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Complex conductivity response to silver nanoparticles in partially saturated sand columns
Abdel Aal, G., E. Atekwana, AND D Werkema. Complex conductivity response to silver nanoparticles in partially saturated sand columns. JOURNAL OF APPLIED GEOPHYSICS. Elsevier Science Ltd, New York, NY, 137:73-81, (2017).
The unique physicochemical properties of nanoparticles such as their small size, reactivity, morphology and surface chemistry resulted in their rapid adaptation and use in consumer goods, technical, manufacturing, medicine, industrial, and remediation technologies (e.g., Delay and Frimmel, 2012, Shi et al., 2015). The Woodrow Wilson International Center for Scholars and the Project on Emerging Nanotechnologies recent update of the Nanotechnology Consumer Products Inventory included over 1800 consumer products (Vance et al., 2015).
The increase in the use of nanoscale materials in consumer products has resulted in a growing concern of their potential hazard to ecosystems and public health from their accidental or intentional introduction to the environment. Key environmental, health, and safety research needs include knowledge and methods for their detection, characterization, fate, and transport. Specifically, techniques available for the direct detection and quantification of their fate and transport in the environment are limited. Their small size, high surface area to volume ratio, interfacial, and electrical properties make metallic nanoparticles, such as silver nanoparticles, good targets for detection using electrical geophysical techniques. Here we measured the complex conductivity response to silver nanoparticles in sand columns under varying moisture conditions (0–30%), nanoparticle concentrations (0–10 mg/g), lithology (presence of clay), pore water salinity (0.0275 and 0.1000 S/m), and particle size (35, 90–210 and 1500–2500 nm). Based on the Cole-Cole relaxation models we obtained the chargeability and the time constant. We demonstrate that complex conductivity can detect silver nanoparticles in porous media with the response enhanced by higher concentrations of silver nanoparticles, moisture content, ionic strength, clay content and particle diameter. Quantification of the volumetric silver nanoparticles content in the porous media can also be obtained from complex conductivity parameters based on the strong power law relationships.