title: Distinguishable transport behavior of zinc oxide nanoparticles in silica sand and soil columns.
abstract: As part of ongoing risk assessments of ZnO nanoparticles (nZnO) in the natural environment, transport behaviors of nZnO in soil need investigation. This work comparatively studied the transport and retention behavior of nZnO in silica sand versus soil, where the effect of input concentration (C₀=34~430 mgL(-1)) and ionic strength (IS=1~50 mM) were investigated. In silica sand, nZnO were highly mobile, especially at low C₀ and the efflux of nZnO generally decreased with increasing C₀ at all tested IS. Conversely, at low C₀, n ZnO were almost entirely immobile in soil and the efflux of nZnO increased with C₀ at all tested IS. In both media, the retention profiles (RPs) were generally hyper-exponentially shaped suggesting nZnO easily deposited near the column inlet. As indicated by DLVO calculations, previously deposited nZnO on the silica sand surface acted as new deposition sites due to the lower energy barrier (Φmax) between nZnO-nZnO than between nZnO-silica sand. However, previously deposited nZnO in soil could enhance Φmax between the soil surface and nZnO which resulted in unfavorable sites for nZnO deposition. The two-site kinetic attachment model provided good descriptions for the breakthrough curves of nZnO. Detachment was more significant than attachment in silica sand (k₁d>k₁a), whereas soil surface attachment of nZnO were strong and irreversible (k₁a>k₁d). The straining interaction parameter (k₂str) increased with increasing C0 in silica sand, but decreased with C0 in soil. Such differences were mainly responsible for the various transport behaviors of nZnO in silica sand and soil.
authors.affiliation: School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, P. R. China.
authors.forename: Peide
authors.initials: P
authors.lastname: Sun
authors.affiliation: School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, P. R. China.
authors.forename: Altantuya
authors.initials: A
authors.lastname: Shijirbaatar
authors.affiliation: School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, P. R. China. Electronic address: rceesfangjing@126.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Fang
authors.affiliation: Environmental Contaminants Group, Mawson Institute, University of South Australia, Mawson Lakes, South Australia SA 5095, Australia.
authors.forename: Gary
authors.initials: G
authors.lastname: Owens
authors.affiliation: Department of Environmental Science, Zhejiang University, Hangzhou 310058, P. R. China.
authors.forename: Daohui
authors.initials: D
authors.lastname: Lin
authors.affiliation: School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012, P. R. China.
authors.forename: Keke
authors.initials: K
authors.lastname: Zhang
mesh_terms: D007700:Kinetics; D008956:Models, Chemical; D053758:Nanoparticles / Q000737:chemistry*; D009994:Osmolar Concentration; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D012987:Soil; D012822:Silicon Dioxide; D015034:Zinc Oxide
keywords: ZnO nanoparticles; concentration; modeling; silica sand; soil; transport