Monitoring nanoparticle progression and fate in the soil using spectral induced polarization

The fate and transport of metallic nanoparticles (NPs) in the soil has been a major concern over the last decade due to the increasing use of NPs in many industries and their appearance in the environment. However, the study of NP fate and transport traditionally relies on intensive sample collection ana chemical analysis. In this work we use spectral induced polarization (SIP) to monitor the transport of metallic NPs in soils. In SIP, an alternating current in wide range of frequencies is injected, and the phase and amplitude difference between the injected and induced potential are measured. Our experimental setup involves flow-through columns packed with different types of soil, through which a suspension of NPs with different ionic compositions is passed. Electrical potentials are recorded at three locations along the column. The analyzed SIP measurements allow not only non-invasive, non-destructive monitoring of the NP’s progression through the soil but also deduction of the NPs’ fate and transport patterns through combination with elemental analysis. The sensitivity of SIP to the presence of the NPs is high and was found to be correlated to their progression in the soil even in low and environmentally relevant NP concentrations (<5mg/L).  Our results indicate that SIP is a promising method for monitoring of NPs in the soil and with further research may serve as an easy and efficient alternative to the standard methods that involve extensive water and soil sampling.