Investigation of Nanoparticle Transport Inside Coarse-Grained Geological Media Using Magnetic Resonance Imaging

Quantifying nanoparticle (NP) transport inside saturated porous geological media is imperative for understanding their fate in a range of natural and engineered water systems. While most studies focus upon finer grained systems representative of soils and aquifers, very few examine coarse-grained sy...

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Bibliographic Details
Published in:Environmental science & technology 2012-01, Vol.46 (1), p.360-366
Main Authors: Ramanan, B, Holmes, W. M, Sloan, W. T, Phoenix, V. R
Format: Article
Language:English
Subjects:
Applied sciences
Aquifers
Biological and physicochemical properties of pollutants. Interaction in the soil
Calibration
Drainage
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Environmental Measurements Methods
Exact sciences and technology
Geologic Sediments - chemistry
Groundwaters
Magnetic resonance imaging
Magnetic Resonance Spectroscopy - methods
Models, Chemical
Motion
Nanoparticles
Nanoparticles - chemistry
Natural water pollution
NMR
Nuclear magnetic resonance
Pollution
Pollution, environment geology
Porosity
Quartz - chemistry
Soil and sediments pollution
Soils
Water treatment and pollution
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Summary:Quantifying nanoparticle (NP) transport inside saturated porous geological media is imperative for understanding their fate in a range of natural and engineered water systems. While most studies focus upon finer grained systems representative of soils and aquifers, very few examine coarse-grained systems representative of riverbeds and gravel based sustainable urban drainage systems. In this study, we investigated the potential of magnetic resonance imaging (MRI) to image transport behaviors of nanoparticles (NPs) through a saturated coarse-grained system. MRI successfully imaged the transport of superparamagnetic NPs, inside a porous column composed of quartz gravel using T 2-weighted images. A calibration protocol was then used to convert T 2-weighted images into spatially resolved quantitative concentration maps of NPs at different time intervals. Averaged concentration profiles of NPs clearly illustrates that transport of a positively charged amine-functionalized NP within the column was slower compared to that of a negatively charged carboxyl-functionalized NP, due to electrostatic attraction between positively charged NP and negatively charged quartz grains. Concentration profiles of NPs were then compared with those of a convection-dispersion model to estimate coefficients of dispersivity and retardation. For the amine functionalized NPs (which exhibited inhibited transport), a better model fit was obtained when permanent attachment (deposition) was incorporated into the model as opposed to nonpermanent attachment (retardation). This technology can be used to further explore transport processes of NPs inside coarse-grained porous media, either by using the wide range of commercially available (super)paramagnetically tagged NPs or by using custom-made tagged NPs.
ISSN:0013-936X
1520-5851
DOI:10.1021/es2012726