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Christoph Neukum - One of the best experts on this subject based on the ideXlab platform.
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Transport and deposition of stabilized engineered silver nanoparticles in water saturated Loamy Sand and silty loam.
The Science of the total environment, 2014Co-Authors: Anika Braun, Erwin Klumpp, Rafig Azzam, Christoph NeukumAbstract:It is considered inevitable that the increasing production and application of engineered nanoparticles will lead to their release into the environment. However, the behavior of these materials under environmentally relevant conditions is still only poorly understood. In this study the transport and deposition behavior of engineered surfactant stabilized silver nanoparticles (AgNPs) in water saturated porous media was investigated in transport experiments with glass beads as reference porous medium and in two natural soils under various hydrodynamic and hydrochemical conditions. The transport and retention processes of AgNPs in the porous media were elucidated by inverse modeling and possible particle size changes occurring during the transport through the soil matrix were analyzed with flow field-flow fractionation (FlFFF). A high mobility of AgNPs was observed in Loamy Sand under low ionic strength (IS) conditions and at high flow rates. The transport was inhibited at low flow rates, at higher IS, in the presence of divalent cations and in a more complex, fine-grained silty loam. The slight decrease of the mean particle size of the AgNPs in almost all experiments indicates size selective filtration processes and enables the exclusion of homoaggregation processes.
C.e. Heijnen - One of the best experts on this subject based on the ideXlab platform.
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Metabolic activity and population dynamics of rhizobia introduced into unamended and bentonite-amended Loamy Sand.
Applied and environmental microbiology, 1993Co-Authors: C.e. Heijnen, S. L. G. E. Burgers, J.a. Van VeenAbstract:Respiration measurements showed that the cumulative amount of CO2 respired by rhizobia introduced into sterile bentonite-amended Loamy Sand was significantly higher than it was in unamended Loamy Sand. The maintenance respiration of rhizobial cells was not influenced by the presence of bentonite clay. Carbon was used more efficiently during growth in bentonite-amended than in unamended Loamy Sand. The presence of bentonite clay increased the growth rate of rhizobia introduced into sterile soil. Survival studies performed in nonsterile bentonite-amended Loamy Sand showed that the use of high (1010 cells per g of dry soil) rather than lower (104 to 107 cells per g of dry soil) inoculum densities increased the final survival levels of introduced rhizobia. In unamended Loamy Sand, the application of 1010 or 107 cells per g of dry soil resulted in similar final survival levels. Pore shape and the continuity of the water-filled pore system were suggested to largely determine the colonization rate of protective microhabitats.
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Micro-morphological studies on clay-amended and unamended Loamy Sand, relating survival of introduced bacteria and soil structure
Geoderma, 1993Co-Authors: C.e. Heijnen, Claire Chenu, M. RobertAbstract:Abstract With the use of Cryo Scanning Electron Microscopy (SEM performed at low temperatures) the microstructure of clay- (bentonite and kaolinite) amended and unamended Loamy Sand was studied. A wide range of pore sizes could be recognized in all three treatments, but pore size distributions clearly differed between the soil types. The bentonite clay was present as a very porous matrix, containing pores with an average maximum length of ∼ 3 μm, and an average minimum width of ∼ 2 μm. Pores of similar sizes were also present in kaolinite- and unamended Loamy Sand, but they were much less frequent. Previous results, suggesting that the protective effects of bentonite clay on the survival of introduced bacteria in soil could be caused by an increase in the number of pores with an equivalent neck diameter
Nathalie Tufenkji - One of the best experts on this subject based on the ideXlab platform.
