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Laboratory Assessment of the Mobility of Water-Dispersed Engineered Nanoparticles in a Red Soil (Ultisol)
Citation:
Wang, D., C. Su, W. Zhang, X. Hao, L. Cang, Y. Wang, AND D. Zhou. Laboratory Assessment of the Mobility of Water-Dispersed Engineered Nanoparticles in a Red Soil (Ultisol). JOURNAL OF HYDROLOGY. Elsevier Science Ltd, New York, NY, 519(Part B):1677-1687, (2014).
Impact/Purpose:
Submitting to Journal of Hydrology.
Description:
Soils are major sinks of engineered nanoparticles (ENPs) as results of land applications of sewage sludge, accidental spills, or deliberate applications of ENPs (e.g., nano-pesticides). In this study, the transport behaviors of four widely used ENPs (titanium dioxide [TiO2], buckminsterfullerene [C60], single-walled carbon nanotube [SWNT], and elemental silver [Ag0]) were investigated in water-saturated columns packed with either a quartz sand, a red soil (Ultisol), or sand/soil mixtures with soil mass fraction (λ) from 0 to 100% at slightly acidic solution pH (4.0–5.0). The mobility of tested ENPs decreased significantly with increasing λ, which was attributed to increased surface area and/or retention sites imparted by iron oxides, clay minerals, and organic matter in the red soil. Breakthrough curves of all ENPs exhibited blocking effects (decreasing deposition rate over time) and were well-described using an unfavorable and favorable, two-site kinetic attachment model accounting for random sequential adsorption on the favorable site. Modeled maximum retention capacity and first-order attachment rate coefficient on the favorable site both increased linearly with increasing λ, suggesting that transport parameters of ENPs in natural soils may be accurately extrapolated from transport parameters in the sand/soil mixtures. Overall, our study highlights that the average hydrodynamic diameter of ENPs is the dominant physicochemical property controlling their mobility in the Ultisol.
