3 results
Search Results
Now showing 1 - 3 of 3
- ItemSoot reference materials for instrument calibration and intercomparisons: A workshop summary with recommendations(München : European Geopyhsical Union, 2012) Baumgardner, D.; Popovicheva, O.; Allan, J.; Bernardoni, V.; Cao, J.; Cavalli, F.; Cozic, J.; Courcoux, Y.; Diapouli, E.; Eleftheriadis, K.; Genberg, P.J.; Gonzalez, C.; Gysel, M.; John, A.; Kirchstetter, T.W.; Kuhlbusch, T.A.J.; Laborde, M.; Lack, D.; Müller, T.; Niessner, R.; Petzold, A.; Piazzalunga, A.; Putaud, J.P.; Schwarz, J.; Sheridan, P.; Subramanian, R.; Swietlicki, E.; Valli, G.; Vecchi, R.; Viana, M.Soot, which is produced from biomass burning and the incomplete combustion of fossil and biomass fuels, has been linked to regional and global climate change and to negative health problems. Scientists measure the properties of soot using a variety of methods in order to quantify source emissions and understand its atmospheric chemistry, reactivity under emission conditions, interaction with solar radiation, influence on clouds, and health impacts. A major obstacle currently limiting progress is the absence of established standards or reference materials for calibrating the many instruments used to measure the various properties of soot. The current state of availability and practicability of soot standard reference materials (SRMs) was reviewed by a group of 50 international experts during a workshop in June of 2011. The workshop was convened to summarize the current knowledge on soot measurement techniques, identify the measurement uncertainties and limitations related to the lack of soot SRMs, and identify attributes of SRMs that, if developed, would reduce measurement uncertainties. The workshop established that suitable SRMs are available for calibrating some, but not all, measurement methods. The community of users of the single-particle soot-photometer (SP2), an instrument using laser-induced incandescence, identified a suitable SRM, fullerene soot, but users of instruments that measure light absorption by soot collected on filters did not. Similarly, those who use thermal optical analysis (TOA) to analyze the organic and elemental carbon components of soot were not satisfied with current SRMs. The workshop, and subsequent, interactive discussions, produced a number of recommendations for the development of new SRMs, and their implementation, that would be suitable for the different soot measurement methods.
- ItemPollution events observed during CARIBIC flights in the upper troposphere between South China and the Philippines(München : European Geopyhsical Union, 2010) Lai, S.C.; Baker, A.K.; Schuck, T.J.; van Velthoven, P.; Oram, D.E.; Zahn, A.; Hermann, M.; Weigelt, A.; Slemr, F.; Brenninkmeijer, C.A.M.; Ziereis, H.A strong pollution episode in the upper troposphere between South China and the Philippines was observed during CARIBIC flights in April 2007. Five pollution events were observed, where enhancements in aerosol and trace gas concentrations including CO, CO2, CH4, non-methane hydrocarbons (NMHCs) and halocarbons were observed along the flight tracks during four sequential flights. The importance of the contribution of biomass/biofuel burning was investigated using chemical tracers, emission factor analysis, back-trajectory analysis and satellite images. The Indochinese peninsula was identified as the probable source region of biomass/biofuel burning. However, enhancements in the urban/industrial tracer C2Cl4 during the events also indicate a substantial contribution from urban anthropogenic emissions. An estimation of the contribution of fossil fuel versus biomass/biofuel to the CO enhancement was made, indicating a biomass/biofuel burning contribution of ~54 to ~92% of the observed CO enhancements. Biomass/biofuel burning was found to be the most important source category during the sampling period.
- ItemCorrelation between traffic density and particle size distribution in a street canyon and the dependence on wind direction(München : European Geopyhsical Union, 2006) Voigtländer, J.; Tuch, T.; Birmili, W.; Wiedensohler, A.Combustion of fossil fuel in gasoline and diesel powered vehicles is a major source of aerosol particles in a city. In a street canyon, the number concentration of particles smaller than 300 nm in diameter, which can be inhaled and cause serious health effects, is dominated by particles originating from this source. In this study we measured both, particle number size distribution and traffic density continuously in a characteristic street canyon in Germany for a time period of 6 months. The street canyon with multistory buildings and 4 traffic lanes is very typical for larger cities. Thus, the measurements also are representative for many other street canyons in Europe. In contrast to previous studies, we measured and analyzed the particle number size distribution with high size resolution using a Twin Differential Mobility Analyzer (TDMPS). The measured size range was from 3 to 800 nm, separated into 40 size channels. Correlation coefficients between particle number concentration for integrated size ranges and traffic counts of 0.5 were determined. Correlations were also calculated for each of the 40 size channels of the DMPS system, respectively. We found a maximum of the correlation coefficients for nucleation mode particles in the size range between 10 and 20 nm in diameter. Furthermore, correlations between traffic and particles in dependence of meteorological data were calculated. Relevant parameters were identified by a multiple regression method. In our experiment only wind parameters have influenced the particle number concentration significantly. High correlation coefficients (up to 0.8) could be observed in the lee side of the street canyon for particles in the range between 10 and 100 nm in diameter. These values are significantly higher than correlation coefficients for other wind directions and other particle sizes. A minimum was found in the luff side of the street. These findings are in good agreement with theory of fluid dynamics in street canyons.