Long-Term Toxicity and Uptake of Silver Nanomaterials to Relevant Plant Species

Abstract

Over the past decade, the use of silver nanomaterials has grown significantly, predominantly due to the favorable properties that they can impart upon new and existing products (e.g. effects include antimicrobial, optical, electronic). However, due to the increased use, concerns have arisen over increased silver nanomaterial presence in the environment and their potential toxicological impacts to various organisms, especially to agricultural plants. To investigate an aspect of these concerns, we performed a study to analyze the long-term impact of differently shaped silver nanomaterials on the growth of the plant species Lolium multiflorum (ryegrass) in a soil medium over 28 days. An uptake study was developed in collaboration with researchers at Virginia Tech using Raman-based particle tracking to determine the location of the silver material within plant roots. While short-term studies in aqueous media with these plant species in earlier literature showed significant growth inhibition of both roots and shoots, this was not observed in the long-term soil study. Like short-term studies, the shoots in soil showed greater toxicological differences and a more consistent trend of growth inhibition than roots. However, the long-term soil study also reflected that significant toxicity differences were inconsistent between roots and shoots based on both the silver nanomaterial shape and dose, showing results of both inhibited and enhanced growth. The Raman-based particle tracking was inconclusive and yielded fluorescent bands with weak intensity of the silver materials, so localization within the roots could not be accurately determined. While shape-dependence of silver nanomaterials still requires significant research in both short- and long-term studies of various plants, this research shows silver nanomaterials interact differently in a soil medium compared to an aqueous medium.