Electron Microscopic Analyses On Nanoparticles in Biosolid Products.

With the dramatic growth of nanotechnology, the production and use of engineered nanoparticles has been rapidly increasing for the past few years. Engineered nanoparticles that are produced and/or incorporated into consumer products will enter the environment after and/or during the term of use, which in turn has raised concerns about their potentially adverse impact on the environment. In order to predict the environmental impact of engineered nanoparticles, their associations and characterization within environmental matrices should be determined, yet very few field-scale studies are available to date. Lack of such studies is in part due to technical challenges in discovering and monitoring the environmental occurrence of engineered and incidental nanoparticles present at trace levels. An excellent opportunity leading towards a better understanding of engineered and incidental nanoparticles in the natural environment is the study of residual biosolid materials from wastewater treatment plants because these materials are often used in agricultural soil amendments. Engineered nanoparticles that are in the wastewater stream entering the plant, or nanoparticles that formed as a result of the wastewater treatment process, may be incorporated into this biosolid matrix through aggregation and/or particle sorption reactions and be concentrated over time. In this study, we report the presence of nano-sized metal oxide and sulfide nanoparticles in biosolid samples identified and characterized by analytical high resolution transmission electron microscopy. Their size, morphology, elemental compositions, and degree of crystallinity and aggregation are studied in detail. The results of our work clearly show a great degree of nanoparticle heterogeneity and complexity in biosolid products. We believe this study will help us to evaluate further risks when nanoparticle-bearing biosolid products enter the soil environment through agricultural land applications.