Nanomaterial Probes in the Environment: Gold Nanoparticle Soil Retention and Environmental Stability as a Function of Surface Chemistry

The increased prevalence of functionalized nanomaterials in a range of applications will inevitably lead to nanoparticle contamination of soil and groundwater. Here, we investigate how gold nanoparticles’ (AuNPs) shape and surface chemistry influence their retention in soil columns and stability in simulated groundwater. When AuNPs are eluted from soil columns with simulated groundwater, spherical particles are more strongly retained in the soil than the rod-shaped AuNPs, regardless of the surface chemistry (as determined by ICP-OES). In a deionized water eluent, however, the same AuNPs showed a retention profile dependent upon surface chemistry (positively charged AuNPs are strongly retained by soil, while negatively charged particles are quickly eluted). This change in retention behavior suggests that the spherical AuNPs may undergo a physiochemical transformation (likely aggregation) during the elution process which reduces their mobility. AuNP stability against aggregation in simulated groundwater was...