The rapidly increasing commercial application of metallic nanoparticles within products will inevitably enhance the amount of NPs being released into soil. Assessment of the impact of metallic... Show moreThe rapidly increasing commercial application of metallic nanoparticles within products will inevitably enhance the amount of NPs being released into soil. Assessment of the impact of metallic nanoparticles (NPs) in soil ecosystems is a necessity for ensuring their safe and sustainable application. In this thesis, we integrated exposure routes and exposure dynamics of NPs to investigate the uptake, translocation and impacts of metallic NPs in plants upon long-term exposure. We furthermore investigated the long-term impacts of NPs on the rhizosphere soil bacterial community and the potential transfer and biomagnification within the lettuce - terrestrial snails food chain. Our results demonstrate that 1) root exposure induced more phytotoxicity than foliar exposure at equal exposure concentrations; 2) the phytotoxicity and accumulation of AgNPs in plants was shape- and size-dependent; 3) nanoparticulate Ag present in AgNPs suspensions that predominantly drive their impacts on green leafy plants; 4) the dissolution of AgNPs in soil is the dominant process influencing Ag uptake and translocation in lettuce; 5) long-term exposure to high concentrations of AgNPs altered the structure and composition of rhizosphere bacterial community; 6) NPs can be transferred from lettuce leaves to snails, as associated with increased potential risks to higher trophic level organisms. Show less
Carnivores are an important component of many ecological systems and they play a vital role in maintaining ecosystem health (Terborgh et al., 1999; Terborgh et al., 2002; Ray et al., 2005). Being... Show moreCarnivores are an important component of many ecological systems and they play a vital role in maintaining ecosystem health (Terborgh et al., 1999; Terborgh et al., 2002; Ray et al., 2005). Being at the top of the food chain, carnivores have important ecological impacts, such as the regulation of mesopredators and prey numbers present in an area (Terborgh et al., 1999). Important cascading trophic effects, caused by population changes of their prey or of sympatric mesopredators, may result when some of these large carnivores are extirpated from ecosystems. Unexpected effects of trophic cascades on various taxa and processes include changes to other vertebrates and herpetofaunal abundance or diversity. It could also have indirect effects and altered disease dynamics; carbon sequestration; modified stream morphology; and crop damage (Ray, 2005). Therefore, promoting tolerance and coexistence with large carnivores is a more crucial societal challenge now than ever before. The removal of top predators from ecosystems commonly results in dramatic changes in biodiversity and community structure, and as a result these areas can have severe consequences for the functioning of ecosystems (Berger et al., 2001; Terborgh et al., 1999). Show less
The mechanisms underlying Cd trophic transfer along the soil–lettuce–snail food chain were investigated. The fate of Cd within cells, revealed by assessment of Cd chemical forms and of subcellular... Show moreThe mechanisms underlying Cd trophic transfer along the soil–lettuce–snail food chain were investigated. The fate of Cd within cells, revealed by assessment of Cd chemical forms and of subcellular partitioning, differed between the two examined lettuce species that we examined (L. longifolia and L. crispa). The species-specific internal Cd fate not only influenced Cd burdens in lettuce, with higher Cd levels in L. crispa, but also affected Cd transfer efficiency to the consumer snail (Achatina fulica). Especially, the incorporation of Cd chemical forms (Cd in the inorganic, water-soluble and pectates and protein-integrated forms) in lettuce could best explain Cd trophic transfer, when compared to dietary Cd levels alone and/or subcellular Cd partitioning. Trophically available metal on the subcellular partitioning base failed to shed light on Cd transfer in this study. After 28-d of exposure, most Cd was trapped in the viscera of Achatina fulica, and cadmium bio-magnification was noted in the snails, as the transfer factor of lettuce-to-snail soft tissue was larger than one. This study provides a first step to apply a chemical speciation approach to dictate the trophic bioavailability of Cd through the soil–plant–snail system, which might be an important pre-requisite for mechanistic understanding of metal trophic transfer. Show less
