<i>In Situ</i> Measurement of CuO and Cu(OH)<sub>2</sub> Nanoparticle Dissolution Rates in Quiescent Freshwater Mesocosms

Recent studies have characterized copper-based nanoparticles (CBNPs) as relatively insoluble, raising potential persistence, accumulation, and toxicological concerns about their long-term application as agricultural pesticides. The dissolution rates of two CBNPs were measured in natural and artificial waters under both saturated and unsaturated conditions with respect to CuO<sub>(s)</sub> (total Cu, <1 mg/kg). Kocide 3000, an agricultural pesticide formulation with nanoscale Cu­(OH)<sub>2</sub> particles, rapidly dissolved with an experimental half-life of <8 h in natural water. Copper oxide nanoparticles were longer-lived, with an experimental half-life of 73 h in natural water. In contrast to prior reports of CuONP dissolution, our results suggest that even in moderately alkaline waters, CuO and Cu­(OH)<sub>2</sub> NPs may persist as particles for days to weeks under quiescent conditions in a freshwater environment.