Charge distributions and coagulation of radioactive aerosols

Clement, C.F.; Clément, Rémi; Harrison, Giles

doi:10.1016/0021-8502(95)00525-0

Cited by 43 publications

(38 citation statements)

References 13 publications

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“…In principle, aggregation of smaller particles might shift the size distribution towards larger sizes and in our context it may be relevant that aggregation of aerosol particles can be enhanced by charging under some circumstances (Clement et al, 1995). It is also possible that the settling is counteracted to some extent by the electric field itself, provided that gravitational separation of positively and negatively charged particles is taking place, leading to the emergence of a dipole.…”

Section: Discussionmentioning

confidence: 95%

Alignment of atmospheric mineral dust due to electric field

et al. 2007

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Abstract. Optical polarimetry observations on La Palma, Canary Islands, during a Saharan dust episode show dichroic extinction indicating the presence of vertically aligned particles in the atmosphere. Modelling of the extinction together with particle orientation indicates that the alignment could have been due to an electric field of the order of 2 kV/m. Two alternative mechanisms for the origin of the field are examined: the effect of reduced atmospheric conductivity and charging of the dust layer, the latter effect being a more likely candidate. It is concluded that partial alignment may be a common feature of Saharan dust layers. The modelling indicates that the alignment can significantly alter dust optical depth. This "Venetian blind effect" may have decreased optical thickness in the vertical direction by as much as 10% for the case reported here. It is also possible that the alignment and the electric field modify dust transport.

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Section: Discussionmentioning

confidence: 95%

Alignment of atmospheric mineral dust due to electric field

et al. 2007

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“…For a monodisperse collection of particles (i.e., uniform in shape, size, and composition), the rate of aggregation between particles with like charges is lower than that for neutral particles, while the rate is enhanced for particles with unlike charges. The effect of a charge distribution on particles frequently leads to more complicated aggregation behaviour (Clement et al 1995), as the tails of the charge distribution also contribute to the changes in aggregation asymmetrically, favouring enhancement of the coagulation rate. In atmospheric regions of unipolar ions, where multiple aerosol charges occur, this effect would slow the production of larger aerosol particles from smaller particles.…”

Section: Electrical Effects On Aggregationmentioning

confidence: 99%

Electrification of volcanic plumes

2006

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Volcanic lightning, perhaps the most spectacular consequence of the electrification of volcanic plumes, has been implicated in the origin of life on Earth, and may also exist in other planetary atmospheres. Recent years have seen volcanic lightning detection used as part of a portfolio of developing techniques to monitor volcanic eruptions. Remote sensing measurement techniques have been used to monitor volcanic lightning, but surface observations of the atmospheric electric Potential Gradient (PG) and the charge carried on volcanic ash also show that many volcanic plumes, whilst not sufficiently electrified to produce lightning, have detectable electrification exceeding that of their surrounding environment. Electrification has only been observed associated with ash-rich explosive plumes, but there is little evidence that the composition of the ash is critical to its occurrence. Different conceptual theories for charge generation and separation in volcanic plumes have been developed to explain the disparate observations obtained, but the ash fragmentation mechanism appears to be a key parameter. It is unclear which mechanisms or combinations of electrification mechanisms dominate in different circumstances. Electrostatic forces play an important role in modulating the dry fallout of ash from a volcanic plume. Beyond the local electrification of plumes, the higher stratospheric particle concentrations following a large explosive eruption may affect the global atmospheric electrical circuit. It is possible that this might present another, if minor, way by which large volcanic eruptions affect global climate. The direct hazard of volcanic lightning to communities is generally low compared to other aspects of volcanic activity.

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“…Charging has been suggested to reduce particle sedimentation (Ulanowski et al, 2007). On the other hand, if charging enhances coagulation between large and small-sized aerosol (Clement et al, 1995), this could also result in larger particles and shorter residence times. Figure 21 also depicts the values of D max derived from the measured volume size spectra.…”

Section: Ash Mass Concentration Propertiesmentioning

confidence: 99%

Airborne observations of the Eyjafjalla volcano ash cloud over Europe during air space closure in April and May 2010

et al. 2011

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Abstract. Airborne lidar and in-situ measurements of aerosols and trace gases were performed in volcanic ash plumes over Europe between Southern Germany and Iceland with the Falcon aircraft during the eruption period of the Eyjafjalla 1 volcano between 19 April and 18 May 2010. Flight planning and measurement analyses were supported by a refined Meteosat ash product and trajectory model analysis. The volcanic ash plume was observed with lidar directly over the volcano and up to a distance of 2700 km downwind, and up to 120 h plume ages. Aged ash layers were between a few 100 m to 3 km deep, occurred between 1 and 7 km altitude, and were typically 100 to 300 km wide. Particles collected by impactors had diameters up to 20 µm diameter, with size and age dependent composition. Ash mass concentrations were derived from optical particle spectrometers for aCorrespondence to: U. Schumann (ulrich.schumann@dlr.de) 1 Also known as Eyjafjallajökull or Eyjafjöll volcano, http://www.britannica.com/EBchecked/topic/1683937/ Eyjafjallajokull-volcano particle density of 2.6 g cm −3 and various values of the refractive index (RI, real part: 1.59; 3 values for the imaginary part: 0, 0.004 and 0.008). The mass concentrations, effective diameters and related optical properties were compared with ground-based lidar observations. Theoretical considerations of particle sedimentation constrain the particle diameters to those obtained for the lower RI values. The ash mass concentration results have an uncertainty of a factor of two. The maximum ash mass concentration encountered during the 17 flights with 34 ash plume penetrations was below 1 mg m −3 . The Falcon flew in ash clouds up to about 0.8 mg m −3 for a few minutes and in an ash cloud with approximately 0.2 mg m −3 mean-concentration for about one hour without engine damage. The ash plumes were rather dry and correlated with considerable CO and SO 2 increases and O 3 decreases. To first order, ash concentration and SO 2 mixing ratio in the plumes decreased by a factor of two within less than a day. In fresh plumes, the SO 2 and CO concentration increases were correlated with the ash mass concentration. The ash plumes were often visible slantwise as faint dark layers, even for concentrations below 0.1 mg m −3 .Published by Copernicus Publications on behalf of the European Geosciences Union. U. Schumann et al.: Airborne observations of the Eyjafjalla volcano ash cloud over EuropeThe large abundance of volatile Aitken mode particles suggests previous nucleation of sulfuric acid droplets. The effective diameters range between 0.2 and 3 µm with considerable surface and volume contributions from the Aitken and coarse mode aerosol, respectively. The distal ash mass flux on 2 May was of the order of 500 (240-1600) kg s −1 . The volcano induced about 10 (2.5-50) Tg of distal ash mass and about 3 (0.6-23) Tg of SO 2 during the whole eruption period. The results of the Falcon flights were used to support the responsible agencies in their decisions concerning air traffic in the presence of v...

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Charge distributions and coagulation of radioactive aerosols

Cited by 43 publications

References 13 publications

Alignment of atmospheric mineral dust due to electric field

Alignment of atmospheric mineral dust due to electric field

Electrification of volcanic plumes

Airborne observations of the Eyjafjalla volcano ash cloud over Europe during air space closure in April and May 2010

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