Quantum dot transport in soil, plants, and insects |
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Authors: | Al-Salim Najeh Barraclough Emma Burgess Elisabeth Clothier Brent Deurer Markus Green Steve Malone Louise Weir Graham |
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Affiliation: | a Industrial Research Ltd, P.O. Box 31310, Lower Hutt 5040, New Zealandb The New Zealand Institute for Plant and Food Research Ltd, Private Bag 92169, Victoria Street West, Auckland 1142, New Zealandc The New Zealand Institute for Plant and Food Research Ltd, Private Bag 11600, Manawatu Mail Centre, Palmerston North 4442, New Zealand |
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Abstract: | Environmental risk assessment of nanomaterials requires information not only on their toxicity to non-target organisms, but also on their potential exposure pathways. Here we report on the transport and fate of quantum dots (QDs) in the total environment: from soils, through their uptake into plants, to their passage through insects following ingestion. Our QDs are nanoparticles with an average particle size of 6.5 nm. Breakthrough curves obtained with CdTe/mercaptopropionic acid QDs applied to columns of top soil from a New Zealand organic apple orchard, a Hastings silt loam, showed there to be preferential flow through the soil's macropores. Yet the effluent recovery of QDs was just 60%, even after several pore volumes, indicating that about 40% of the influent QDs were filtered and retained by the soil column via some unknown exchange/adsorption/sequestration mechanism. Glycine-, mercaptosuccinic acid-, cysteine-, and amine-conjugated CdSe/ZnS QDs were visibly transported to a limited extent in the vasculature of ryegrass (Lolium perenne), onion (Allium cepa) and chrysanthemum (Chrysanthemum sp.) plants when cut stems were placed in aqueous QD solutions. However, they were not seen to be taken up at all by rooted whole plants of ryegrass, onion, or Arabidopsis thaliana placed in these solutions. Leafroller (Lepidoptera: Tortricidae) larvae fed with these QDs for two or four days, showed fluorescence along the entire gut, in their frass (larval feces), and, at a lower intensity, in their haemolymph. Fluorescent QDs were also observed and elevated cadmium levels detected inside the bodies of adult moths that had been fed QDs as larvae. These results suggest that exposure scenarios for QDs in the total environment could be quite complex and variable in each environmental domain. |
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Keywords: | CDE, convection-dispersion equation Cys, cysteine Gly, glycine EDC, 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide hydrochloride ICP-MS, inductively coupled plasma mass spectrometry MPA, mercaptopropionic acid MSA, mercaptosuccinic acid PBS, phosphate buffered saline PV, pore volume QD, quantum dot |
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