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| Titel |
Nanoparticles at the interface between atmosphere and hydrosphere |
| VerfasserIn |
T. Baumann, S. Huckele, R. Niessner |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064860
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| Zusammenfassung |
| In the light of increasing use of engineered nanoparticles and reports of reports of adverse
effects of nanoparticles on aquatic ecosystems and possible health issues, assessment
of the transport of nanoparticles is of high importance. In this study we address
the transport of airborne nanoparticles through the unsaturated zone in an urban
environment.
Aquifers and soils are the primary filter systems to remove engineered nanoparticles.
These effects are used e.g., for bank filtration. Recent flooding events, on the other hand,
show the limited capacity of this filter. While engineered nanoparticles are tailored to specific
applications, one has to assume that they nonetheless interact with dissolved organic matter
(DOM) present in surface water and top soil in larger quantities. A coating with DOM has a
stabilizing effect on most nanoparticles. Thus, a transport of engineered nanoparticles
through the soil seems likely.
A monitoring program was performed at the Munich vadose zone field laboratory, a shaft
reaching from the top soil to the groundwater table at 10 m below the ground surface. Wet
and dry deposition were collected and analyzed to assess the input function. Seepage water
was collected and analyzed in nine depths to assess the transport of nanoparticles. For all
samples the size distribution and the elemental composition of the particles was measured
using ultrafiltration, AF4, and ICP/MS.
Nanoparticles deposited during dry periods may accumulate on the plant leaves and
on the top soil. Here a first interaction with organic matter occurs. Heavy rainfall
after a dry period will mobilize the nanoparticles. Through cracks in the top soil,
preferential flow can transport the surface modified particles to the groundwater.
During winter, particles are deposited on the snow cover. Sublimation of snow may
lead to relatively high concentrations in the remaining snow. Cracks in the top soil
caused by freezing ease the transport of nanoparticles together with the melting
snow. During winter, however, aging and masking of the nanoparticles should be
different.
Laboratory experiments in undisturbed soil columns indicate that the transport of
unaltered, dispersed nanoparticles (TiO2, SiO2) is very limited. Filtration efficiency is on the
order of 98.5 % for a sand column which was 10 cm long. This is in contradiction to field
observations and underlines the importance of preferential flow and masking for nanoparticle
transport. |
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