Document Type

Thesis

Date of Degree

Fall 2014

Degree Name

MS (Master of Science)

Degree In

Civil and Environmental Engineering

First Advisor

Jerald L. Schnoor

Abstract

Nanomaterials are widely used in many different products, such as electronics, cosmetics, industrial goods, biomedical uses, and other material applications. The heavy emission of nanomaterials into the environment has motived increasing concern regarding the effects on ecosystems, food chains, and, human health. Plants can tolerate a certain amount of natural nanomaterials, but large amounts of ENMs released from a variety of industries could be toxic to plants and possibly threaten the ecosystem.

Employing phytoremediation as a contamination treatment method may show promise. However a pre-requisite to successful treatment is a better understanding of the behavior and effects of nanomaterials within plant systems. This study is designed to investigate the uptake, translocation, bioavailability, and toxicity of gold nanorods in maize plants. Maize is an important food and feed crop that can be used to understand the potential hazardous effects of nanoparticle uptake and distribution in the food chain. The findings could be an important contribution to the fields of phytoremediation, agri-nanotechnology, and nanoparticle toxicity on plants.

In the first experiment, hydroponically grown maize seedlings were exposed to similar doses of commercial non-coated gold nanorods in three sizes, 10x34 nm, 20x75 nm, and 40x96 nm. The three nanorod species were suspended in solutions at concentrations of 350 mg/l, 5.8 mg/l, and 14 mg/l, respectively. Maize plants were exposed to all three solutions resulting in considerably lower transpiration and wet biomass than control plants. Likewise, dry biomass was reduced, but the effect is less pronounced than that of transpiration and wet biomass. The reduced transpiration and water content, which eventually proved fatal to exposed plants, were most likely a result of toxic effect of gold nanorod, which appeared to physically hinder the root system. TEM images proved that maize plants can uptake gold particles and accumulate them in root and leaf cells. However, the translocation factor of gold nanorods from root to leaf was very low in this experiment.

In the second experiment, maize seedlings were exposed to different (lower) concentrations of gold nanorods measured at 4.5x10-3 mg/l, 0.45 mg/l, and 2.25 mg/l for 10 days. Transpiration and biomass measurements demonstrated that the higher concentration of gold nanorods caused lower water uptake and growth, but lower concentrations did not show a significant toxic effect. According to ICP-MS results, root systems of the exposed plants were surrounded by high concentrations of sorbed nanorods, which physically interfered with uptake pathways and, thus, inhibited plant growth and nutritional uptake.

Public Abstract

Contaminated soil and water is one of the major environmental issues in the last decades. Due to increasing applications in industry and medicine, nano-materials are recent but serious componentof man-made pollution. The effects of nano-material contamination on plant-life and the ecosystem is drawing the interest of many researchers, but better understanding of the toxicity, fate, and, transport of nano-materials in plants is still needed.

This study is designed to investigate the uptake, translocation, toxicity and bioavailability of gold nanorods in maize plants.

In the first experiment, maize seedlings were exposed to high concentrations of gold nanorods of a variety of sizes in hydroponic systems. In the second experiment, maize plants were exposed to different, lower concentrations of gold nanorods. Results demonstrated that high concentrations of gold nanorods can be toxic to maize plants and cause lower water uptake and growth which is most likely a toxic inhibitory effect of gold nanorods on maize plants roots. Also the TEM images of tissue samples from plants exposed to gold nanorods demonstrated that maize plants are able to uptake nanorods from the hydroponic system and accumulate them in root and leaf cells. Since maize is a common agriculture crop, which is widely consumed, toxic effects of NPs in the food chain are essential to be known and understood. Furthermore, findings from this research can be helpful for fields of study in phytoremediation and agri-nanotechnology.

Keywords

publicabstract, Gold nanorod, Maize, nano-agriculture, Phytoremediation

Pages

x, 66 pages

Bibliography

Includes bibliographical references (pages 56-60).

Comments

This thesis has been optimized for improved web viewing. If you require the original version, contact the University Archives at the University of Iowa: http://www.lib.uiowa.edu/spec-coll/contact/index.html.

Copyright

Copyright 2014 Nastaran Moradi Shahmansouri

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