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Experimental and Numerical Investigations of Silver Nanoparticle Transport under Variable Flow and Ionic Strength in Soil
journal contribution
posted on 2017-02-08, 15:20 authored by Joanna Makselon, Dan Zhou, Irina Engelhardt, Diederik Jacques, Erwin KlumppUnsaturated
column experiments were conducted with an undisturbed
loamy sand soil to investigate the influence of flow interruption
(FI) and ionic strength (IS) on the transport and retention of surfactant-stabilized
silver nanoparticles (AgNP) and the results were compared to those
obtained under continuous flow conditions. AgNP concentrations for
breakthrough curves (BTCs) and retention profiles (RPs) were analyzed
by ICP-MS. Experimental results were simulated by the numerical code
HP1 (Hydrus-PhreeqC) with the DLVO theory, extended colloid filtration
theory and colloid release model. BTCs of AgNP showed a dramatic drop
after FI compared to continuous flow conditions. Evaporation increased
due to FI, resulting in increased electrical conductivity of the soil
solution, which led to a totally reduced mobility of AgNP. A reduction
of IS after FI enhanced AgNP mobility slightly. Here the strongly
increased Al and Fe concentration in the effluent suggested that soil
colloids facilitated the release of AgNP (cotransport). The numerical
model reproduced the measured AgNP BTCs and indicated that attachment
to the air–water interface (AWI) occurring during FI was the
key process for AgNP retention.