Effect of dispersion stability on the deposition of citrate-capped silver nanoparticles in natural soils.

Although little is known about the behavior of engineered nanomaterials after exposure to terrestrial areas, recent studies indicate that silver nanoparticles (AgNPs) can perturb the soil environment due to their biocidal and catalytic properties. The fundamental evaluation of the environmental fate of AgNPs would be a significant step toward a comprehensive understanding of the harmful effects of such particles on ecosystems. Therefore, from an eco-toxicological perspective, the estimation of AgNP behavior in soil should be investigated. Among the various environmental characteristics, the deposition of nanoparticles in the soil constitute is a critical step in their migration into surface or groundwater and interaction with organisms, which is determined by the stability of aqueous dispersions in a soil micro-environment. In the present study, we observed the aggregation and deposition of AgNPs to natural soil surfaces by comparing the partitioning of AgNPs in a soil/water interface with that of Ag+ ion. Both AgNPs and Ag+ ion were selectively quantified by means of inductively coupled plasma (ICP) spectrometry and an ion-selective electrode (ISE). We interpreted the partitioning of AgNPs and Ag+ ion using the Freundlich isotherm and the findings indicate that AgNPs with reduced dispersion stability in a soil micro-environment were aggregated and deposited on the surface of natural soil. This study provides a fundamental basis for understanding the deposition of AgNPs, which will enable their accumulation and mobility in a soil environment to be predicted.