The widespread use of nanoparticles (NPs) in consumer goods could put these materials in the waste stream, potentially to soil and sediments. However, little is known about their transport in water and soils. In this study, transport behavior and attachment of ZnO NPs in soil components were studied through column experiments and sequential extraction, respectively. Bare and sodium citrate coated ZnO NP suspended in CaCl2 solutions at different ionic strengths, were passed through glass columns packed with sandy soils (SS) and sandy loam soils (SLS) and the effluents were analyzed by ICP-OES. The distribution of Zn in soil particles was studied by electron microprobe (EMP). Results showed that 99% of Zn/ZnO NPs was retained in SLS and 68% ~ 99% was retained in SS, for ionic strengths varying from 0 to 1 mM. Travel distances (cm) for bare ZnO NPs in SS and SLS were 19.2 and 5.3, respectively, while for coated NPs the distances were 21.4 and 6.9 cm, respectively. The surface coating reduced deposition rates from 0.73 to 0.65 and from 2.28 to 1.74 for SS and SLS, respectively. In both soils the amounts of uncoated NPs in the exchangeable fraction were less than 1%; however, 30% of coated NPs remained in the exchangeable fraction. EMP mapping showed that Zn/ZnO NPs associated with silica and aluminum, which are indicators of soil clay minerals. Long term observations are still needed to evaluate the bioavailability to plants of Zn released from coated and uncoated ZnO NPs.
Evaluation of the long-term antibiofilm effect of a surface coating with dual functionality of antibacterial and protein-repellent effects
