Limited transport of functionalized multi-walled carbon nanotubes in two natural soils

Column experiments were conducted in undisturbed and in repacked soil columns at water contents close to saturation (85-96%) to investigate the transport and retention of functionalized C-14-labeled multi-walled carbon nanotubes (MWCNT) in two natural soils. Additionally, a field lysimeter experiment was performed to provide long-term information at a larger scale. In all experiments, no breakthrough of MWCNTs was detectable and more than 85% of the applied radioactivity was recovered in the soil profiles. The retention profiles exhibited a hyper-exponential shape with greater retention near the column or lysimeter inlet and were successfully simulated using a numerical model that accounted for depth-dependent retention. In conclusion, results indicated that the soils acted as a strong sink for MWCNTs. Little transport of MWCNTs is therefore likely to occur in the vadose zone, and this implies limited potential for groundwater contamination in the investigated soils. (C) 2013 Elsevier Ltd. All rights reserved.