Transatlantic Initiative for Nanotechnology and the Environment - A new robust insitu tool for measuring nanoparticles and assessing their effects

Lead Research Organisation: Lancaster University
Department Name: Lancaster Environment Centre


We have developed a life cycle perspective inspired conceptual model (CM) that suggests the importance of terrestrial ecosystems as a major repository of ZnO, TiO2, and Ag (Tier 1) manufactured nanomaterials (MNMs) introduced via the land application of MNM-containing biosolids. We propose to investigate the transport, fate, behavior, bioavailability, and effects of MNMs in(to) agroecosystems under environmentally realistic scenarios organized around three key hypotheses: Hypothesis (H1) Surface chemistry is the primary factor influencing the fate and transport of MNMs in the terrestrial environment as well as the bioavailability and effects to biological receptors; Hypothesis (H2) Once released to the environment, pristine MNM surfaces will be modified by interactions with organic and inorganic ligands (macromolecules) or via other biogeochemical transformations (aging effects forming a-MNMs); Hypothesis (H3) Ecoreceptors will respond to interactions with pristine metal and metal oxide MNMs, a-MNMs, and/or dissolved constituent metal ions and bulk oxides by specific ecological and toxicogenomic responses that will reflect their combined effects. Experimental Approach: Detailed physicochemical characterization will be conducted on Tier 1 and Tier 2 (CeO2, carbon nanotubes) MNMs and a-MNMs produced by simulating aging and these materials will be utilized in column transport (Tier 1 and 2), bioavailability, and effects (Tier 1) studies to key ecoreceptors (bacteria, soil invertebrates, and plants). Data needed to calibrate and validate the pBRM will be collected for Tier 1 MNMs using a subset of ecoreceptor species. The CM and model results from the simulated aging of MNMs will then be validated by repeating studies of Tier 1 MNMs subjected to actual WWTP using a pilot scale WWT facility. To facilitate these and future investigations of MNMs under environmentally relevant scenarios, novel in situ tools will be developed. Expected Results: The proposed research will generate among the first data on the transformations of important classes of MNMs subjected to WWTP as well as those added to and aged in soil. These data will be critical for evaluating potential direct and indirect ecological and human health risks of MNMs introduced to agroecosystems. Data generated on the simulated aged materials and on the MNM containing biosolids and soils to test H1 & H2, may indicate that the permutations of MNM properties required to be experimentally considered under realistic environmental scenarios can be significantly reduced. Furthermore, the results of this work will provide the first validation of using gene and protein expression profiles generated in laboratory controlled experiments as an indicator of exposure or effects under environmentally realistic conditions. An important output from the proposed research and modeling efforts will be the development of first generation validated predictive models of the environmental fate, behavior, bioavailability, and effects of several important classes of MNMs in agroecosystems.
Description Rapid growth in finding new applications for manufactured nanomaterials (MNM) has recently been accompanied by awareness about their related adverse toxicological and environmental impacts. Due to their intrinsic nature, measuring available concentrations of MNMs in the environment is a major challenge. This research is a launching point toward filling this gap, as it presents the potential of the well-established diffusive gradients in thin films (DGT) technique to determine MNMs concentrations in situ. Two binding layers commonly used in DGT devices were shown to be able to bind ZnO nanoparticles (ZnO NPs). The use of different types of diffusive layers demonstrated the critical role of their pore size for selective function of the DGT devices. The ZnO NPs can pass through the open pore diffusive layer used in standard DGT devices and be retained by the binding resin layer. However, the diffusion of ZnO NPs can be prevented when a 1000 MWCO (molecular weight cut off) dialysis membrane is placed in the front of the diffusive gel layer. A combination of two or more DGT devices with known diffusive layer properties should enable deduction of concentrations of available ZnO NPs in the environment. Unlike metal ions, determining diffusion coefficient values for ZnO NPs is challenging and greatly affected by shape, morphology, and solution-induced changes of the particles. Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) demonstrated that retention of ZnO NPs by Chelex and Metsorb binding layers occurs through chemisorption. The superior uptake kinetic for Chelex indicates that it is a better candidate for further development of DGT devices to measure ZnO NPs. These initial results are promising and important for further developing the DGT technique to measure available concentrations of manufactured nanomaterials in the different environmental media (waters, soils, and sediments). Further experiments investigating the effects of pH, ionic strength, and solution chemistry on the performance of DGT for measuring MNM concentrations are needed.

DGT has also developed successfully for measuring nano Ag species. Long-term speciation and lability of silver (Ag-), silver chloride (AgCl-), and silver sulfide nanoparticles (Ag2S-NPs) in soil were studied by X-ray absorption spectroscopy (XAS), and newly developed "nano" Diffusive Gradients in Thin Films (DGT) devices. These nano-DGT devices were designed specifically to avoid confounding effects when measuring element lability in the presence of nanoparticles. The aging profile and stabilities of the three nanoparticles and AgNO3 (ionic Ag) in soil were examined at three different soil pH values over a period of up to 7 months. Transformation of ionic Ag, Ag-NP and AgCl-NPs were dependent on pH. AgCl formation and persistence was observed under acidic conditions, whereas sulfur-bound forms of Ag dominated in neutral to alkaline soils. Ag2S-NPs were found to be very stable under all conditions tested and remained sulfur bound after 7 months of incubation. Ag lability was characteristically low in soils containing Ag2S-NPs. Other forms of Ag were linked to higher DGT-determined lability, and this varied as a function of aging and related speciation changes as determined by XAS. These results clearly indicate that Ag2S-NPs, which are the most environmentally relevant form of Ag that enter soils, are chemically stable and have profoundly low Ag lability over extended periods. This may minimize the long-term risks of Ag toxicity in the soil environment.
Exploitation Route Further research are needed to test the methods in different environmental conditions. The technique can be applied in field by other scientist to advance our understanding of the behavior, transport and fate our manufactured nanoparticles.
Sectors Agriculture, Food and Drink,Environment