Remobilization of Ag NP retained in sediments of an artificial riverbank filtration system

Abstract

Nanoparticles (NP) can enter aquatic environments via various pathways such as industrial or municipalwaste water or surface run-off from farmland. Once they enter aquatic systems they may impair the quality of the environment and drinking water reservoirs. Riverbank filtration systems can prevent contaminants from reaching such resources. The retention capacity of riverbank filtration systems and the reversibility of NP immobilization are therefore important aspects for risk assessment.<BR>To simulate a riverbank filtration scenario, Ag NP aged in different media (soil solution, river water, Millipore water) were applied to a water-saturated column (length 1.5 m) filled with medium quartz sand.All types of particles were mainly retained in the first 10 cm of the sediment column, ranging from 50 % for soil-aged particles to approximately 100 % for particles aged in Millipore and river water. However, it is unclear under which conditions the retained Ag NP can be remobilized. Therefore, the aim of our study is to determine the remobilization of the NP and the physico-chemical factors (i.e. shear forces and hydrochemical properties) controlling this process. <BR>In batch experiments, the sediment containing NP will be exposed to varying shear forces (i.e. ultrasonic treatment of 1.5 W/cṃand horizontal shaking of 1 h up to 7 days) in the presence of dissolved organic matter and reduced ionic strength. The total amount of remobilized silver in the supernatantwill be measured by ICP-MS following acid microwave digestion. The size and composition of mobilized homo-and heteroaggregates will be analysed by HDC-ICP-MS.<BR>First results show that strong shear forces induced by ultrasonic treatment lead to highest remobilization of the retained Ag NP of up to 60 % for particles aged in river water. One hour of shaking remobilizes 15-20 % of the Ag NP in the sediment. Further results of the remobilization experiments will be presented.<P>In: Degenkolb, L; Klitzke, S Metreveli, G; Kumahor, S; Schaumann, G; Baumann, T; Vogel, HJ; Kaupenjohann, M; Lang, F (2016):Remobilization of Ag NP retained in sediments of an artificial riverbank filtration system. In: Abstract Booklet of the InternationalWorkshop "Nanoparticles in Soils and Waters: Fate, Transport and Effects", p. 32, 20 th - 21 st October, Landau in der Pfalz<BR>