Neonicotinoid Insecticide Adsorption on Montmorillonite Clay Sheets

Abstract

Neonicotinoid pesticide use over the last 30 years has been shown to have negative effects on honeybee and bumble bee populations, calling into question the fate and transport of these chemicals in the environment. Though there has been research conducted into the sorption of neonicotinoids to soil, there has been little studied on the effect of smectite clays on sorption. With the emerging prevalence of smectite clays to sorption of polar organic contaminants, this study seeks to understand the sorption capabilities of smectite clays on polar neonicotinoids. The methodology for this is twofold. Batch sorption experiments were conducted for clothianidin sorption to Ca-montmorillonite, which showed favorable sorption to the smectite mineral. This favorability was corroborated through molecular dynamics simulations making use of a metadynamics method. These simulations were also used to analyze adsorption sites and showed a strong preference by clothianidin for the clay interlayer region as well as top and bottom clay surfaces. Together, these results show a strong affinity for clothianidin sorption to Ca-montmorillonite and suggest that smectite clays should be studied further for their effects on the sorption of neonicotinoids in the environment.