2014 Progress Report: Transatlantic Initiative for Nanotechnology and the Environment

EPA Grant Number: R834574
Title: Transatlantic Initiative for Nanotechnology and the Environment
Investigators: Unrine, Jason M. , Bertsch, Paul M. , Wiesner, Mark R. , Lowry, Gregory V. , Tsyusko, Olga V. , Casman, Elizabeth , Liu, Jie , Kabengi, Nadine
Current Investigators: Bertsch, Paul M. , Dorey, Robert A , Rocks, Sophie A , McNear, David H. , Unrine, Jason M. , Wiesner, Mark R. , Lowry, Gregory V. , Tsyusko, Olga V. , Neal, Andy , Jefferson, Bruce , Svendsen, Claus , Spurgeon, David , Casman, Elizabeth , Zhang, Hao , Harris, J. , Liu, Jie , Ritz, Karl , Kabengi, Nadine , McGrath, Steve , Lofts, Steve
Institution: University of Kentucky , Carnegie Mellon University , Lancaster University , Cranfield University , Centre for Ecology and Hydrology , Duke University , Rothamsted Research
Current Institution: University of Kentucky , Carnegie Mellon University , Centre for Ecology and Hydrology , Cranfield University , Duke University , Lancaster University , Rothamsted Research
EPA Project Officer: Klieforth, Barbara I
Project Period: August 1, 2010 through September 30, 2014 (Extended to June 30, 2016)
Project Period Covered by this Report: October 1, 2013 through September 23,2014
Project Amount: $2,000,000
RFA: Environmental Behavior, Bioavailability and Effects of Manufactured Nanomaterials - Joint US – UK Research Program (2009) RFA Text |  Recipients Lists
Research Category: Chemical Safety for Sustainability

Objective:

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 manufactured nanomaterials (MNMs) introduced via the land application of MNM-containing biosolids. In this project we are investigating 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); and

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.

The overall objectives are to:

O1 - Compare the transport, fate, behavior, bioavailability, and effects of MNMs, a-MNMs, and/or dissolved free metals/bulk oxides to organisms with key terrestrial ecosystem functions, as well as exposure pathways involving humans;

O2 - Determine MNM, surface modified MNM and a-MNM interactions with important biological targets relevant to the BLM and pBRM models and relate these interactions to physicochemical properties;

O3 - Validate models with information generated from experiments designed to address O1 for MNMs introduced through a pilot-scale Waste Water Treatment Process (WWTP) to key terrestrial ecoreceptors, including effects of MNMs on the WWTP itself;

O4 - Determine realistic MNM emission scenarios for Tier 1 MNMs in wastewater from the WWT pilot plant data and develop first generation Life-Cycle-Analysis-inspired Risk Assessment (LCA-RA) model components for terrestrial effects of Tier 1 MNMs and a-MNMS based on data generated in experiments designed to address O1, O2, & O3; and

O5 - Provide tools for in situ detection, monitoring, and characterization of pristine MNMs and a-MNMs in environmental media and biota.

Progress Summary:

Toxicity and bioavailability of nano and bulk metals in fresh and aged sewage sludge biosolids mixtures to Medicago truncatula and Sinorhizobium melliloti (UKY): During this reporting period we completed a series of major pot experiments investigating the toxicity of the nano-metal and bulk metal spiked sewage sludge biosolids to the model legume Medicago truncatula and Sinorhizobium melliloti. The sewage sludge biosolids were generated at a pilot wastewater treatment plant facility at Cranfield University. We published a paper detailing the speciation of metals in the biosolids as measured using synchrotron-based X-ray absorption spectroscopy (XAS) as received and after composting. These results suggested no difference in the speciation of the nano and bulk metals as measured by XAS. The first experiments included exposures to fresh sewage sludge biosolids mixtures containing 50% sewage sludge (simulating 10 years of sludge application) mixed with a natural sandy loam soil from the United Kingdom. These mixtures had a very high salinity so that even the control soil/sludge mixtures did not support adequate plant growth. Subsequent experiments were performed on 25% sludge-75% biosolids mixtures (simulating 5 years of application). Relatively minor effects on plant growth were noted in both the nano and bulk treatments; however, none of the plants nodulated. The next round of experiments focused on the 50% sludge/soil mixture after leaching in outdoor lysimiters at Rothamstead Research in the United Kingdom for 6 months. These mixtures appeared to have lower salinity, perhaps more reflective of actual field exposures, which would be subject to leaching. In this experiment we noted a complete inhibition of nodulation of Medicago in the nano treatment, but not in the control and bulk treatments. We attempted to explain this difference in toxicity by performing a number of standard extractions aimed at estimating phytoavailability of the metals but there were no differences in the extractable total or dissolved metals. The next steps are to perform XAS on the leached sewage sludge biosolids mixtures and to perform SEM-BSE to determine if differences in particle size of the minerals formed during wastewater treatment differs (Ag2S, Zn3(PO4)2 and ZnS) or if the speciation of the metals as measured by XAS has changed during outdoor leaching.
 