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Reduced transport potential of a palladium-doped zero valent iron nanoparticle in a water saturated Loamy Sand
Water research, 2015Co-Authors: M. Basnet, Caroline Di Tommaso, Subhasis Ghoshal, Nathalie TufenkjiAbstract:Direct in situ injection of palladium-doped nanosized zero valent iron (Pd-NZVI) particles can contribute to remediation of various environmental contaminants. A major challenge encountered is rapid aggregation of Pd-NZVI and hence very limited mobility. To reduce aggregation and concurrently improve particle mobility, the surface of bare Pd-NZVI can be modified with stabilizing surface modifiers. Selected surface-modified Pd-NZVI has shown dramatically improved stability and transport. However, little is known regarding the effects of aquifer grain geochemical heterogeneity on the transport and deposition behavior of surface-modified Pd-NZVI. Herein, the mobility of surface stabilized Pd-NZVI in two granular matrices representative of model ground water environments (quartz Sand and Loamy Sand) was assessed over a wide range of environmentally relevant ionic strengths (IS). Carboxymethyl cellulose (CMC), soybean flour and rhamnolipid biosurfactant were used as Pd-NZVI surface modifiers. Our results show that, both in quartz Sand and Loamy Sand, an increase in solution IS results in reduced Pd-NZVI transport. Moreover, at a given water chemistry, Pd-NZVI transport is notably attenuated in Loamy Sand implying that geochemical heterogeneity associated with Loamy Sand is a key factor influencing Pd-NZVI transport potential. Experiments conducted at a higher Pd-NZVI particle concentration, to be more representative of field conditions, show that rhamnolipid and CMC are effective stabilizing agents even when 1 g/L Pd-NZVI is injected into quartz Sand. Overall, this study emphasizes the extent to which variation in groundwater chemistry, coupled with changes in aquifer geochemistry, could dramatically alter the transport potential of Pd-NZVI in the subsurface environment.
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Mobility of Functionalized Quantum Dots and a Model Polystyrene Nanoparticle in Saturated Quartz Sand and Loamy Sand
Environmental science & technology, 2012Co-Authors: Ivan R. Quevedo, Nathalie TufenkjiAbstract:Quantum dots (QDs) are one example of engineered nanoparticles (ENPs) with demonstrated toxic effects. Yet, little is known about the behavior of QDs in the natural environment. This study assessed the transport of two commercial carboxylated QDs (CdTe and CdSe) and carboxylated polystyrene latex (nPL) as a model nanoparticle using saturated laboratory-scale columns. The influence of solution ionic strength (IS) and cation type (K+ or Ca2+) on the transport potential of these ENPs was examined in two granular matrices – quartz Sand and Loamy Sand. The retention of all three particles was generally low in the quartz Sand columns within the range of studied IS (0.1–100 mM) for the monovalent salt (KCl). In contrast, the retention of the three ENPs in the quartz Sand was significant in the presence of 10 mM Ca2+. Moreover, ENP attachment efficiencies (α) were enhanced by at least 1 order of magnitude in columns packed with Loamy Sand (for IS between 0.1–10 mM KCl). Although all three ENPs used here are carbo...
Anika Braun - One of the best experts on this subject based on the ideXlab platform.
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Transport and deposition of stabilized engineered silver nanoparticles in water saturated Loamy Sand and silty loam.
The Science of the total environment, 2014Co-Authors: Anika Braun, Erwin Klumpp, Rafig Azzam, Christoph NeukumAbstract:It is considered inevitable that the increasing production and application of engineered nanoparticles will lead to their release into the environment. However, the behavior of these materials under environmentally relevant conditions is still only poorly understood. In this study the transport and deposition behavior of engineered surfactant stabilized silver nanoparticles (AgNPs) in water saturated porous media was investigated in transport experiments with glass beads as reference porous medium and in two natural soils under various hydrodynamic and hydrochemical conditions. The transport and retention processes of AgNPs in the porous media were elucidated by inverse modeling and possible particle size changes occurring during the transport through the soil matrix were analyzed with flow field-flow fractionation (FlFFF). A high mobility of AgNPs was observed in Loamy Sand under low ionic strength (IS) conditions and at high flow rates. The transport was inhibited at low flow rates, at higher IS, in the presence of divalent cations and in a more complex, fine-grained silty loam. The slight decrease of the mean particle size of the AgNPs in almost all experiments indicates size selective filtration processes and enables the exclusion of homoaggregation processes.
M. Robert - One of the best experts on this subject based on the ideXlab platform.
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Micro-morphological studies on clay-amended and unamended Loamy Sand, relating survival of introduced bacteria and soil structure
Geoderma, 1993Co-Authors: C.e. Heijnen, Claire Chenu, M. RobertAbstract:Abstract With the use of Cryo Scanning Electron Microscopy (SEM performed at low temperatures) the microstructure of clay- (bentonite and kaolinite) amended and unamended Loamy Sand was studied. A wide range of pore sizes could be recognized in all three treatments, but pore size distributions clearly differed between the soil types. The bentonite clay was present as a very porous matrix, containing pores with an average maximum length of ∼ 3 μm, and an average minimum width of ∼ 2 μm. Pores of similar sizes were also present in kaolinite- and unamended Loamy Sand, but they were much less frequent. Previous results, suggesting that the protective effects of bentonite clay on the survival of introduced bacteria in soil could be caused by an increase in the number of pores with an equivalent neck diameter