GQ10: Groundwater Quality Management in a Rapidly Changing World (Proc. 7th International Groundwater Quality Conference held in Zurich, Switzerland, 13–18 June 2010). IAHS Publ 342, 2011. 50 Manufactured nanoparticle movement in the groundwaters of a redbed sandstone: laboratory experiments and field observations JOHN TELLAM 1 , RICHARD GRESWELL 1 , MICHAEL RILEY 1 & SYED RAHMAN 2 1 School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK j.h.tellam@bham.ac.uk 2 Environmental Sciences, Jahangirnagar University, Dhaka 1342, Bangladesh Abstract Production of manufactured nanoparticles (mNPs) is likely to increase significantly in the near future. To investigate mNP mobility in sandstone groundwaters, column experiments have been completed on intact continental redbed sandstone. SiO 2 mNP breakthrough concentrations decrease as ionic strength increases, with reversibility indicating secondary minimum attachment: a maximum retention capacity is observed. In contrast, initial metal oxide mNP breakthrough concentrations in deionized water gradually fall as clogging occurs, mobility being in the order (Si >) Ti, Sb > Ce, Ag: no detectable breakthrough occurs for artificial groundwater solutions, even after many 100s of pore volumes. These results suggest that most particles have limited mobility, consistent with measured ζ potentials, but that remobilization can occur if conditions change. A small proportion of particles appear to be more mobile, and this is confirmed by the presence of small amounts of mNPs in wellwaters. Key words manufactured nanoparticles; colloids; urban; groundwater INTRODUCTION A significant increase in the production and use of manufactured nanoparticles (mNPs) is likely in the near future (e.g. RS/RAEng, 2004). Increased production will almost inevitably result in discharge to the subsurface, causing groundwater contamination if mNPs are mobile in groundwaters. Although at present it is uncertain what effect each type of mNP has on human health, it could be serious. In addition, mNPs may affect indigenous subsurface bacterial populations (Handy et al., 2008). It is therefore important to determine the fate of mNPs in groundwater systems. To date, most studies have been concerned with artificial media or unconsolidated sediments (e.g. Guzman et al., 2006). Here we report laboratory experiments on intact sandstones, using a range of oxide mNPs. In addition, wellwater samples have been analysed to determine if mNPs already exist in deep groundwaters. LABORATORY EXPERIMENTS Approach Over 40 column experiments were completed using intact redbed continental sandstone. A range of ionic strength, ionic composition, pH, flow rate, and flow direction conditions were investigated. mNP surface charge (as indicated by ζ Copyright © 2011 IAHS Press