We also have completed transcriptomic analysis of the plants from the leached sewage sludge biosolids mixtures where we observed differences in nodulation between the nano and bulk metal treatments. There were 1032 differentially expressed genes in the nano treatment shoots that were not expressed in the bulk treatment and 2261 in the roots. Many of the differentially expressed genes in the nano treatment were involved in flavonoid biosynthesis, which controls signaling of rhizobia for nodulation as well as the nodulation genes themselves. The bulk treatment had more differentially expressed genes in common with the control treatment (Figure 1).
 
Figure 1. Clustering histogram of differentially expressed genes in M. truncatula roots.
 
These differences in toxicity and gene expression are correlated with greater uptake of Zn from the soil sludge mixtures into plant shoots. There were no differences in metal bioaccumulation observed for Ti or Ag. In addition, phospholipid fatty acid analyses conducted at University of Kentucky indicate that the soil microbial communities were distinct among the treatments. We currently are preparing a series of three manuscripts for submission describing these results that will be submitted over the course of the next 3 months.
 
Similar experiments conducted with the earthworm E. fetida using the same leached sewage sludge biosolids mixtures at the Center for Ecology and Hydrology (CEH) in the United Kingdom concluded that the toxicity of the nano biosolids was greater than the bulk biosolids.
 
The coherence of all of these observations is beginning to suggest that the U.S. biosolids application regulations (CFR 40 part 503) may not be protective for nanomaterials. The level of protection of these regulations for nanomaterials should be investigated further. Currently, we are analyzing data from a pot experiment with M. truncatula where we diluted the metal dosed biosolids/soil mixtures with control biosolid/soil mixture.

Bioavailability and toxicity of Ag and ZnO NPs and selected transformed (weathered) MNMs to C. elegans (UKY). Ongoing studies of pristine and aged (fully sulfidized) Ag NPs in C. elegans are complete and the first manuscript describing these results is accepted for publication with minor revisions. The results indicated that there are particle specific effects and that the relative importance of Ag ions as a contributor to toxicity decreases with increasing Ag concentration. The results of imaging and toxicogenomic studies suggested that toxicity of pristine and aged Ag NPs differs from each other and from that of Ag ions. The mechanism of fully sulfidized Ag NP toxicity is likely related to damage to the cuticle. We now have completed whole genome gene expression profiling of pristine and sulfidized Ag NPs. Little overlap between differentially expressed genes in the pristine, sulfidized and Ag ion treatments suggested distinct modes of toxicity. The importance of several of the differentially expressed genes was investigated using RNA interference and knock out strains. The results of these toxicogenomic experiments are in preparation for publication and will be submitted to a journal prior to the end of the 2014 calendar year.

