Uptake and accumulation of silver nanoparticles by wheat (Triticum aestivum L.)

Abstract

The rapid product development and intense production, consumer use, and disposal of engineered nanomaterials like silver nanoparticles (Ag NPs) are leading to increased levels of Ag NP-containing waste. This waste can enter natural ecosystems by direct release or when biosolids from sewage sludge are applied on agricultural land as fertilisers. Silver NPs display physicochemical properties that differ from their bulk materials and their physical and chemical interactions with the environment are often poorly understood. As such, there is an urgent need for exposure studies of Ag NPs that can be used for comprehensive risk assessments. Recent research shows that Ag from Ag NPs enters roots through vascular tissues and is translocated to the stem, leaves and fruit of plants. Previous studies have reported that Ag from Ag NPs can have an impact on the cell structures of plants and their physiological and biochemical functions. This thesis focusses on the uptake, translocation and accumulation of Ag from Ag NPs and their ready soluble form (AgNO3) by wheat (Triticum aestivum L.) and their effects on a biological level in a series of exposures. In detail, the work presented in this thesis aims to: (i) provide quantitative data on the uptake and accumulation of Ag from Ag NPs and AgNO3 on wheat in an environmentally relevant exposure; (ii) focus on the effects of Ag on a biological level in an environmentally relevant Ag NP and AgNO3 exposure; (iii) delve into the uptake of Ag from Ag NPs, Ag2S NPs and AgNO3 in a multimedia exposure and into the use of hydroponic systems as a substitute for soil testing; and (iv) identify the mechanisms of Ag uptake from Ag NPs and AgNO3 under water stress through split root experiments.