Explicit Simulations of Parameters Impacting Nanoparticles Transport in Saturated Soils: Monte Carlo Approach

The production and worldwide market of manufactured nanoparticles (NPs) are steadily growing past years. They open new opportunities for many industrial applications such as agriculture, pharmaceutical components or even everyday products. Proportionally, release of NPs in the environment is increasing drastically: Release in environment can be intentional (e.g., fertilizers, nanopesticides) or non-intentional due to products’ alteration, degradation, recycling etc. Then, concerns on the environmental fate and toxicity of NPs are rising. All environmental compartments are concerned: air, water and soil. Soil is a critical environmental compartment due to the potential NPs ecotoxicity on soil organisms, groundwater contamination, etc. Understanding NPs transport processes in soils is a complex topic owing to the number of influencing factors and interactions: Computer simulations can help in addressing this issue. To get further insight into mechanisms and processes controlling NPs transport in soils, such as NPs and soil matrix interactions, soil porosity, etc. we present a new and original Monte Carlo approach: Based on an explicit (off lattice) representation of NPs and soil grains, simulations and NPs transport in porous matrices are performed by considering attachment/detachment efficiencies of NPs with soil grains, putting in front the impact of soil porosities. As highlighted by Cornelis et al.1 and Bradford et al.2, specific and detailed interactions between NPs and soils are crucial points to consider. With the explicit representation of soil grains and NPs, we investigate the impact of size exclusion of NPs and aggregates in pores (straining effects), as well as surface affinity of NPs to soil grains/soil surface. The reversibility of NPs adsorption, i.e. NPs detachment, which has been shown experimentally to be a key process, is also considered. All these parameters, including NPs aggregation, are systematically explored and their effect on breakthrough curves investigated. 1-Cornelis, G.; Hund-Rinke, K.; Kuhlbusch, T.; Brink, N. van den; Nickel, C. Fate and Bioavailability of Engineered Nanoparticles in Soils: A Review. Critical Reviews in Environmental Science and Technology 2014, 44 (24), 2720–2764. 2-Bradford, S. A.; Simunek, J.; Bettahar, M.; van Genuchten, M. T.; Yates, S. R. Modeling Colloid Attachment, Straining, and Exclusion in Saturated Porous Media. Environ. Sci. Technol. 2003, 37 (10), 2242–2250.