Similar exposures were conducted at CEH on pristine and aged ZnO nanomaterials in C. elegans. Researchers from UKY worked with CEH researchers to quantify the uptake and speciation of Zn in these nematodes using a synchrotron-based X-ray microprobe at Brookhaven National Laboratory in the United States. As part of this experiment, pristine, pH 8 aged, and pH 6 phosphate aged materials were compared. The data from these experiments currently are being analyzed. These aged materials were generated as part of an experiment that investigated the influence of pH on phosphate transformations of ZnO nanomaterials. This experiment demonstrated that at pH 6 ZnO completely dissolves and re-precipitates as hopeite Zn3(PO4)2 2H2O, while at pH 8 a ZnO core Zn3(PO4)2 shell structure forms. The core-shell structure and the hopeite have similar surface chemistry and solublility, the pH 8 aged material was shown to be more bioavailable and more toxic to wheat (Triticum aestivum) seedlings.

Exposure Modeling (CMU and Duke). We have developed a 1-dimensional mass balance diagenetic model of the sulfide- and oxygen-dependent chemical transformations of AgNPs in sediments. Results show that the relative abundance of the toxic species Ag+ is extremely low (< 0.01 wt-%), and that environmental conditions play an important role in AgNP fate. The half-life of sulfidized AgNPs can vary from 6.6 years to more than a century depending on oxygen availability in the sediments.

A watershed-scale model whose backbone is a hybrid of the EPA models HSPF and WASP7 is near completion. This model simulates watershed hydrology and agricultural practices, including biosolids application to crop lands and runoff to stream during storms, and has capabilities necessary to track point- and non-point nanoparticle sources, sinks, advection, and transformations in the environment. This model was the result of a collaboration with the EPA Chesapeake Bay Program.
 
A WWTP model was completed for Ag, ZnO, and TiO2 using transformation data gathered and experimental distribution data. In addition, work has been completed to investigate the transformations and distribution of CeO2 as a function of coating.


Journal Articles on this Report : 7 Displayed | Download in RIS Format

Other project views: All 68 publications 38 publications in selected types All 38 journal articles
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Journal Article Barton LE, Auffan M, Bertrand M, Barakat M, Santaella C, Masion A, Borschneck D, Olivi L, Roche N, Wiesner MR, Bottero J-Y. Transformation of pristine and citrate-functionalized CeO2 nanoparticles in a laboratory-scale activated sludge reactor. Environmental Science & Technology 2014;48(13):7289-7296.
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  • Journal Article Barton LE, Therezien M, Auffan M, Bottero J-Y, Wiesner MR. Theory and methodology for determining nanoparticle affinity for heteroaggregation in environmental matrices using batch measurements. Environmental Engineering Science 2014;31(7):421-427.
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  • Journal Article Choi J, Tsyusko OV, Unrine JM, Chatterjee N, Ahn J-M, Yang X, Thornton BL, Ryde IT, Starnes D, Meyer JN. A micro-sized model for the in vivo study of nanoparticle toxicity: what has Caenorhabditis elegans taught us? Environmental Chemistry 2014;11(3):227-246.
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  • Journal Article Dale AL, Lowry GV, Casman EA. Modeling nanosilver transformations in freshwater sediments. Environmental Science & Technology 2013;47(22):12920-12928.
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  • Journal Article Ma R, Levard C, Judy JD, Unrine JM, Durenkamp M, Martin B, Jefferson B, Lowry GV. Fate of zinc oxide and silver nanoparticles in a pilot wastewater treatment plant and in processed biosolids. Environmental Science & Technology 2014;48(1):104-112.
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  • Journal Article Money ES, Barton LE, Dawson J, Reckhow KH, Wiesner MR. Validation and sensitivity of the FINE Bayesian network for forecasting aquatic exposure to nano-silver. Science of The Total Environment 2014;473-474:685-691.
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  • Journal Article Rathnayake S, Unrine JM, Judy J, Miller A-F, Rao W, Bertsch PM. A multitechnique investigation of the pH dependence of phosphate induced transformations of ZnO nanoparticles. Environmental Science & Technology 2014;48(9):4757-4764.
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  • Supplemental Keywords:

    environmental nanotechnology, nanotoxicology, environmental chemistry, ecological and human health risks of manufactured nanomaterials, chemical speciation, biosensors, environmental chemistry, biogeochemistry

    Progress and Final Reports:

    Original Abstract
  • 2011 Progress Report
  • 2012 Progress Report
  • 2013 Progress Report
  • 2015 Progress Report
  • Final Report