Investigating the Fate and Uptake of Copper Oxide Nanoparticles in the Environment.

Duckweed, L. (Spirodela) punctata (G. Mey.) Les & D. J. Crawford, was used as a model organism to investigate potential uptake and growth effects of CuO nano-particles (CuO-NP in aquatic plants. The size and surface charge of CuO-NPs were characterized by transmission electron microscopy (TEM), electrophoretic mobility, and dynamic light scattering (DLS). CuO-NP dissolution was characterized at varying pH and solute concentrations. Treatments for the growth study included controls, 1 mg L^-1 CuO nano-particles (CuO-NP), 0.2 mg L^-1 copper chloride (CuCl₂), and 0.6 mg L^-1 CuCl₂. Additional experiments were performed to evaluate the effect of ligands, Elliot soil humic acid (HA) and Ethylenediaminetetraacetic acid (EDTA), on duckweed health in the presence of CuO-NP and CuCl₂. A 50% growth inhibition was measured for both the 0.6 mg L⁻¹ CuCl^­₂ treatment and for the 1.0 mg L⁻¹ CuO-NP that released only 0.16 mg L⁻¹ soluble Cu into the growth medium. On a soluble Cu basis, 1.0 mg L^-1 CuO-NP was found to inhibit duckweed growth significantly more than comparable soluble Cu concentrations from CuCl₂. The inhibitory growth effects of CuO-NP are expected to be reduced in the presence of HA and EDTA due to the chelation of soluble Cu.