Search results for "Soot particles"
showing 5 items of 5 documents
Airborne Measurements of Contrail Ice Properties—Dependence on Temperature and Humidity
2021
The largest share in the climate impact of aviation results from cirrus clouds. Here, the dependence of microphysical contrail ice properties and extinction on temperature and humidity is investigated. Contrail measurements were performed at various altitudes during the 2018 ECLIF II/NDMAX campaign with the NASA DC-8 chasing the DLR A320. Ice number concentrations and contrail extinction coefficients are largest at altitudes near 9.5 km, typical for short- and medium-range air traffic. At higher altitudes near 11.5 km, low ambient water vapor concentrations lead to smaller contrail particle sizes and lower extinction coefficients. In addition, contrails were detected below 8.2 km near the S…
In Situ Observations of Ice Particle Losses in a Young Persistent Contrail
2018
We describe results of in situ observations of a 1 to 2-min old contrail in the vortex Phase generated from soot-rich exhaust (> 10^15 emitted soot particles per kg-fuel burned). Simultaneous measurements of soot (EIsoot) and apparent ice (AEIice) particle number emission indices show a pronounced anti-correlation in the vertical contrail profile. AEIice decrease by about 75% with increasing distance below the contrail-producing aircraft,while EIsoot increase by an equivalent relative fraction, therefore strongly suggesting sublimation causing the ice particle losses. Quantifying these losses in measurements helps to validate and improve contrail parameterizations used to estimate the clima…
Contrail Formation: Analysis of Sublimation Mechanisms
2018
We study losses of ice crystals in a persistent, soot-rich contra i l in the wake behind a medium-sized aircraft at cru i se. Constrain i n g a model covering ice nucleation, growth, and subl i m a t i o n phases with a n aircraft data set, we track the subl i m a t i o n history over two minutes of cont r a i l age and rela t e ice crystal numbers to the number of soot particles emitted by th e aircraft engines.
Soot-exposed mononuclear cells increase inflammatory cytokine mRNA expression and protein secretion in cocultured bronchial epithelial cells.
2000
<i>Background:</i> Soot particles are air pollutants capable of inducing airway and lung parenchymal injury. Mononuclear and bronchial epithelial cells are central to the maintenance of homeostasis and inflammation in the airways. <i>Objectives:</i> The aim of this study was to evaluate the contribution of mononuclear cells to the release of inflammatory mediators by bronchial epithelial cells. <i>Methods:</i> To model the in vivo situation, an in vitro system of cocultured blood monocytes and BEAS-2B cells was established in a transwell system. Blood monocytes were exposed to soot particles (FR 101) at concentrations of up to 100 μg/10<sup>6</su…
Chemie von Aerosolen
2007
Atmospharische Aerosolpartikel sind keine chemisch inerten Teilchen, deren Bildungsmechanismen, Verweildauer oder Funktion in der Atmosphare lediglich von mechanischen oder physikalischen Prozessen abhangen. Sowohl bei der Bildung von Aerosolpartikeln als auch im Verlauf ihres Verbleibs in der Atmosphare spielen chemische Reaktionen eine wesentliche Rolle. Chemische Reaktionen laufen an der Oberflache und im Inneren von Aerosolpartikeln ab und konnen sowohl die atmospharische Gasphasenchemie beeinflussen, z.B. indem sie sowohl als Reaktionsmedium fur ansonsten langsam verlaufende Gasphasenreaktionen dienen, als auch die Eigenschaften der Partikel, beispielsweise ihre Funktion als Kondensati…