The impact of wastewater-borne titanium dioxide nanoparticles on metal uptake by potato plants receiving synthetic wastewater irrigation

Increasingly a source of water for irrigation, wastewater (WW) poses risks to crops due to potential contaminants. It can harbor metals and organic contaminants known to impact harmfully on human and environmental health. Nanoparticles (NPs) detected in wastewater raises questions about their possible interactions with co-contaminants, and their effects on soil-water systems (e.g., WW-irrigated agriculture). Titanium dioxide nanoparticles (TiO2 NPs), commonly found in industrial and consumer products and observed in wastewater, could potentially influence the mobility of soil contaminants and metal uptake by crops. Accordingly, we conducted a two-year (2017 and 2018) field lysimeter study to investigate the impacts of titanium dioxide nanoparticles on the mobility of metals (Cd, Cr, Cu, Fe, Pb and Zn) and their uptake by potato plants (Solanum tuberosum L. cv. ‘Russet Burbank’). The potatoes, grown in sandy soil under controlled conditions, were irrigated with synthetic wastewater (WW), or with wastewater + titanium dioxide nanoparticles (WW+TiO2 NPs). At harvest, the potato tubers, plant parts and soil samples were analyzed for their metal concentrations. The presence of 1 mg L−1 TiO2 NPs in the irrigation wastewater significantly reduced the uptake of cadmium, copper and zinc by the potato flesh, skin and roots in both treatment years (p ≤ 0.05), but did not significantly change the uptake of chromium, lead and iron into any plant parts. We conclude therefore that titanium dioxide nanoparticles in the wastewater appeared to reduce the bioavailability of cadmium, copper and zinc in the soil.