Interactions of metal-based engineered nanoparticles with aquatic higher plants: A review of state of current knowledge

Abstract

The rising potential for the release of engineered nanoparticles (ENPs) into aquatic environments requires evaluation of risks in order to protect ecological health. The present review examined knowledge pertaining the interactions of metal-based ENPs with aquatic higher plants, identified information gaps and raised considerations for future research to advance knowledge on the subject. The discussion focused on ENPs' (i) bioaccessibility; (ii) uptake, adsorption, translocation and bioaccumulation, and (iii) their toxicity effects on aquatic higher plants. An information deficit surrounds the uptake of ENPs and associated dynamics because the influence of ENP characteristics and water quality conditions has not been well documented. Dissolution appears to be a key mechanism driving bioaccumulation of ENPs, whereas nanoparticulates often adsorb to plant surfaces with minimal internalisation. However, few reports document the internalisation of ENPs by plants, thus the role of nanoparticulates' internalisation in bioaccumulation and toxicity remain unclear, requiring further investigation. The toxicities of metal-based ENPs have mainly been associated with dissolution as a predominant mechanism, although nano toxicity has also been reported. To advance knowledge in this domain, future investigations need to integrate the influence of ENPs' characteristics and water physico-chemical parameters, as their interplay determines ENPs' bioaccessibility and influences their risk to health of aquatic higher plants. Furthermore, harmonisation of test protocols is recommended for fast tracking the generation of comparable data.