the initial isotopic composition of the ore-forming fluids. As scapolite is more resistant to recrystallization, it is more likely to reflect the original lead isotope signature of the deposit. This is illustrated using scapolite and sulfides from the Pahtohavare Cu-Au deposit in northern Sweden, which is hosted by Palaeoproterozoic mafic tuffites and graphitic schists and was affected by a mild thermal metamorphism during the Caledonian orogeny.
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| 9. |
- Swietlicki, Erik, et al.
(författare)
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Source identification during the Great Dun Fell Cloud Experiment 1993
- 1997
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Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2441-2451
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Tidskriftsartikel (refereegranskat)abstract
- A characterisation of the sources influencing the site for the final field campaign of the EUROTRAC subproject GCE (Ground-based Cloud Experiment) at Great Dun Fell, Cumbria, Great Britain in April-May 1993 is presented. The sources were characterised mainly by means of aerosol filter and cascade impactor data, single particle analysis, gas data, data on aromatic organic compounds, cloud water ionic composition, measurements of aerosol size distributions and hygroscopic properties and various meteorological information. Receptor models applied on the aerosol filter and impactor data sets separately revealed two major source types being a marine sea spray source and a long-range transported anthropogenic pollution source. The results of the receptor models were largely consistent with the other observations used in the source identification. Periods of considerable anthropogenic pollution as well as almost pure marine air masses were clearly identified during the course of the experiment.
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| 10. |
- Versluis, M., et al.
(författare)
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2-D absolute OH concentration profiles in atmospheric flames using planar LIF in a bi-directional laser beam configuration
- 1997
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Ingår i: Applied Physics B: Lasers and Optics. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 65:3, s. 411-417
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Tidskriftsartikel (refereegranskat)abstract
- A technique has been developed to measure the absolute OH concentration at atmospheric pressures by using a combination of direct absorption and laser-induced fluorescence (LIF) detection. The technique is independent of collisions, because it uses laser beams in a bi-directional configuration, thereby eliminating collisional quenching. The absolute OH concentration is measured spatially resolved in two dimensions by using absorption on the Q(1)(6) rotational line in the A(2) Sigma(+) (upsilon' = 0) <-- X-2 Pi(upsilon '' = 0) band of OH at 309 nm. The requirements for obtaining a good signal-to-noise ratio for the technique are discussed and the possibilities of single-shot measurements are investigated.
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